Download Mucosal Vaccines: Where Do We Stand?

Send Orders for Reprints to [email protected]
Current Topics in Medicinal Chemistry, 2013, 13, 2609-2628
2609
Mucosal Vaccines: Where Do We Stand?
Jean-Pierre Kraehenbuhl1,* and Marian R. Neutra2
1
Health Sciences eTraining (HSeT) Foundation, 155 Chemin des Boveresses, 1066 Epalinges, Switzerland; 2GI Cell
Biology Research Laboratory, Children’s Hospital and Department of Pediatrics, Harvard Medical School, Boston,
Massachusetts 02115, USA
Abstract: Mucosal vaccinology is a relatively young but rapidly expanding discipline. At present the vast majority of
vaccines are administered by injection, including vaccines that protect against mucosally acquired pathogens such as influenza virus and human papilloma virus. However, mucosal immune responses are most efficiently induced by the administration of vaccines onto mucosal surfaces. The small number of currently licensed mucosal vaccines have reduced
the burden of disease and mortality caused by enteric pathogens including rotavirus, V. cholerae and S. typhi, or those that
spread to affect distal organs such as poliovirus. Expanding knowledge about the special features of the mucosal immune
system promises to accelerate development of mucosal vaccines that could contribute significantly to protection against
pathogens that colonize or invade via mucosal surfaces including HIV, Shigella, ETEC, Campylobacter jejuni, Helicobacter pylori and many others.
Keywords: Epithelia, mucosae, vaccines, pathogens.
1. INTRODUCTION
The majority of human pathogens that are responsible for
infectious diseases worldwide invade the host through mucosal surfaces of the digestive, respiratory or urogenital
tracts. Vaccines administered mucosally are most effective at
eliciting mucosal immune responses and enhancing immune
defenses at mucosal surfaces, and can provide more effective
protection against infection by mucosal pathogens. Most
licensed vaccines, however, are administered by injection
and do not efficiently elicit mucosal immunity.
Why Mucosal Vaccination ?
For protection against mucosally-acquired pathogens,
mucosal administration of vaccines offers several advantages
over injected vaccines: i/ Mucosal vaccination generally
triggers both systemic and mucosal immune responses
whereas the response to injected vaccines is largely systemic
ii/ Mucosal vaccination is non-invasive and needle-free. This
increases vaccine acceptance and safety, avoiding problems
of blood borne infections due to needle re-use, especially in
developing countries; iii/ Mucosal vaccination avoids adverse effects such as inflammation at the injection site ; iv/
Mucosal vaccines allow frequent boosting ; and v/ Preexisting systemic immunity generally does not interfere with
entry of vaccine into mucosal inductive sites, thus increasing
the rate of vaccine “take”, for example in infants with maternally acquired serum antibodies.
What are the Challenges?
Development, testing and approval of mucosal vaccines
for human use have been slowed by both technical and regu*Address correspondence to this author at the 155 Chemin des Boveresses,
1066 Epalinges, Switzerland; Tel:/Fax: +4121 692 5856;
E-mail: [email protected]
1873-5294/13 $58.00+.00
latory challenges. Mucosally-delivered vaccines, especially
those given orally, have to be designed to be stable in a
harsh mucosal milieu and they will inevitably be diluted in
mucosal secretions, caught in mucus gels and attacked by
enzymes. Mucosal vaccines must then cross a well-defended
epithelial barrier and be captured by mucosal antigenpresenting cells (APCs). Thus, unlike injected vaccines, the
actual dose of mucosally-administered vaccine that enters the
body and is “seen” by the immune system can only be estimated. Mucosal vaccine formulations and delivery systems
must also be designed to activate innate immune responses
in mucosal cells, much as invasive pathogens would do, and
this requires the use of live vectors or strong adjuvants.
Selection and approval of vaccine candidates requires
accurate measurement of immune responses, and this poses
additional challenges. Unlike serum antibodies and cells that
are readily sampled, secretory antibodies and mucosal effector cells are more difficult to capture and functionally test,
and the local variability of mucosal tissues and secretions
makes exact quantitation of total body-wide mucosal immune responses impossible. Mucosal immunization is most
efficient with live microorganisms, but the use of attenuated
pathogens or genetically modified live vectors raises regulatory concerns. For all of the above reasons, and because injected vaccines have long been the norm, mucosal vaccines
face skepticism from the scientific community and regulatory agencies.
Drawbacks of using Mucosal Vaccines
Although mucosal administration of foreign substances is
generally safer than injection, some mucosal vaccine candidates have been withdrawn from the market because of unexpected adverse reactions. For example, the rotavirus vaccine RotaShield® increased the risk for intussusception; one
© 2013 Bentham Science Publishers
2610 Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
or two cases of intussusception occurred among each 10,000
infants vaccinated. The Advisory Committee on Immunization Practices (ACIP) withdrew its recommendation to vaccinate infants with RotaShield® vaccine, and the manufacturer voluntarily withdrew RotaShield® from the market in
October 1999.
Nasalflu, an experimental inhaled influenza vaccine has
been linked with Bell's palsy, an illness that causes temporary facial paralysis. In this case, the adjuvant used (a modified toxin from E. coli) may have been transported retrograde to the brain via olfactory nerves. Switzerland's Berna
Biotech ended its development and a trial of some 11,000
patients after reviewing data collected from 4,000 of
them[1]. Experimental oral vaccines against enteric diseases
consisting of live attenuated bacteria have induced unacceptable gastrointestinal symptoms, apparently due to the host’s
innate immune responses to bacterial components. In general
the potential toxicity of vaccines administered mucosally has
proven difficult to predict because of our limited understanding of events within the mucosa.
2. SPECIAL FEATURES OF THE MUCOSAL IMMUNE SYSTEM
Mucosal vaccination has to take into account the fact that
the mucosal immune system differs from its systemic counterpart in several important respects. Mucosal tissues have
specialized antigen sampling strategies [2], and specialized
immune effector mechanisms such as secretory immunoglobulin A (sIgA) [3], that can prevent entry of pathogens
into the body. Effector cells induced by mucosal immunization have distinctive homing programs which allow them to
circulate and then return to appropriate mucosal sites [4]. In
contrast to the systemic immune system whose cells generally function in a sterile environment, the mucosal immune
system is constantly exposed to exogenous antigens. Mucosal immune responses are regulated by a variety of suppressive mechanisms [5], that maintain tolerance to environmental antigens such as those present in food and inhaled
air and that avoid dysregulated inflammation against innocuous antigens and commensal microorganisms inhabiting
mucosal surfaces. Mucosal tissues maintain a delicate balance between these suppressive mechanisms and defensive
immune responses through the unique functions of mucosal
dendritic cells (DCs) and macrophages, the activities of
which are largely conditioned by factors released by epithelial cells and lamina propria stromal cells. Understanding
how these special features translate into immunological
function is key to the rational design of prophylactic vaccines to protect against mucosal infections.
3. ANTIGEN AND VACCINE SAMPLING BY MUCOSAL TISSUES
Mucosal surfaces are vulnerable to infectious agents because they represent vast surface areas lining internal organs
that are open to the outside world. Thus it is not surprising
that the vast majority of initial antigen encounters occurs at
mucosal surfaces such as the gastrointestinal, respiratory and
urogenital tracts. As examples, HIV and polio virus gain
entry to the body via the gastrointestinal surface, influenza
and adenoviruses via the respiratory surface, and HIV and
Kraehenbuhl and Neutra
herpes simplex virus through the genital mucosae. All mucosal surfaces have an epithelial lining, the organization of
which is adapted to its location in the body, and an underlying loose connective tissue (lamina propria) located between
the epithelium and the submucosa. The area covered by mucosal surfaces in a human adult is about 400 m2, while the
area covered by the skin is only about 2 m2.
Antigen sampling strategies are adapted to the diverse
epithelial barriers that cover mucosal surfaces throughout the
body, but all involve collaboration with dendritic cells (DCs)
[6]. Antigen sampling strategies differ among different mucosal tissues depending on whether they are covered by a
stratified (oral cavity, esophagus, lower genital tract) or a
simple epithelium (airways, gastrointestinal tract, upper
genital tract).
3.1. Organ Specific Sampling
Continuous antigen sampling at specific mucosal sites is
of crucial importance for initiation of mucosal immune responses against pathogens as diverse as HIV, poliovirus and
Salmonella. Antigen sampling at these locations is also important for the induction and maintenance of immunological
tolerance to harmless foreign antigens that are best "tolerated", such as food antigens in the gut and air-borne particles
in the airways. Mucosal antigen sampling is complicated by
the fact that antigens are separated from inductive immune
sites (organized lymphoid tissue, either within the mucosa or
in draining lymph nodes) by epithelial barriers and thus must
be transported across the epithelium in order to be sampled
by cells of the immune system. Antigen-sampling strategies
at diverse mucosal sites are adapted to the cellular organization of the local epithelial barrier (Fig. 1).
3.2. Targeting Mucosal Sites
The induction of immune responses against vaccines that
are mucosally delivered requires the presence of organized
lymphoid tissue, either within the mucosa or in draining
lymph nodes [6].
Organized mucosa-associated lymphoid tissues (MALT)
are concentrated in areas where pathogens are most likely to
enter the body, for example, the palatine & lingual tonsils
and the adenoids in the oral and nasopharyx. They also are
abundant at sites of high microbial density such as the aggregates of follicles (Peyer’s patches) in the distal ileum, the
abundant isolated follicles in the appendix, colon and rectum
[3], and the isolated follicles in the bronchi of young children [8]. The follicular epithelium that covers lymphoid follicles contains M cells. M cells form intraepithelial pockets
into which lymphocytes and DCs migrate, and these specialized epithelial cells deliver samples of foreign material including vaccines, by vesicular transport from the intestinal
lumen directly into the pocket and to underlying DCs.
In the absence of organized MALT, antigens and vaccines may also be sampled on mucosal surfaces through another type of epithelial–dendritic cell (DC) collaboration.
Throughout epithelia whether stratified or simple, motile
DCs can migrate into the narrow spaces between epithelial
cells and even to the outer limit of the epithelium where they
can obtain samples of foreign material directly from the lu-
Mucosal Vaccines: Where Do We Stand?
Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
A
C
B
D
2611
Fig. (1). A and B. Mucosae covered by simple epithelium contain subepithelial organized lymphoid tissue with follicles, located at specific
sites. At such sites, specialized microfold (M) cells in the follicle-associated epithelium (FAE) sample antigens and deliver them across the
epithelial barrier directly to subepithelial DCs that then present antigen locally in adjacent mucosal T-cell areas. In the absence of organized
lymphoid tissues, DCs located under epithelia or within intraepithelial spaces may sample antigens or microorganisms that breach the barrier,
and can even extend their dendrites into the lumen to capture antigens. Upon antigen uptake, such DCs travel to the nearest draining lymph
node (LN) to present antigen to T cells. C and D. Mucosae covered by stratified epithelium are generally devoid of organized lymphoid tissues but are drained by regional lymph nodes. In such mucosae, antigens are sampled by DCs present within and beneath the epithelial layer.
Upon antigen uptake, these cells migrate to draining lymph nodes for antigen presentation to naive lymphocytes. The tonsils are an exception: their stratified epithelium covers many lymphoid follicles but the epithelium is thinned in spots to accommodate M cells.
minal compartment [9]. This might be most immunologically
significant at mucosal locations such as the female genital
tract, where there are no organized MALT and the epithelium lacks M cells. Intraepithelial and subepithelial DCs that
have captured vaccines could potentially interact with local
memory lymphocytes to stimulate memory responses [10] or
immune tolerance [11]. They also could exit the mucosa
through lymphatics to present antigens to naive T cells in
organized lymphoid tissues of draining lymph nodes [12].
Different DC subpopulations have distinct roles in determining the nature of immune responses in vivo, including
those in the Peyer’s patches [13]. Migration of DCs following immunization from the Peyer’s patches and intestinal
mucosa has been studied in some detail but it is still poorly
understood. Recently, it has been reported that transcutaneous immunization can result in mucosal immune responses,
and DCs from skin have been found to migrate to Peyer’s
patches [14].
3.3. Mimicking Infectious Agents
The design of efficient mucosal vaccines may take advantage of what is known about the pathogenesis of infectious microbes that are able to trigger protective mucosal
immune responses [12]. Efficient T and B cell responses
depend on the structure and localization of the antigen, its
dose, and how it is available, but also on the coordinated
action of adjuvants and antigen delivery systems: In general,
mucosal vaccines are most effective when they mimic successful mucosal pathogens. Ideally, mucosal vaccines should
be live mucosa-tropic vectors or microbe-sized particles that
adhere to mucosal surfaces (preferably to the FAE), are
transported by M cells, are avidly endocytosed by mucosal
DCs, and trigger innate immune responses. Some salient
observations are:
•
Particulate vaccines are taken up most efficiently by
follicle-associated M cells and underlying dendritic cells
when they are in the size range of viruses (30-200 nm
2612 Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
diameter) and can adhere to the epithelium [2, 15]. Bacteria-size particles (1m in diameter) are taken up less
efficiently, and larger particles are relatively poor delivery vehicles.
•
Co-administration of antigens and TLR ligands [16],
lactosyl cerebroside [17] or co-stimulatory receptor
ligands (CD 40-specific antibodies) [18] triggers enhanced CD8 T cell responses.
•
Bad timing of adjuvant delivery may impair crosspresentation [19]: antigen and adjuvant are best delivered together to the same DC.
•
Administration of antigens and adjuvants separately or
combined in a mixture or conjugated, also affects the
immune response. Co-localization in phagosomes may
play an important role in presentation by antigenpresenting cells [20].
•
How mucosal vaccination schedules and coordination of
the delivery of antigens and adjuvants affect mucosal responses and translate into effective mucosal vaccines
has been extensively studied in animal models but is not
yet firmly established for humans. In general, nonreplicating vaccines require multiple doses to achieve a
booster effect, while live vaccines can be effective as a
single dose, due to continued production of antigen over
time.
3.4. Choosing the Mucosal Immunization Route
As mentioned above, lymphocytes activated in organized
mucosa-associated lymphoid tissues express specific adhesion molecules and chemokines called “homing receptors”
that recognize endothelial counter-receptors in the mucosal
vasculature [21,22]. Some of these receptors and chemokine
partners are broadly expressed: for example, IgA-secreting B
cells induced in mucosal tissues express CCR10, the receptor
for CCL28, which is secreted by epithelial cells throughout
the small and large intestines, salivary glands, tonsils, respiratory tract and lactating mammary gland. This explains why
mucosal immunization at one site can result in secretion of
specific IgA antibodies throughout mucosal and glandular
tissues: the so-called "common mucosal immune system"
[23].
However, the regional nature of mucosal immune responses is now well documented in mice, nonhuman primates and humans. Receptor-mediated recognition systems
serve to focus the mucosal immune response at the site
where antigen or pathogen was initially encountered. For
example, IgA+ B cells generated in the intestine express the
“homing receptor” 4/ 7 integrin that interacts strongly with
MADCAM1, an "addressin" expressed by venules in the
small and large intestine (and lactating mammary gland) but
not in other mucosal tissues [21,22]. T cells activated in the
small intestine express both 4/ 7 and CCR9 which attracts
them to CCL25, a chemokine secreted by epithelia of the
small (but not large) intestine [24]
Local vaccination, infection or inflammation can upregulate local expression of chemokines, receptors and addressins
[25]. Thus, the choice of mucosal vaccination route requires
consideration of the nature of the vaccine and the expected
site of challenge.
Kraehenbuhl and Neutra
Mucosal immunization, especially via the intranasal and
sublingual routes, also can induce substantial levels of IgA
and IgG in serum [26] because mucosal DCs may migrate
and carry antigen to systemic inductive sites (lymph nodes
and spleen) [27,28] and a fraction of the B cells activated in
the mucosa or mucosa-draining lymph nodes express the
“peripheral” or systemic homing receptors, 4/ 1 and Lselectin [22]. By contrast, systemic immunization is usually
not effective for induction of mucosal responses because in
non-mucosal tissues, DCs that capture antigen are not exposed to retinoic acid and don’t induce expression of mucosal homing or chemokine receptors on lymphocytes [29].
An ideal vaccine should provide “front-line” protection at
the relevant mucosal surface and also “back-up” protection
against systemic spread. For example, to assure protection
against mucosal pathogens such as HIV that enter via mucosal surfaces and spread systemically, both mucosal effectors in the rectal or genital mucosa and systemic effectors
will be required. In this regard, nasal and sublingual vaccination routes are of great current interest [26]. Intra-nasal administration of vaccines in animals and humans has been
shown to induce IgA antibody responses in the salivary
glands, upper and lower respiratory tracts, male and female
genital tracts, and the small and large intestines as well as
CTLs in distant mucosal tissues including the female genital
tract [30]. Importantly, either nasal and sublingual immunization produced greater systemic antibody responses than
other mucosal immunization routes, sometimes at levels
comparable to those induced by systemic vaccination routes
[28]. On the other hand, levels of local mucosal protection
should be optimized. Rectal immunization is much more
effective than nasal or oral routes for inducing strong responses at the rectal mucosa [12]. Nasal immunization is
particularly effective for protection against respiratory
pathogens, but oral or vaginal vaccines are more effective for
protection of the upper gastrointestinal tract or female genital
tract, respectively. To activate both humoral and cellmediated immune effector mechanisms distributed both mucosally and systemically, some vaccine strategies currently
under investigation are prime-boost combinations involving
both mucosal and systemic delivery.
While the vast majority of pathogens invade the host
through mucosal surfaces, some remain localized to mucosal
tissues, while others spread systemically. This may dictate
which route of immunization should be chosen as described
below.
Mucosal Entry of Systemic Pathogens
Some pathogens, i.e. Hepatitis B, Hepatitis A, Measles,
Polio, Mumps viruses or group B streptococci and Hemophilus influenzae B, enter the host via genital, respiratory or
digestive mucosal tissues and infect distant internal organs.
Non mucosal vaccine delivery provides protection against
these systemic pathogens. The mechanism of protection is
probably mediated by systemic IgG antibodies or T cells that
inhibit viral replication. Whether mucosal IgG antibodies
that are transported across the mucosal tissues mediate protection is yet not established.
Mucosal Pathogens and Non Mucosal Vaccine Delivery
Non mucosal vaccine delivery, whether subcutaneous or
intramuscular, has been shown to mediate protection against
Mucosal Vaccines: Where Do We Stand?
certain mucosal pathogens, (i.e. Streptococcus pneumoniae,
human papilloma virus, influenza virus, Hemophilus influenzae B, Salmonella typhi) that infect mucosal tissues. The
mechanism of protection for such pathogens is not fully understood. It is believed that systemic antibody-mediated inhibition of replication and spread is involved, although one
cannot rule out a role for IgG antibodies that are transported
into secretions by mucosal epithelia.
Pathogens for which both Mucosal and Non Mucosal Vaccines are Effective
Mucosal and non mucosal vaccines exist for at least three
pathogens. For all three vaccines the correlates of protection
still have to be identified, although it is likely that protection
is mediated by neutralizing and/or non-neutralizing antibodies.
Polio
The Oral Polio Vaccine (OPV) is a live attenuated virus
that generates both systemic IgG antibodies and intestinal
sIgA antibodies. The vaccine is easy to administer and it
generates herd immunity, probably due to the shedding of
inactivated virus in the stools. In developing countries, the
oral polio vaccine is less immunogenic than the injected vaccine, which consists of inactivated polio virus.
Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
2613
the subepithelial lamina propria. Whether vaccines mucosally administered in humans inhibit mucosal replication
of viral (influenza, rotavirus, polio) and bacterial (pertussis,
typhoid) pathogens through locally secreted IgA or via transcytosed IgG present on mucosal surfaces is not yet known
and remains to be established [35]. Studies on IgA-deficient
mice and humans show that serum IgG can indeed be sufficient to provide protection against infection in mucosal tissues. In most individuals with IgA deficiency, there is no
increased susceptibility to infections. Probably the major role
of sIgA is to control the gut flora and prevent entry of potentially harmful commensals [36], but the presence of sIgA has
also been correlated with protection against pathogens such
as Vibrio cholerae and Salmonella species. Serum IgG can
also be actively transported through human epithelial cells in
the gut [37,38], the airways [39] and the genital tract [40] via
the neonatal Fc IgG receptor (FcRn). FcRn-mediated transport is a mechanism by which IgG can act locally on mucosal surfaces and play a role in immune surveillance and in
host defense against mucosally transmitted pathogens.
Table 1.
Effect of Infection Pressure on Typhoid Vaccine
Efficacy [32].
Influenza
The intranasal live attenuated vaccine generates herd
immunity and its efficacy is marginally higher when compared to the injected vaccine, which consists of a cocktail of
viral surface antigens [31]
S. typhi. The oral Ty21 and the Vi polysaccharide vaccine are administered mucosally and systemically, respectively. The efficacy of the Ty21a vaccine is dependent on the
disease incidence (Table 1).
4. CORRELATES OF PROTECTION
The identification of correlates of protection against mucosal pathogens is crucial for the rational design of effective
mucosal vaccines and adjuvants [5,15,33] but has proven
very difficult to achieve. The lack of reliable and sensitive
techniques for measuring humoral and cellular responses in
mucosal tissues contributes to the difficulty to identify correlates of mucosal protection and explains in part why few
mucosal vaccines have been developed so far.
4.2. Role of T Cells
4.1. Role of Secretory IgA and IgG Antibodies
Cellular immunity at mucosal surfaces is critical both for
regulating the differentiation and activities of B and T effector cells and providing direct effector responses. The role of
T cells as the immunological correlate of protection following vaccination has been documented for a few vaccines.
Secretory IgA functions mainly as a preventive antibody,
but its special functions in the mucosal milieu are not always
reflected in classical in vitro neutralizing antibody assays. It
is a poor activator of the complement system due to the lack
of C1q binding site. IgA’s main role is to function on mucosal surfaces, preventing uptake of commensals by “immune exclusion”, a mechanism that prevents inflammation
[34]. Secretory IgAs can mediate protection by i/ neutralization of pathogens in the intestinal lumen, ii/ neutralization
within intestinal epithelial cells as antibodies are transported
by the polymeric immunoglobulin receptor through vesicular
transport across the epithelial cells, and iii/ neutralization in
Mucosal (intranasal) administration of the live attenuated
vaccine FluMist triggers cytotoxic CD8+ T cells that are
thought to contribute significantly to cross-reactive protection against variant influenza strains [41]. The contribution
of systemic and pulmonary T cell effectors to vaccineinduced protection from H5N1 influenza virus infection in
mice demonstrates that airway influenza-specific lymphocytes are the main contributors to clearance of challenge
virus from the lungs [42], The contribution of serum influenza-specific antibodies in serum and splenic CD8+ T cells is
negligible, and the contribution of airway secretory IgA is
not established.
2614 Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
Kraehenbuhl and Neutra
Fig. (2). Under appropriate stimulation, dendritic cells (DC) produce interleukin (IL)-1 and IL-6 that trigger Th17 differentiation in humans.
IL-6 signaling is STAT3-dependent. Th17 cells produce IL-21, which contributes to Th17 differentiation. DCs also produce IL-23 that reinforces Th17 T cell development. Signaling by both IL-21 and IL-23 is in part mediated by STAT3. Th17 cell-derived cytokines play an important role in the protection of the host against various bacteria and fungi, particularly at mucosal surfaces. Indeed, Th17 cells are constitutively present in the human and mouse intestinal mucosa. Th17 cells coordinate immune defense against pathogens through their ability to i/
enhance the recruitment and facilitate the activation of neutrophils, and ii/ stimulate the production of defensins by epithelial cells.
Fig. (3). The live polio vaccines now in widespread use were developed by Albert Sabin in 1961. The vaccines were developed from circulating strains that had been adapted to laboratory conditions. The viruses were grown using sub-optimal conditions and different host cells, and
the resulting progeny viruses were tested for virulence, usually using monkeys. (Adapted from Minor PD, 2004 [49]).
Mucosal Vaccines: Where Do We Stand?
Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
2615
4.3. Role of Th17 T Cells
5.1. Live-Attenuated or Inactivated Vaccines
The role of Th17 cells and IL-17 secretion during infection (Fig. 2) provides new insight into host defense at mucosal surfaces and vaccine-induced immunity [43]. Peripherally-induced regulatory T cells and Th17 effector cells arise
in a mutually exclusive fashion, Thus CX3CR1+ dendritic
cells (DC) promote Th1/Th17 cell differentiation [44],
whereas CD103+ DCs induce T regulatory cell differentiation in mouse colonic lamina propria.
Many vaccines consist of intact microbes (virus or bacteria) that are either live-attenuated or inactivated (killed).
They are administered for prevention, amelioration, or treatment of infectious diseases.
IL-17 has been shown to be required for some vaccineinduced protection, including S. pneumoniae, M. tuberculosis, and influenza [45]. IL-17 alone or in combination with B
cell-activating factor (BAFF) controls the survival and proliferation of human B cells and their differentiation into IgAsecreting cells [46] and IL-17 triggers sIgA secretion in the
airway mucosa following up-regulation of the polymeric
immunoglobulin receptor and polymeric IgA transcytosis
[47].
5. DESIGN OF MUCOSAL VACCINES
Mucosal immune responses are most efficiently triggered
when the vaccine is delivered directly onto mucosal tissues.
Mucosal immunization, however, is difficult to achieve for
the reasons cited.. In order to enhance efficacy, mucosal vaccines should be designed to mimic physicochemical properties of opportunistic pathogens, specifically charge and size
[12]. To achieve this, the following strategies have been proposed [14]: i/ overcoming physiological barriers at mucosal
surfaces; ii/ targeting of mucosal antigen presenting cells for
appropriate processing of antigens that lead to specific T and
B cell activation ; iii/ controlling the kinetics and location of
antigen and adjuvant presentation in order to promote longlived, protective adaptive immune memory responses.
In order to cope with the increased number of vaccinations that children around the world receive, new needle-free
methods of immunization are being developed [48] such as
liquid jet injectors, topical or transdermal application to the
skin, sublingual application, oral pills, and nasal sprays.
Live attenuated vaccines contain weakened forms of the
organism that causes the disease. There are many examples
of highly successful vaccines that have been developed using
live attenuated viruses, .i.e. measles, mumps, rubella,
chicken pox, oral polio (Sabin vaccine), yellow fever, nasalspray flu vaccine (including the seasonal flu nasal spray and
the 2009 H1N1 flu nasal spray), rabies (now available in two
different attenuated forms, one for use in humans, and one
for animal usage), or bacteria, i.e. BCG and typhoid vaccine.
Several live-attenuated vaccines administered via the mucosal (oral) route are licensed for enteric infections, including cholera, typhoid, and rotavirus.
Inactivated microbial vaccines (or killed vaccine) consist of virus particles or bacteria which are grown in culture
and then killed using a method such as heat or formaldehyde.
These include: viral, i.e. polio vaccine (Salk vaccine) & influenza vaccine, and bacterial vaccines for typhoid fever (Vi
capsular polysaccharide (Typhim Vi®, Sanofi Pasteur; Typherix®, GSK) and cholera (Dukoral R, Crucell, Netherlands).
Vaccines consisting of live attenuated or intact inactivated microorganisms are the only vaccines approved for
mucosal delivery for which protection efficacy has been correlated with measurements of effector mucosal immune responses [4]. The success of live-attenuated and inactivated
vaccines is thought to result from the fact that they present
multiple immunogens combined with adjuvant activity that
triggers strong antibody and cellular responses as well as
long-term memory.
Attenuation, however, presents the risk of reversion
which compromises safety, as documented for the oral polio
vaccine (e.g., Sabin 3) [50]. For this reason inactivation of
viruses and bacteria has been the preferred approach, since
Fig. (4). Virosomes are virus-like particles, consisting of reconstituted influenza virus envelopes, which do not contain the genetic material
of the native virus.
2616 Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
inactivated vaccines are much safer. Inactivation, however,
may reduce immunogenicity and lose adjuvanticity, with a
rapid waning of protective immunity.
5.2. Subunit and Conjugate Vaccines
Subunit Vaccines
Pathogen-specific proteins or protein conjugated polysaccharides represent the second largest category of licensed
prophylactic vaccines. The vaccines, i.e. diphtheria and tetanus toxoid vaccines, however, are administered primarily by
subcutaneous or intramuscular routes and not mucosally. The
cholera vaccine is the only licensed mucosally administered
vaccine that contains protein subunits: The cholera vaccine
(Dukoral) consists of the cholera toxin B subunit along with
inactivated bacteria (Vibrio cholerae O1 strain). Oral, but not
parenteral, immunization protects against V. cholera colonization and toxin binding, induces protective mucosal IgA
antibodies against the bacterium and its toxin, and provides
long-lasting intestinal immunological memory [51].
Conjugate Vaccines
No licensed conjugate vaccines for mucosal administration are presently available. Several novel approaches tested
in experimental animals highlight the potential of mucosal
vaccine development. For instance:
Intranasal administration of soluble influenza hemagglutinin protein, linked to a targeting peptide specific for
Claudin-4 on M cells, induced both specific serum IgG
and mucosal sIgA antibodies [52].
a Herpes simplex virus 2 subunit vaccine (HSV-2 envelope glycoprotein fused to the IgG Fc) given intranasally
induced mucosal B and T cell responses and conferred
protection from intravaginal challenge with HSV-2 [53].
Repeated intravaginal immunization of recombinant
HIV gp140 protein elicited systemic and mucosal neutralizing IgG antibodies [54].
5.3. Virus-Like Particles (VLP) and Virosomes
Virus-like particles and virosomes constitute a category
of subunit vaccines in which immunogens are derived from
viral components that have the capacity to self-assemble into
higher-order three-dimensional structures that maintain the
conformational structure of virus immunogens [55].
Virus-like particles (VLP) resemble viruses, but are noninfectious because they do not contain any viral genetic material. The expression of viral structural proteins, such as
envelope or capsid, can result in the self-assembly of VLPs.
The hepatitis B vaccine, the first VLP to become a commercially viable vaccine. is produced in yeast by expression of
the hepatitis B surface antigen (HBsAg) that self-assembles
into particles [56]. The human papillomavirus (HPV) vaccine is the only other VLP since to be licensed for human
use. The quadrivalent HPV vaccine (Gardasil, from Merck &
Co.) is composed of the L1 capsid proteins of HPV-6, -11, 16, and -18 types expressed in yeast [57]. The mechanism of
protection mediated by the HPV vaccines is not fully understood, and no immune correlates have been linked definitely
to protection. Protection is believed to be due to serum neu-
Kraehenbuhl and Neutra
tralizing IgG antibodies that are transported across the cervical epithelium where they bind HPV and prevent infection.
The licensed VLP vaccines require co-administration with
adjuvants to be efficient. In the light of a pandemic threat,
influenza VLPs have been recently developed as a new generation of non-egg based, cell culture-derived vaccine candidates against influenza infection [58,59].
A nasal vaccine candidate (NASVAC), comprising hepatitis B virus (HBV) surface (HBsAg) and core antigens
(HBcAg), was tested in a phase I trial in healthy adults and
shown to be safe, well tolerated and immunogenic. This was
the first demonstration of safety and immunogenicity for a
nasal vaccine candidate comprising HBV antigens [60].
Virosomes are vaccine delivery systems (Fig. 4) consisting of mono- or bi-layer phospholipid vesicles incorporating
virus derived proteins. Virosome fusion with target cells is
mediated by functional viral envelope glycoproteins such as
influenza virus hemagglutinin (HA) and neuraminidase
(NA). Lipids, antigens, adjuvants, or other materials can be
added to the dissolved viral membrane components or can be
included in the virosome during reconstitution. The vaccines
Inflexal® for influenza and Epaxal® for Hepatitis A are approved products on the market, both using virosomes from
influenza as a delivery platform.
A Phase 1 evaluation of intranasal virosomal influenza
vaccine with and without Escherichia coli heat-labile toxin
(HLT) was conducted in adult volunteers. Two nasal spray
vaccinations with HLT-adjuvanted virosomal influenza vaccine induced a humoral immune response comparable to that
induced by a single parenteral vaccination. A significantly
higher induction of influenza virus-specific immunoglobulin
A was noted in the saliva after two nasal applications. The
immune response after a single spray vaccination was significantly lower. HLT as a mucosal adjuvant was necessary
to obtain a humoral immune response comparable to that
with parenteral vaccination. In this study, all vaccines were
well tolerated. Later, however, the formulation with HLT
was withdrawn because of toxicity of HTL, but virosomes
without HTL remained immunogenic [61].
5.4. Polymer-Based Carrier Systems
Another approach to improve the effectiveness of mucosal vaccines is based on nanotechnologies [62]. These new
carrier systems are expected to overcome oral, nasal, intestinal, rectal and genital mucosal barriers through i/ encapsulation of vaccine components to protect them from the harsh
mucosal environment and target them to the mucosal immune system; and ii/ incorporation of mucosal adjuvants
which enhance immune responses.
These new carriers have been made from natural or synthetic polymers, lipids, proteins, or inorganic material, to
form particles and capsules of controlled size and structure.
Nanocapsules [62,63] (Table 2) constitute a slow release
delivery system in which the vaccine can be enclosed within
an aqueous (water-in-oil) or oil-based (oil-in-watercore) surrounded by a solid or semisolid material shell. They vary in
size from 20 to 200 nm. Three major nanocapsules have
been used for mucosal vaccination: i/ Water-in-oil emulsion,
ii/ Oil-in-water emulsion, and iii/ liposomes [63].
Mucosal Vaccines: Where Do We Stand?
Table 2.
2617
Features of Nanocapsules.
Nanoparticles [68, 69] are solid particles in which the
vaccine antigens and adjuvants are dispersed within the
polymer matrix or adsorbed to the particle surface (Table 3).
Specific types of nanoparticles include micelles, dendrimers,
and solid matrix nanoparticles composed of biodegradable or
bioeliminable synthetic polymers, e.g., polyesters, polyanhydrides, poly(amino acids), natural polymers (chitosan, alginate, albumin) and copolymers [70].
Recently, a large intestine–targeted oral delivery system
with pH-dependent microparticles containing vaccine
nanoparticles was shown to induce colorectal immune responses in mice at levels comparable to what is obtained
with colorectal vaccination using the same vaccine delivery
system [71]. This new vaccine delivery system also protected mice against rectal and vaginal viral challenge.
Whether this system will protect nonhuman primates and
humans remains to be established.
Table 3.
Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
Features of Nanoparticles.
Adapted from Chadwick et al [69].
6. MUCOSAL ADJUVANTS
Mucosal vaccine formulations have to overcome the
normal mechanisms operating in mucosal tissues that suppress unwanted immune and inflammatory responses to digested food antigens and harmless commensal bacteria, a
phenomenon called "mucosal tolerance". This is particularly
true for subunit vaccines. Induction of tolerance can be overcome by adding adjuvants to the vaccine formulation that
provide "danger" signals that activate innate responses in
mucosal epithelial and immune cells (Fig. 5).
Adjuvants can be classified into two broad categories:
i
Immunostimulatory molecules derived from natural
immunostimulants including modified bacterial enterotoxins, Toll-like receptor (TLR) ligands (such as CpG
oligonucleotide), and cytokines.
2618 Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
Kraehenbuhl and Neutra
Fig. (5). Mucosal adjuvants
Mucosal vaccine efficiency can be enhanced by mucosal adjuvants. They can act on epithelial cells or on innate immune cells, .i.e. dendritic
cells, macrophages, present beneath the epithelium. They provide signals that direct and stimulate the immune responses to co-administered
soluble antigen. Adapted from Lawson et al. [73].
ii Delivery vehicles with other forms of immunostimulatory activity including saponin-based systems (described
below), Montanide ISA-51 & 720, MP59, Adjuvant System 3 used with flu vaccine Pandermix, and Adjuvant
System 4 approved for use with injectable vaccines for
hepatitis B and HPV.
Adjuvants may possess both immunostimulating and
antigen delivery properties. There are many classes of adjuvants [72] but only few are effective at promoting mucosal
immune responses [73].
6.1. Bacterial Enterotoxins
The bacterially derived ADP-ribosylating enterotoxins,
i.e. cholera toxin (CT) [74], heat-labile enterotoxin from E.
coli (LT) [75], and their mutants or subunits are the bestcharacterized mucosal adjuvants. These enterotoxins induce
antigen-specific IgA antibodies and long-lasting memory to
co-administered antigens when administered mucosally or
transcutaneously. However, safety issues prevent their use in
mucosal vaccination in humans.
CT, LT, and some LT mutants stimulate antigen capture
by enhancing DC migration from the subepithelial dome to
follicular-associated epithelium in mucosa-associated lymphoid tissue (MALT). After oral administration [76], CT and
LT induce Th2 responses and mixed Th1/Th2 responses,
respectively, These adjuvants also trigger Th17 responses
likely to play a role in vaccine-induced protection [77].
6.2 Toll-Like Receptor (TLR) Ligands
TLR ligands activate TLRs, triggering intracellular signaling pathways that lead to cytokine secretion and immune
cell activation [78]. This innate immune response in turn
promotes an adaptive immune response. Thus, TLR ligands
are used to enhance the induction of vaccine-specific responses. In mucosal tissues the following cell types express
TLRs and respond to TLR ligands: i/ epithelial cells, ii/ dendritic cells (DC) located in the subepithelial lamina propria
and sometimes extending processes between epithelial cells,
and iii/ B lymphocytes. TLR-stimulation of these cells induces the following:
•
On B cells, TLR signaling enhances thymusindependent IgA class switching through the activation
of BAFF and APRIL, two members of the TNF family
[79].
•
TLR2 ligands stimulate IgA production by B cells and
gut homing receptor expression [80].
•
In gut enterocytes, flagellin, the ligand of TLR5, rapidly
induces expression of the chemokine CCL20 which re-
Mucosal Vaccines: Where Do We Stand?
Table 4.
2619
Mucosal Adjuvants and Delivery Technologies.
cruits DCs to the lamina propria [81]. Flagellin also
stimulates the mucosal production of IL-17 and IL-22
and the subsequent expression of target genes [82].
•
Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
In DCs, TLR ligands induce production of cytokines and
chemokines that guide the responses of many neighboring cells, resulting in adaptive immunity and/or inflammation.
6.3. Delivery Vehicles with Saponin-Based Immunostimulatory Activity
Several lipid-based or lipid-containing mucosal adjuvants
are currently being evaluated for mucosal vaccination
[83.84]. Their toxicity, stability and manufacturing methods
as well as efficacy remains to be established.
Quil A is a complex mixture of chemically related triterpenoid saponins extracted from the bark of the Chilean
tree Quillaja saponaria Molina. The adjuvant activity of
Quil A is mediated through an aldehyde group on the saponins' triterpene aglycone forming a Schiff base with amino
groups on costimulatory T cell receptors [84]. Quil A may
potentially be able to replace CD80 as a costimulatory signal
and preferentially induce Th1 type immune responses.
QS-21 is a highly purified triterpene glycoside saponin
from Quillaja saponaria that contains two functional groups
likely to be involved in the adjuvant mechanism of action
through charge or Schiff base interaction with a cellular target.
ISCOM (Immune stimulating complex) was described in
1982 by Morein and colleagues [85]. The Iscom-matrix
technology is based on Quillaja saponins and the complex
formed when saponin fractions are mixed with cholesterol
and phospholipids at defined ratios resulting in the assembly
of homogeneous cage-like structures ~ 40 nm in diameter.
When the antigen is incorporated in the structure, the resulting particle is referred to as an ISCOM. The integrity of antigens co-administered with the ISCOM-matrix adjuvant is
thought to be maintained but incorporation of antigen into
ISCOMS requires a denaturation step. Saponins are known
to interact irreversibly with cholesterol in cell membranes
and this can be associated with adverse reactions at the immunization site. However, this toxicity has been considera-
bly reduced in current generation ISCOM-matrix formulations.
7. MEASURING MUCOSAL IMMUNE RESPONSES.
The assessment of mucosal immune responses to mucosal vaccine candidates remains difficult despite current
efforts to develop, standardize and validate methods for
measuring mucosal vaccine-specific antibodies or T cells
that are suitable for use in large-scale field trials. The major
problem is the sampling of mucosal secretions and tissues
since respiratory, gut or genital mucosal surfaces are not
readily accessible. Mucosal sampling requires cumbersome
and invasive procedures. Key aspects are described in more
detail below:
8.1. Sampling Secretions and Tissues
Mucosal sampling involves collecting secretions and
mucosal tissues from i/ the airways including nasal secretions, bronchoalveolar lavage and bronchial biopsies; ii/ the
digestive tract including saliva collection, small intestinal
biopsies, rectal secretions by sponge and cells by cytobrush,
rectal and sigmoidal biopsies; iii/ the genital tract including
semen and vaginal and cervical secretions by lavage or
sponge and cells by cytobrush.
Cytobrushes usually yield cell numbers (mean= 100,000
cells for rectal or cervical sampling) that allow phenotyping,
but are too low for functional assays.
Sponge collection is usually sufficient to capture enough
undiluted secretion to detect and directly measure luminal
antigen-specific antibodies.
Mucosal lavage collects diluted secretions, so that specific antibody concentrations must be expressed relative to
total immunoglobulin levels.
8.2. Assays Currently used in Human Vaccine Trials
Most vaccine trials rely on determination of serum antibody levels, which usually do not accurately reflect mucosal
secretory antibody levels [86]. Measurements of vaccine
specific antibody secreting cells (ASCs) in the bloodstream
that bear mucosal homing markers and thus are transiently
migrating in the circulation on their way to the mucosa are
2620 Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
Table 5.
Kraehenbuhl and Neutra
Licensed Mucosal Vaccines.
known to better reflect local immune responses [87,88].
Standard operating procedures (SOP) have been developed
by several laboratories including those of the HIV Vaccine
Trial Network to outline the procedures that site staff follow
to collect and process mucosal secretions samples for antibody and T cell testing.
8.3. Antibody Assays
Three assays are usually used to evaluate vaccine antibody responses: i/ ELISA, ii/ ELISPOT, and iii/ Antibodies
in Lymphocyte Supernatant (ALS) assay.
ELISA stands for Enzyme-Linked Immunosorbent Assay
[89]. ELISA is a sensitive method used in immunology to
detect and/or quantitate the presence of a protein (e.g. antigen, antibody, cytokine) in a test solution such as body fluids
(serum, plasma, urine) or cell culture supernatants. This
method utilizes enzyme-linked antibodies hence the name of
the assay. The two most commonly used versions of ELISA
are the indirect ELISA which utilizes an unique labeled antibody and the sandwich ELISA which utilizes an unlabeled
primary antibody in conjunction with a labeled secondary
antibody.
ELISPOT. The Enzyme Linked Immunosorbent SPOT
assay [90], initially designed to enumerate B cells secreting
antigen-specific antibodies, has been adapted to enumerate
cytokine-producing cells at the single cell level [91]. Each
spot that develops in the assay represents a single reactive
cell. Thus, the ELISPOT assay provides both qualitative
(type of immune protein) and quantitative (number of responding cells) information. The ELISPOT assay has been
adapted to measure serum IgA secreting cells which serve as
surrogate markers for mucosal antibody responses. ELISPOT tests traditionally used to evaluate ASC responses are
not adapted for large-scale vaccine trials because i/ they are
time-consuming; ii/ require relatively large volumes of
blood; iii/ cannot be repeated using the same cell samples;
iv/ do not properly reflect mucosal booster responses.
ALS assay. A simplified ALS assay, in which cells are
incubated in the absence of antigen and stored for later
analysis of antibody content by ELISA, makes it possible to
analyze pre- and post-vaccination samples in the same test.
The ALS assay has been used to monitor antibody responses
to an oral cholera vaccine, an oral ETEC candidate vaccine,
and a novel typhoid vaccine [88].
8.4. Mucosal T Cell Assays
To address the frequency of antigen-specific CD8+ and
CD4+ T-cells in mucosal tissues and to determine their cytokine production patterns, several assays are available. The
limiting factor, however, is the sampling of mucosal tissues
and the collection of enough lymphocytes to perform quantitative assays. To address this limitation, polyclonal T cell
amplification procedures have been developed [92].
The most used assays are i/ ELISPOT assays [93],
ii/intracellular cellular cytokine staining assays, and iii/
MHC class I tetramer staining assay.
9. LICENSED MUCOSAL VACCINES
•
The eight vaccines that are currently approved and administered mucosally to humans target three of the main
enteric pathogens (i.e. Vibrio cholerae, Salmonella typhi, and rotavirus), the respiratory pathogen, influenza
virus, and the mucosally-transmitted neuropathogen poliovirus.
•
Vaccines have been developed but are not yet approved,
and are thus still lacking against other important causes
of enteric diseases, i.e. enterotoxigenic Escherichia coli
(ETEC) and Shigella.
•
The main features of the licensed vaccines [94,95] are
summarized in Table 5.
10. MUCOSAL VACCINES IN THE PIPELINE
Several mucosal vaccines to protect against mucosally
acquired pathogens are currently under development and a
few have entered clinical trials. These include: Shigella vaccines, Enterotoxicogenic E. coli vaccines, HIV vaccines, and
Mycobacterium tuberculosis vaccines( [96,97].
10.1. Shigella Vaccines
Shigellae, the cause of bacterial dysentery, are Gramnegative, nonmotile, facultatively anaerobic, non-spore-
Mucosal Vaccines: Where Do We Stand?
forming rods. About 165 million cases of shigellosis are reported each year, with a death toll of ~ 1.1 million people. It
is an antigenically diverse pathogen with four species (or
groups) and 50 serotypes and subserotypes. A Shigella vaccine should be broad enough to protect against multiple serotypes, including S. dysenteriae 1, all 14 S. flexneri types and
S. sonnei, which are the most important serotypes worldwide
[98].
Immune responses against Shigella infection. Natural
Shigella infection protects (~75%) protection against Shigellosis upon subsequent exposure to the homologous Shigella
serotype and in some instances against heterologous serotypes. Antibodies (serum or mucosal) directed against the
LPS O-antigen appear to play a major role in protection [99].
Orally administered Shigella-specific immunoglobulins prevent shigellosis, indicating that the first line of defense occurs at the gut surface [100]. In healthy adult volunteers, gutderived O-specific IgA ASCs circulating in the bloodstream
after oral vaccination reflects intestinal priming that correlates with vaccine efficacy [98]. The immune response to
Shigella is a predominantly a Th1-type response, indicating
that cell-mediated immunity may also contribute to the defense against this intracellular pathogen [101].
A detailed description of the Shigella vaccines currently
in development is provided in a review by Levine and colleagues [98]. The main features of vaccines currently in development are summarized in Table 6.
10.2. ETEC Vaccines
Enterotoxigenic Escherichia coli (ETEC) is the most
common cause of bacterial diarrhea in children in Africa,
Asia and Latin America and in travelers to these regions.
Despite this, no effective vaccine for ETEC is available
[112]. ETEC causes disease by colonizing the small intestine
with colonization factors including fimbriae, and production
of heat-labile and/or heat-stable enterotoxins.
Antibodies against heat-labile enterotoxin (LT) and the
colonization factors (CF) that act synergistically have been
shown to be protective in rabbit models [113], and local immunity in the gut seems to be of prime importance for protection.
Several inactivated and live candidate ETEC vaccines
consisting of toxin antigens, alone or together with colonization factors, have been evaluated in clinical trials (see Table
7).
10.3. HIV Vaccines
HIV might be considered a mucosal pathogen, because
transmission occurs mainly through exposure of genital and
rectal surfaces to HIV and HIV-infected cells [114]. Therefore, an ideal HIV-1 vaccine candidate should induce protective responses in these mucosal tissues and at their surfaces
[114].
Systemic delivery of HIV-1 vaccines has been shown in
some studies to induce HIV-specific immune responses at
the mucosa [115], but in the vast majority of HIV vaccine
studies including human trials, mucosal immune responses
were not measured. One report indicates that systemic deliv-
Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
2621
ery of HIV-1 vaccines can compromise the quality or avidity
of the HIV-specific immune responses at mucosal sites
[116].
Most of the vaccine formulations in preclinical trials in
nonhuman primates and in humans were designed to induce
antiviral T cell mediated responses rather than antibodies,
and of these only a few have been evaluated specifically for
their ability to generate CTLs in mucosal tissues. These studies have been extensively reviewed [117] and are summarized in Table 8.
10.4. Mucosal Vaccines for Tuberculosis
Mycobacterium tuberculosis is clearly a mucosallytransmitted pathogen but the only licensed TB vaccine, the
Bacille Calmette-Guérin (BCG) vaccine, is administered by
intradermal injection and is efficient in children but not in
adults. In addition, BCG can cause disseminated mycobacterial disease in immuno-compromised individuals including
HIV-infected children [127]. Thus, a safe mucosal vaccine to
prevent M. tuberculosis infections is urgently needed. .
Live Attenuated M. tuberculosis Vaccines
A highly attenuated M. tuberculosis strain (aMtb) orally
administered at birth to newborn rhesus macaques (Macaca
mulatta) induced mucosal and systemic immune responses
and protected against TB infection. All vaccinated animals
developed M. tuberculosis -specific plasma IgG antibodies to
the PSTS1 antigen measured after oral or intradermal vaccination. The vaccine was effective in inducing TB-specific
CD4+ and CD8+T cell immune responses systemically and in
mucosal tissues.
The recombinant aMtb strain mc26435, harboring attenuations in genes critical for replication (panCD and
leuCD) and immune evasion (secA2), was safe after oral or
intradermal administration in SIV-uninfected and SIVinfected infant macaques [128]. Safety was defined as absence of clinical symptoms, lack of histopathological
changes indicative of M. tuberculosis infection, and lack of
mycobacterial dissemination. These data represent an important step in the development of novel TB vaccines and suggest that an oral recombinant aMtb vaccine could be a safe
alternative to BCG for the pediatric population as a whole,
and more importantly for the high risk group of HIVinfected infants.
Nanoparticle-Based Vaccine
A synthetic vaccine delivery platform with Pluronicstabilized polypropylene sulfide nanoparticles (NPs), which
target antigen-presenting cells in lymphoid tissues due to
their small size (~30 nm) and which activate the complement
cascade by their surface chemistry, has been developed by
Ballester and coworkers [129]. The tuberculosis antigen
Ag85B was conjugated to the NPs (NP-Ag85B) and the efficacy of the conjugate in eliciting relevant immune responses
was assessed in mice after intradermal or pulmonary administration.
Pulmonary administration of NP-Ag85B with the adjuvant CpG induced higher levels of antigen-specific polyfunctional Th1 responses in the spleen, the lung and lungdraining lymph nodes as compared to pulmonary
2622 Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
Table 6.
Shigella Vaccines Under Development.
Table 7.
ETEC Vaccines Under Development.
Kraehenbuhl and Neutra
Mucosal Vaccines: Where Do We Stand?
Table 8.
Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
Mucosal and Systemic Immune Responses to HIV Vaccines Administered to non Human Primates and Humans.
administration of soluble Ag85B with CpG and to intradermally-delivered formulations. Mucosal and systemic Th17
responses were also observed with this adjuvanted NP formulation and vaccination route, especially in the lung. Following a Mtb aerosol challenge, animals vaccinated with
NP-Ag85B and CpG via the pulmonary route showed a substantial reduction of the lung bacterial burden, compared to
either soluble Ag85B with CpG or to the corresponding intradermally delivered formulations. These findings highlight
the potential of NP-based formulations administered by
aerosol for TB vaccination.
models reflect the situation in human children is not
clear, so comparative studies should be performed.
•
The role of mucosal and systemic IgG antibodies should
be better characterized. In the human gut, for instance,
the fenestrated capillaries are likely to allow IgGs to
reach neonatal Fc receptors present on epithelial cells
and be transported in the lumen by receptor mediated
transcytosis. Whether such transport mechanisms also
operate in respiratory, genital and urinary mucosal tissues remains to be established. In a murine model of enteropathogenic E. coli (EPEC) disease, it was shown that
IgG but not IgA mediated protection [130]. The human
papilloma virus (HPV) vaccine is administered systemically and elicits neutralizing antibodies in genital secretions [131]. This suggests that IgG in secretions or mucosal tissues was important but the immunological correlates of protection are still not identified.
•
We should better define the differences in nature, duration and intensity of humoral and cell-mediated immunity at specific mucosal sites following non-mucosal and
mucosal vaccination via different routes of administration in humans.
11. PERSPECTIVES
Current licensed mucosal vaccines have reduced the burden of disease and mortality caused by enteric pathogens
including rotavirus, V. cholerae and S. Typhi, and those that
enter mucosally and spread to affect distal organs such as
poliovirus. Recent advances promise to accelerate development of mucosal vaccines that will contribute significantly to
protection against pathogens that invade the host via mucosal
surfaces, including HIV, Shigella, ETEC, Campylobacter,
Helicobacter and probably many others.
What Do We Need to Learn More About?
•
2623
We must know how to better induce effective longlasting mucosal immunity during the neonatal period
and childhood. The extent to which neonatal animal
Which Immunization Strategies Need to be Explored
And Exploited?
In cases where mucosal immunity is essential for protection against mucosal pathogens, the following approaches
should be studied and tested:
2624 Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
•
•
•
•
•
Find new ways to protect antigens from the harsh mucosal environment and to promote their delivery into the
inductive sites where immune responses are initiated to
achieve the necessary range of immune responses for
protection. As examples, the new delivery systems described in this review are designed to facilitate the preservation of antigenicity and appropriate mucosal targeting of antigens.
Enhance the recruitment of professional antigen presenting cells to immunization sites, including the airways,
the digestive, urinary and genital tracts, and the skin.
Define better strategies for induction of appropriate secretory or systemic antibody and/or T cells responses.
The mechanisms that underlie the generation of effective immune responses in mucosal tissues following
mucosal immunization are complex and probably distinct for the different mucosal surfaces.
Kraehenbuhl and Neutra
[2]
[3]
[4]
[5]
[6]
[7]
[8]
Define more clearly the interactions of vaccine antigens
and adjuvants with innate immune cells in mucosal tissues and how these interactions modulate adaptive immunity
[9]
Develop additional safe yet effective mucosal adjuvants
that can be used with mucosal vaccines and more effieient delivery systems.
[10]
•
Better understand the processes of lymphocyte trafficking and homing to specific mucosal effector sites
•
Develop ways to more effectively induce robust and
persistent mucosal immunological memory.
•
Improve tools for evaluation of antibodies and other
immune effectors at mucosal surfaces and in mucosal
secretions, particularly in infants and young children.
12. CONCLUSION
Mucosal vaccines hold great promise for reducing the
burden of disease and mortality caused by mucosally acquired pathogens.
Inducing mucosal immunity is complex and challenging.
Mucosal delivery of vaccines may be optimal for protection
against some diseases but for others, mucosal delivery may
not be critical and other routes should be prioritized. Nevertheless, mucosal vaccination has many practical and safety
advantages and may also trigger protective systemic responses [123]. Thus, mucosal vaccines may not only prevent
initial pathogen entry but may also protect against systemic
disease.
[11]
[12]
[13]
[14]
[15]
[16]
[17]
[18]
[19]
CONFLICT OF INTEREST
The author(s) confirm that this article content has no conflicts of interest.
[20]
ACKNOWLEDGEMENTS
[21]
Declared none.
REFERENCES
[1]
Mutsch, M.; Zhou, W.; Rhodes, P.; Bopp, M.; Chen, R. T.; Linder,
T.; Spyr, C.; Steffen, R. Use of the inactivated intranasal influenza
[22]
[23]
vaccine and the risk of Bell's palsy in Switzerland. N Engl J Med.,
2004, 350, 896-903.
Neutra, M. R.; Pringault, E.; Kraehenbuhl, J. P. Antigen sampling
across epithelial barriers and induction of mucosal immune
responses. Annu. Rev. Immunol., 1996, 14, 275-300.
Mantis, N. J.; Rol, N.; Corthésy, B. Secretory IgA's complex roles
in immunity and mucosal homeostasis in the gut. Mucosal
Immunol., 2011, 4, 603-611.
Czerkinsky, C.; Holmgren, J. Mucosal delivery routes for optimal
immunization: targeting immunity to the right tissues. Curr Top
Microbiol Immunol, 2012, 354, 1-18
Holmgren, J.; Czerkinsky, C. Mucosal immunity and vaccines. Nat.
Med., 2005, 11(4 Suppl), S45-S53.
Brandtzaeg, P.; Farstad, I. N.; Haraldsen, G. Regional
specialization in the mucosal immune system: primed cells do not
always home along the same track. Immunol. Today, 1999, 20, 267277.
O'Leary, A. D.; Sweeney, E. C. Lymphoglandular complexes of the
colon: structure and distribution, Histopathology, 1986 10, 267283.
Tschernig, T.; Pabst, R. Bronchus-associated lymphoid tissue
(BALT) is not present in the normal adult lung but in different
diseases. Pathobiology, 2000, 68, 1-8.
Rescigno, M.; Urbano, M.; Valzasinam, B.; Francolini, M.;
Bonasio, R.; Rotta, G.,; Kraehenbuhl, J. P.; Granucci, F.; RicciardiCastagnoli, P. Dendritic cells express tight junction proteins and
penetrate gut epithelial monolayers to sample bacteria. Nat.
Immunol., 2001, 2, 361-367.
Fagarasan, S.; Kawamoto, S.; Kanagawa, O.; Suzuki, K. Adaptive
immune regulation in the gut: T cell-dependent and T cellindependent IgA synthesis. Annu. Rev. Immunol. 2010, 28, 243273.
Mayer, L.; Shao, L. Therapeutic potential of oral tolerance. Nat Rev
Immunol., 2004, 4, 407-419.
Neutra, M. R.; Kozlowski, P. A. Mucosal vaccines: the promise
and the challenge. Nat. Rev. Immunol., 2006, 6, 148-158
Iwasaki, A. Mucosal dendritic cells. Annu. Rev. Immunol., 2007,
25, 381-418.
Belyakov, I. M.; Ahlers, J. D. Simultaneous approach using
systemic, mucosal and transcutaneous routes of immunization for
development of protective HIV-1 vaccines, Curr. Med. Chem.,
2011, 18, 3953-3962
Mantis, N.J.; Frey, A.; Neutra, M.R.. Accessibility of glycolipid
and oligosaccharide epitopes on rabbit villus and follicle-associated
epithelium. Am. J. Physiol., 2000, 278, G915-G923.
van Duin, D.; Medzhitov, R.; Shaw, A. C. Triggering TLR
signaling in vaccination. Trends Immunol., 2006, 27, 49-55.
Fujii, S.; Shimizu, K.; Hemmi, H.; Fukui, M.; Bonito, A. J.; Chen,
G.; Franck, R. W.; Tsuji, M.; Steinman, R. M. Glycolipid alpha-Cgalactosylceramide is a distinct inducer of dendritic cell function
during innate and adaptive immune responses of mice. Proc. Natl.
Acad. Sci. U.S.A., 2006, 103, 11252-11257.
Cairing, J.; Barr, T.; Heath, A. W. Adjuvanticity of anti-cD40 in
vaccine development. Curr. Opin. Mol. Ther., 2005, 7, 73-77.
Wilson, N. S.; Behrens, G. M.; Lundie, R. J.; Smith, C. M.;
Waithman, J.; Young, L.; Forehan, S. P.; Mount, A.; Steptoe, R. J.;
Shortman K. D.; de Koning-Ward, T. F.; Belz, G. T.; Carbone, F.
R.; Crabb, B. S.; Heath, W. R.; Villadangos, J. Systemic activation
of dendritic cells by Toll-like receptor ligands or malaria infection
impairs cross-presentation and antiviral immunity. Nat. Immunol.,
2006, 7, 165-172.
Blander, J. M.; Medzhitov, R. On regulation of phagosome
maturation and antigen presentation. Nat. Immunol., 2006, 75,
1029-1035.
Kunkel, E. J.; Butcher, E. C. Plasma-cell homing. Nat. Rev.
Immunol., 2003, 3, 822-829.
Sigmundsdottir, Butcher, E. C. Environmental cues, dendritic cells
and the programming of tissue-selective lymphocyte trafficking.
Nat. Immunol., 2008, 9, 981-987.
Woof, J. M.; J, Mestecky. Mucosal immunoglobulins. Immunol.
Rev., 2005, 206,64–82.
Mucosal Vaccines: Where Do We Stand?
[24]
[25]
[26]
[27]
[28]
[29]
[30]
[31]
[32]
[33]
[34]
[35]
[36]
[37]
[38]
[39]
[40]
[41]
[42]
[43]
[44]
Hieshima, K. CC chemokine ligands 25 and 28 play essential roles
in intestinal extravasation of IgA antibody-secreting cells. J.
Immunol., 2004, 173, 3668-3675.
Lindholm, C.; Naylor, A.; Johansson, E. L.; Quiding-Jarbrink, M.
Mucosal vaccination increases endothelial expression of mucosal
addressin cell adhesion molecule 1 in the human gastrointestinal
tract. Infect Immun., 2004, 7, 1004-1009.
Shim B. S.; Choi, Y. K.; Yun, C. H.; Lee, E. G.; Jeon, Y. S.; Park,
S. M.; Cheon, I. S.; Joo, D.H.; Cho, C. H.; Song, M. S.; Seo, S. U.;
Byun, Y. H.; Park, H. J.; Poo, H.; Seong, B. L.; Kim, J. O.;
Nguyen, H. H.; Stadler, K.; Kim, D. W.; Hong, K. J.; Czerkinsky,
C.; Song, M. K. Sublingual Immunization with M2-Based Vaccine
Induces Broad Protective Immunity against Influenza. PLoS One.,
2011, 6: e27953.
MacPherson, G. G.; Liu, L. M. Dendritic cells and Langerhans cells
in the uptake of mucosal antigens. Curr. Top. Microbiol. Immunol.,
1999, 236, 33-53.
Macpherson, A. J.; McKoy, K. D.; Johansen, F. E.; Brandtzaeg, P.
The immune geography of IgA induction and function. Mucosal
Immunol., 2008, 1:11–22.
Mora, J. R.; M. Iwata; B. Eksteen; Song, S. Y.; Junt, T.; Senman
B.; Otipoby K. L.; Yokota, A.; Takeuchi, H.; Ricciardi-Castagnoli,
P. Generation of gut-homing IgA-secreting B cells by intestinal
dendritic cells. Science., 2006, 314:1157-1160.
Staats, H. F.; Montgomery, S. P.; Palker, T. J. Intranasal
immunization is superior to vaginal, gastric, or rectal immunization
for induction of systemic and mucosal anti-HIV antibody
responses. AIDS Res. Hum. Retroviruses., 1998, 13, 945-952.
Nichol, K. L. Efficacy and effectiveness of influenza vaccination.
Vaccine., 2008, 26 Suppl 4, D17-22
Fraser, A.; Paul, M.; Goldberg, E.; Acosta, C. J.; Leibovici, L.
Typhoid fever vaccines: systematic review and meta-analysis of
randomised controlled trials. Vaccine., 2007, 25, 7848-785.
Lambert, P. H.; Liu, M.; Siegrist, C. A. Can successful vaccines
teach us how to induce efficient protective immune responses. Nat.
Med., 2005, 11, S54-62.
Brandtzaeg, P. Mucosal immunity: induction, dissemination, and
effector functions. Scand J Immunol., 2009, 70, 505-515.
Plotkin, S. A. Correlates of protection induced by vaccination. Clin
Vaccine Immunol., 2010, 3, 1055-1065.
Hooper, L. V.; Littman, D. R.; Macpherson, A. J. Interactions
between the microbiota and the immune system. Science., 2012,
336, 1268-1273.
Israel, E. J.; Taylor, S.; Wu, Z.; Mizoguchi, E.; Blumberg, R. S.;
Bhan, A.; Simister, N. E., Expression of the neonatal Fc receptor,
FcRn, on human intestinal epithelial cells. Immunology., 1998, 92,
69-74.
Baker, K.; Qiao, S. W.; Kuo, T.; Kobayashi, K.; Yoshida, M.;
Lencer, W. I.; Blumberg, R. S. Immune and non-immune functions
of the (not so) neonatal Fc receptor, FcRn. Springer Semin Immun.,
2009, 31, 223-236.
Roopenian, D. C.; Akilesh, S. FcRn: the neonatal Fc receptor
comes of age. Nat. Rev. Immunol., 2007, 7, 715-725.
Li, Z.; Palaniyandi, S.; Zeng, R.; Tuo, W.; Roopenian, D. C.; Zhu,
X. Transfer of IgG in the female genital tract by MHC class Irelated neonatal Fc receptor (FcRn) confers protective immunity to
vaginal infection. Proc. Natl. Acad. Sci. U.S.A., 2011, 108, 43884393.
Sun, K.; Ye, J., Perez, D. R.; Metzger, D. W. Seasonal FluMist
vaccination induces cross-reactive T cell immunity against H1N1
2009, influenza and secondary bacterial infections. J. Immunol.,
2011, 186, 987-993.
Lau, Y. F.; Wright, A. R.; Subbarao, K. The contribution of
systemic and pulmonary immune effectors to vaccine-induced
protection from H5N1 influenza virus infection. J. Virol., 2012, 86,
5089-5098.
Mucida, D.; Salek-Ardakani, S. Regulation of Th17 cells in the
mucosal surfaces. J. Allergy Clin. Immunol., 2009, 123, 997-1003.
Niess, J. H.; Adler, G. Enteric flora expands gut lamina propria
CX3CR1+ dendritic cells supporting inflammatory immune
responses under normal and inflammatory conditions. J. Immunol.,
2010, 184, 2026-2037.
Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
[45]
[46]
[47]
[48]
[49]
[50]
[51]
[52]
[53]
[54]
[55]
[56]
[57]
[58]
[59]
[60]
[61]
[62]
[63]
[64]
[65]
2625
Lin, Y.; Slight, S. R.; Khader, S. A. Th17 cytokines and vaccineinduced immunity. Springer Semin Immun., 2010, 32, 79-90.
Doreau, A.; Belot, A.; Bastid, J.; Riche, B.; Trescol-Biemont, M.
C.; Ranchin, B.; Fabien, N.; Cochat, P.; Pouteil-Noble, C.; Trolliet,
P.; Durieu, I.; Tebib, J.; Kassai, B.; Ansieau, S.; Puisieux, A.;
Eliaou, J. F.; Bonnefoy-Bérard, N. Interleukin 17 acts in synergy
with B cell-activating factor to influence B cell biology and the
pathophysiology of systemic lupus erythematosus. Nat. Immunol.,
2009, 10, 778-785.
Jaffar, Z. ; Ferrini, M. E. ; Herritt, L. A. ; Roberts, K. Cutting edge:
lung mucosal Th17-mediated responses induce polymeric Ig
receptor expression by the airway epithelium and elevate secretory
IgA levels. J. Immunol., 2009, 182, 4507-4511.
Mitragotri, S. Immunization without needles. Nat Rev Immunol.,
2005, 5, 905-916.
Minor, P. D. Polio eradication, cessation of vaccination and reemergence of disease. Nat. Rev. Microbiol., 2004, 2, 73-82.
Minor, P. D.; Dunn, G. The effect of sequences in the 5' noncoding region on the replication of polioviruses in the human gut.
J. Gen. Virol., 1988, 69, 1091-1096.
Holmgren, J.; Svennerholm, A. M. Vaccines against mucosal
infections. Curr. Opin. Immunol., 2012, 24, 1-11.
Eckelhoefer, H. A.; Rajapaksa, T. E.; Wang, J.; Hamer, M.;
Appleby, N. C.; Ling, J.; Lo, D. D. Claudin-4: functional studies
beyond the tight junction. Methods Mol Biol. 2011, 762, 115-1128.
Ye, L.; Zeng, R.; Bai, Y.; Roopenian, D. C.; Zhu, X. Efficient
mucosal vaccination mediated by the neonatal Fc receptor. Nat.
Biotechnol., 2011, 29, 158-163.
Cranage, M. P.; Fraser, C. A.; Stevens, Z.; Huting, J.; Chang, M.;
Jeffs, S. A.; Seaman, M. S.; Cope , A.; Cole, T.; Shattock, R. J.
Repeated vaginal administration of trimeric HIV-1 clade C gp140
induces serum and mucosal antibody responses. Mucosal Immunol.,
2010, 3, 57-68.
Plummer, E. M.; Manchester, M. Viral nanoparticles and virus-like
particles: platforms for contemporary vaccine design. Wiley
Interdiscip. Rev. Nanomed. Nanobiotechnol., 2010, Sept 24, 174196.
Hilleman, M. R. Yeast recombinant hepatitis B vaccine. Infection.,
1987, 15, 3-7.
Koutsky, L. A.; Ault, K. A.; Wheeler, C. M.; Brown, D. R.; Barr,
E.; Alvarez, F. B.; Chiacchierini, L. M.; Jansen, K. U. Proof of
Principle Study Investigators. A controlled trial of a human
papillomavirus type 16 vaccine. N. Engl. J. Med., 2002, 347, 16451651.
Kang, S. M.; Song, J. M.; Quan, F. S.; Compans, R. W. Influenza
vaccines based on virus-like particles. Virus Res., 2009, 143, 140146.
Hossain, M. J.; Bourgeois, M.; Quan, F. S.; Lipatov, A. S.; Song, J.
M.; Chen, L. M.; Compans, R. W.; York, I.; Kang, S. M.; Donis, R.
O. Virus-like particle vaccine containing hemagglutinin confers
protection against 2009 H1N1 pandemic influenza. Clin. Vaccine
Immunol., 2011,18, 2010-2017.
Betancourt, A. A.; Delgado, C. A.; Estévez, Z. C.; Martínez, J. C.;
Ríos, G. V. Phase I clinical trial in healthy adults of a nasal vaccine
candidate containing recombinant hepatitis B surface and core
antigens. Int. J. Infect. Dis., 2007, 11, 394-401.
Glück, U.; Gebbers, J. O.; Glück, R. Phase 1 evaluation of
intranasal virosomal influenza vaccine with and without
Escherichia coli heat-labile toxin in adult volunteers. J. Virol.,
1999, 73:7780-7786.
Vauthier, C.; Bouchemal, K. Methods for the preparation and
manufacture of polymeric nanoparticles. Pharm. Res., 2009, 26,
1025-1058.
Chadwick, S.; Kriegel, C.; Amiji, M. Nanotechnology solutions for
mucosal immunization. Adv Drug Deliv Rev., 2010, 62, 394-407.
Romero, E. L.; Morilla, M. J. Topical and mucosal liposomes for
vaccine delivery. Wiley Wiley Interdiscip Rev Nanomed
Nanobiotechnol., 2011, 3, 356-375.
Tanaka, Y.; Kasai, M.; Taneichi, M.; Naito, S.; Kato, H.; Mori, M.;
Nishida, M.; Maekawa, N.; Yamamura, H.; Komuro, K.; Uchida,
T. Liposomes with differential lipid components exert differential
2626 Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
[66]
[67]
[68]
[69]
[70]
[71]
[72]
[73]
[74]
[75]
[76]
[77]
[78]
[79]
[80]
[81]
[82]
adjuvanticity in antigen-liposome conjugates via differential
recognition by macrophages. Bioconjug Chem., 2004, 155, 35-40.
Rosada, R. S.; de la Torre, L. G.; Frantz, F. G.; Trombone, A. P.;
Zárate-Bladés, C. R.; Fonseca, D. M.; Souza, P. R.; Brandão, I. T.;
Masson, A. P.; Soares, E. G.; Ramos, S. G.; Faccioli, L. H.; Silva,
C. L.; Santana, M. H.; Coelho-Castelo, A. A. Protection against
tuberculosis by a single intranasal administration of DNA-hsp65
vaccine complexed with cationic liposomes. BMC immunology.,
2012, 9, 38-51.
Baca-Estrada, M. E.; Foldvari, M.; Babiuk, S. L.; Babiuk, L. A.
Vaccine delivery: lipid-based delivery systems. J. Biotechnol.,
2000, 83, 91-104.
Vauthier, C.; Bouchemal, K. Methods for the preparation and
manufacture of polymeric nanoparticles. Pharm. Res., 2009, 26,
1025-105.
Chadwick, S.; Kriegel, C.; Amiji, M. Nanotechnology solutions for
mucosal immunization. Adv. Drug Deliv. Rev., 2010, 62, 394-407.
des Rieux, A. ; Fievez, V.; Garinot, M. ; Schneider, Y. J. ; Préat, V.
Nanoparticles as potential oral delivery systems of proteins and
vaccines: a mechanistic approach. J. Control Release., 2006, 116,
1-27.
Zhu, Q.; Talton, J.; Zhang, G.; Cunningham, T.; Wang, Z., Waters,
R. C.; Kirk, J.; Eppler, B.; Klinman, D. M.; Sui, Y.; Gagnon, S.;
Belyakov, I. M.; Mumper, R. J.; Berzofsky, J. A. Large intestinetargeted, nanoparticle-releasing oral vaccine to control genitorectal
viral infection. Nat Med., 2012, 18, 1291-1296.
Wilson-Welder, J. H.; Torres, M. P.; Kipper, M. J.; Mallapragada,
S. K.; Wannemuehler, M. J.; Narasimhan, B. Vaccine adjuvants:
current challenges and future approaches. J. Pharm Sci., 2009, 98,
1278-1316.
Lawson, L. B.; Norton, E. B.; Clements, J. D. Defending the
mucosa: adjuvant and carrier formulations for mucosal immunity.
Curr. Opin. Immunol., 2011, 23, 414-420.
Czerkinsky, C.; Holmgren, J. Enteric vaccines for the developing
world: a challenge for mucosal immunology. Mucosal Immunol.
2009, 2, 284-72.
Stephenson, I.; Zambon, M. C.; Rudin, A.; Colegate, A.; Podda, A.;
Bugarini, R.; Del Giudice, G.; Minutello, A.; Bonnington, S.;
Holmgren, J.; Mills, K. H.; Nicholson, K. G. Phase I evaluation of
intranasal trivalent inactivated influenza vaccine with nontoxigenic
Escherichia coli enterotoxin and novel biovector as mucosal
adjuvants, using adult volunteers. J. Virol., 2006, 80, 4962-4970.
Anosova, N. G.; Chabot, S.; Shreedhar, V.; Borawski, J. A.;
Dickinson, B. L.; Neutra, M. R. Cholera toxin, E. coli heat-labile
toxin, and non-toxic derivatives induce dendritic cell migration into
the follicle-associated epithelium of Peyer's patches. Mucosal
Immunol., 2008, 1, 59-67.
Datta, S. K.; Sabet, M.; Nguyen, K. P.; Valdez, P. A.; GonzalezNavajas, J. M.; Islam, S.; Mihajlov, I.; Fierer, J.; Insel, P. A.;
Webster, N. J.; Guiney, D. G.; Raz, E. Mucosal adjuvant activity of
cholera toxin requires Th17 cells and protects against inhalation
anthrax. Proc. Natl. Acad. Sci. U.S.A., 2010, 107, 10638-10643.
Steinhagen, F.; Kinjo, T.; Bode, C.; Klinman, D. M. TLR-Based
Immune Adjuvants. Vaccine., 2011, 29, 3341-3355.
Puga, I.; Cols, M.; Cerutti, A. Innate signals in mucosal
immunoglobulin class switching. J. Allergy Clin. Immunol., 2010,
126, 889-895.
Liang, Y.; Hasturk, H.; Elliot, J.; Noronha, A.; Liu, X.; Wetzler, L.
M.; Massari, P.; Kantarci; A.; Winter, H. S.; Farraye, F. A.;
Ganley-Leal, L. M. Toll-like receptor 2 induces mucosal homing
receptor expression and IgA production by human B cells. Clin
Immunol., 2010, 138, 33-40.
Sierro, F.; Dubois, B.; Coste, A.; Kaiserlian, D.; Kraehenbuhl, J. P.;
Sirard, J. C. Flagellin stimulation of intestinal epithelial cells
triggers CCL20-mediated migration of dendritic cells. Proc. Natl.
Acad. Sci. U.S.A., 2001, 98, 13722-13727.
Van Maele, L.; Carnoy, C.; Cayet, D., Songhet, P.; Dumoutier, L.;
Ferrero, I.; Janot. L.; Erard, F.; Bertout, J.; Leger, H.; Sebbane, F.;
Benecke, A.; Renauld, J. C.; Hardt. W. D.; Ryffel, B.; Sirard, J. C.
TLR5 signaling stimulates the innate production of IL-17 and IL22 by CD3(neg)CD127+ immune cells in spleen and mucosa. J.
Immunol., 2010, 185, 1177-1185.
Kraehenbuhl and Neutra
[83]
[84]
[85]
[86]
[87]
[88]
[89]
[90]
[91]
[92]
[93]
[94]
[95]
[96]
[97]
[98]
[99]
[100]
[101]
Reed, S. G.; Bertholet, S.; Coler, R. N.; Friede, M. New horizons in
adjuvants for vaccine development. Trends Immunol., 2009, 30, 2332.
Wilson-Welder, J. H.; Torres, M. P.; Kipper, M. J,; Mallapragada,
S. K.; Wannemuehler, M. J.; Narasimhan, B. Vaccine adjuvants:
current challenges and future approaches. J. Pharm. Sci., 2009, 98,
1278-1316.
Morein, B.; Sundquist, B.; Höglund, S.; Dalsgaard, K.; Osterhaus,
A. Iscom, a novel structure for antigenic presentation of membrane
proteins from enveloped viruses. Nature, 1984, 308, 457-560.
Forrest, B. D.; LaBrooy, J. T.; Beyer, L.; Dearlove, C. E.;
Shearman, D. J. The human humoral immune response to
Salmonella typhi Ty21a. J. Infect. Dis., 1991, 163, 336-345.
Ahrén, C.; Jertborn, M.; Svennerholm, A. M. Intestinal immune
responses to an inactivated oral enterotoxigenic Escherichia coli
vaccine and associated immunoglobulin A responses in blood.
Infect. Immun. 1998, 66, 3311-3316.
Kantele, A. Peripheral blood antibody-secreting cells in the
evaluation of the immune response to an oral vaccine. J
Biotechnol., 1996, 44, 217-224.
Yalow, R. S.; Berson, S. A. Immunoassay of endogenous plasma
insulin in man. J. Clin. Invest., 1960, 39,1157-75.
Czerkinsky, C. C.; Nilsson, L. A.; Nygren, H.; Ouchterlony, O.;
Tarkowski, A. A solid-phase enzyme-linked immunospot
(ELISPOT) assay for enumeration of specific antibody-secreting
cells. J. Immunol. Methods., 1983, 65, 109-121.
Czerkinsky, C.; Andersson, G.; Ekre, H. P.; Nilsson, L. A.;
Klareskog, L.; Ouchterlony, O. Reverse ELISPOT assay for clonal
analysis of cytokine production. I. Enumeration of gammainterferon-secreting cells. J. Immunol. Methods., 1988, 110, 29-36.
de Jong, A.; van der Hulst, J. M.; Kenter, G. G.; Drijfhout, J. W.;
Franken, K. L.; Vermeij, P.; Offringa, R.; van der Burg, S. H.;
Melief, C. J. Rapid enrichment of human papillomavirus (HPV)specific polyclonal T cell populations for adoptive immunotherapy
of cervical cancer, Int. J. Cancer, 2005, 115, 274-282.
Shacklett, B. L.; Critchfield, J. W.; Lemongello, D. Quantifying
HIV-1-specific CD8 (+) T-cell responses using ELISPOT and
cytokine flow cytometry. Methods Mol. Biol., 2009, 485, 359-374.
Pavot, V.; Rochereau, N.; Genin, C.; Verrier, B.; Paul, S. New
insights in mucosal vaccine development. Vaccine., 2011, 30, 142154.
Pasetti, M. F.; Simon, J. K.; Sztein, M. B.; Levine, M. M.
Immunology of gut mucosal vaccines. Immunol. Rev., 2011, 239,
125-148.
Jensen, K.; Ranganathan, U. D.; Van Rompay, K. K.; Canfield, D.
R.; Khan, I.; Ravindran, R.; Luciw, P. A.; Jacobs, W. R. Jr.;
Fennelly, G.; Larsen, M.; Abel, K. Recombinant attenuated
Mycobacterium tuberculosis vaccine strain is safe in
immunosuppressed SIV-infected infant macaques. Clin. Vaccine
Immunol., 2012, 19, 1170-118.
Ballester, M.; Nembrini, C.; Dhar, N.; de Titta, A.; de Piano, C.;
Pasquier, M.; Simeoni, E.; van der Vlies, A. J.; McKinney, J. D.;
Hubbell, J. A.; Swartz, M. A. Nanoparticle conjugation and
pulmonary delivery enhance the protective efficacy of Ag85B and
CpG against tuberculosis. Vaccine., 2011, 29, 6959-6966.
Levine, M. M.; Kotloff, K. L.; Barry, E. M.; Pasetti, M. F.; Sztein,
M. B. Clinical trials of Shigella vaccines: two steps forward and
one step back on a long, hard road. Nat. Rev. Microbiol., 2007, 5,
540-553.
Cohen, D.; Green, M. S.; Block, C.; Slepon, R.; Ofek, I.
Prospective study of the association between serum antibodies to
lipopolysaccharide O antigen and the attack rate of shigellosis. J.
Clin. Microbiol., 1991, 29, 386-389.
Tacket, C. O.; Binion, S. B.; Bostwick, E.; Losonsky, G.; Roy, M.
J.; Edelman, R. Efficacy of bovine milk immunoglobulin
concentrate in preventing illness after Shigella flexneri challenge.
Am. J. Trop. Med. Hyg., 1992, 47, 276-283.
Samandari, T.; Kotloff, K. L.; Losonsky, G. A.; Picking, W. D.;
Sansonetti. P. J.; Levine, M. M.; Sztein, M. B. Production of IFNgamma and IL-10 to Shigella invasins by mononuclear cells from
volunteers orally inoculated with a Shiga toxin-deleted Shigella
dysenteriae type 1 strain. J. Immunol., 2000. 164, 2221-2232.
Mucosal Vaccines: Where Do We Stand?
[102]
[103]
[104]
[105]
[106]
[107]
[108]
[109]
[110]
[111]
[112]
[113]
[114]
[115]
[116]
[117]
Riddle, M. S.; Kaminski, R. W.; Williams, C.; Porter, C.; Baqar, S.;
Kordis, A.; Gilliland, T.; Lapa, J.; Coughlin, M.; Soltis, C.; Jones,
E.; Saunders, J.; Keiser, P. B.; Ranallo, R. T.; Gormley, R.; Nelson,
M.; Turbyfill, K. R.; Tribble, D.; Oaks, E. V. Safety and
immunogenicity of an intranasal Shigella flexneri 2a Invaplex 50
vaccine. Vaccine., 2011, 29, 7009-7019.
Berlanda Scorza, F.; Colucci, A. M.; Maggiore, L.; Sanzone, S.;
Rossi, O.; Ferlenghi, I.; Pesce, I.; Caboni, M.; Norais, N.; Di
Cioccio, V.; Saul, A.; Gerke, C. High yield production process for
Shigella outer membrane particles. PLoS One., 2012, 7, e35616.
Phalipon, A.; Tanguy, M.; Grandjean, C.; Guerreiro, C.; Bélot, F.;
Cohen, D.; Sansonetti, P. J.; Mulard, L. A. A synthetic
carbohydrate-protein conjugate vaccine candidate against Shigella
flexneri 2a infection. J. Immunol., 2009, 182, 2241-2247.
Mel, D. M.; Arsic, B. L.; Nikolic, B. D.; Radovanic, M. L. Studies
on vaccination against bacillary dysentery. 4. Oral immunization
with live monotypic and combined vaccines. Bull World Health
Organ., 1968, 39, 375-380.
Meitert, T.; Pencu, E.; Ciudin, L.; Tonciu, M. Vaccine strain Sh.
flexneri T32-Istrati. Studies in animals and in volunteers.
Antidysentery immunoprophylaxis and immunotherapy by live
vaccine Vadizen (Sh. flexneri T32-Istrati). Arch. Roum. Pathol.
Exp. Microbiol., 1998, 43, 251-278.
Kotloff, K. L.; Noriega, F.; Losonsky, G. A.; Sztein, M. B.;
Wasserman, S. S.; Nataro, J. P.; Levine, M. M. Safety,
immunogenicity, and transmissibility in humans of CVD 1203, a
live oral Shigella flexneri 2a vaccine candidate attenuated by
deletions in aroA and virG. Infect. Immun., 1996, 64, 4542-4548.
Coster, T. S.; Hoge, C. W.; VanDeVerg, L. L.; Hartman, A. B.;
Oaks, E. V.; Venkatesan, M. M.; Cohen, D.; Robin, G.; FontaineThompson, A.; Sansonetti, P. J.; Hale, T. L. Vaccination against
shigellosis with attenuated Shigella flexneri 2a strain SC602. Infect.
Immun., 1999, 67, 3437-3443.
Kotloff, K. L.; Noriega, F. R.; Samandari, T.; Sztein, M. B.;
Losonsky, G. A.; Nataro, J. P.; Picking, W. D.; Barry, E. M.;
Levine, M. M. Shigella flexneri 2a strain CVD 1207, with specific
deletions in virG, sen, set, and guaBA, is highly attenuated in
humans. Infect. Immun., 2000, 68, 1034-1039.
Launay, O.; Sadorge, C.; Jolly, N.; Poirier, B.; Béchet, S.; van der
Vliet, D.; Seffer, V.; Fenner, N.; Sansonetti, P.; Morand, P.; Poyart,
C.; Lewis, D.; Gougeon, M. L. Safety and immunogenicity of
SC599, an oral live attenuated Shigella dysenteriae type-1 vaccine
in healthy volunteers: results of a Phase 2, randomized, doubleblind placebo-controlled trial. Vaccine., 2009, 27, 1184-1191.
Rahman K. M.; Arifeen, S. E.; Zaman, K.;, Rahman, M.; Raqib, R.;
Yunus, M.; Begum, N.; Islam, M. S.; Sohel, B. M.; Rahman, M.;
Venkatesan, M.; Hale, T. L.; Isenbarger, D. W.; Sansonetti, P. J.;
Black, R. E.; Baqui, A. H. Safety, dose, immunogenicity, and
transmissibility of an oral live attenuated Shigella flexneri 2a
vaccine candidate (SC602) among healthy adults and school
children in Matlab, Bangladesh. Vaccine., 2011, 29, 1347-1354.
Svennerholm, A. M. From cholera to enterotoxigenic Escherichia
coli (ETEC) vaccine development. Indian J. Med. Res., 2011, 133,
188-196.
Ahrén, C. M.; Svennerholm, A. M. Synergistic protective effect of
antibodies against Escherichia coli enterotoxin and colonization
factor antigens. Infect. Immun., 1982, 388, 74-79.
Ruffin, N.; Borggren, M.; Euler, Z.; Fiorino, F.; Grupping, K.;
Hallengärd, D.; Javed, A.; Mendonca, K.; Pollard, C.; Reinhart, D.;
Saba, E.; Sheik-Khalil, E.; Sköld, A.; Ziglio, S.; Scarlatti, G.;
Gotch, F.; Wahren, B.; Shattock, R. JRational design of HIV
vaccines and microbicides: report of the EUROPRISE annual
conference 2011. J Transl Med., 2012, 10, 144-172.
Kaufman, D. R.; Liu, J.; Carville, A.; Mansfield, K. G.; Havenga,
M. J.; Goudsmit, J.; Barouch, D. H. Trafficking of antigen-specific
CD8+ T lymphocytes to mucosal surfaces following intramuscular
vaccination. J. Immunol. 2008, 181, 4188-4198
Ranasinghe, C.; Ramshaw, I. A. Immunisation route-dependent
expression of IL-4/IL-13 can modulate HIV-specific CD8(+) CTL
avidity. Eur. J. Immunol., 2009, 39, 1819-1830.
Duerr, A. Update on mucosal HIV vaccine vectors. Curr. Opin.
HIV AIDS, 2010, 5, 397-403.
Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
[118]
[119]
[120]
[121]
[122]
[123]
[124]
[125]
[126]
[127]
[128]
[129]
[130]
2627
Malkevitch, N. V.; Patterson, L. J.; Aldrich, M. K.; Wu, Y.;
Venzon, D.;, Florese, R. H.; Kalyanaraman, V. S.; Pal, R.; Lee, E.
M.; Zhao, J,; Cristillo, A.; Robert-Guroff, M. Durable protection of
rhesus macaques immunized with a replicating adenovirus-SIV
multigene prime/protein boost vaccine regimen against a second
SIVmac251 rectal challenge: role of SIV-specific CD8+ T cell
responses. Virol., 2006, 353, 83-98.
Enose, Y.; Ui, M.; Miyake, A.; Suzuki, H.; Uesaka, H.; Kuwata, T.;
Kunisawa, J.; Kiyono, H.; Takahashi, H.; Miura, T.; Hayami, M.
Protection by intranasal immunization of a nef-deleted,
nonpathogenic SHIV against intravaginal challenge with a
heterologous pathogenic SHIV. Virol., 2002, 298, 306-316.
Crotty, S.; Miller, C. J.; Lohman, B. L.; Neagu, M. R.; Compton,
L.; Lu, D.; Lü, F. X.; Fritts, L.; Lifson, J. D.; Andino, R. Protection
against simian immunodeficiency virus vaginal challenge by using
Sabin poliovirus vectors. J. Virol., 2001, 75, 7435-7452.
Belyakov, I. M.; Hel, Z.; Kelsall, B.; Kuznetsov, V. A.; Ahlers, J.
D.; Nacsa, J.; Watkins, D. I.; Allen, T. M.; Sette, A.; Altman, J.;
Woodward, R.; Markham, P. D.; Clements, J. D.; Franchini, G.;
Strober, W.; Berzofsky, J. A. Mucosal AIDS vaccine reduces
disease and viral load in gut reservoir and blood after mucosal
infection of macaques. Nat. Med. 2001, 7, 1320-1326.
Wang, S. W.; Kozlowski, P. A.; Schmelz, G.; Manson, K.; Wyand,
M. S.; Glickman, R.; Montefiori, D.; Lifson, J. D.; Johnson, R. P.;
Neutra, M. R.; Aldovini, A. Effective induction of simian
immunodeficiency virus-specific systemic and mucosal immune
responses in primates by vaccination with proviral DNA producing
intact but noninfectious virions. J. Virol., 2000, 74, 10514-10522.
Corbett, M.; Bogers, W. M.; Heeney, J. L.; Gerber, S.; Genin, C.;
Didierlaurent, A.; Oostermeijer, H.; Dubbes, R.; Braskamp, G.;
Lerondel, S.; Gomez, C. E.; Esteban, M.; Wagner, R.; Kondova, I.;
Mooij, P.; Balla-Jhagjhoorsingh, S.; Beenhakker, N.; Koopman, G.;
van der Burg, S.; Kraehenbuhl, J. P.; Le Pape, A. Aerosol
immunization with NYVAC and MVA vectored vaccines is safe,
simple, and immunogenic. Proc. Natl. Acad. Sci. U.S.A. 2008, 105,
2046-2051.
Manrique, M.; Kozlowski, P. A.; Wang, S. W.; Wilson, R. L.;
Micewicz, E.; Montefiori, D. C.; Mansfield, K. G.; Carville, A.;
Aldovini, A. Nasal DNA-MVA SIV vaccination provides more
significant protection from progression to AIDS than a similar
intramuscular vaccination. Mucosal Immunol., 2009, 2, 536-550.
Manrique, M.; Kozlowski, P. A.; Cobo-Molinos, A.; Wang, S. W.;
Wilson, R. L.; Montefiori, D. C.; Mansfield, K. G.; Carville, A.;
Aldovini, A. Long-term control of simian immunodeficiency virus
mac251 viremia to undetectable levels in half of infected female
rhesus macaques nasally vaccinated with simian immunodeficiency
virus DNA/recombinant modified vaccinia virus Ankara. J.
Immunol. 2011, 186, 3581-3593.
Perreau, M.; Welles, H. C.; Harari, A.; Hall, O.; Martin, R.;
Maillard, M.; Dorta, G.; Bart, P. A.; Kremer, E. J.; Tartaglia, J.;
Wagner, R.; Esteban, M.; Levy, Y.; Pantaleo, G. DNA/NYVAC
vaccine regimen induces HIV-specific CD4 and CD8 T-cell
responses in intestinal mucosa. J. Virol., 2011, 85, 9854-9862.
Hesseling, A. C.; Johnson, L. F.; Jaspan, H.; Cotton, M. F.;
Whitelaw, A.; Schaaf, H. S.; Fine, P. E.; Eley, B. S.; Marais, B. J.;
Nuttall, J., Beyers, N., Godfrey-Faussett, P. Disseminated bacille
Calmette-Guérin disease in HIV-infected South African infants,
Bull World Health Organ., 2009, 187, 505-511.
Jensen, K.; Ranganathan, U. D.; Van Rompay, K. K.; Canfield, D.
R.; Khan, I.; Ravindran, R.; Luciw, P. A.; Jacobs, W. R.; Jr
Fennelly, G.; Larsen, M.; Abel, K. A Recombinant attenuated
Mycobacterium tuberculosis vaccine strain is safe in
immunosuppressed SIV-infected infant macaques. Clin. Vaccine
Immunol., 2012, 19, 1170-1181.
Ballester, M.; Nembrini, C.; Dhar, N.; de Titta, A.; de Piano, C.;
Pasquier, M.; Simeoni, E.; van der Vlies, A. J.; McKinney, J. D.;
Hubbell, J. A.; Swartz, M. A. Nanoparticle conjugation and
pulmonary delivery enhance the protective efficacy of Ag85B and
CpG against tuberculosis. Vaccine., 2011, 29, 6959-6966.
Maaser, C.; Housley, M. P.; Iimura, M.; Smith, J. R.; Vallance, B.
A.; Finlay, B. B.; Schreiber, J. R.; Varki, N. M.; Kagnoff, M. F.;
Eckmann, L. Clearance of Citrobacter rodentium requires B cells
2628 Current Topics in Medicinal Chemistry, 2013, Vol. 13, No. 20
[131]
but not secretory immunoglobulin A (IgA) or IgM antibodies.
Infect. Immun., 2004, 72, 3315-3324.
Einstein, M. H.; Baron, M.; Levin, M. J.; Chatterjee, A.; Fox, B.;
Scholar, S.; Rosen, J.; Chakhtoura, N.; Meric, D.; Dessy, F. J.;
Datta, S. K.; Descamps, D.; Dubin, G. HPV-010 Study Group.
Received: September 10, 2012
Revised: December 19, 2012
Accepted: January 05, 2013
Kraehenbuhl and Neutra
Comparative immunogenicity and safety of human papillomavirus
(HPV)-16/18 vaccine and HPV-6/11/16/18 vaccine: follow-up from
months 12-24 in a Phase III randomized study of healthy women
aged 18-45 years. Hum. Vaccine., 2011, 7, 1343-1358.