Download Vaginal microbiota and its role in HIV transmission and infection

REVIEW ARTICLE
Vaginal microbiota and its role in HIV transmission and
infection
Mariya I. Petrova1,2, Marianne van den Broek1,2, Jan Balzarini3, Jos Vanderleyden1 & Sarah Lebeer1,2
1
KU Leuven, Centre of Microbial and Plant Genetics, Leuven, Belgium; 2University of Antwerp, Department of Bioscience Engineering, Antwerp,
Belgium; and 3KU Leuven, Rega Institute for Medical Research, Leuven, Belgium
Correspondence: Sarah Lebeer, KU Leuven,
Centre of Microbial and Plant Genetics,
Kasteelpark Arenberg 20, Box 2460, B-3001
Leuven, Belgium. Tel.: +32 16 321631;
fax: +32 16 321966; e-mails: sarah.lebeer@
biw.kuleuven.be; [email protected]
Received 1 March 2013; revised 10 June
2013; accepted 13 June 2013. Final version
published online July 2013.
DOI: 10.1111/1574-6976.12029
€tz
Editor: Friedrich Go
MICROBIOLOGY REVIEWS
Keywords
urogenital tract; pathogen exclusion;
immunomodulation; epithelial barrier;
probiotics; microbicide.
Abstract
The urogenital tract appears to be the only niche of the human body that
shows clear differences in microbiota between men and women. The female
reproductive tract has special features in terms of immunological organization,
an epithelial barrier, microbiota, and influence by sex hormones such as estrogen. While the upper genital tract is regarded as free of microorganisms, the
vagina is colonized by bacteria dominated by Lactobacillus species, although
their numbers vary considerably during life. Bacterial vaginosis is a common
pathology characterized by dysbiosis, which increases the susceptibility for HIV
infection and transmission. On the other hand, HIV infections are often characterized by a disturbed vaginal microbiota. The endogenous vaginal microbiota may protect against HIV by direct production of antiviral compounds,
through blocking of adhesion and transmission by ligands such as lectins, and/
or by stimulation of immune responses. The potential role of probiotics in the
prevention of HIV infections and associated symptoms, by introducing them
to the vaginal and gastrointestinal tract (GIT), is also discussed. Of note, the
GIT is a site of considerable HIV replication and CD4+ T-cell destruction,
resulting in both local and systemic inflammation. Finally, genetically engineered lactobacilli show promise as new microbicidal agents against HIV.
Introduction
The surfaces of the human body can be divided into four
fundamental microbial niches, which differ in composition, but each play an important role in the entire life of
an individual. These niches include the skin, the oronasopharyngeal cavity, the genital tract, and the gastrointestinal tract (GIT). The microbiota present in each of
the niches provides a vast number of health effects to the
host (Reid et al., 2011). For each of these niches, the
symbiotic microbiota protects the host from pathogenic
colonization by niche-specific metabolic exclusion of
pathogens, by competition for adhesion sites and by
stimulation of immune responses that activate production
of antimicrobial components (Duerkop et al., 2009). The
impact of the mucosal microbiota on the mucosal
immune system is even more broad than the mere stimulation of antipathogenic responses, because more and
more studies, such as with germfree mice, indicate a
crucial role for immune regulation by symbiotic bacteria
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
(Hooper et al., 2012). In addition, the microbiota has
specific functions at each mucosal niche, of which the
role of the GIT microbiota in digesting food components
and energy conversions are probably the best known.
During the last decades, the genital and GIT microbiota have been increasingly recognized as important
factors in the host defense against viral pathogens such as
the human immunodeficiency virus (HIV). HIV is a
member of the Lentivirus family based on its gene
sequence homology, morphology, and life cycle. Two
types of HIV are known, designated as HIV-1 and HIV-2,
which are transmitted in the same way and manifest similar clinical syndromes. However, they differ in genetic
structure, antigenicity, and pathogenicity: that is, HIV-2
is less pathogenic compared with HIV-1. Furthermore,
HIV-2 transmits less efficiently and is almost exclusively
found in West Africa (Reeves & Doms, 2002). This review
aims to describe the role of the human microbiota and
exogenously applied probiotics in relation to HIV
infection, with emphasis on the molecular mechanisms
FEMS Microbiol Rev 37 (2013) 762–792
Human microbiota and HIV infections
involved. In addition to the current state of the literature,
future applications, such as recombinant probiotics as
potential new microbicides, are discussed.
Key immunological and microbiological
aspects of the female reproductive tract
Defense system of the urogenital tract
The mucosal surface of the urogenital tract forms the first
line of defense against microorganisms and viruses in this
niche and separates the external environment from the
internal sterile environment. It is generally believed that
the upper genital tract is free of microorganisms
(Heinonen et al., 1985). The mucosal epithelium in this
upper niche should thus be extremely efficient in recognizing and subsequently responding to microorganisms,
while at the same time avoiding chronic inflammation. In
contrast to the upper genital tract, the cervical and
vaginal epithelia are permanently colonized by microorganisms, mainly endogenous microbiota represented by
lactobacilli in a healthy stage and a broad variety of
potential pathogens during infections (see below). Therefore, this mucosa has adapted to a nonsterile, dynamic
environment, continuously challenged by changes in
hormone levels and a variety of inflammatory stimuli
associated with sexual intercourse. For example, in the
genital tract of premenopausal women, hormones control
the expression of large numbers of genes responsible for
the secretion of cytokines and chemokines, regulating
cellular composition, immunoglobulin (Ig) secretion, and
antigen presentation (Wira & Rossoll, 2003). Such experimental studies clearly show that the vaginal and cervical
epithelium and immune cells provide a natural barrier
against pathogens.
The upper female reproductive tract (FRT), which consists of the endometrium, endocervix, and Fallopian
tubes, is characterized by the presence of Type I mucosae,
a simple columnar epithelium formed by a single layer of
ciliated columnar cells connected via tight junctions
(Fig. 1). The ciliated columnar cells have between 200
and 300 finger-like hairs, called cilia, involved in movement of mucus as well as egg cells toward the Fallopian
tubes and the uterus. Type I mucosae are characterized
by the presence of polymeric Ig receptors, microfold cells
(M-cells), presence of mucosa-associated lymphoid tissue
(MALT), and secretory IgA antibodies (Iwasaki, 2010). A
Type I mucosa is also present in the GIT. However, the
GIT mucosa also shows significant differences with the
upper FRT, such as the presence of Paneth cells and
gut-associated lymphoid tissue (GALT), which includes
Peyer’s patches in the small intestine and isolated
lymphoid follicles in the colon.
FEMS Microbiol Rev 37 (2013) 762–792
763
The lower FRT, that is, the vaginal canal and the ectocervix, contains Type II mucosae. They are characterized
by multiple layers of nonkeratinized stratified squamous
epithelium in which the surface cells are flattened, and
the deeper cells are columnar and attached to a basal
membrane (Robboy & Bentley, 2004). Such a Type II
mucosa is lacking MALT, M- cells, and polymeric Ig
receptors. Nevertheless, Type II mucosae are characterized
by the presence of Langerhans cells (LCs) and high
production of IgG antibodies (Iwasaki, 2010). In addition,
cells of the squamous epithelium have no tight junctions
between each other (Fig. 1). This permits the transport of
small molecules between the cells within the epithelial
space, including small viruses and toxic compounds from
pathogens (Hickey et al., 2011).
The uterine and vaginal epithelial cells are not only a
physical barrier against pathogens, but they are also able
to actively recognize conserved microbe-associated molecular patterns of microorganisms via the expression of
cognate pattern recognition receptors (PRRs). PRRs
include Toll-like receptors (TLRs) and NOD-like receptors, which mediate the secretion of cytokines, chemokines,
and antimicrobial peptides (Schaefer et al., 2004, 2005).
The epithelial cells from Type I and Type II mucosae in
the FRT and in the GIT are also covered by a layer of mucus,
consisting of mucins, which are complex high-molecularmass O-glycoproteins (Andersch-Bjorkman et al., 2007).
The mucus sources in Type I mucosae are specialized
goblet cells, similar to the ones in the GIT, and mucus
glands present in the crypts of the cervix, while the
mucus source in Type II mucosae is local mucus-secreting
epithelial cells (Andersch-Bjorkman et al., 2007). Different types of mucin genes (MUCs) are expressed in the
FRT. For example, the endocervical epithelium expresses
MUCs 1, 4, 5AC, 5B, and 6, while two types of cervicovaginal mucus can be isolated from the FRT, which
strongly depend on the stage of the menstrual cycle
(Gipson et al., 1997). The estrogenic mucus, present at
the proliferative stage and ovulation, is thin and watery
with a low viscosity that permits sperm movement. In
contrast, progestational mucus, present at high concentrations after ovulation and during the secretory phase, is
thick, sticky, and blocks the passage of spermatozoa
(Hickey et al., 2011). An important characteristic of the
cervico-vaginal mucus is the low pH between 4 and 5
that affect the transmission of pathogenic bacteria and
viruses including HIV.
The concentration and distribution of innate immune
cells in the FRT depend on the hormone levels and menstrual cycle, and varies in the different parts of the FRT.
In a steady state, low numbers of neutrophils, dendritic
cells (DCs) or LCs, macrophages, and natural killer (NK)
cells are present in the lower FRT. In contrast, the same
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
764
M.I. Petrova et al.
Fig. 1. General overview of the Type I and Type II mucosae present in the GIT and FRT. GIT and upper FRT (uterus and endocervix) are
characterized by the presence of Type I mucosae. Both GIT and upper FRT are covered by a single layer of columnar epithelium in which the cells
are connected by tight junctions. This epithelium is covered with a thick layer of mucus. IgA is the main antibody isotype detected in Type I
mucosae. A typical characteristic of GIT is the presence of Peyer’s patches, which represent mucosa-associated lymphoid nodes. In comparison, a
unique structure of the upper FRT is the presence of LA. A striking difference between the GIT mucosae and upper FRT mucosae is the presence
of an endogenous microbiota in GIT, while the upper FRT is believed to be sterile. The lower FRT is represented by Type II mucosae, characterized
by a stratified squamous (nonkeratinized) epithelium in which low numbers of subepithelial immune cells are detected. The major antibody
isotypes are IgG and a low concentration of IgA. A unique set of epithelial DCs, called LCs, is also present within this Type II mucosa. In addition,
the figure shows the ectocervix–endocervix transformation zone, where stratified squamous epithelium ‘transforms’ to single columnar
epithelium. This zone is highly enriched with immune cells, mainly CD4+ T cells. The commensal microbiota for each of these niches is also
highlighted. The GIT microbiota includes a diverse number of microorganisms with three main enterotypes, dominated by resp. Bacteroides,
Prevotella, and Ruminococcus. On the other hand, the vaginal microbiota is generally Lactobacillus dominated with commonly isolated species
including Lactobacillus iners, Lactobacillus crispatus, Lactobacillus gasseri, and Lactobacillus jensenii. The vaginal microbiota is characterized by the
production of lactic acid, which lowers the pH in the vaginal epithelium to the range of 4–5; production of H2O2 and bacteriocins, as well as
bacteriophage release which affects community dynamics. In addition, some lactobacilli can be isolated from the ectocervix, in comparison with
the endocervix and the upper FRT, which are considered to be sterile niches.
cells are present in high concentration in the upper FRT,
possibly related to the fact that this niche needs to be
kept sterile (Pudney et al., 2005). FRT DCs are localized
in the subepithelial stroma of the endometrium, while
they are present within the epithelial layers in the vaginal
epithelium and known as LCs (Fig. 1; Ginhoux et al.,
2006). DCs are essential mediators in capturing the HIV
virions by the DC-specific intercellular adhesion molecule
3 (ICAM3)-grabbing nonintegrin (DC-SIGN) receptor,
which mediates subsequent transmission to T cells
(Cameron et al., 1992; Geijtenbeek et al., 2000). Macrophages represent around 10% of the immune cells present
in the upper FRT, but because their concentration is
estrogen- and progesterone dependent, the upper FRT
exhibits relatively high levels prior to menstruation (Giª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
van et al., 1997). An important characteristic of vaginally
presented macrophages in comparison with the GIT macrophages is the higher expression of the CD4, CCR5, and
CXCR4 receptors. CD4 is known to be the main receptor
for HIV virus, while CCR5 and CXCR4 function as coreceptors, which is in agreement with the greatest affinity
of HIV virions to vaginal macrophages (Shen et al.,
2009). Other important innate immune cells in the FRT
are NK cells, which are account for 10–30% of the leukocytes. The numbers of NK cells do not change, except for
the ones in the endometrium which can reach up to 70%
during the menstruation period (Givan et al., 1997; Wira
et al., 2005). The FRT NK cells – similarly to blood NK
cells – produce a variety of pro-inflammatory cytokines
such as granulocyte–macrophage colony-stimulating
FEMS Microbiol Rev 37 (2013) 762–792
765
Human microbiota and HIV infections
factor (GM-CSF), interleukin-8 (IL-8) and interferon
(IFN) and subsequently promote the inflammatory
response, induce macrophage activation and cytotoxic Tcell generation (Hickey et al., 2011). However, the FRT
NK cells are characterized by specific activities such as the
production of angiogenic growth factors and leukemia
inhibitory factors essential for blood vessel development
(Hickey et al., 2011). The importance of NK cells in the
female innate defense is also demonstrated by the
increased susceptibility of patients with defects in NK cell
function for Herpes simplex virus-2 (HSV-2; Bloomfield
& Lopez, 1980). In addition, vaginal NK cells – but not
blood NK cells – can inhibit infection of target cells by
HIV X4 strains but not R5 strains via secretion of
CXCL12 (Mselle et al., 2009).
The number of leukocytes in the FRT approximately
accounts for between 6% and 20% of the total number of
immune cells with higher numbers in the upper FRT
(Givan et al., 1997; Hickey et al., 2011), while the number
of leukocytes in the vaginal epithelium is remarkably low.
By comparison, higher numbers of leukocytes, predominantly CD4+ T and CD8+ T cells, can be detected in the
vaginal lamina propria, but still in lower numbers
compared with the other parts of the FRT (Pudney et al.,
2005). T cells in both the vaginal epithelium and the vaginal lamina propria appear to be predominantly of the
memory phenotype. Furthermore, Pudney et al. (2005)
reported that the ectocervical mucosa contained higher
concentrations of CD4+ intraepithelial lymphocytes. These
researchers have also shown that T cells and antigen
presenting cells are most prevalent in the cervical transformation zone where the ectocervix transforms into endocervix and where the stratified epithelium ends and
columnar monolayer begins. This suggests that this site
functions as an immunological barrier to bacterial and
viral pathogens and is the major inductive and effector site
for cell-mediated immunity in the lower FRT (Fig. 1).
Unique for the upper FRT mucosae is the presence of
several lymphoid aggregates (LA) consisting of an inner
core of B cells surrounded by mainly CD8+ T cells and
an outer halo of macrophages (Fig. 1). The size of the
aggregates was found to vary throughout the stages of
the menstrual cycle, with larger sizes during the secretory
stage as compared with the proliferative stage (Yeaman
et al., 1997, 2001). The absence of these aggregates in
postmenopausal women provided evidence that these
aggregates are under hormonal control. The functions of
these LAs are not well documented yet. However, a
potential role has been suggested in the suppression of
cell-mediated immunity in the uterus during the secretory phase of the cycle, when ovulation and implantation
are most likely to happen (Yeaman et al., 1997, 2001).
This would imply that the presence of aggregates of
FEMS Microbiol Rev 37 (2013) 762–792
immune cells is not dependent on the presence of
infection.
In conclusion, the FRT is – in comparison with GIT
mucosal systems – under strong hormonal control and is
characterized by a unique distribution and phenotypes of
DCs, LCs, NK cells, macrophages, neutrophils, B and T
cells as well as unique set of Ig isotype. This indicates the
presence of multiple levels of protection to minimize the
risk of infection by potential bacterial and viral
pathogens.
Healthy vaginal microbiota
Prior to the development of molecular methods, vaginal
lactobacilli were identified by culture-dependent methods.
The first reports on the presence of vaginal microbiota
date from 1892 when the German scientist Albert D€
oderlein, reported on the presence of ‘Gram-positive, nonspore-forming rods, sometimes quite long and slender,
with square or very tapering ends, occurring single or in
chain, producing lactic acid that could inhibit the growth
of pathogens’ (D€
oderlein, 1892). Till 1980, it was believed
that the vaginal microbiota was dominated by Lactobacillus
acidophilus, as determined by culture-dependent and
microscopic methods, since in 1928, Stanley Thomas
identified the D€
oderlein’s bacillus as L. acidophilus
(Thomas, 1928). However, after 1980, the group of
microorganisms known as L. acidophilus was shown to be
highly diverse. Based on different molecular methods, the
group was separated into DNA-homology groups, which
could not be distinguished biochemically and which form
nine separate species of the L. acidophilus complex, that is,
L. acidophilus, Lactobacillus amylolyticus, Lactobacillus
amylovorus, Lactobacillus crispatus, Lactobacillus gallinarium, Lactobacillus gasseri, Lactobacillus iners, Lactobacillus
jensenii, and Lactobacillus johnsonii (Du Plessis & Dicks,
1995; Falsen et al., 1999). As mentioned above, the
culture-dependent methods excluded various Lactobacillus
species. For example, most culture-dependent methods
fail to identify L. iners, because it grows only on blood
agar, but not in the normal Rogosa or de Man, Rogosa
and Sharpe medium, typical for the growth of Lactobacillus (de Man et al., 1960). Lactobacillus iners was first isolated in a woman with a healthy vaginal microbiota and
described based on culture-independent methods in 2002
(Burton & Reid, 2002). Recently, it was reported that
L. iners has the smallest Lactobacillus genome consisting
of a 1.3-Mbp single chromosome (Macklaim et al., 2011).
Yet, the genome of L. iners contains a number of genes
putatively involved in adaptation to the fluctuating vaginal environment. For example, L. iners has an iron-sulfur
cluster (Fe-S) mainly detected in vaginal Lactobacillus isolates. For example, an Fe-S cluster was also recently
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
766
reported in the genome of Lactobacillus pentosus KCA1
(Anukam et al., 2013) and Lactobacillus rhamnosus GR-1
(J. Macklaim, M.I. Petrova, A.S. Rodriguez, J. Vanderleyden, K. Marchal, G. Gloor, S. Lebeer and G. Reid, unpublished data). The Fe-S cluster from L. iners shares
similarities with similar clusters from L. crispatus and
L. johnsonii, common vaginal isolates, and is suggested to
be involved in resistance to oxidative stress, especially in
the vaginal niche where high levels of H2O2 are produced
by other lactobacilli (Macklaim et al., 2011). In addition,
several unique r-factors were detected in the genome of
L. iners. The r-factors were reported to regulate gene transcription of various stress response genes and suggested to
further contribute to survival in the presence of H2O2
(Macklaim et al., 2011). Up till now, L. iners is one of the
most frequently isolated strains from vaginal mucosa of
healthy premenopausal women (Lamont et al., 2011).
The composition of the vaginal microbiota changes
drastically over time, based on changing estrogen levels
during the maturation of women (Cribby et al., 2008).
Soon after birth, the vaginal epithelium is colonized by a
vast number of microorganisms. The majority of the vaginal bacteria originate from the GIT microbiota through a
natural ascension independent of hygiene or from the
surrounding skin epithelium. During this early stage of
infancy, maternal estrogen induces thickening of the vaginal epithelium and, in this process, regulates the deposition of glycogen in the epithelial cells. During exfoliation
of the epithelial cells, glycogen is released. Glycogen is a
source of glucose, thereby favoring glucose-fermenting
microorganisms (Boskey et al., 1999). The degradation of
extracellular glycogen by lactobacilli is not yet well documented, but it was recently reported that L. iners differentially expresses genes responsible for breakdown of
glycogen under vaginal conditions (Macklaim et al.,
2013). This suggests that some lactobacilli are able to use
the released glycogen as carbohydrate source. Postnatally,
the maternal estrogen is metabolized, resulting in a thinning of the mucosa, and reduction of glycogen. A subsequent reduction in glucose-fermenting microorganisms,
including lactobacilli, facilitates an increase in the vaginal
pH, encouraging the proliferation of a wide range of
aerobes and facultative anaerobes (Fig. 2). The vaginal
microbiota is therefore during childhood mostly dominated by Gram-negative anaerobe bacteria including
Veillonella, Bacteroides, Fusobacteria, and some Gramnegative cocci as well as Gram-positive anaerobe bacteria
including Actinomyces, Bifidobacteria, Peptococcus, Peptostreptococcus, and Propionibacterium (Dei et al., 2010;
Randelovic et al., 2012). The vaginal microbiota can
include also some aerobic bacteria such as Staphylococcus
aureus, Staphylococccus epidermidis, Streptococcus viridans,
Enterococcus faecalis, Corynebacterium, and Diphteroides.
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
Typical for the vaginal microbiota of prepuberal girls is
the low frequency of lactobacilli, Gardnerella vaginalis,
Prevotella bivia, Mycoplasma hominis, and yeast (Hill
et al., 1995; Randelovic et al., 2012). With the beginning
of puberty, the vaginal epithelium, under estrogenic control, once again thickens. As mentioned before, this glycogen-rich environment selects for glucose-fermenting
microorganisms, provided glycogen can be broken down
(Mac Bride et al., 2010). The microbiota present in this
period of life has also been studied and is predominantly
colonized by Lactobacillus species. Yamamoto et al. (2009)
reported that the microbiota of adolescent girls is similar
to the vaginal microbiota of adult women and dominated
by L. iners, L. crispatus, L. jensenii, and L. gasseri. It
remains to be investigated how this estrogen-induced
increase of glycogen and its subsequent metabolism by
vaginal lactobacilli is regulated at the molecular level.
The vaginal microbiota in healthy adult women is
mostly dominated by Lactobacillus species as mentioned
above. In the last decade, the interest in the vaginal
microbiota has strongly increased. The most frequently
occurring species are L. crispatus, L. gasseri, L. iners, and
L. jensenii (Table 1; Fig. 3). In a recent study, Ravel et al.
(2011) showed that the vaginal microbiota can be divided
in five major microbial communities based on samples
from four ethnic groups (white, black, Hispanic, and
Asian in North America; Fig. 3), as also nicely reviewed
by Ma et al. (2012). According to Ravel et al. (2011),
microbial communities belonging to group I (26, 2%), II
(6, 3%), III (34, 1%), and V (5, 3%) were dominated by
L. crispatus, L. gasseri, L. iners, and L. jensenii, respectively, and were isolated mainly from white and Asian
women. The remaining 27% of the women forming community group IV, mainly black and Hispanic, were found
to be part of a heterogeneous group. Group IV was
characterized by strictly anaerobic bacteria, including
Prevotella, Dialister, Atopobium, Gardnerella, Megasphaera,
and Peptoniphilus (Ravel et al., 2011; Table 1). Other
studies also reported that some women’s vaginal ecosystems can be healthy without a Lactobacillus-dominant
vaginal microbiota. Studies identified women with Atopobium vaginae, Megasphaera, and/or Leptotrichia species as
dominant vaginal phylotype (Zhou et al., 2004, 2007;
Srinivasan et al., 2012). The same species, which belong
to the lactic acid producers, were also detected by Ravel
et al. (2011) in group IV, suggesting that lactic acid production is crucial for an adult healthy vaginal ecosystem
(Witkin et al., 2007; Ravel et al., 2011). In addition,
diversity in the vaginal microbiota of different geographic
area was also observed. For example, the vaginal microbiota of Nigerian, Belgian, and Brazilian women appears to
be dominated mainly by L. iners (Anukam et al., 2006;
Vitali et al., 2007; Martinez et al., 2008), whereas in
FEMS Microbiol Rev 37 (2013) 762–792
Human microbiota and HIV infections
767
Fig. 2. Changes in the vaginal mucosae during different stages of a woman’s life. During prepuberty, the low levels of estrogen result in thin
mucosae and low levels of glycogen, which stimulate the growth of diverse microbial species. In adult stage of life, the glycogen levels increase,
due to the increase in the levels of estrogen. The degradation of glycogen to glucose selects for glucose-fermenting microorganisms such as
Lactobacillus sp., which lower the vaginal pH and prevent growth of pathogenic bacteria. Postmenopause, the levels of estrogen once again
decline, reducing the deposition of glycogen thereby selecting for a high diversity of bacterial species.
Swedish, German, and Turkish women, L. crispatus is
most commonly isolated (Kilic et al., 2001; Vasquez et al.,
2002; Thies et al., 2007). In addition, the vaginal microbiota of Indian and Bulgarian women is dominated by
Lactobacillus reuteri, L. gasseri, and Lactobacillus fermentum (Dimitonova et al., 2008; Garg et al., 2009; Table 1).
Nevertheless, the exact number of vaginal community
types is under discussion (Ma et al., 2012), in agreement
with the discussion on the importance of GIT enterotypes
(Arumugam et al., 2011). Recently, Koren et al. (2013)
showed with data from the Human Microbiome Project
that the differences in number of enterotypes across the
human body depend on the sensitivity of enterotyping to
the taxonomic depths used in constructing operational
taxonomic units (Koren et al., 2013).
Until now, most studies are based on the collection of
vaginal samples at a single time point. However, a recent
study highlights the dynamics of the vaginal microbiota
over a short period of time (16 weeks; Gajer et al., 2012).
The authors were able to isolate five community groups in
agreement with the Ravel et al. (2011). Groups or community states I–III were dominated by L. crispatus, L. gasseri,
or L. iners, respectively, while community states IV-A and
IV-B were heterogeneous in composition (Fig. 3). Community state IV-A was characterized by a modest proportion
of either L. crispatus, L. iners or other Lactobacillus species
as well as low numbers of strict anaerobic bacteria. Group
IV-B was dominated by diverse number of bacteria belongs
mainly to genus Atopobium, Prevotella, Parvimonas,
Sneathia, Gardnerella, or Mobiluncus (Gajer et al., 2012).
FEMS Microbiol Rev 37 (2013) 762–792
The authors were able to show that some of the vaginal bacterial communities markedly change over time switching
from one to other class, whereas other stays relatively stable. For example, the vaginal communities dominated by
L. crispatus often transform to a community state III dominated by L. iners, or to IV-A. In addition, community
group III dominated by L. iners shifts more often to
community type IV-B, but in rare cases to IV-A. In comparison, the community group dominated by L. gasseri
rarely transits to other types and stays stable over time. Furthermore, the authors reported that the fluctuation of the
vaginal communities and their constancy are affected by
time in the menstruation cycle and to a certain extent by
sexual activity. Nevertheless, the vaginal community function was maintained despite the changes in bacterial
composition as indicated from the metabolite profiles
(Gajer et al., 2012).
Of particular interest, these vaginal microbiota were
recently shown to play a key role in the colonization of
newly born infants (Dominguez-Bello et al., 2010). The
authors showed that vaginally delivered infants acquire
bacterial communities that resemble their own mother’s
vaginal microbiota, dominated mainly by Lactobacillus. In
contrast, C-section infants were shown to harbor bacteria
similar to those found on skin surface, which is dominated
by Staphylococcus, Corynebacterium, and Propionibacterium. It has been suggested that this might explain the
susceptibility of C-section-delivered infants to certain
pathogens, but this requires further study (DominguezBello et al., 2010). Furthermore, the vaginal microbiota
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
768
M.I. Petrova et al.
Table 1. Composition of vaginal microbiota during healthy and disease*
Vaginal microbiota in health
Vaginal microbiota associated with BV
Dominant vaginal Lactobacillus strains
L. iners, L. crispatus, L. gasseri, L. jensenii
Common species isolated during BV
Mycoplasma hominis, Gardnerella vaginalis, Prevotella spp., Mobiluncus
spp., Staphylococcus epidermidis, Staphylococcus aureus, Streptococcus
spp., E. coli
Other species detected during BV
Atopobium vaginae, Megasphaera spp., Leptotrichia spp., Clostridiales
order, Dialister spp., Streptobacillus spp., Chloroflexi spp., Olsenella spp.,
Porphyromonas asaccharolytica, Shuttleworthia spp., Eggerthella
hongkongensis
Less common Lactobacillus species
L. vaginalis, L. reuteri, L. rhamnosus, L. salivarius, L. plantarum
Rarely isolated vaginal Lactobacillus species
L. fermentum, L. brevis, L. agilis, L. coleohominis, L. suntoryeus
Other groups isolated in some women
Prevotella, Dialister, Atopobium, Gardnerella, Megasphaera,
Peptoniphilus, Sneathia, Eggethella, Aerococcus, Finegoldia,
Mobiluncus, Cryptobacterium, Gemella, Ruminococcus,
Anaeroglobus, Leptotrichia, Parvimonas, Gardnerella
BV, bacterial vaginosis.
*Based on Wertz et al. (2008), Ravel et al. (2011), Lamont et al. (2011), Gajer et al. (2012), and Ma et al. (2012).
Fig. 3. Composition of vaginal microbiota in healthy adult women. The vaginal microbiota in healthy adult women can be divided into five
community groups. Group I, II, III, and V are dominated by Lactobacillus species belongs to Lactobacillus crispatus, Lactobacillus gasseri,
Lactobacillus iners, and Lactobacillus jensenii respectively, while group IV is diverse in composition. In addition, community group IV can be
separated into two subgroups – IV-A and IV-B. Community group IVA is characterized by the presence of L. crispatus or L. iners and strict
anaerobes, while IVB has a higher proportion of members of the genus Atopobium, Prevotella, Parvimonas, Sneathia, Gardnerella, and
Mobiluncus. Figure mainly based on Ravel et al. (2011) and Gajer et al. (2012).
has been shown to change drastically during pregnancy,
characterized by a reduction in overall diversity and
richness, but an increase of Lactobacillus species, Clostridiales, Bacteroidales, and Actinomycetales (Aagaard et al.,
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
2012). This might be related to the vertical transmission of
these microorganisms during vaginal delivery. The importance of vaginal transmission of beneficial lactobacilli from
mother to child needs to be taken into account when the
FEMS Microbiol Rev 37 (2013) 762–792
Human microbiota and HIV infections
application of intrapartum antibiotics is considered upon
maternal Group B streptococcal colonization (Ohlsson &
Shah, 2013), which is currently a common practice that
could have unforeseen side effects.
In postmenopausal women with a decrease in estrogen
levels, the vaginal microbiota changes (Fig. 2). The
microbiota in this stage was reported to be dominated by
L. iners and G. vaginalis and was characterized by a lower
abundance of Candida, Mobiluncus, Staphylococcus, Sneathia, Bifidobacterium, and Gemella. Also, the presence of
other lactobacilli is strongly reduced, and consequently,
growth of potential pathogenic bacteria is increased
(Gupta et al., 2006; Hummelen et al., 2011b).
Overall, the microbiota of the human vaginal tract is
characterized by a much lower diversity and number of
microbial species in comparison with the GIT microbiota.
The reason for the lower diversity of the vaginal microbiota is still unclear, but may be linked to differences in
the nutrient availability, reduced competition with indigenous organisms, but also different immune activity and
functioning, as described above (Cribby et al., 2008).
Vaginal microbiota during bacterial vaginosis
In comparison with the healthy vaginal microbiota dominated by lactobacilli, an abnormal vaginal microbiota is
characterized by an increased diversity of species, mostly
pathogens. These pathogens are able to infect the vaginal
epithelium of the host, which subsequently results in
severe infections such as bacterial vaginosis (BV), yeast
vaginitis, or urogenital tract infections, when pathogens
from the genital tract migrate to the bladder epithelium.
For example, yeast vaginitis is characterized by an overgrowth of fungal pathogens mainly consisting of Candida
albicans, but also Candida glabrata, Candida krusei, and
Candida tropicalis. BV is associated with an abnormal
growth of vaginal bacterial pathogens and a reduced
number of vaginal Lactobacillus species. Symptomatic BV
is mostly detected using the Amsel clinical criteria (Amsel
et al., 1983) or the Nugent score (Nugent et al., 1991).
The Amsel criteria are based on the presence of three or
four symptoms such as vaginal pH higher than 4.5, a
milky homogeneous vaginal discharge, detection of fishy
odor and significant presence of clue cells (Amsel et al.,
1983). The Nugent score is based on Gram staining of
the vaginal fluid and quantification of the number of
lactobacilli. The score ranges between normal (0–3)
through intermediate (4–6) to BV (7–10) (Nugent et al.,
1991). Common species detected by culture-dependent
techniques from women with BV are anaerobes such as
M. hominis, G. vaginalis, Prevotella spp., and Mobiluncus
spp. as well as a variety of Gram-positive (S. epidermidis,
S. aureus, Streptococcus spp.) and Gram-negative bacteria
FEMS Microbiol Rev 37 (2013) 762–792
769
(Escherichia coli; Table 1). Recent molecular methods
demonstrated that specific microorganisms are detected
in particular stages of BV. Many species present during
BV were prior to the use of molecular-based techniques
not detected. For example, species belonging to the
Clostridiales order, Megasphaera spp., Leptotrichia spp.,
Dialister spp., Chloroflexi spp. Olsenella spp., and Streptobacillus spp. can now also be detected (Wertz et al., 2008;
Table 1). A typical example is A. vaginae, which was isolated for the first time in 1999 based on 16S rRNA gene
sequencing (Rodriguez et al., 1999). Since then, it has
been often isolated and detected in women with BV,
much more than in those with a healthy vaginal microbiota (Lamont et al., 2011). Furthermore, some species
previously designated as Lactobacillus minutus and Lactobacillus rimae within the lactic-acid-producing bacteria
have now been reclassified to the genus Atopobium.
A typical characteristic for the species associated with
BV is the formation of thick adherent biofilms on the
vaginal epithelium, which are resistant to treatment with
a broad range of antibiotics. Some studies suggest a role
for H2O2-producing Lactobacillus in the prevention of
BV, although this is not yet clear. Most studies report
that the number of H2O2-producing Lactobacillus species,
such as L. crispatus and L. jensenii, decrease during BV
(Antonio et al., 1999; Song et al., 1999; Balkus et al.,
2012). On the other hand, the less H2O2-producing
L. iners is often detected during BV. The presence of
L. iners during BV might be explained by better adaptation of this strain to the changes in the environment
during BV, for example, better adaptation to the
increased pH (Wertz et al., 2008). Furthermore, unknown
factors during BV might be toxic for the other lactobacilli
but not for L. iners.
In conclusion, the cause of BV and the associated
reduction of lactobacilli are still unknown. One study
suggests that lysogenic phages might be involved in the
depletion of vaginal Lactobacillus (Kilic et al., 2001). The
authors reported that four morphotypes of phage isolates
from vaginal lactobacilli were able to infect a broad host
range of Lactobacillus species of other women. Most
lactobacilli containing lysogenic phage DNA were able to
release phage particles into the environment, suggesting
that these lactobacilli could be a source of infective
phages and could drastically reduce the Lactobacillus
population and by extension could lead to BV (Kilic
et al., 2001), but the exact trigger is unknown. Martin
et al. (2009) investigated whether chemotherapeutic and
antibiotic treatment inducing SOS responses could be
an important trigger, by the induction of resident prophages from their lysogenic hosts. Their results provide a
complicated picture on the role of lysogenic phages. The
authors found that lysogeny appears to be widespread
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
770
among the tested vaginal Lactobacillus strains, although
half of the strains harbored prophage sequences that were
not responsive to SOS activation. In addition, in some
cases when prophage induction could be achieved by
treatment with mitomycin C, viable phages were not generated. Furthermore, most of the tested lactobacilli were
able to produce H2O2, which is also an inducer of the
SOS response and induction of lytic cycle. Taken
together, their results suggest that H2O2 production
selects for strains that harbor SOS-insensitive, defective
prophages in vaginal lactobacilli, which are unable to promote phage lysis. They suggest that resident phages in
H2O2-producing lactobacilli might have coevolved with
their hosts, resulting in a more stable population (Martin
et al., 2009). Nevertheless, this needs to be further documented. Damelin et al. (2011) showed higher levels of
lysogeny in L. crispatus in comparison with L. jensenii,
the former being also more frequently isolated from
patients with BV. The authors propose that the high levels of lysogeny might be related to the better survival of
L. crispatus compared with L. jensenii under the changing
conditions in the vaginal environment during BV, by the
presence of survival and/or adherence promoting genes
by the lysogens (Damelin et al., 2011), but this remains
to be further documented. On the other hand, in a more
recent study, Macklaim et al. (2013) reported that
CRISPRs genes, responsible for antibacteriophage defense,
are highly expressed in L. iners under BV conditions, suggesting that L. iners is able to response to the changes in
the phage load during BV. In addition, CRISPRs genes
were recently also detected in the genome of L. pentosus
KCA1 together with abortive infection (Abi) systems that
can target different phases of phage development
(Anukam et al., 2013). These mechanisms were also
recently supported by Reyes et al. (2010), who propose
that changes in the phage population in the human fecal
microbiota are related with changes in the bacterial community and therefore can be used as markers for disease
states. The obtained results are also supported by the
metagenomic data from the Human Microbiome Project,
which show that the CRISPRs genes are most abundant
in Lactobacillus-targeting phages sequences in the vagina
(Rho et al., 2012). Clearly, the exact role of bacteriophages in the vaginal environment and BV pathogenesis
is still not well understood, and future studies are needed.
In addition, it is also of interest to mention that the
urogenital tract appears to be the only microbial niche in
the human body that shows clear differences in microbiota between women and men (M€andar, 2013). In male,
the microbiota is present in the lower genital tract, mostly
in urethra and coronal sulcus. Recently, 16S rRNA gene
sequencing was used to characterize the microbiota of the
coronal sulcus and urine collected from 18 adolescent
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
men over three consecutive months. The coronal sulcus
microbiota of most participants was more stable than
their urine microbiota, and the composition was strongly
influenced by circumcision. BV-associated taxa, including
Mycoplasma, Ureaplasma and Sneathia, were detected in
the corona sulcus specimens from sexually experienced
and inexperienced participants (Nelson et al., 2012).
Nevertheless, whether this is related to the pathogenesis
of BV remains to be further investigated.
Key immunological and microbiological
aspects of HIV infection
The process of HIV infection
The female genital tract mucosa is a portal of entry for
several clinically relevant sexually transmitted viruses
including HIV. At present, 34 million people are estimated to be infected with HIV, and c. 2.7 million new
infections occurred worldwide in 2010 (http://www.
unaids.org/globalreport/global_report.htm). Women appear
to be more easily infected with HIV than men. Differences in social rank, behavior, sex hormone regulation,
and especially organization of the mucosal surface appear
to be involved (Iwasaki, 2010). The FRT mucosa – as
described above – has indeed a unique structure and
function, under the control of a variety of sex hormones
(Wira & Rossoll, 2003).
Sexual transmission of HIV is mediated by exposure to
infectious virions and/or infected lymphocytes and monocytes present in the semen. The ratio of transmissibility
of cell-free vs. cell-associated viruses is still uncertain, but
both are sources of infections and should be targeted by
intervention strategies. Under normal circumstances, the
incidence of HIV transmission from males to females is
very low, within the range of one productive infection for
every 200–2000 exposures (Schellenberg & Plummer,
2012). This can probably be explained by the presence of
the protective Type II mucosa of the female vaginal
epithelium cells (Schellenberg & Plummer, 2012). In contrast, the endocervix mucosa, as described above, is a single layer of columnar epithelium, which can easily
support HIV transmission (Lederman et al., 2006). However, the endocervix is protected by a thick mucus layer
that provides a physical barrier that efficiently can trap
HIV virions or infected donor cells (Maher et al., 2005).
Yet, free HIV virions can eventually cause infection in
many different ways. For example, it has been reported
that HIV-1 can bind to and enter epithelial cells from the
lower FRT by transcytosis, or endocytosis and subsequent
exocytosis, thereby causing productive infection (Wu
et al., 2003; Stoddard et al., 2009; Fig. 4). Transcytosis of
HIV virions has been demonstrated in vitro using genital
FEMS Microbiol Rev 37 (2013) 762–792
Human microbiota and HIV infections
771
Fig. 4. Vaginal invasion by HIV virions. The vaginal mucosa belongs to Type II and is therefore covered by a multicellular layer of nonkeratinized
squamous cells. Mucus secreted by cervical glands and local epithelial cells provides a barrier to invading pathogens. In and underneath the
epithelial cell layer, many innate immune cells are located, including LCs, cdT cells, DCs, and macrophages. Free HIV virions can eventually cause
infection in many different ways. (1) Infection by free HIV virions: Free HIV virions trapped by the mucus layer can penetrate the epithelium
through gaps between the epithelial cells and therefore reach the stroma and the submucosa. Furthermore, infected donor cells could also be
trapped in the mucus layer and in this way release new virions. The virions can also be captured by LCs located in the epithelium layer and
subsequently transferred to the submucosa. (2) HIV virions can also infect cd CD4+ T cells on the epithelium. (3) Transcytosis: free virions or those
released from the donor cells can be transferred through the basal epithelium cells by transcytosis, productively infecting these cells or
penetrating between epithelial cells. (4) Migration of HIV virions to the submucosa: free virions or infected donor cells can migrate through a
disrupted vaginal mucosa and reach the vaginal submucosa. (5) Infection of immune cells and local immune response: once in the stroma, free
virions can infect the underlying CD4+ T cells or macrophages. Furthermore, the virions could also make contact with DCs and subsequently get
transported to CD4+ T cells. (6) Spreading the infection: infected DCs, CD4+ T cells, macrophages, and LCs transport the virions subsequently to
the submucosa and to the local lymph nodes. Figure mainly based on (Lederman et al. (2006), Hladik & McElrath (2008) and Iwasaki (2010).
tract–derived cell lines and primary human endocervical
tissue (Stoddard et al., 2009). Once released from the epithelial cells, the virions can infect underlying leukocytes
(Fig. 4). As mentioned above, the squamous epithelial
cells also lack tight junctions, so that particles such as
HIV-1 can be transported through the narrow gaps
between the cells to the draining lymphatics as single particles or by infected donor lymphocytes and macrophages
(Maher et al., 2005; Fig. 4). Moreover, disruption of the
integrity of the vaginal mucosa, which can occur during
sexual intercourse, BV, or other inflammatory conditions
of the vagina, could allow direct contact of the virus
FEMS Microbiol Rev 37 (2013) 762–792
particles with intraepithelial LCs and cd CD4+ T cells, or
might allow HIV-1 to reach suprabasal or basal epithelial
cells that are more susceptible to viral transcytosis.
Furthermore, viral entry could occur close to the transformation zone of the endocervix, which is highly
enriched with CD4+ T cells (Fig. 1), thereby causing productive infection (Pudney et al., 2005).
Another possible way of HIV invasion occurs through
LCs. Vaginal LCs were shown to efficiently internalize
HIV-1 into their cytoplasmic compartment. After the LCs
exit, the epithelium at the basal site, they are able to
transport the HIV virions and spread the infection (Hladik
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
772
et al., 2007). However, it is not well documented whether
LCs can produce and release new HIV-1 virions. LCs
express HIV receptors including CD4, CCR5, and the
C-type lectin receptor langerin, but they do not express
CXCR4 and DC-SIGN. Several studies suggest that HIV
virions can efficiently bind to the LCs in different ways
resulting in endocytosis of the virus and subsequent transport to the lymph nodes (Hussain & Lehner, 1995; Hladik
et al., 2007). However, it has also been shown that LCs
may act as a natural barrier to HIV-1 infection, by internalizing HIV-1 particles through langerin and degrading
them intracellularly (de Witte et al., 2007). Another possible and more likely mechanism of infection with HIV is
through DCs, which express both DC-SIGN and CCR5,
unlike LCs, and therefore can support HIV infection.
However, their exact role in mucosal transmission is not
clear. In situ studies in a human explant model did not
succeed to identify infected DCs in the cervico-vaginal
stroma (Collins et al., 2000; Cummins et al., 2007). On
the other hand, HIV-infected DCs were identified in tissue
biopsies of the vaginal stroma of HIV-1-infected women.
Although it is not clear whether HIV can efficiently infect
DCs, the importance of DCs in capturing (trapping) the
virus and transferring it by an ‘infectious synapse’ to CD4+
T cells and thus transmitting the viral infection is well documented (Cameron et al., 1992; Geijtenbeek et al., 2000).
CD4+ T cells are the main target cells for HIV. They are
present within the vaginal and the endocervical mucosa as
memory T cells expressing high levels of CCR5 coreceptor
(Hladik et al., 2007). In addition, macrophages and/or
NKs cells present in the vaginal mucosa can also be a
target for HIV (Cummins et al., 2007; Harada et al.,
2007).
Although several types of innate immune cells can be
targeted by HIV, the human body and particularly the
innate immune system provide a response to the HIV
infection by induction of several different cytokine and
activation of several chemokine pathways. The innate
immune response toward HIV is a double-edged sword,
of which some responses efficiently restrict the virus,
while other responses actually promote virus replication
and/or transmission to target cells. The main recognition
of HIV nucleic acid is through TLRs. TLR7 and TLR8 are
able to recognize single-stranded viral RNA (ssRNA; Heil
et al., 2004), while TLR3 recognizes double-stranded viral
RNA (dsRNA; Alexopoulou et al., 2001). TLR3, TLR7,
and TLR8 are localized in the endosome of macrophages,
monocytes, and DCs (Heil et al., 2004). Hence, TLR3,
TLR7, and TLR8 play important roles in antiviral innate
immune response such as against HIV. Recognition of
HIV RNA by one of the TLRs activates the NF-jB
pathway and the production of TNF as well as activation
of IFN-inducible genes, followed by production of Type I
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
IFN (IFN-a/b). Increased levels of type I IFN are followed
by a decline of HIV load by induction of a large number
of signaling pathways, some of which can contribute to
HIV-1 restriction (Florey et al., 2011). In addition, the
expression of the viral accessory protein Nef by HIV
stimulates production of the pro-inflammatory cytokines
TNF and IL-6, which could stimulate proliferation of
naive T cells (Swingler et al., 1999; Olivetta et al., 2003).
Furthermore, TLR2 receptors present on the surface of
innate immune cells and epithelial cells are able to specifically recognize gp120 from the viral envelope and subsequently to increase the production of TNF (Olivetta
et al., 2003). Additionally, gp120 binds to the CCR5 coreceptor, which results in the release of chemokines such as
macrophage inflammatory protein 1a/b (MIP-1a/b),
MCP-1, and RANTES from macrophages. These chemokines recruit T cells and monocytes to the site of virus
infection (Fantuzzi et al., 2001). Some of the cytokines
produced by innate immune cells, CD4+ T and CD8+ T
cells, can also have a significant impact on HIV replication and progression of the disease. For example, TNF
can – depending on the receptor used – increase apoptosis of HIV-infected cells or initiate NF-jB signaling,
resulting in increased production of virus (Herbein &
Khan, 2008). IL-2 also plays a crucial role in HIV
infection by initiating a Th1 CD4+ T-cell response and
activating expression of IFN-c and TNF (Duh et al.,
1989; Reuter et al., 2012). Yet, Akinsiku et al. (2011)
demonstrated that IL-2-expressing CD8+ T cells are
related to high levels of protection during HIV infection
(Akinsiku et al., 2011). Furthermore, IL-7 and IL-15, similarly to IL-2, can drive a CD8+ T-cell response, which
might benefit the host during an HIV infection. Nevertheless, IL-2 as well as IL-7 and IL-15 can also induce
HIV replication in T cells (Moran et al., 1993; Ferrari
et al., 1995; Mueller et al., 2008). One of the important
cytokines with well-known antiviral activity is IFN-c.
However, during HIV infections, IFN-c has a dual role
similar to the other cytokines described above and can
both enhance HIV infection and inhibit viral replication
(Reuter et al., 2012). In addition, some chemokines such
as RANTES and MIP-1b can be considered as a potential
inhibitors of HIV by recognizing CCR5, a major coreceptor used by HIV and predominantly responsible for viral
transmission (Handen & Rosenberg, 1997).
BV associated with increased susceptibility to
HIV
BV is associated with increased cases of spontaneous
abortion, premature birth, and endometritis. Furthermore,
BV is associated with increased susceptibility to sexually
transmitted infections (STIs) such as HSV-2, gonorrhea,
FEMS Microbiol Rev 37 (2013) 762–792
773
Human microbiota and HIV infections
Trichomonas vaginalis, and Chlamydia trachomatis as well
as HIV. For example, a study in Kenya showed that the
presence of BV and absence of lactobacilli are significantly
associated with acquisition of HIV (Martin et al., 1999).
Furthermore, the presence of H2O2-producing lactobacilli
showed to be protective, not only against HIV, but also
against Neisseria gonorrhoeae, C. trachomatis, and T. vaginalis (Martin et al., 1999). However, three studies
performed respectively in Thailand (Cohen et al., 1995),
Uganda (Sewankambo et al., 1997), and Malawi (Taha
et al., 1998, 1999) could not provide a clear relationship
between BV and HIV infection. Different mechanisms are
proposed for the increased susceptibility to HIV in the
case of BV, including: (1) activation of the immune
response and subsequent inflammation during BV; (2)
disruption of the vaginal epithelium and subsequent transmission of HIV to the subepithelium where immune cells
are present; and (3) reduced number of Lactobacillus
species resulting in an increased pH and reduced H2O2
concentration compromising the protection of the vaginal
epithelium. Indeed, an activated immune response appears
to occur during yeast vaginitis and BV (Witkin et al.,
2007). For example, levels of pro-inflammatory cytokines
such as TNF, IL-1, IL-6, and IL-8 were shown to be significantly increased in BV (Spear et al., 2007). Furthermore,
higher levels of IL-8 recruit immune cells and therefore
may increase the risk of HIV infection (Narimatsu et al.,
2005). Some in vitro studies using vaginal fluids from
women with a normal vaginal microbiota and women
with BV also highlight the potential role of BV in HIV
infectivity. For example, the vaginal fluid from women
with BV was shown to induce HIV expression and virus
production in latently HIV-1-infected monocyte U1 cells,
as compared with the vaginal fluid from women with a
normal vaginal microbiota. In addition, it was shown that
the levels of HIV-1 RNA in vaginal fluid of HIV-positive
women were significantly increased in the presence of BV
and Candida vaginitis, as compared with the levels in
women with a normal vaginal microbiota (Cu-Uvin et al.,
2001; Sha et al., 2005). Specific studies have focussed on
the exact role of vaginal pathogens on their ability to
stimulate HIV expression. For example, it was shown that
G. vaginalis and M. hominis can significantly induce HIV
expression in a monocyte cell lines. Other pathogens such
as Peptostreptococcus asaccharolyticus, P. bivia, Streptococcus
agalactie, and Streptococcus constellatus also have the ability
to induce HIV expression in vitro (Al-Harthi et al., 1999;
Hashemi et al., 1999, 2000; Simoes et al., 2001). In contrast, L. acidophilus appears not to stimulate HIV expression (Hashemi et al., 2000). Furthermore, it was shown
that vaginal fluids from women with BV, but not from
healthy women, induced IL-12 and IL-23 production in
monocyte-derived DCs as well as CD40 and CD83 denFEMS Microbiol Rev 37 (2013) 762–792
dritic maturation markers (St. John et al., 2007). BV fluids
also caused a decrease in the endocytotic ability of monocyte-derived DCs and an increased proliferation of T cells
as compared with fluids from women with a normal vaginal microbiota (St. John et al., 2007). In agreement with
St. John, Rebbapragada et al. (2008) also reported
increased levels of pro-inflammatory cytokines and CD4+
T cells in HIV-infected women with BV, which was related
with increased levels of HIV-1 RNA. Taken together, these
results might be important for understanding the increased
susceptibility of HIV infections during BV, because DCs
are important cells in the recognition of the virus and subsequent transmission to the CD4+ T cells. Although St.
John et al. (2009) found that BV fluids do not appear to
increase transinfection from DCs to T cells, indirect effects
of DC maturation on HIV transmission during BV cannot
be ruled out.
Vaginal microbiota in HIV-infected women
In a first detailed molecular study performed in the USA,
the diversity of the vaginal microbiota in HIV-infected
women was reported (Spear et al., 2008). The study compared the diversity of the vaginal microbiota in HIVinfected women with BV or without BV, as well as in
HIV-negative women with and without BV. Higher
microbial diversity was detected in HIV+BV+ women in
comparison with the HIV BV+ women. Furthermore, in
HIV+BV+ women, three additional taxa were detected
belonging to Propionibacteriaceae, Anaerococcus, and
Citrobacter. The higher diversity of vaginal microbiota in
HIV+ women might be related to suppressed immunity
and promoted growth of vaginal pathogens. In addition,
the authors report no significant differences between the
HIV+ BV and HIV BV women, where the microbiota
is dominated by Lactobacillus species. However, the
microbiota in HIV+BV showed also the presence of
Bifidobacteriaceae, Catonella, Coriobacterineae, and Prevotella, although in low concentrations (Spear et al., 2008).
Some reports have shown that Candida spp. vaginitis is
also frequently found in HIV-infected women (Minkoff
et al., 1999; Ohmit et al., 2003), suggesting indeed that
immunity in the lower genital tract is severely compromised during HIV infections. A study of the vaginal microbiota of HIV+ Tanzanian women confirmed the results
reported above (Hummelen et al., 2010a). Indeed, a BV
microbiota was detected in several microbial profiles of
HIV-infected women. The most prevalent isolated species
belong to P. bivia or members of the order Clostridiales
(probably originating from the gut) and the family Lachospiraceae. BV appears to be more prevalent in HIV+
women with CD4+ counts of ≤ 200 cells mm 3. The
percentage of L. crispatus in women with CD4+ cell
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
774
counts of ≤ 200 cells mm 3 is also significantly lower
than in women with high CD4+ cell counts (Spear et al.,
2011). Nevertheless, in some HIV+ women, a normal vaginal microbiota represented by H2O2-producing L. crispatus or L. jensenii, but also L. iners and L. gasseri was also
shown (Hummelen et al., 2010a; Spear et al., 2011; Balkus et al., 2012). Of particular interest, the presence of
normal vaginal microbiota dominated by Lactobacillus in
HIV-positive women was not associated with increased
levels of HIV RNA, suggesting that Lactobacillus could be
involved in reducing HIV shedding and subsequent transmission of the virus. In addition, detection of L. crispatus
was reported to be associated with a 35% lower risk of
HIV-1 RNA shedding (Mitchell et al., 2012). In case of
women using highly active antiviral therapy (HAART),
L. jensenii was associated with decreased levels of HIV-1
RNA (Mitchell et al., 2012). These results form an important incentive to study the potential of exogenously
applied Lactobacillus species as probiotics for the treatment of BV and prevention of HIV transmission.
Potential role of endogenous vaginal
microbiota for the prevention of HIV
infection
As yet indicated, the vaginal microbiota dominated by
lactobacilli seems to play a key role in the prevention of a
number of urogenital diseases such as BV, yeast infections, and STIs such as HSV-2 and HIV. Postulated
mechanisms against HIV include a direct inhibitory effect
of the vaginal microbiota by production of lactic acid,
H2O2, bacteriocins, and lectin molecules. In addition,
indirect mechanisms such as prevention of the growth of
microorganisms associated with BV, stimulation of the
immune system and/or by the epithelial barrier function
can also be envisaged (Fig. 5). However, many details still
need to be unraveled.
Production of antiviral components by the
vaginal microbiota
As mentioned before, the presence of lactic-acid–producing
bacteria is a hallmark of a healthy vaginal ecosystem.
The vaginal mucosa is characterized by a pH of 4–5
depending on the Lactobacillus strains present. For example, when the microbiota is dominated by L. crispatus,
the vaginal mucosa reaches a pH of 4.0 0.3, while the
presence of L. gasseri, L. iners, and L. jensenii results,
respectively, in pH values of 5.0, 4.4, and 4.7 of the
mucosal vagina (Ravel et al., 2011). Generally, the low
pH of the vaginal mucosa is believed to be the main
strategy to prevent bacterial and viral infections in the
vaginal niche. For example, cell-free HIV-1 is inactivated
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
at an acid pH (Martin et al., 1985). The same results were
also reported by Ongradi et al. (1990), showing that the
infectivity of cell-free HIV particles depends of the pH
value and the time of incubation. The authors observed
that incubation at pH 5.7 for 2 h is enough to inhibit the
infectivity of HIV, whereas at lower pH in the range of
5.4, only 20 min are sufficient to completely inactivate
the virus. However, the cell-associated viral infectivity was
not inhibited by low pH values (Ongradi et al., 1990).
On the other hand, O’Connor et al. (1995) observed that
HIV is more acid stabile with no substantial reduction in
infectivity occurring at pH levels as low as 4.5. On the
other hand, an acidic environment appears to result in a
decreased activation of T lymphocytes, which may result
in decreased lymphocyte susceptibility to HIV-1 infection
(Fig. 5; Hill & Anderson, 1992; Olmsted et al., 2005).
Monocytes, macrophages, and lymphocytes, which might
act as vectors for sexual transmission of HIV, were found
to completely lose motility at a pH slightly below 6.0
(Olmsted et al., 2005). Lai et al. (2009) also reported that
acid human cervico-vaginal mucus, obtained from donors
with normal lactobacilli-dominated vaginal microbiota,
efficiently traps HIV, causing it to diffuse > 1000-fold
more slowly than it does in water. At an acidic pH 4, lactic acid, but not HCl, could abolish the negative surface
charge on HIV without lysing the viral envelope, which
may alter HIV surface protein structures and/or possibly
inactivate the virus by disrupting the envelope membrane
and exposing the capsid (Lai et al., 2009). Taken together,
these results support the idea that maintaining a low pH
in the vaginal lumen by production of lactic acid is
important to reduce HIV transmission. This is also relevant for other sexually transmitted viruses such as HSV2. For example, a significant inhibition of the replication
of HSV-2 by acidic (pH 4.5) supernatant of L. fermentum
301 isolated from healthy Bulgarian women was reported
(Dimitonova et al., 2007).
Apart from the maintenance of a low vaginal pH by the
production of lactic acid, H2O2 has been suggested as an
important antipathogenic strain-specific characteristic of
vaginal lactobacilli. Various strains of L. crispatus, L. jensenii, and L. gasseri have been shown to produce H2O2
(Antonio et al., 1999; Song et al., 1999; Balkus et al.,
2012). The production of H2O2 by Lactobacillus species
seems to be a nonspecific host defense mechanism against
different pathogens. The effect of H2O2 on the survival of
different sexually transmitted viruses including HIV is not
well studied. Klebanoff & Coombs (1991) could demonstrate a virucidal effect of a natural L. acidophilus isolate
on HIV, based on its ability to produce and release H2O2.
The authors were able to show that their L. acidophilus
isolate, producing H2O2, at a density of 107 CFU mL 1
was virucidal to HIV by measuring the decrease of
FEMS Microbiol Rev 37 (2013) 762–792
Human microbiota and HIV infections
775
Fig. 5. Postulated strategies of vaginal probiotic Lactobacillus strains to prevent HIV infections in humans. (1) In the vaginal lumen, Lactobacillus
strains can inhibit HIV directly by producing lactic acid, H2O2, bacteriocins, and other inhibitory agents; (2) Lactobacilli can also preserve the
integrity of the vaginal epithelium and compete with BV pathogens for receptors on the vaginal epithelium; (3) By producing different inhibitory
agents, lactobacilli can directly kill bacterial and other viral pathogens; (4) The vaginal lactobacilli could also capture HIV by lectin-mediated
binding to the HIV glycoproteins and in this way prevent infection; (5) The vaginal lactobacilli might enhance the local immune system during
health and disease and thereby inhibit HIV infection. Nevertheless, all these postulated mechanisms remain to be substantiated, especially in vivo.
Figure based on Klebanoff & Coombs (1991), Olmsted et al. (2005), Pretzer et al. (2005), Corey (2007b) and Hummelen et al. (2010b).
the viral replication in T lymphoblast CEM cells. The
anti-HIV activity was not observed when this L. acidophilus
strain was treated for 15 min at 100 °C or when it was
replaced by a strain unable to produce H2O2, suggesting
the important role of H2O2 in eventual inhibition of the
HIV infections. Furthermore, the virucidal effect was
inhibited by catalase, but not by heat-inactivated catalase
(Klebanoff & Coombs, 1991). Besides these results, no
other reports on the effect of H2O2 against HIV have been
published so far, to the best of our knowledge.
A third and also strain-specific characteristic of lactobacilli is the production of bacteriocins. Bacteriocins are
defined as microbial small peptide molecules with activity
against closely related microorganisms (Cotter et al.,
2013). However, recently, a broader activity spectrum
against a wide variety of microorganisms and viruses was
documented for several bacteriocins. For example, vagiFEMS Microbiol Rev 37 (2013) 762–792
nally isolated L. fermentum and Lactobacillus brevis strains
were shown to produce bacteriocin-like molecules against
HSV-2 (Dimitonova et al., 2007). Although the authors
were not able to completely characterize or purify the
bacteriocin-like molecules, they were able to show that
supernatant isolated from L. fermentum and L. brevis at
neutral pH and treated with catalase showed activity
against HSV-2, thereby postulating that bacteriocin molecules could be responsible for this activity (Dimitonova
et al., 2007). It has been shown that genital lesions caused
by HSV-2 are an important cofactor to increase the rate
of HIV transmission and infection (Corey, 2007a).
Recently, HSV-2 infection of keratinocytes was even
shown to enhance the susceptibility of LCs to R5-tropic
virus (which require CCR5, but not X4 for cell entry) by
an indirect mechanism that involves the antimicrobial
peptide LL-37 (Ogawa et al., 2013). Therefore, products
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
776
from vaginal Lactobacillus strains that inhibit HSV-2
would potentially have benefits in indirectly preventing
HIV infection.
An interesting specific class of bacteriocins includes
lantibiotics, ribosomally synthesized peptides, produced by
Staphylococcus, Lactobacillus, and Actinomycetes. A typical
characteristic of lantibiotics is the presence of the amino
acid residues lanthionine or methyllanthionine (Willey &
van der Donk, 2007). The best studied lantibiotic, nisin
(belonging to the type I lantibiotics), is widely used as a
food preservative (Cotter et al., 2005), but we recently
showed that it has no activity against HIV (Ferir et al.,
2013). Another interesting bacteriocin is LabyA1, which
belongs to a novel class of type III lantibiotics containing
labionin, known as labyrinthopeptins (Meindl et al.,
2010). Although LabyA1 was isolated from the actinomycete Actinomadura namibiensis DSM 6313 (Wink et al.,
2003), we could show that it exhibits a broad anti-HIV
activity in different T-lymphocytic cell cultures as well as
in peripheral blood mononuclear cells (PBMCs). Furthermore, it was also shown to inhibit viral cell–cell transmission between persistently HIV-infected T cells and
uninfected CD4+ T cells. LabyA1 did not inhibit HIV
binding to DC-SIGN; nevertheless, it subsequently inhibited the transmission of HIV captured by DC-SIGN+-cells
to uninfected CD4+ T cells. In addition, the safety profile
of LabyA1 revealed no effect on the growth of vaginal
lactobacilli populations at concentrations up to 120 lM
(Ferir et al., 2013).
The genome sequences of various vaginal lactobacilli
show the presence of bacteriocin-related genes. For example, in the genome of L. iners, three genes were found to
encode putative bacteriocin immunity proteins, together
with bacitracin resistance protein and a putative enterocin
A immunity protein (Macklaim et al., 2011). The fact that
L. iners has various defense systems against other bacteriocinproducers suggest they are commonly produced in this
vaginal ecosystem, but this remains to be further substantiated. Furthermore, in the genome of the vaginal isolate
L. pentosus KCA1, a cluster responsible for the biosynthesis
of a novel antibacterial bacteriocin designated pentocin
KCA1 was detected (Anukam et al., 2013). In addition, the
draft genome sequence of the vaginal strain L. rhamnosus
GR-1 suggest the presence of a bacteriophage peptidoglycan hydrolase related to lysostaphin (J. Macklaim, M.I.
Petrova, A.S. Rodriguez, J. Vanderleyden, K. Marchal, G.
Gloor, S. Lebeer and G. Reid, unpublished data), a special
class of bacteriocins first identified in Staphylococcus strains
(Donovan, 2007). Interestingly, Liu et al. (2011) showed
that lysostaphin-expressing Lactobacillus plantarum
WCFS1 could inhibit S. aureus in a modified genital tract
secretion medium (Liu et al., 2011). However, similar bacteriocin activity against HIV remains to be documented.
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
Blocking HIV by binding to lectins of the
vaginal microbiota
Molecules on the cell surface of the vaginal microbiota
that directly interact with pathogens or host cells are postulated to play a role in the exclusion of bacterial and/or
viral pathogens. Such interactions could be established
via carbohydrate-binding proteins known as lectins,
which interact specifically with carbohydrates on surface
of pathogens and are highly specific for the ligand of
interaction. Therefore, lectins on the cell surface of vaginal microorganisms could play a role in pathogen exclusion by (1) competitively binding to the same glycans on
the host surface, thereby blocking adhesion or (2) by
binding glycans on the pathogenic surfaces, thereby
blocking virulence mechanisms such as adhesion and
invasion (Fig. 5). Recently, some lectins, especially the
ones highly specific for recognition of mannose (e.g.
actinohivin and griffithsin) and N-acetylglucosamine
(GlcNAc) residues (e.g. Urtica dioica agglutinin, UDA),
have been shown to possess activity against HIV by binding of the glycans on the viral envelope and thereby
blocking the virus entry process (Balzarini, 2007). Some
of these lectins can inhibit the infection of T cells by cellfree virions through binding to the HIV gp120 glycoprotein. They can also block the interaction between HIV
and the macrophage mannose receptor, thereby preventing the infection of macrophages. Furthermore, some lectins inhibit syncytia formation between virus-infected
T lymphocytes and uninfected T cells. Lectins can also
prevent the capture of HIV-1 particles to DC-SIGNexpressing cells. Additionally, lectins can block the
DC-directed transmission of the virus to uninfected T
cells (Balzarini, 2007).
Nevertheless, the information on lectins encoded by
Lactobacillus species and especially vaginal isolates is still
limited. Only a few studies reported on the presence of
lectin-like proteins on the cell surface of probiotics that
are involved in their adhesion capacity. The best documented lectin from a Lactobacillus strain is the mannosespecific adhesin (Msa) from L. plantarum WCFS1 (Pretzer et al., 2005). In silico analyses of the Msa protein
revealed that this protein shows similarity with a mucusbinding protein (Mub) from L. reuteri and with SasA, an
LPxTG-containing cell surface protein from S. aureus,
referred to as a Concanavalin A-like lectin (Pretzer et al.,
2005). The mannose-specific recognition was determined
by pronounced agglutination of Saccharomyces cerevisiae
cells (having mannans on their surface) by L. plantarum
WCFS1 (Pretzer et al., 2005). The fact that Msa is highly
mannose specific highlights the potential of using this
strain or the protein for prevention and/or treatment of
infections caused by pathogens that contain mannose
FEMS Microbiol Rev 37 (2013) 762–792
777
Human microbiota and HIV infections
residues on their surface, such as HIV and C. albicans.
Some other studies suggest the presence of lectin-like
molecules on the surface of lactobacilli. For example, Sun
et al. (2007) demonstrated that L. plantarum Lp6 adheres
to mucus in a lectin-like manner and significantly agglutinates S. cerevisiae as reported for L. plantarum WCFS1. A
more recent study suggests that L. acidophilus FN001 also
adheres in a lectin-like manner by recognition of
carbohydrate moieties (Sun et al., 2010). The adhesion
capacity of L. acidophilus FN001 was shown to be
strongly inhibited in the presence of D-mannose and
methyl-a-D-mannoside, suggesting that L. acidophilus
FN001 contains mannose-specific protein(s) on its surface
that mediate its adhesion to the Peyer’s patches. Furthermore, L. acidophilus FN001 showed agglutination activity
toward rabbit red blood cells in a mannose-specific
manner, which decreased after protease pretreatment,
and was able to strongly inhibit the adhesion of E. coli
ATCC25922 to Peyer’s patches in vitro (Sun et al., 2010).
However, the lectin-like protein of L. acidophilus FN001
remains to be identified.
These few examples of lectins from Lactobacillus species
were only reported for GIT isolates. Recently, we were
able to detect three putative lectin-like proteins in the
draft genome of L. rhamnosus GR-1 (J. Macklaim, M.I.
Petrova, A.S. Rodriguez, J. Vanderleyden, K. Marchal,
G. Gloor, S. Lebeer and G. Reid, unpublished data).
Functional characterization of one of these lectin-like
proteins by mutant analysis showed that such proteins
are involved in tissue-specific adhesion of L. rhamnosus
GR-1 to vaginal epithelial cells (M.I. Petrova, S. Malik,
T.L.A. Verhoeven, M. van den Broek, J. Macklaim, G.
Gloor, G. Reid, J. Balzarini, J. Vanderleyden and S. Lebeer, unpublished data). Other molecules on the surface of
vaginal lactobacilli might also show activity against HIV.
For example, Su et al. (2013) recently reported a ‘CD4like receptor’ localized on the cell surface of Lactobacillus
casei ATCC393 that can bind HIV and described its
potential role in the inhibition of HIV infection in vitro.
In addition, the ability of some vaginal lactobacilli to autoaggregate through interaction of cell wall proteins or
lectins might be important factor in inhibition of HIV
infections. The autoaggregating strains could inhibit HIV
by direct capture of the virus or by strong adhesion to
the epithelial cells, thereby competiting for epithelial cell
receptors. Recently, we were able to show that sortasedependent proteins are involved in the high autoaggregation and adhesion capacity of the vaginal isolate
L. plantarum CMPG5300 (Malik et al., 2013). However,
future studies are required to investigate the potential of
L. plantarum CMPG5300 and other vaginal lactobacilli
and their surface proteins for the prevention of HIV and
related infections.
FEMS Microbiol Rev 37 (2013) 762–792
Stimulation of the immune system by the
vaginal microbiota
As described above, the human vaginal epithelium is less
densely populated by immune cells as compared with the
GIT. Based on comparison with the GIT (Lebeer et al.,
2010) and skin (Naik et al., 2012), it is tempting to
speculate that the vaginal microbiota could regulate and
stimulate the immune system to efficiently prevent bacterial and fungal pathogens as well as viral infections such
as HIV. However, little is known about the relationship
between the vaginal microbiota and the immune system.
As described above, HIV infections are characterized by
an increase of pro-inflammatory cytokines and proinflammatory responses. This has been linked with a
disruption of the integrity of the vaginal mucosa and
consequently further activation of HIV in infected people.
Therefore, vaginal microbiota that can reduce a proinflammatory response could contribute to a decreased
activation of HIV. This postulated mechanism has only
been fragmentarily documented. For example, in vaginal
epithelial multilayers treated with TLR agonists, significant reduction of IL-6 and IL-8 expression after treatment
with L. crispatus ATCC 33820 was observed (Rose et al.,
2012). Also, L. crispatus ATCC 33820 and to lesser extend
L. jensenii ATCC25258 could induce a significant reduction of TNF secretion as well as some pro-inflammatory
chemokines (MIP-1b and RANTES; Rose et al., 2012).
In another recent study, the role of the vaginal isolates
L. rhamnosus GR-1 and L. reuteri RC-14, in the prevention of C. albicans vulvaginitis by stimulation and modulation of the vaginal immune responses was reported
(Wagner & Johnson, 2012). These lactobacilli were shown
to suppress C. albicans-induced NF-jB inhibitor kinase
alpha (Ijja), TLR2, TLR6, IL-8, and TNF expression,
suggesting that they inhibit NF-jB signaling. In addition,
C17b-estradiol was also shown to suppress expression of
IL-1a, IL-6, IL-8, and TNFa mRNA, which is of high
interest given the crucial role of estrogen hormones in
the regulation of the vaginal ecosystem. As mentioned
before, it has been shown that initiation of NF-jB signaling results in increased production of HIV, which
enhances progression of the virus. Therefore, vaginal
lactobacilli might be involved in controlling HIV infections by suppressing NF-jB effects (Wagner & Johnson,
2012). On the other hand, the vaginal strain L. rhamnosus
GR-1 was also shown to stimulate TLR4 at both mRNA
and protein level in cells challenged with E. coli, with
concomitant increased NF-jB activation and TNF release
(Karlsson et al., 2012). The role of these findings in
relation to HIV expression remains to be studied.
Of interest, a recent study showed an important role for
a new type of cytokine, designated IFN-ɛ, with potential
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
778
antipathogenic activity against HSV-2 and Chlamydia muridarum. INF-ɛ was reported to be exclusively expressed
by epithelial cells in the FRT (uterus, cervix, vagina, and
ovary). Interestingly, IFN-ɛ expression was not induced by
typical PRR signaling such as stimulation with synthetic
TLR ligands or in vivo infection with pathogens, but
showed to be clearly under hormonal regulation (Fung
et al., 2013). However, the interplay between vaginal microbiota and IFN-ɛ production remains to be studied.
Inhibition of BV pathogens by the vaginal
microbiota
As outlined above, the presence of vaginal pathogens and
progression to BV or yeast vaginitis is significantly associated with a higher risk of a subsequent HIV infection,
progression of disease and increased transmission of the
virus to noninfected individuals. Therefore, the role of a
healthy vaginal microbiota in the prevention of HIV
could also be indirect by inhibiting urogenital infections
(Fig. 5). Inhibition of bacterial or yeast pathogens by
vaginal microbiota can be due to production of lactic
acid, H2O2, and bacteriocins, as described to be also
important for protection against HIV, as well as competition for receptor sites on the vaginal epithelium or by
modulation of the vaginal immune system. Indeed,
several studies have shown the importance of vaginal
lactobacilli in the prevention of BV. For example, it was
shown that four vaginal isolates – L. acidophilus CRL
1259, L. crispatus CRL 1266, Lactobacillus paracasei ssp.
paracasei CRL 1289, and Lactobacillus salivarius CRL
1328 – were able to inhibit the adhesion capacity of
S. aureus to vaginal epithelial cells by exclusion and
competition (Zarate & Nader-Macias, 2006). Lactobacillus
acidophilus CRL 1259 and L. paracasei ssp. paracasei CRL
1289 were also able to inhibit the adhesion of Group B
streptococci. In a more recent study, the potential role of
vaginal lactobacilli against G. vaginalis, P. bivia, Mobiluncus spp., and Bacteroides fragillis was reported (Matu
et al., 2010). The vaginal lactobacilli were isolated from
107 Caucasian women, with L. jensenii as the dominant
species. None of the strains was able to inhibit the
growth of B. fragillis, but several strains were able to
inhibit the growth of P. bivia, G. vaginalis, and Mobiluncus
spp. based mainly on the production of lactic acid and
possibly bacteriocins (Matu et al., 2010). In another
study, the effect of cervico-vaginal lavage (CVL) from
healthy women in the prevention of E. coli infection was
recently reported (Kalyoussef et al., 2012). The CVL
inhibited clinically isolated E. coli strains, but showed no
activity against Lactobacillus. The inhibition of E. coli was
related to the concentration of two human and four
lactobacilli proteins present in the CVL. The bacterial
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
proteins corresponded to L. jensenii and L. crispatus
proteins and showed similarity to Lactobacillus cripatus
S-layer proteins (Kalyoussef et al., 2012). S-layers proteins of lactobacilli have been previously shown to be
involved in pathogen exclusion such as of enterohemorrhagic E. coli O157:H7 (Johnson-Henry et al., 2008) and
Junin virus (JUNV; Martinez et al., 2012), as well as
immune stimulation via DC–SIGN interaction (Konstantinov et al., 2008).
Finally, lactobacilli could also inhibit other STIs such
as HSV-2 and in this way may prevent infections of HIV.
For instance, Conti et al. (2009) have reported that the
capacity of lactobacilli to adhere to vaginal epithelial cells
is related to the degree of inhibition of HSV-2 infection.
Lactobacillus brevis CD2 was reported to have a higher
inhibition capacity related to a high adhesion to epithelial
cells, whereas L. plantarum FV9 and L. salivarius FV2
showed intermediate and low adhesion and inhibition of
HSV-2, respectively. Recently, the antimicrobial peptide
LL-37 produced by HSV-2-infected keratinocytes was
shown to be involved in the enhancement of HIV infection of LCs by strongly upregulating the expression of
HIV receptors in LCs (Ogawa et al., 2013). Whether
vaginal lactobacilli have an inhibitory effect on this LL-37
induction remains to be studied.
Importance of the GIT for HIV
replication and progression of disease
HIV infections have also a profound impact on the GIT.
They are characterized by increased GIT inflammation,
increased permeability and malabsorption, inflammatory
infiltrates of lymphocytes and damage to the GIT epithelial layer, including villous atrophy, crypt hyperplasia, loss
of tight junctions, and villous blunting (Brenchley &
Douek, 2008). These events have a detrimental effect on
the function of the intestine and increase the risk of GIT
infections and disorders (Kelly et al., 2009). Furthermore,
the hallmarks of HIV infection include chronic activation
of the immune system and a depletion of CD4+ T cells,
which is more prominent in the GIT than in peripheral
blood and lymph nodes (Mehandru et al., 2004). The
GIT is thus considered as a preferable site for progression
of HIV infection. Furthermore, other leukocyte subsets in
the GIT are altered because the majority of the body’s
lymphocytes are localized in the GIT (MacDonald, 2008).
Indeed, increased turnover, cell cycle perturbations,
apoptosis, and altered functionality among CD8+ T cells,
B cells, and innate immune cells are observed (Fig. 6). Of
note, DCs are significantly decreased, including abnormal levels of plasmacytoid and myeloid DCs, and loss
of mucosal CD103+ DCs (Klatt et al., 2012; Fig. 6).
Also, macrophages, which are potential targets for HIV
FEMS Microbiol Rev 37 (2013) 762–792
Human microbiota and HIV infections
infection, have been shown to have a reduced capacity to
phagocyte bacterial products in mucosal tissues of HIV
patients (Pugliese et al., 2005).
During HIV infection, the virus appears also to switch
the immune system by activation of Th2 responses over
Th1 (Clerici & Shearer, 1993). Indeed, HIV patients with
progressive disease have symptoms that closely resemble
allergies (Rancinan et al., 1997). Th2 skewing induces an
increase of the production of IL-4, IL-5, and IL-13 with
779
deleterious effects on the humoral and cellular immunity,
similar to the immune deficiency of allergic patients
(Clerici & Shearer, 1993). The increased levels of IL-4
subsequently hyperactivate B cells and increase the production of IgE (Fig. 6). Furthermore, it has been
suggested that CD4+ Th2 cells efficiently support HIV
replication, while Th1 dominant do not (Maggi et al.,
1994). As expected, Th1 cytokines are drastically suppressed in HIV patients. It seems that the early antiviral
Fig. 6. GIT mucosa during chronic infection with HIV. Typical characteristics of HIV infections are the morphological changes in the GIT mucosa,
such as blended villi and crypt hyperplasia, as well as a compromised barrier function due to damaged tight junctions between epithelial cells.
Apoptosis of epithelial cells induces an increased microbial translocation and permeability and causes chronic inflammation. Furthermore,
decreased numbers of immune cells, especially CD4+ T cells, are observed. Th17 cells playing an important role in maintaining the integrity of the
mucosa and defense against pathogens are easy targets for the HIV virions and are especially depleted. In addition, skewing of the dominant
Th2/Th1 in favor of Th2 T cells is also observed with subsequent increased levels of IgE antibodies. Increased numbers of Th2 T cells activate
further HIV replication and cause bacterial translocation. Figure based on Brenchley et al. (2006), Brenchley & Douek (2008), Hummelen et al.
(2010b), and Lackner et al. (2012).
FEMS Microbiol Rev 37 (2013) 762–792
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
780
cytotoxic T-lymphocyte response against HIV fails, while
IgE synthesis prevents the production of effective antiviral
Ig. This immune imbalance may induce an increased
inflammation and barrier dysfunction in the GIT, as the
increased IL-4 levels can compromise the antimicrobial
function of Th17 (Harrington et al., 2005). Although the
Th17 response could have a protective role against HIV
infection, Th17 cells appear to be an easy target for
HIV replication, which results in a depletion of CD4+
IL-17-producing cells in humans in vivo (Brenchley et al.,
2008). Furthermore, depletion of Th17 cells from the gut
in HIV-1 infection is associated with microbial translocation, chronic immune activation, and disease progression
(Chege et al., 2011). Taken together, HIV infection and
progression could be considered as a disease of the GIT
tract.
The source of systemic inflammation during HIV infection remained unidentified until 2006 when it was demonstrated for the first time that depletion of intestinal
mucosal immune cells in the GIT results in systemic
immune activation through the increased translocation of
microorganisms and bacterial products from the intestinal
tract (Brenchley et al., 2006). Indeed, Brenchley et al.
reported that HIV-infected humans with progressive disease show increased levels of plasma lipopolysaccharide
(LPS) in the bloodstreams, as an indicator of increased
microbial translocation. Furthermore, chronic in vivo
stimulation of monocytes by the increased levels of LPS
associated with activation of innate and adaptive immune
was reported. The pro-inflammatory environment may
then cause further damage to the gut barrier function,
increasing bacterial translocation and subsequently systemic inflammation (Fig. 6), although this remains to be
further documented. Interestingly, a decrease in plasma
levels of LPS and reconstruction of CD4+ T cells was
observed after HAART (Brenchley et al., 2006). The
authors also reported that in nonprogression patients,
plasma LPS was shown to be lower than in those patients
with progressive HIV infection (Brenchley et al., 2006).
The intestinal microbiota of HIV patients is also significantly altered and appears to contain higher numbers of
pathogens and lower numbers of beneficial microorganisms. For example, Gori et al. (2008) reported that the
relative amount of bifidobacteria and especially lactobacilli
in the HIV-positive population were significantly lower
in comparison with healthy people. In addition, higher
levels of Pseudomonas aeruginosa in HIV-positive individuals were reported compared with the levels of healthy
individuals. Similarly, C. albicans was detected in 100%
of the feces samples of HIV-positive individuals (Gori
et al., 2008). The observation that HIV patients are especially susceptible to C. albicans infection could be
explained by the diminished amount of Th17 cells, which
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
are easy targets for HIV and of crucial importance for
anti-Candida host defenses. An abnormal GIT microbiota
during HIV infections was also reported by Merlini et al.
(2011). More than 90% of HIV-infected patients harbored a bacterial population enriched with Enterobacteriales, while < 60% harbored Lactobacilllales (Merlini et al.,
2011). In a more recent study, higher levels of Enterobacteriales were also reported in HIV-positive subjects compared with controls. Furthermore, the proportions of
Enterobacteriales and Bacteroidales were significantly correlated with duodenal CD4+ T-cell depletion and peripheral CD8+ T-cell activation, respectively (Ellis et al.,
2011).
Future studies need to focus on the role of GIT microbiota in the possible prevention of HIV infections similar
to the vaginal microbiota. It was reported that transmission of HIV through GIT varied within the range of one
productive infection for every 20–200 exposures for rectal
transmission, one over 2500 for the upper GIT transmission, and one over 5–10 for upper GIT transmission with
breastmilk (Hladik & McElrath, 2008). However, recent
studies show that mouse mammary tumor virus, also a
retrovirus, interacts with the GIT microbiota, which
induces immune evasion pathways (Kane et al., 2011).
Therefore, the successful transmission of the virus probably depends on the commensal microbiota. Furthermore,
the GIT microbiota can have a large impact on viral
infections at other sites in the human body. Nevertheless,
this requires further study.
Probiotics and their potential role in HIV
infection
During the last decades, an increased number of scientific
studies highlight the potential of exogenously applied
probiotics to promote human health, such as for the prevention and treatment of viral infections. Probiotics are
defined as ‘live microorganisms which, when administrated in adequate amounts, confer health benefits on the
host’ (WHO/FAO, 2001). Only rather recently, intervention trials have been performed with exogenously applied
probiotic Lactobacillus bacteria in which their potential
for improving the lives of HIV-infected patients or even
for preventing HIV infections is investigated. The rationale behind this is that probiotics can have a dual role
depending on the site of the body they are active. On the
one hand, they can be used to increase the Lactobacillus
numbers in the vaginal mucosa, which is the entry point
for HIV infection as well as for transmission of the virus.
Furthermore, exogenously applied lactobacilli can be used
for the treatment and prevention of BV, often associated
with HIV infections. For example, it was shown that daily
oral intake of L. rhamnosus GR-1 and L. reuteri RC-14
FEMS Microbiol Rev 37 (2013) 762–792
Human microbiota and HIV infections
resulted in colonization of the vagina, with a concomitant
reduction in bacterial and yeast pathogens in this niche
(Reid et al., 2003; Reid, 2008).
On the other hand, exogenously applied probiotics
may also exert health benefits by enhancing the GIT
mucosa, because the GIT is identified as a site of considerable early HIV replication, CD4+ T-cell destruction, and
systemic inflammation, as mentioned above. The question
then is whether blocking the first step of the cascade –
the leaky gut – could prevent HIV from proceeding
forward and eventually keep infected individuals healthier
(Wenner, 2009). Various probiotic organisms applied in
the GIT, mainly lactobacilli and bifidobacteria, have been
shown to enhance intestinal epithelial barrier function,
reduce inflammation, and support effective Th-1
responses. For example, probiotics can enhance the gut
barrier function and reduce bacterial translocation (Luyer
et al., 2005; Forsyth et al., 2009) by improving the
beneficial interactions between the commensal enteric
microbiota and the host during health and disease. Moreover, probiotics can restore GALT homeostasis by, for
example, inducing regulatory mechanisms to downregulate inflammation (Pessi et al., 2000; Braat et al.,
2004). In vitro studies showed evidence that probiotics
can skew away the immune system from a Th-2 dominant state (Iwabuchi et al., 2009; Hougee et al., 2010)
and influence DCs to skew T cells toward Th-1 polarization (Mohamadzadeh et al., 2005), thereby causing a
recovery in intestinal tolerance. Furthermore, probiotics
are able to make the intestinal environment less hospitable for pathogens by producing antimicrobial compounds, lowering the pH, and reducing the adhesion and
invasion of pathogens. These beneficial characteristics
could prevent GIT infections and improve the quality of
life of HIV patients (Hummelen et al., 2010b).
Intervention studies with probiotics in HIV
patients
In recent studies, several intervention studies with HIV/
AIDS patients were reported. The best studied probiotic
organisms for these applications are L. rhamnosus GR-1
and L. reuteri RC-14, originally isolated from a healthy
female urogenital tract with the capacity to adhere to
urogenital epithelial and vaginal cells (Reid et al., 1987).
These strains have also a documented capacity to inhibit
the growth and adhesion of urogenital and intestinal
pathogens, such as inhibition of the growth, adhesion,
and biofilm formation of C. albicans by L. rhamnosus
GR-1 (McMillan et al., 2011; Kohler et al., 2010). Moreover, L. rhamnosus GR-1 and L. reuteri RC-14 produce
lactic acid that kills bacteria and viruses, including HIV
(G. Reid, pers. commun.), H2O2, and bacteriocin-like
FEMS Microbiol Rev 37 (2013) 762–792
781
compounds. Lactobacillus rhamnosus GR-1 can colonize
the vagina (Reid et al., 1994; Gardiner et al., 2002) and
the intestine (Reid et al., 2001) upon exogenous application. In addition, they show a good survival capacity in
milk and hence have the ability to be delivered in a yogurt
form without deterioration of taste or structure (Hekmat
et al., 2008). These characteristics define L. rhamnosus
GR-1 as a potential vaginal probiotic that is active in the
GIT, the vagina, and the distal urethra and could restore
health in these areas.
An initial study conducted in Nigeria administrated
yogurt supplemented with L. rhamnosus GR-1 and
L. reuteri RC-14 to 24 female HIV/AIDS patients for 15
and 30 days, respectively, which was associated with
complete resolution of diarrhea, nausea, and flatulence in
all tested subjects and a slight increase in CD4+ counts
for selected patients (Anukam et al., 2008). These positive
results have led to the development of specialized kitchens in Mwanza (Tanzania), and the production of Fiti
probiotic yogurt supplemented with L. rhamnosus GR-1.
Thirty days after the consumption of Fiti probiotic
yogurt, almost all participants showed improvement in
their weight and higher levels of vitamins and micronutrients than the controls. Furthermore, consumers of the
probiotic yoghurt had fewer fungal infections, less
episodes of diarrhea, and a lower degree of tiredness
(Reid, 2010).
These promising results led to a second study using the
same L. rhamnosus GR-1 Fiti probiotic from the Mwanza
community kitchen (Irvine et al., 2010). Probiotic consumption for 70 days by 68 participants, compared with
a control group of 82 participants, showed to increase the
CD4+ count while most treated patients could also work
2 h longer a day, had less frequency of fever, and no diarrheal symptoms. A more recent study investigated the
effect of long-term intake of capsulated L. rhamnosus
GR-1 and L. reuteri RC-14 strains on the health of HIV/
AIDS patients (Hummelen et al., 2011a). From baseline
to 10 and 25 weeks of probiotic intake, the CD4+ counts
increased in the probiotic group, while no differences in
the immune markers IFNc, IL-10, IgG, and IgE, diarrhea
incidence or adverse events were observed. In addition, in
a study performed in Canada, consumption of L. rhamnosus GR-1 yogurt supplemented with micronutrients was
shown to support the immune system of HIV-infected
individuals and improve their ability to perform daily
tasks (Hemsworth et al., 2012). Further studies will be
important to investigate the mechanisms by which
L. rhamnosus GR-1 and L. reuteri RC-14 support health
benefits.
Of note, a recent study also reported a possible role for
a probiotic yogurt containing L. casei Shirota in the clearance of human papillomavirus (HPV)-related cervical
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
782
lesions (Verhoeven et al., 2013). Whether such protection
against HPV-related lesions of the vaginal epithelium will
indirectly results in decreased susceptibility for HIV infection remains to be investigated. The results indirectly can
be implemented for the prevention of HIV infections by
protecting the vaginal epithelium from other pathogens
such as HPV.
Recombinant lactic acid bacteria as
microbicidal agents against HIV
Over the last 10 years, there is an increased interest to
enlarge the anti-HIV potential of Lactobacillus species and
other lactic acid bacteria by genetic engineering. Potential
anti-HIV molecules for expression by probiotic bacteria
are proteins targeting the cell binding and fusion processes of HIV, thereby blocking infection and transmission. Hereby, the glycoproteins on the cell surface of
HIV, that is, the transmembrane gp41 and the external
gp120, which are important for the virus entry into the
cells, are important targets (Botos & Wlodawer, 2005). In
the process of infection, gp120 binds to the CD4 receptor
and CXCR4 or CCR5 coreceptor on the host T cells and
macrophages, which triggers a conformational change in
gp41 and initiates fusion of the viral envelope with the
host cell. Soluble CD4 receptors, chemokines, neutralizing
antibodies, and other active molecules such as lectins or
carbohydrate-binding agents have yet been reported to
inhibit the initial binding of gp120 to the host cell, while
peptides that bind the amino-terminal domain of gp41
are reported to block the fusion and entry into the host
cell (Nikolic & Piguet, 2010). These are all interesting ‘antiHIV’ molecules for genetic engineering in lactobacilli.
Certain studies have delivered proof of concept that
bioengineered probiotic strains can be used for delivery
of different active molecules against HIV. The first study
that succeeded in the expression of active anti-HIV
molecules was carried out in the vaginal L. jensenii strain
Xna-651 (Chang et al., 2003). Lactobacillus jensenii was
genetically modified to secrete the first two extracellular
domains of the human CD4 receptor (2D CD4) responsible for high-affinity binding to HIV gp120. Lactobacillusderived 2D CD4 molecules were able to inhibit HIV-1
infections of cultured cells in a dose-dependent manner
in vitro (Chang et al., 2003). Furthermore, coincubation
of the engineered bacteria with HIV-1 led to a significant
decrease in virus infectivity of HeLa cells expressing
CD4_CXCR4_CCR5. Anchoring of the 2D CD4 on the
Lactobacillus surface was later successfully achieved using
a natural vaginally isolated L. jensenii strain 1153 (Liu
et al., 2008). Other authors investigated the role of different natural immune inhibitors, which are ligands for HIV
receptors such as CCR5 and ICAM-1. For example,
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
Chancey et al. (2006) designed a L. casei 393 strain
expressing a single-chain variable fragment (scFV) specific
for the intracellular adhesion molecule 1 (ICAM-1).
ICAM-1 molecules are involved in cell–cell interactions
and presentation of HIV antigens of infected monocytes
and CD4+ T lymphocytes to uninfected cells. The
recombinant anti-ICAM-1 scFV antibody was indeed
shown to block cell-associated HIV-1 transmission across
an in vitro culture model of the cervical epithelium
(Chancey et al., 2006). Furthermore, Liu et al. (2007)
were also able to express a range of HIV inhibitors by stable chromosomal integration in the genome of L. reuteri
RC-14. Four different HIV inhibitors were included in
the study: MIP-1b (inhibiting CCR5 coreceptor binding),
T-1249, a next-generation T-20 peptide inhibitor (inhibiting hairpin formation and membrane fusion between the
virus and host cell), CD4D1D2-IgKLC, and CD4D1D2IgG2HC (the light- or heavy-chain variable domain of
human IgG2 replaced by the D1D2 domain of human
CD4). The authors achieved two different cellular locations for the recombinant HIV inhibitors – cell wall
anchored and secreted in the surrounding medium. All
recombinant inhibitors used by the authors proved to
inhibit HIV and SHIV infections in human PBMCs (Liu
et al., 2007). More recently, Vangelista et al. (2010) were
able to construct a recombinant L. jensenii 1153 strain,
which secretes the anti-HIV-1 chemokine RANTES and
C1C5 RANTES, a mutated analogue that acts as a CCR5
antagonist and is devoid of pro-inflammatory activity.
The recombinant wild-type RANTES and C1C5 RANTES
showed inhibitory activity against HIV-1 infection in
CD4+ T cells and macrophages in vitro. The authors were
able to show a similar antiviral activity against six
different R5 HIV strains, suggesting in vitro cross-clade
protection (Vangelista et al., 2010).
Other authors have used fusion inhibitor peptides
derived from the gp41 transmembrane envelope glycoprotein, which exhibit virus-blocking properties upon
overexpression. Rao et al. (2005) were able to construct a
recombinant probiotic strain of E. coli Nissle 1917 that
secretes an HIV–gp41–hemolysin A hybrid peptide, which
blocks the fusion and entry into target cells. Remarkably,
the recombinant E. coli Nissle 1917 was able to colonize
the murine colon and cecum, and in low concentration
also rectum, vagina, and small intestine and to persist
for a period of weeks to months. Furthermore, the
recombinant strain was able to grow and secrete
HIV–gp41–hemolysin A hybrid peptide in situ (Rao et al.,
2005). In addition, Pusch et al. (2006) were also able to
engineer L. plantarum ATCC 14917 and L. gasseri ATCC
9857 in a way that they secrete various HIV-1 C-peptide
fusion inhibitors (FI-1, FI-2, and FI-3) targeting the highly
conserved heptad repeat-1 region in the transmembrane
FEMS Microbiol Rev 37 (2013) 762–792
783
Human microbiota and HIV infections
ectodomain of gp41 and therefore neutralizing HIV
infections.
A different approach to target the HIV envelope and
thereby inhibit HIV infection is through the use of lectins.
The first recombinant lectin secreted by probiotic bacteria
was cyanovirin-N (CV-N). Giomarelli et al. (2002) studied
the anti-HIV-1 activity of the microbicidal compound
CV-N, secreted by recombinant Streptococcus gordonii.
CV-N, derived from the cyanobacterium Nostoc ellipsosporum, was shown to have antiviral activity by binding to
high mannose residues on the HIV-1 viral envelope,
thereby blocking the fusion of HIV-1 with the cell membrane and the transmission of its infection. The authors
showed that soluble recombinant CV-N was able to specifically bind gp120 in a concentration-dependent manner,
and recombinant strains expressing CV-N on their surface
were able to capture HIV virion (Giomarelli et al., 2002).
In further studies, Pusch et al. (2005) used two different
strains, Lactococcus lactis MG1363 and L. plantarum
NCIMB8826, for expression of CV-N and two different
cell locations – intracellular and extracellular. The low
concentration of extracellular recombinant CV-N at first
was successfully increased after codon optimization and
recharging of the N-terminal domain of the fused CV-N
(Pusch et al., 2005). Liu et al. (2006) were able to express
CV-N in the natural vaginal isolate L. jensenii 1153.
Recombinant CV-N was shown to decrease the infectivity
of both CCR5-tropic HIV and CXCR4-tropic HIV in vitro.
The recombinant L. jensenii strain was capable of colonizing the vagina and producing full-length CV-N in situ
when administered intravaginally to mice during the estrus
phase (Liu et al., 2006). Furthermore, the recombinant
L. jensenii was able to colonize the vaginal mucosa of
Chinese rhesus macaques and to reduce by 63% the
transmission of simian/human immunodeficiency virus.
Colonization and prolonged antiviral protein secretion by
the genetically engineered lactobacilli did not cause any
increase of pro-inflammatory markers (Lagenaur et al.,
2011). Nevertheless, more studies are required to conclude
the safety of the recombinant Lactobacillus strain. For
example, other studies have shown that CV-N promotes
secretion of pro-inflammatory cytokines and chemokines
from human PBMCs (Huskens et al., 2008). Moreover,
CV-N has a mitogenic activity that results in morphological changes in subpopulations of the treated cells. This
mitogenic characteristic of CV-N can cause the development of cells that are more susceptible to HIV infection
(Huskens et al., 2008). Other studies have reported that it
also activates quiescent CD4+ T cells and promotes T-cell
proliferation (Balzarini et al., 2006; Huskens et al., 2008).
These side effects of CV-N as a microbicidal drug suggest
that it is not an ideal agent for the prevention and treatment of HIV infection.
FEMS Microbiol Rev 37 (2013) 762–792
Recombinant Lactobacillus strains can be also used to
induce specific immune responses against HIV. For
example, Kajikawa et al. (2012) were able to design
L. acidophilus NCFM expressing HIV-1 Gag protein on
the bacterial surface with coexpression of Salmonella
flagellin used as adjuvant. The authors were able to show
that the recombinant L. acidophilus strain induces a specific immune response in vitro and in vivo and therefore
can serve as a vaccine vector to promote an immune
response against HIV (Kajikawa et al., 2012).
Thus, the use of bioengineered probiotic strains in the
prevention of HIV infections has already shown promising results. However, most of the studies performed so
far were only carried out in vitro. Future studies need to
investigate the potential role of the recombinant probiotics in vivo in order to proof the safety profile and efficacy of the bioengineered probiotic strains as mucosal
delivery system and as potential new microbicides. In
addition, the recombinant strains or the recombinant
proteins produced by the lactobacilli should not interfere
with the normal vaginal microbiota. For example, some
abiotic microbicides were reported to modify cervicovaginal innate immunity and actually reduce the number
of Lactobacillus species in vitro (Fichorova et al., 2011).
Furthermore, some abiotic microbicides were shown to
affect the vaginal microbiota and shift the colonization
of the vaginal mucosa to the presence of strict anaerobes
and a significantly reduction in lactobacilli (Ravel et al.,
2012). These results suggest that culture-dependent and
independent evaluation of candidate microbicides on the
vaginal microbiota should be considered. For example,
we recently were able to show that different lectins with
activity against HIV do not inhibit the growth of a wide
variety of vaginal lactobacilli, do not affect the viability
of these bacterial isolates, and have no significant impact
on their adhesion properties to human epithelial HeLa
cell monolayers (Petrova et al., 2013). In addition,
ethical and moral considerations should be also taken
into account, because the bioengineered probiotics are
genetically modified organisms. Nevertheless, the future
of recombinant lactobacilli is still open, because new
technics of gene expression will be developed and
optimized.
Conclusion and perspectives
The human microbiota plays an important role during the
entire life of humans of which protection against pathogenic infections is well known. Although various studies
have already addressed the importance of the GIT microbiota and its relation with diseases as well as HIV, studies
on the urogenital microbiota are lagging behind. Nevertheless, an emerging number of studies have documented
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
784
the role of the vaginal microbiota in the prevention of BV
and related diseases. Because the vaginal epithelium is an
important entry point for HIV, a better understanding of
the vaginal microbiota and its relationship with the
immune system is needed. Such detailed understanding
includes focused genetic studies on the members of the
beneficial vaginal microbiota in search for probiotic factors. Ultimately, molecular studies should allow tailored
application of specific probiotic strains, either orally via
the GIT or vaginally, based on well-documented modes of
action. Future studies should also exploit the promise of
genetic engineering of vaginal microbiota with specific
anti-HIV molecules. Other strategies can also be envisaged,
which are perhaps more plausible. Of note, applications
such as replenishment of lactic acid – in comparison with
short-chain fatty acids in the GIT or application of
glycogen like sugars – in comparison with the prebiotics
for the GIT, can be considered, given the apparent important role of the latter in the establishment of a healthy
vaginal ecosystem.
It can be concluded that the reported studies that focus
on the reconstitution of a healthy vaginal microbiota to
improve the life of HIV patients have shown promising
results so far in combination with standard medical treatments. Evidently, these studies need to be carried out on
a larger scale and with more parameters analyzed in order
to make the conclusions more firm. The very convincing
studies addressing the important role of the GIT microbiota on bowel diseases and functioning of the gut epithelium are a good driver to further invest in these types of
studies.
Acknowledgements
Part of the research of the authors is supported by the
KU Leuven (PF 10/18). We acknowledge the valuable
help of Shweta Malik, Hanne Tytgat, Marijke Segers, and
Elke Lievens for carefully reading the manuscript.
References
Aagaard K, Riehle K, Ma J et al. (2012) A metagenomic
approach to characterization of the vaginal microbiome
signature in pregnancy. PLoS ONE 7: e36466.
Akinsiku OT, Bansal A, Sabbaj S, Heath SL & Goepfert PA
(2011) Interleukin-2 production by polyfunctional
HIV-1-specific CD8 T cells is associated with enhanced
viral suppression. J Acquir Immune Defic Syndr 58:
132–140.
Alexopoulou L, Holt AC, Medzhitov R & Flavell RA (2001)
Recognition of double-stranded RNA and activation
of NF-kappaB by Toll-like receptor 3. Nature 413:
732–738.
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
Al-Harthi L, Roebuck KA, Olinger GG, Landay A, Sha BE,
Hashemi FB & Spear GT (1999) Bacterial
vaginosis-associated microflora isolated from the female
genital tract activates HIV-1 expression. J Acquir Immune
Defic Syndr 21: 194–202.
Amsel R, Totten PA, Spiegel CA, Chen KC, Eschenbach D &
Holmes KK (1983) Nonspecific vaginitis. Diagnostic criteria
and microbial and epidemiologic associations. Am J Med 74:
14–22.
Andersch-Bjorkman Y, Thomsson KA, Holmen Larsson JM,
Ekerhovd E & Hansson GC (2007) Large scale identification
of proteins, mucins, and their O-glycosylation in the
endocervical mucus during the menstrual cycle. Mol Cell
Proteomics 6: 708–716.
Antonio MA, Hawes SE & Hillier SL (1999) The identification
of vaginal Lactobacillus species and the demographic and
microbiologic characteristics of women colonized by these
species. J Infect Dis 180: 1950–1956.
Anukam KC, Osazuwa EO, Ahonkhai I & Reid G (2006)
Lactobacillus vaginal microbiota of women attending a
reproductive health care service in Benin city, Nigeria. Sex
Transm Dis 33: 59–62.
Anukam KC, Osazuwa EO, Osadolor HB, Bruce AW & Reid G
(2008) Yogurt containing probiotic Lactobacillus rhamnosus
GR-1 and L. reuteri RC-14 helps resolve moderate diarrhea
and increases CD4 count in HIV/AIDS patients. J Clin
Gastroenterol 42: 239–243.
Anukam KC, Macklaim JM, Gloor GB, Reid G, Boekhorst J,
Renckens B, van Hijum SA & Siezen RJ (2013) Genome
sequence of Lactobacillus pentosus KCA1: vaginal isolate from
a healthy premenopausal woman. PLoS ONE 8: e59239.
Arumugam M, Raes J, Pelletier E et al. (2011) Enterotypes of
the human gut microbiome. Nature 473: 174–180.
Balkus JE, Mitchell C, Agnew K, Liu C, Fiedler T, Cohn SE,
Luque A, Coombs R, Fredricks DN & Hitti J (2012)
Detection of hydrogen peroxide-producing Lactobacillus
species in the vagina: a comparison of culture and
quantitative PCR among HIV-1 seropositive women. BMC
Infect Dis 12: 188–193.
Balzarini J (2007) Targeting the glycans of glycoproteins: a
novel paradigm for antiviral therapy. Nat Rev Microbiol 5:
583–597.
Balzarini J, Van LK, Peumans WJ, Van Damme EJ, Bolmstedt
A, Gago F & Schols D (2006) Mutational pathways,
resistance profile, and side effects of cyanovirin relative to
human immunodeficiency virus type 1 strains with N-glycan
deletions in their gp120 envelopes. J Virol 80: 8411–8421.
Bloomfield SE & Lopez C (1980) Herpes infections in the
immunosuppressed host. Ophthalmology 87: 1226–1235.
Boskey ER, Telsch KM, Whaley KJ, Moench TR & Cone RA
(1999) Acid production by vaginal flora in vitro is
consistent with the rate and extent of vaginal acidification.
Infect Immun 67: 5170–5175.
Botos I & Wlodawer A (2005) Proteins that bind
high-mannose sugars of the HIV envelope. Prog Biophys Mol
Biol 88: 233–282.
FEMS Microbiol Rev 37 (2013) 762–792
Human microbiota and HIV infections
Braat H, van den BJ, van TE, Hommes D, Peppelenbosch M &
van DS (2004) Lactobacillus rhamnosus induces peripheral
hyporesponsiveness in stimulated CD4+ T cells via
modulation of dendritic cell function. Am J Clin Nutr 80:
1618–1625.
Brenchley JM & Douek DC (2008) HIV infection and the
gastrointestinal immune system. Mucosal Immunol 1: 23–30.
Brenchley JM, Price DA, Schacker TW et al. (2006) Microbial
translocation is a cause of systemic immune activation in
chronic HIV infection. Nat Med 12: 1365–1371.
Brenchley JM, Paiardini M, Knox KS et al. (2008) Differential
Th17 CD4 T-cell depletion in pathogenic and
nonpathogenic lentiviral infections. Blood 112: 2826–2835.
Burton JP & Reid G (2002) Evaluation of the bacterial vaginal
flora of 20 postmenopausal women by direct (Nugent score)
and molecular (polymerase chain reaction and denaturing
gradient gel electrophoresis) techniques. J Infect Dis 186:
1770–1780.
Cameron PU, Freudenthal PS, Barker JM, Gezelter S, Inaba
K & Steinman RM (1992) Dendritic cells exposed to
human immunodeficiency virus type-1 transmit a vigorous
cytopathic infection to CD4+ T cells. Science 257: 383–
387.
Chancey CJ, Khanna KV, Seegers JF, Zhang GW, Hildreth J,
Langan A & Markham RB (2006) Lactobacilli-expressed
single-chain variable fragment (scFv) specific for
intercellular adhesion molecule 1 (ICAM-1) blocks
cell-associated HIV-1 transmission across a cervical
epithelial monolayer. J Immunol 176: 5627–5636.
Chang TL, Chang CH, Simpson DA et al. (2003) Inhibition of
HIV infectivity by a natural human isolate of Lactobacillus
jensenii engineered to express functional two-domain CD4.
P Natl Acad Sci USA 100: 11672–11677.
Chege D, Sheth PM, Kain T et al. (2011) Sigmoid Th17
populations, the HIV latent reservoir, and microbial
translocation in men on long-term antiretroviral therapy.
AIDS 25: 741–749.
Clerici M & Shearer GM (1993) A TH1–>TH2 switch is a
critical step in the etiology of HIV infection. Immunol
Today 14: 107–111.
Cohen CR, Duerr A, Pruithithada N, Rugpao S, Hillier S,
Garcia P & Nelson K (1995) Bacterial vaginosis and HIV
seroprevalence among female commercial sex workers in
Chiang Mai, Thailand. AIDS 9: 1093–1097.
Collins KB, Patterson BK, Naus GJ, Landers DV & Gupta P
(2000) Development of an in vitro organ culture model to
study transmission of HIV-1 in the female genital tract. Nat
Med 6: 475–479.
Conti C, Malacrino C & Mastromarino P (2009) Inhibition of
herpes simplex virus type 2 by vaginal lactobacilli. J Physiol
Pharmacol 60: 19–26.
Corey L (2007a) Herpes simplex virus type 2 and HIV-1: the
dialogue between the 2 organisms continues. J Infect Dis
195: 1242–1244.
Corey L (2007b) Synergistic copathogens–HIV-1 and HSV-2.
N Engl J Med 356: 854–856.
FEMS Microbiol Rev 37 (2013) 762–792
785
Cotter PD, Ross RP & Hill C (2013) Bacteriocins – a viable
alternative to antibiotics? Nat Rev Microbiol 11: 95–105.
Cotter PD, Hill C & Ross RP (2005) Bacteriocins: developing
innate immunity for food. Nat Rev Microbiol 3: 777–788.
Cribby S, Taylor M & Reid G (2008) Vaginal microbiota and
the use of probiotics. Interdiscip Perspect Infect Dis 29:
256490.
Cummins JE Jr, Guarner J, Flowers L, Guenthner PC, Bartlett J,
Morken T, Grohskopf LA, Paxton L & Dezzutti CS (2007)
Preclinical testing of candidate topical microbicides for
anti-human immunodeficiency virus type 1 activity and
tissue toxicity in a human cervical explant culture.
Antimicrob Agents Chemother 51: 1770–1779.
Cu-Uvin S, Hogan JW, Caliendo AM, Harwell J, Mayer KH &
Carpenter CC (2001) Association between bacterial vaginosis
and expression of human immunodeficiency virus type 1
RNA in the female genital tract. Clin Infect Dis 33: 894–896.
Damelin LH, Paximadis M, Mavri-Damelin D, Birkhead M,
Lewis DA & Tiemessen CT (2011) Identification of
predominant culturable vaginal Lactobacillus species and
associated bacteriophages from women with and without
vaginal discharge syndrome in South Africa. J Med Microbiol
60: 180–183.
de Man JC, Rogosa M & Sharpe ME (1960) A medium for the
cultivation of lactobacilli. J Appl Bacteriol 23: 130–135.
de Witte L, Nabatov A, Pion M, Fluitsma D, de Jong MA, de
GT, Piguet V, van KY & Geijtenbeek TB (2007) Langerin is
a natural barrier to HIV-1 transmission by Langerhans cells.
Nat Med 13: 367–371.
Dei M, Di MF, Di PG & Bruni V (2010) Vulvovaginitis in
childhood. Best Pract Res Clin Obstet Gynaecol 24: 129–137.
Dimitonova SP, Danova ST, Serkedjieva JP & Bakalov BV
(2007) Antimicrobial activity and protective properties of
vaginal lactobacilli from healthy Bulgarian women. Anaerobe
13: 178–184.
Dimitonova SP, Bakalov BV, Eksandrova-Georgieva RN &
Danova ST (2008) Phenotypic and molecular identification
of lactobacilli isolated from vaginal secretions. J Microbiol
Immunol Infect 41: 469–477.
D€
oderlein A (1892) Das Scheidensekret und seine Bedeutung
f€
ur das Puerperalfieber. Zentbl Bakteriol Microbiol Hyg Abt
11: 699.
Dominguez-Bello MG, Costello EK, Contreras M, Magris M,
Hidalgo G, Fierer N & Knight R (2010) Delivery mode
shapes the acquisition and structure of the initial microbiota
across multiple body habitats in newborns. P Natl Acad Sci
USA 107: 11971–11975.
Donovan DM (2007) Bacteriophage and peptidoglycan
degrading enzymes with antimicrobial applications. Recent
Pat Biotechnol 1: 113–122.
Du Plessis EM & Dicks LM (1995) Evaluation of random
amplified polymorphic DNA (RAPD)-PCR as a method to
differentiate Lactobacillus acidophilus, Lactobacillus crispatus,
Lactobacillus amylovorus, Lactobacillus gallinarum,
Lactobacillus gasseri, and Lactobacillus johnsonii. Curr
Microbiol 31: 114–118.
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
786
Duerkop BA, Vaishnava S & Hooper LV (2009) Immune
responses to the microbiota at the intestinal mucosal
surface. Immunity 31: 368–376.
Duh EJ, Maury WJ, Folks TM, Fauci AS & Rabson AB (1989)
Tumor necrosis factor alpha activates human
immunodeficiency virus type 1 through induction of
nuclear factor binding to the NF-kappa B sites in the long
terminal repeat. P Natl Acad Sci USA 86: 5974–5978.
Ellis CL, Ma ZM, Mann SK et al. (2011) Molecular
characterization of stool microbiota in HIV-infected subjects
by panbacterial and order-level 16S ribosomal DNA (rDNA)
quantification and correlations with immune activation.
J Acquir Immune Defic Syndr 57: 363–370.
Falsen E, Pascual C, Sjoden B, Ohlen M & Collins MD (1999)
Phenotypic and phylogenetic characterization of a novel
Lactobacillus species from human sources: description of
Lactobacillus iners sp. nov. Int J Syst Bacteriol 49(Pt 1):
217–221.
Fantuzzi L, Canini I, Belardelli F & Gessani S (2001) HIV-1
gp120 stimulates the production of beta-chemokines in
human peripheral blood monocytes through a
CD4-independent mechanism. J Immunol 166: 5381–5387.
Ferir G, Petrova MI, Andrei G et al. (2013) The lantibiotic
peptide labyrinthopeptin A1 demonstrates broad anti-HIV
and anti-HSV activity with potential for microbicidal
applications. PLoS ONE 8: e64010.
Ferrari G, King K, Rathbun K, Place CA, Packard MV, Bartlett
JA, Bolognesi DP & Weinhold KJ (1995) IL-7 enhancement
of antigen-driven activation/expansion of HIV-1-specific
cytotoxic T lymphocyte precursors (CTLp). Clin Exp
Immunol 101: 239–248.
Fichorova RN, Yamamoto HS, Delaney ML, Onderdonk AB &
Doncel GF (2011) Novel vaginal microflora colonization
model providing new insight into microbicide mechanism
of action. MBio 2: e00168–11.
Florey O, Kim SE, Sandoval CP, Haynes CM & Overholtzer M
(2011) Autophagy machinery mediates macroendocytic
processing and entotic cell death by targeting single
membranes. Nat Cell Biol 13: 1335–1343.
Forsyth CB, Farhadi A, Jakate SM, Tang Y, Shaikh M &
Keshavarzian A (2009) Lactobacillus GG treatment
ameliorates alcohol-induced intestinal oxidative stress, gut
leakiness, and liver injury in a rat model of alcoholic
steatohepatitis. Alcohol 43: 163–172.
Fung KY, Mangan NE, Cumming H et al. (2013)
Interferon-epsilon protects the female reproductive tract
from viral and bacterial infection. Science 339:
1088–1092.
Gajer P, Brotman RM, Bai G et al. (2012) Temporal dynamics
of the human vaginal microbiota. Sci Transl Med 4:
132ra52.
Gardiner GE, Heinemann C, Bruce AW, Beuerman D & Reid
G (2002) Persistence of Lactobacillus fermentum RC-14 and
Lactobacillus rhamnosus GR-1 but not L. rhamnosus GG in
the human vagina as demonstrated by randomly amplified
polymorphic DNA. Clin Diagn Lab Immunol 9: 92–96.
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
Garg KB, Ganguli I, Das R & Talwar GP (2009) Spectrum of
Lactobacillus species present in healthy vagina of Indian
women. Indian J Med Res 129: 652–657.
Geijtenbeek TB, Kwon DS, Torensma R et al. (2000)
DC-SIGN, a dendritic cell-specific HIV-1-binding protein
that enhances trans-infection of T cells. Cell 100: 587–597.
Ginhoux F, Tacke F, Angeli V, Bogunovic M, Loubeau M,
Dai XM, Stanley ER, Randolph GJ & Merad M (2006)
Langerhans cells arise from monocytes in vivo. Nat Immunol
7: 265–273.
Giomarelli B, Provvedi R, Meacci F, Maggi T, Medaglini D,
Pozzi G, Mori T, McMahon JB, Gardella R & Boyd MR
(2002) The microbicide cyanovirin-N expressed on the
surface of commensal bacterium Streptococcus gordonii
captures HIV-1. AIDS 16: 1351–1356.
Gipson IK, Ho SB, Spurr-Michaud SJ, Tisdale AS, Zhan Q,
Torlakovic E, Pudney J, Anderson DJ, Toribara NW & Hill
JA III (1997) Mucin genes expressed by human female
reproductive tract epithelia. Biol Reprod 56: 999–1011.
Givan AL, White HD, Stern JE, Colby E, Gosselin EJ, Guyre
PM & Wira CR (1997) Flow cytometric analysis of
leukocytes in the human female reproductive tract:
comparison of fallopian tube, uterus, cervix, and vagina. Am
J Reprod Immunol 38: 350–359.
Gori A, Tincati C, Rizzardini G et al. (2008) Early impairment
of gut function and gut flora supporting a role for
alteration of gastrointestinal mucosa in human
immunodeficiency virus pathogenesis. J Clin Microbiol 46:
757–758.
Gupta S, Kumar N, Singhal N, Kaur R & Manektala U (2006)
Vaginal microflora in postmenopausal women on hormone
replacement therapy. Indian J Pathol Microbiol 49: 457–461.
Handen JS & Rosenberg HF (1997) Suppression of HIV-1
transcription by beta-chemokines RANTES, MIP1-alpha,
and MIP-1beta is not mediated by the NFAT-1 enhancer
element. FEBS Lett 410: 301–302.
Harada H, Goto Y, Ohno T, Suzu S & Okada S (2007)
Proliferative activation up-regulates expression of CD4 and
HIV-1 co-receptors on NK cells and induces their infection
with HIV-1. Eur J Immunol 37: 2148–2155.
Harrington LE, Hatton RD, Mangan PR, Turner H, Murphy
TL, Murphy KM & Weaver CT (2005) Interleukin
17-producing CD4+ effector T cells develop via a lineage
distinct from the T helper type 1 and 2 lineages. Nat
Immunol 6: 1123–1132.
Hashemi FB, Ghassemi M, Roebuck KA & Spear GT (1999)
Activation of human immunodeficiency virus type 1
expression by Gardnerella vaginalis. J Infect Dis 179: 924–930.
Hashemi FB, Ghassemi M, Faro S, Aroutcheva A & Spear GT
(2000) Induction of human immunodeficiency virus type 1
expression by anaerobes associated with bacterial vaginosis.
J Infect Dis 181: 1574–1580.
Heil F, Hemmi H, Hochrein H, Ampenberger F, Kirschning C,
Akira S, Lipford G, Wagner H & Bauer S (2004)
Species-specific recognition of single-stranded RNA via
toll-like receptor 7 and 8. Science 303: 1526–1529.
FEMS Microbiol Rev 37 (2013) 762–792
Human microbiota and HIV infections
Heinonen PK, Teisala K, Punnonen R, Miettinen A, Lehtinen
M & Paavonen J (1985) Anatomic sites of upper genital
tract infection. Obstet Gynecol 66: 384–390.
Hekmat S, Soltani H & Reid G (2008) Growth and survival of
Lactobacillus reuteri RC-14 and Lactobacillus rhamnosus
GR-1 in yogurt for use as a functional food. Innov Food Sci
Emerg Technol 10: 293–296.
Hemsworth JC, Hekmat S & Reid G (2012) Micronutrient
supplemented probiotic yogurt for HIV-infected adults
taking HAART in London, Canada. Gut Microbes 3:
414–419.
Herbein G & Khan KA (2008) Is HIV infection a TNF
receptor signalling-driven disease? Trends Immunol 29:
61–67.
Hickey DK, Patel MV, Fahey JV & Wira CR (2011) Innate and
adaptive immunity at mucosal surfaces of the female
reproductive tract: stratification and integration of immune
protection against the transmission of sexually transmitted
infections. J Reprod Immunol 88: 185–194.
Hill JA & Anderson DJ (1992) Human vaginal leukocytes and
the effects of vaginal fluid on lymphocyte and macrophage
defense functions. Am J Obstet Gynecol 166: 720–726.
Hill GB, St Claire KK & Gutman LT (1995) Anaerobes
predominate among the vaginal microflora of prepubertal
girls. Clin Infect Dis 20: S269–S270.
Hladik F & McElrath MJ (2008) Setting the stage: host
invasion by HIV. Nat Rev Immunol 8: 447–457.
Hladik F, Sakchalathorn P, Ballweber L, Lentz G, Fialkow M,
Eschenbach D & McElrath MJ (2007) Initial events in
establishing vaginal entry and infection by human
immunodeficiency virus type-1. Immunity 26: 257–270.
Hooper LV, Littman DR & Macpherson AJ (2012) Interactions
between the microbiota and the immune system. Science
336: 1268–1273.
Hougee S, Vriesema AJ, Wijering SC, Knippels LM, Folkerts G,
Nijkamp FP, Knol J & Garssen J (2010) Oral treatment with
probiotics reduces allergic symptoms in
ovalbumin-sensitized mice: a bacterial strain comparative
study. Int Arch Allergy Immunol 151: 107–117.
Hummelen R, Fernandes AD, Macklaim JM, Dickson RJ,
Changalucha J, Gloor GB & Reid G (2010a) Deep
sequencing of the vaginal microbiota of women with HIV.
PLoS ONE 5: e12078.
Hummelen R, Vos AP, van’t Land B, van Norren K & Reid G
(2010b) Altered host-microbe interaction in HIV: a target
for intervention with pro- and prebiotics. Int Rev Immunol
29: 485–513.
Hummelen R, Changalucha J, Butamanya NL, Koyama TE,
Cook A, Habbema JD & Reid G (2011a) Effect of 25 weeks
probiotic supplementation on immune function of HIV
patients. Gut Microbes 2: 80–85.
Hummelen R, Macklaim JM, Bisanz JE, Hammond JA,
McMillan A, Vongsa R, Koenig D, Gloor GB & Reid G
(2011b) Vaginal microbiome and epithelial gene array in
post-menopausal women with moderate to severe dryness.
PLoS ONE 6: e26602.
FEMS Microbiol Rev 37 (2013) 762–792
787
Huskens D, Vermeire K, Vandemeulebroucke E, Balzarini J &
Schols D (2008) Safety concerns for the potential use of
cyanovirin-N as a microbicidal anti-HIV agent. Int
J Biochem Cell Biol 40: 2802–2814.
Hussain LA & Lehner T (1995) Comparative investigation of
Langerhans’ cells and potential receptors for HIV in oral,
genitourinary and rectal epithelia. Immunology 85: 475–484.
Irvine SL, Hummelen R, Hekmat S, Looman CW, Habbema
JD & Reid G (2010) Probiotic yogurt consumption is
associated with an increase of CD4 count among
people living with HIV/AIDS. J Clin Gastroenterol 44:
e201–e205.
Iwabuchi N, Takahashi N, Xiao JZ, Yonezawa S, Yaeshima T,
Iwatsuki K & Hachimura S (2009) Suppressive effects of
Bifidobacterium longum on the production of Th2-attracting
chemokines induced with T cell-antigen-presenting cell
interactions. FEMS Immunol Med Microbiol 55: 324–334.
Iwasaki A (2010) Antiviral immune responses in the genital
tract: clues for vaccines. Nat Rev Immunol 10: 699–711.
Johnson-Henry KC, Donato KA, Shen-Tu G, Gordanpour M
& Sherman PM (2008) Lactobacillus rhamnosus strain GG
prevents enterohemorrhagic Escherichia coli O157:
H7-induced changes in epithelial barrier function. Infect
Immun 76: 1340–1348.
Kajikawa A, Zhang L, Long J, Nordone S, Stoeker L, LaVoy A,
Bumgardner S, Klaenhammer T & Dean G (2012)
Construction and immunological evaluation of dual cell
surface display of HIV-1 gag and Salmonella enterica serovar
Typhimurium FliC in Lactobacillus acidophilus for vaccine
delivery. Clin Vaccine Immunol 19: 1374–1381.
Kalyoussef S, Nieves E, Dinerman E et al. (2012) Lactobacillus
proteins are associated with the bactericidal activity against
E. coli of female genital tract secretions. PLoS ONE 7:
e49506.
Kane M, Case LK, Kopaskie K, Kozlova A, MacDearmid C,
Chervonsky AV & Golovkina TV (2011) Successful
transmission of a retrovirus depends on the commensal
microbiota. Science 334: 245–249.
Karlsson M, Scherbak N, Reid G & Jass J (2012) Lactobacillus
rhamnosus GR-1 enhances NF-kappaB activation in
Escherichia coli-stimulated urinary bladder cells through
TLR4. BMC Microbiol 12: 15.
Kelly P, Todd J, Sianongo S, Mwansa J, Sinsungwe H,
Katubulushi M, Farthing MJ & Feldman RA (2009)
Susceptibility to intestinal infection and diarrhoea in
Zambian adults in relation to HIV status and CD4 count.
BMC Gastroenterol 9: 7.
Kilic AO, Pavlova SI, Alpay S, Kilic SS & Tao L (2001)
Comparative study of vaginal Lactobacillus phages isolated
from women in the United States and Turkey: prevalence,
morphology, host range, and DNA homology. Clin Diagn
Lab Immunol 8: 31–39.
Klatt NR, Estes JD, Sun X et al. (2012) Loss of mucosal
CD103+ DCs and IL-17+ and IL-22+ lymphocytes is
associated with mucosal damage in SIV infection. Mucosal
Immunol 5: 646–657.
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
788
Klebanoff SJ & Coombs RW (1991) Viricidal effect of
Lactobacillus acidophilus on human immunodeficiency virus
type 1: possible role in heterosexual transmission. J Exp Med
174: 289–292.
Kohler GA, Assefa S & Reid G (2010) Probiotic interference of
Lactobacillus rhamnosus GR-1 and Lactobacillus reuteri
RC-14 with the opportunistic fungal pathogen Candida
albicans. Infect Dis Obstet Gynecol 2010: 636474.
DOI: 10.1155/2012/636474.
Konstantinov SR, Smidt H, de Vos WM et al. (2008) S layer
protein A of Lactobacillus acidophilus NCFM regulates
immature dendritic cell and T cell functions. P Natl Acad
Sci USA 105: 19474–19479.
Koren O, Knights D, Gonzalez A, Waldron L, Segata N,
Knight R, Huttenhower C & Ley RE (2013) A guide to
enterotypes across the human body: meta-analysis of
microbial community structures in human microbiome
datasets. PLoS Comput Biol 9: e1002863.
Lackner AA, Lederman MM & Rodriguez B (2012) HIV
pathogenesis: the host. Cold Spring Harb Perspect Med 2:
a007005.
Lagenaur LA, Sanders-Beer BE, Brichacek B, Pal R, Liu X, Liu Y,
Yu R, Venzon D, Lee PP & Hamer DH (2011) Prevention of
vaginal SHIV transmission in macaques by a live recombinant
Lactobacillus. Mucosal Immunol 4: 648–657.
Lai SK, Hida K, Shukair S, Wang YY, Figueiredo A, Cone R,
Hope TJ & Hanes J (2009) Human immunodeficiency virus
type 1 is trapped by acidic but not by neutralized human
cervicovaginal mucus. J Virol 83: 11196–11200.
Lamont RF, Sobel JD, Akins RA, Hassan SS, Chaiworapongsa
T, Kusanovic JP & Romero R (2011) The vaginal
microbiome: new information about genital tract flora using
molecular based techniques. BJOG 118: 533–549.
Lebeer S, Vanderleyden J & De Keersmaecker SC (2010) Host
interactions of probiotic bacterial surface molecules:
comparison with commensals and pathogens. Nat Rev
Microbiol 8: 171–184.
Lederman MM, Offord RE & Hartley O (2006) Microbicides
and other topical strategies to prevent vaginal transmission
of HIV. Nat Rev Immunol 6: 371–382.
Liu X, Lagenaur LA, Simpson DA et al. (2006) Engineered
vaginal lactobacillus strain for mucosal delivery of the
human immunodeficiency virus inhibitor cyanovirin-N.
Antimicrob Agents Chemother 50: 3250–3259.
Liu JJ, Reid G, Jiang Y, Turner MS & Tsai CC (2007) Activity
of HIV entry and fusion inhibitors expressed by the human
vaginal colonizing probiotic Lactobacillus reuteri RC-14. Cell
Microbiol 9: 120–130.
Liu X, Lagenaur LA, Lee PP & Xu Q (2008) Engineering of a
human vaginal Lactobacillus strain for surface expression of
two-domain CD4 molecules. Appl Environ Microbiol 74:
4626–4635.
Liu H, Gao Y, Yu LR, Jones RC, Elkins CA & Hart ME (2011)
Inhibition of Staphylococcus aureus by lysostaphin-expressing
Lactobacillus plantarum WCFS1 in a modified genital tract
secretion medium. Appl Environ Microbiol 77: 8500–8508.
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
Luyer MD, Buurman WA, Hadfoune M, Speelmans G, Knol J,
Jacobs JA, Dejong CH, Vriesema AJ & Greve JW (2005)
Strain-specific effects of probiotics on gut barrier integrity
following hemorrhagic shock. Infect Immun 73: 3686–3692.
Ma B, Forney LJ & Ravel J (2012) Vaginal microbiome:
rethinking health and disease. Annu Rev Microbiol 66:
371–389.
Mac Bride MB, Rhodes DJ & Shuster LT (2010) Vulvovaginal
atrophy. Mayo Clin Proc 85: 87–94.
MacDonald T (2008) The gut is still the biggest lymphoid
organ in the body. Mucosal Immunol 1: 246–247.
Macklaim JM, Gloor GB, Anukam KC, Cribby S & Reid G
(2011) At the crossroads of vaginal health and disease, the
genome sequence of Lactobacillus iners AB-1. P Natl Acad
Sci USA 108(suppl 1): 4688–4695.
Macklaim J, Fernandes AD, Di Bella JM, Hammond JA, Reid
G & Gloor GB (2013) Comparative meta-RNA-seq of the
vaginal microbiota and differential expression by
Lactobacillus iners in health and dysbiosis. Microbiome 1: 12.
Maggi E, Mazzetti M, Ravina A et al. (1994) Ability of HIV to
promote a TH1 to TH0 shift and to replicate preferentially
in TH2 and TH0 cells. Science 265: 244–248.
Maher D, Wu X, Schacker T, Horbul J & Southern P (2005)
HIV binding, penetration, and primary infection in human
cervicovaginal tissue. P Natl Acad Sci USA 102: 11504–11509.
Malik S, Petrova MI, Claes IJ et al. (2013) The high
auto-aggregative and adhesive phenotype of the vaginal
Lactobacillus plantarum strain CMPG5300 is
sortase-dependent. Appl Environ Microbiol 79: 4576–4585.
M€andar R (2013) Microbiota of male genital tract: Impact on
the health of man and his partner. Pharmacol Res 69: 32–41.
Martin LS, McDougal JS & Loskoski SL (1985) Disinfection
and inactivation of the human T lymphotropic virus type
III/Lymphadenopathy-associated virus. J Infect Dis 152:
400–403.
Martin HL, Richardson BA, Nyange PM, Lavreys L, Hillier SL,
Chohan B, Mandaliya K, Ndinya-Achola JO, Bwayo J &
Kreiss J (1999) Vaginal lactobacilli, microbial flora, and risk
of human immunodeficiency virus type 1 and sexually
transmitted disease acquisition. J Infect Dis 180: 1863–1868.
Martin R, Soberon N, Escobedo S & Suarez JE (2009)
Bacteriophage induction versus vaginal homeostasis: role of
H(2)O(2) in the selection of Lactobacillus defective
prophages. Int Microbiol 12: 131–136.
Martinez RC, Franceschini SA, Patta MC, Quintana SM,
Nunes AC, Moreira JL, Anukam KC, Reid G & De Martinis
EC (2008) Analysis of vaginal lactobacilli from healthy and
infected Brazilian women. Appl Environ Microbiol 74: 4539–
4542.
Martinez MG, Prado AM, Candurra NA & Ruzal SM (2012)
S-layer proteins of Lactobacillus acidophilus inhibits JUNV
infection. Biochem Biophys Res Commun 422: 590–595.
Matu MN, Orinda GO, Njagi EN, Cohen CR & Bukusi EA
(2010) In vitro inhibitory activity of human vaginal
lactobacilli against pathogenic bacteria associated with
bacterial vaginosis in Kenyan women. Anaerobe 16: 210–215.
FEMS Microbiol Rev 37 (2013) 762–792
Human microbiota and HIV infections
McMillan A, Dell M, Zellar MP et al. (2011) Disruption of
urogenital biofilms by lactobacilli. Colloids Surf B
Biointerfaces 86: 58–64.
Mehandru S, Poles MA, Tenner-Racz K, Horowitz A, Hurley
A, Hogan C, Boden D, Racz P & Markowitz M (2004)
Primary HIV-1 infection is associated with preferential
depletion of CD4+ T lymphocytes from effector sites in the
gastrointestinal tract. J Exp Med 200: 761–770.
Meindl K, Schmiederer T, Schneider K et al. (2010)
Labyrinthopeptins: a new class of carbacyclic lantibiotics.
Angew Chem Int Ed Engl 49: 1151–1154.
Merlini E, Bai F, Bellistri GM, Tincati C, d’Arminio MA &
Marchetti G (2011) Evidence for polymicrobic flora
translocating in peripheral blood of HIV-infected patients
with poor immune response to antiretroviral therapy. PLoS
ONE 6: e18580.
Minkoff HL, Eisenberger-Matityahu D, Feldman J, Burk R &
Clarke L (1999) Prevalence and incidence of gynecologic
disorders among women infected with human
immunodeficiency virus. Am J Obstet Gynecol 180: 824–836.
Mitchell C, Balkus JE, Fredricks D et al. (2012) Interaction
between Lactobacilli, bacterial vaginosis-associated bacteria,
and HIV type 1 RNA and DNA genital shedding in U.S.
and Kenyan women. AIDS Res Hum Retroviruses 29: 13–19.
Mohamadzadeh M, Olson S, Kalina WV, Ruthel G, Demmin
GL, Warfield KL, Bavari S & Klaenhammer TR (2005)
Lactobacilli activate human dendritic cells that skew T cells
toward T helper 1 polarization. P Natl Acad Sci USA 102:
2880–2885.
Moran PA, Diegel ML, Sias JC, Ledbetter JA & Zarling JM
(1993) Regulation of HIV production by blood
mononuclear cells from HIV-infected donors: I. Lack of
correlation between HIV-1 production and T cell activation.
AIDS Res Hum Retroviruses 9: 455–464.
Mselle TF, Howell AL, Ghosh M, Wira CR & Sentman CL
(2009) Human uterine natural killer cells but not blood
natural killer cells inhibit human immunodeficiency virus
type 1 infection by secretion of CXCL12. J Virol 83: 11188–
11195.
Mueller YM, Do DH, Altork SR et al. (2008) IL-15 treatment
during acute simian immunodeficiency virus (SIV) infection
increases viral set point and accelerates disease progression
despite the induction of stronger SIV-specific CD8+ T cell
responses. J Immunol 180: 350–360.
Naik S, Bouladoux N, Wilhelm C et al. (2012)
Compartmentalized control of skin immunity by resident
commensals. Science 337: 1115–1119.
Narimatsu R, Wolday D & Patterson BK (2005) IL-8 increases
transmission of HIV type 1 in cervical explant tissue. AIDS
Res Hum Retroviruses 21: 228–233.
Nelson DE, Dong Q, Van der PB et al. (2012) Bacterial
communities of the coronal sulcus and distal urethra of
adolescent males. PLoS ONE 7: e36298.
Nikolic DS & Piguet V (2010) Vaccines and microbicides
preventing HIV-1, HSV-2, and HPV mucosal transmission.
J Invest Dermatol 130: 352–361.
FEMS Microbiol Rev 37 (2013) 762–792
789
Nugent RP, Krohn MA & Hillier SL (1991) Reliability of
diagnosing bacterial vaginosis is improved by a standardized
method of gram stain interpretation. J Clin Microbiol 29:
297–301.
O’Connor TJ, Kinchington D, Kangro HO & Jeffries DJ (1995)
The activity of candidate virucidal agents, low pH and
genital secretions against HIV-1 in vitro. Int J STD AIDS 6:
267–272.
Ogawa Y, Kawamura T, Matsuzawa T et al. (2013)
Antimicrobial peptide LL-37 produced by HSV-2-infected
keratinocytes enhances HIV infection of langerhans cells.
Cell Host Microbe 13: 77–86.
Ohlsson A & Shah VS (2013) Intrapartum antibiotics for
known maternal Group B streptococcal colonization.
Cochrane Database Syst Rev 1: CD007467.
Ohmit SE, Sobel JD, Schuman P, Duerr A, Mayer K, Rompalo
A & Klein RS (2003) Longitudinal study of mucosal
Candida species colonization and candidiasis among human
immunodeficiency virus (HIV)-seropositive and at-risk
HIV-seronegative women. J Infect Dis 188: 118–127.
Olivetta E, Percario Z, Fiorucci G et al. (2003) HIV-1 Nef
induces the release of inflammatory factors from human
monocyte/macrophages: involvement of Nef endocytotic
signals and NF-kappa B activation. J Immunol 170: 1716–
1727.
Olmsted SS, Khanna KV, Ng EM, Whitten ST, Johnson ON
III, Markham RB, Cone RA & Moench TR (2005) Low pH
immobilizes and kills human leukocytes and prevents
transmission of cell-associated HIV in a mouse model. BMC
Infect Dis 5: 79.
Ongradi J, Ceccherini-Nelli L, Pistello M, Specter S &
Bendinelli M (1990) Acid sensitivity of cell-free and
cell-associated HIV-1: clinical implications. AIDS Res Hum
Retroviruses 6: 1433–1436.
Pessi T, Sutas Y, Hurme M & Isolauri E (2000) Interleukin-10
generation in atopic children following oral Lactobacillus
rhamnosus GG. Clin Exp Allergy 30: 1804–1808.
Petrova MI, Mathys L, Lebeer S, Noppen S, Van Damme EJ,
Tanaka H, Igarashi Y, Vaneechoutte M, Vanderleyden J &
Balzarini J (2013) Inhibition of infection and transmission
of HIV-1 and lack of significant impact on the vaginal
commensal lactobacilli by carbohydrate-binding agents.
J Antimicrob Chemother, DOI: 10.1093/jac/dkt152.
Pretzer G, Snel J, Molenaar D, Wiersma A, Bron PA, Lambert
J, de Vos WM, van der MR, Smits MA & Kleerebezem M
(2005) Biodiversity-based identification and functional
characterization of the mannose-specific adhesin of
Lactobacillus plantarum. J Bacteriol 187: 6128–6136.
Pudney J, Quayle AJ & Anderson DJ (2005) Immunological
microenvironments in the human vagina and cervix:
mediators of cellular immunity are concentrated in
the cervical transformation zone. Biol Reprod 73: 1253–
1263.
Pugliese A, Vidotto V, Beltramo T & Torre D (2005)
Phagocytic activity in human immunodeficiency virus type
1 infection. Clin Diagn Lab Immunol 12: 889–895.
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
790
Pusch O, Boden D, Hannify S, Lee F, Tucker LD, Boyd MR,
Wells JM & Ramratnam B (2005) Bioengineering lactic acid
bacteria to secrete the HIV-1 virucide cyanovirin. J Acquir
Immune Defic Syndr 40: 512–520.
Pusch O, Kalyanaraman R, Tucker LD, Wells JM, Ramratnam
B & Boden D (2006) An anti-HIV microbicide engineered
in commensal bacteria: secretion of HIV-1 fusion inhibitors
by lactobacilli. AIDS 20: 1917–1922.
Rancinan C, Morlat P, Chene G et al. (1997) [Prevalence of
clinical manifestations of allergic reactions in HIV infection.
Cross sectional study of 115 subjects]. Rev Med Interne 18:
691–694.
Randelovic G, Mladenovic V, Ristic L, Otasevic S, Brankovic S,
Mladenovic-Antic S, Bogdanovic M & Bogdanovic D (2012)
Microbiological aspects of vulvovaginitis in prepubertal
girls. Eur J Pediatr 171: 1203–1208.
Rao S, Hu S, McHugh L, Lueders K, Henry K, Zhao Q, Fekete
RA, Kar S, Adhya S & Hamer DH (2005) Toward a live
microbial microbicide for HIV: commensal bacteria
secreting an HIV fusion inhibitor peptide. P Natl Acad Sci
USA 102: 11993–11998.
Ravel J, Gajer P, Abdo Z et al. (2011) Vaginal microbiome of
reproductive-age women. P Natl Acad Sci USA 108: 4680–
4687.
Ravel J, Gajer P, Fu L, Mauck CK, Koenig SS, Sakamoto J,
Motsinger-Reif AA, Doncel GF & Zeichner SL (2012)
Twice-daily application of HIV microbicides alter the
vaginal microbiota. MBio 3: e00370–12.
Rebbapragada A, Howe K, Wachihi C, Pettengell C, Sunderji
S, Huibner S, Ball TB, Plummer FA, Jaoko W & Kaul R
(2008) Bacterial vaginosis in HIV-infected women induces
reversible alterations in the cervical immune environment.
J Acquir Immune Defic Syndr 49: 520–522.
Reeves JD & Doms RW (2002) Human immunodeficiency
virus type 2. J Gen Virol 83: 1253–1265.
Reid G (2008) Probiotic Lactobacilli for urogenital health in
women. J Clin Gastroenterol 42: S234–S236.
Reid G (2010) The potential role for probiotic yogurt for
people living with HIV/AIDS. Gut Microbes 1: 411–414.
Reid G, Cook RL & Bruce AW (1987) Examination of strains
of lactobacilli for properties that may influence bacterial
interference in the urinary tract. J Urol 138: 330–335.
Reid G, Millsap K & Bruce AW (1994) Implantation of
Lactobacillus casei var rhamnosus into vagina. Lancet 344:
1229.
Reid G, Bruce AW, Fraser N, Heinemann C, Owen J &
Henning B (2001) Oral probiotics can resolve urogenital
infections. FEMS Immunol Med Microbiol 30: 49–52.
Reid G, Charbonneau D, Erb J, Kochanowski B, Beuerman D,
Poehner R & Bruce AW (2003) Oral use of Lactobacillus
rhamnosus GR-1 and L. fermentum RC-14 significantly
alters vaginal flora: randomized, placebo-controlled trial in
64 healthy women. FEMS Immunol Med Microbiol 35:
131–134.
Reid G, Younes JA, Van der Mei HC, Gloor GB, Knight R &
Busscher HJ (2011) Microbiota restoration: natural and
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
supplemented recovery of human microbial communities.
Nat Rev Microbiol 9: 27–38.
Reuter MA, Pombo C & Betts MR (2012) Cytokine
production and dysregulation in HIV pathogenesis: lessons
for development of therapeutics and vaccines. Cytokine
Growth Factor Rev 23: 181–191.
Reyes A, Haynes M, Hanson N, Angly FE, Heath AC,
Rohwer F & Gordon JI (2010) Viruses in the faecal
microbiota of monozygotic twins and their mothers.
Nature 466: 334–338.
Rho M, Wu YW, Tang H, Doak TG & Ye Y (2012) Diverse
CRISPRs evolving in human microbiomes. PLoS Genet 8:
e1002441.
Robboy SJ & Bentley RC (2004) Histology for pathologists.
3rd edn, Stacey Mills, Wolters Kluwers Health, Lippincott
Williams & Wilkins, Philadelphia.
Rodriguez JM, Collins MD, Sjoden B & Falsen E (1999)
Characterization of a novel Atopobium isolate from the
human vagina: description of Atopobium vaginae sp. nov.
Int J Syst Bacteriol 49(Pt 4): 1573–1576.
Rose WA, McGowin CL, Spagnuolo RA, Eaves-Pyles TD,
Popov VL & Pyles RB (2012) Commensal bacteria modulate
innate immune responses of vaginal epithelial cell multilayer
cultures. PLoS ONE 7: e32728.
Schaefer TM, Desouza K, Fahey JV, Beagley KW & Wira CR
(2004) Toll-like receptor (TLR) expression and
TLR-mediated cytokine/chemokine production by human
uterine epithelial cells. Immunology 112: 428–436.
Schaefer TM, Fahey JV, Wright JA & Wira CR (2005) Innate
immunity in the human female reproductive tract: antiviral
response of uterine epithelial cells to the TLR3 agonist poly
(I:C). J Immunol 174: 992–1002.
Schellenberg JJ & Plummer FA (2012) The microbiological
context of HIV resistance: vaginal microbiota and mucosal
inflammation at the viral point of entry. Int J Inflam 14:
131243.
Sewankambo N, Gray RH, Wawer MJ et al. (1997) HIV-1
infection associated with abnormal vaginal flora morphology
and bacterial vaginosis. Lancet 350: 546–550.
Sha BE, Zariffard MR, Wang QJ, Chen HY, Bremer J, Cohen
MH & Spear GT (2005) Female genital-tract HIV load
correlates inversely with Lactobacillus species but positively
with bacterial vaginosis and Mycoplasma hominis. J Infect
Dis 191: 25–32.
Shen R, Richter HE, Clements RH et al. (2009) Macrophages
in vaginal but not intestinal mucosa are monocyte-like and
permissive to human immunodeficiency virus type 1
infection. J Virol 83: 3258–3267.
Simoes JA, Hashemi FB, Aroutcheva AA, Heimler I, Spear GT,
Shott S & Faro S (2001) Human immunodeficiency virus
type 1 stimulatory activity by Gardnerella vaginalis:
relationship to biotypes and other pathogenic characteristics.
J Infect Dis 184: 22–27.
Song YL, Kato N, Matsumiya Y, Liu CX, Kato H & Watanabe
K (1999) Identification of and hydrogen peroxide
production by fecal and vaginal lactobacilli isolated from
FEMS Microbiol Rev 37 (2013) 762–792
Human microbiota and HIV infections
Japanese women and newborn infants. J Clin Microbiol 37:
3062–3064.
Spear GT, St JE & Zariffard MR (2007) Bacterial vaginosis and
human immunodeficiency virus infection. AIDS Res Ther 4:
25.
Spear GT, Sikaroodi M, Zariffard MR, Landay AL, French AL
& Gillevet PM (2008) Comparison of the diversity of the
vaginal microbiota in HIV-infected and HIV-uninfected
women with or without bacterial vaginosis. J Infect Dis 198:
1131–1140.
Spear GT, Gilbert D, Landay AL, Zariffard R, French AL, Patel
P & Gillevet PM (2011) Pyrosequencing of the genital
microbiotas of HIV-seropositive and -seronegative women
reveals Lactobacillus iners as the predominant Lactobacillus
species. Appl Environ Microbiol 77: 378–381.
Srinivasan S, Hoffman NG, Morgan MT et al. (2012) Bacterial
communities in women with bacterial vaginosis: high
resolution phylogenetic analyses reveal relationships of
microbiota to clinical criteria. PLoS ONE 7: e37818.
St. John EP, Martinson J, Simoes JA, Landay AL & Spear GT
(2007) Dendritic cell activation and maturation induced by
mucosal fluid from women with bacterial vaginosis. Clin
Immunol 125: 95–102.
St. John EP, Zariffard MR, Martinson JA, Simoes JA, Landay
AL & Spear GT (2009) Effect of mucosal fluid from women
with bacterial vaginosis on HIV trans-infection mediated by
dendritic cells. Virology 385: 22–27.
Stoddard E, Ni H, Cannon G, Zhou C, Kallenbach N,
Malamud D & Weissman D (2009) gp340 promotes
transcytosis of human immunodeficiency virus type 1 in
genital tract-derived cell lines and primary endocervical
tissue. J Virol 83: 8596–8603.
Su Y, Zhang B & Su L (2013) CD4 detected from Lactobacillus
helps understand the interaction between Lactobacillus and
HIV. Microbiol Res 168: 273–277.
Sun J, Le GW, Shi YH & Su GW (2007) Factors involved in
binding of Lactobacillus plantarum Lp6 to rat small
intestinal mucus. Lett Appl Microbiol 44: 79–85.
Sun J, Zhou TT, Le GW & Shi YH (2010) Association of
Lactobacillus acidophilus with mice Peyer’s patches. Nutrition
26: 1008–1013.
Swingler S, Mann A, Jacque J et al. (1999) HIV-1 Nef
mediates lymphocyte chemotaxis and activation by infected
macrophages. Nat Med 5: 997–1003.
Taha TE, Hoover DR, Dallabetta GA, Kumwenda NI,
Mtimavalye LA, Yang LP, Liomba GN, Broadhead RL,
Chiphangwi JD & Miotti PG (1998) Bacterial vaginosis and
disturbances of vaginal flora: association with increased
acquisition of HIV. AIDS 12: 1699–1706.
Taha TE, Gray RH, Kumwenda NI, Hoover DR, Mtimavalye
LA, Liomba GN, Chiphangwi JD, Dallabetta GA & Miotti
PG (1999) HIV infection and disturbances of vaginal flora
during pregnancy. J Acquir Immune Defic Syndr Hum
Retrovirol 20: 52–59.
Thies FL, Konig W & Konig B (2007) Rapid characterization
of the normal and disturbed vaginal microbiota by
FEMS Microbiol Rev 37 (2013) 762–792
791
application of 16S rRNA gene terminal RFLP fingerprinting.
J Med Microbiol 56: 755–761.
Thomas S (1928) D€
oderlein’s Bacillus: Lactobacillus acidophilus.
J Infect Dis 43: 218–227.
Vangelista L, Secchi M, Liu X, Bachi A, Jia L, Xu Q & Lusso P
(2010) Engineering of Lactobacillus jensenii to secrete
RANTES and a CCR5 antagonist analogue as live HIV-1
blockers. Antimicrob Agents Chemother 54: 2994–3001.
Vasquez A, Jakobsson T, Ahrne S, Forsum U & Molin G
(2002) Vaginal lactobacillus flora of healthy Swedish
women. J Clin Microbiol 40: 2746–2749.
Verhoeven V, Renard N, Makar A, Van RP, Bogers JP, Lardon F,
Peeters M & Baay M (2013) Probiotics enhance the clearance
of human papillomavirus-related cervical lesions: a
prospective controlled pilot study. Eur J Cancer Prev 22: 46–51.
Vitali B, Pugliese C, Biagi E, Candela M, Turroni S, Bellen G,
Donders GG & Brigidi P (2007) Dynamics of vaginal
bacterial communities in women developing bacterial
vaginosis, candidiasis, or no infection, analyzed by
PCR-denaturing gradient gel electrophoresis and real-time
PCR. Appl Environ Microbiol 73: 5731–5741.
Wagner RD & Johnson SJ (2012) Probiotic lactobacillus and
estrogen effects on vaginal epithelial gene expression
responses to Candida albicans. J Biomed Sci 19: 58.
Wenner M (2009) A cultured response to HIV. Nat Med 15:
594–597.
Wertz J, Isaacs-Cosgrove N, Holzman C & Marsh TL (2008)
Temporal shifts in microbial communities in nonpregnant
African-American women with and without bacterial
vaginosis. Interdiscip Perspect Infect Dis 27: 181253.
WHO/FAO (2001) Evaluation of health and nutritional
properties of powder milk and live lactic acid bacteria. Food
and Agriculture Organization of the United Nations and
World Health Organization Expert Consultation Report.
Willey JM & van der Donk WA (2007) Lantibiotics: peptides
of diverse structure and function. Annu Rev Microbiol 61:
477–501.
Wink J, Kroppenstedt RM, Seibert G & Stackebrandt E (2003)
Actinomadura namibiensis sp. nov. Int J Syst Evol Microbiol
53: 721–724.
Wira CR & Rossoll RM (2003) Oestradiol regulation of
antigen presentation by uterine stromal cells: role of
transforming growth factor-beta production by epithelial
cells in mediating antigen-presenting cell function.
Immunology 109: 398–406.
Wira CR, Fahey JV, Sentman CL, Pioli PA & Shen L (2005)
Innate and adaptive immunity in female genital tract: cellular
responses and interactions. Immunol Rev 206: 306–335.
Witkin SS, Linhares IM & Giraldo P (2007) Bacterial flora of
the female genital tract: function and immune regulation.
Best Pract Res Clin Obstet Gynaecol 21: 347–354.
Wu Z, Chen Z & Phillips DM (2003) Human genital epithelial
cells capture cell-free human immunodeficiency virus type 1
and transmit the virus to CD4+ Cells: implications for
mechanisms of sexual transmission. J Infect Dis 188:
1473–1482.
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
792
Yamamoto T, Zhou X, Williams CJ, Hochwalt A & Forney LJ
(2009) Bacterial populations in the vaginas of healthy
adolescent women. J Pediatr Adolesc Gynecol 22: 11–18.
Yeaman GR, Guyre PM, Fanger MW, Collins JE, White HD,
Rathbun W, Orndorff KA, Gonzalez J, Stern JE & Wira CR
(1997) Unique CD8+ T cell-rich lymphoid aggregates in
human uterine endometrium. J Leukoc Biol 61: 427–435.
Yeaman GR, Collins JE, Fanger MW, Wira CR & Lydyard PM
(2001) CD8+ T cells in human uterine endometrial
lymphoid aggregates: evidence for accumulation of cells by
trafficking. Immunology 102: 434–440.
Zarate G & Nader-Macias ME (2006) Influence of probiotic
vaginal lactobacilli on in vitro adhesion of urogenital
ª 2013 Federation of European Microbiological Societies
Published by John Wiley & Sons Ltd. All rights reserved
M.I. Petrova et al.
pathogens to vaginal epithelial cells. Lett Appl Microbiol 43:
174–180.
Zhou X, Bent SJ, Schneider MG, Davis CC, Islam MR & Forney
LJ (2004) Characterization of vaginal microbial communities
in adult healthy women using cultivation-independent
methods. Microbiology 150: 2565–2573.
Zhou X, Brown CJ, Abdo Z, Davis CC, Hansmann MA, Joyce
P, Foster JA & Forney LJ (2007) Differences in the
composition of vaginal microbial communities found in
healthy Caucasian and black women. ISME J 1: 121–133.
FEMS Microbiol Rev 37 (2013) 762–792