Download Extracellular Products of Streptococcus pyogenes and Their

Extracellular Products of Streptococcus pyogenes and Their Involvement
in Pathogenesis
Debbie Soefie Retnoningrum
School of Pharmacy, Institut Teknologi Bandung, Bandung
e-mail: [email protected]
Received 24 March 2008, accepted for publication 14 May 2009
Abstract
Streptococcus pyogenes or group A streptococcus (GAS) is an exclusive human pathogen. To be a successful pathogen,
this pathogen is equipped with various surface-exposed and secreted virulence factors. The functions of secreted
virulence factors are particularly important since they interact with host components to establish infections and cause
diseases in human. They include a number of proteases, DNase, superantigens, and plasminogen activator. How these
secreted factors interact with host protein(s) define this pathogen’s ability to bring out various diseases. Several
proteases act independently to target immunoglobulin molecules in order to evade host defense system and modulate
host proteins to induce host-mediated damages. Besides producing proteases, many pathogenic strains of GAS also
produce DNase; however, its involvement in host pathogenesis remains elusive. Superantigen, another secreted protein
is responsive for serious host-destruction by bypassing antigen presentation to induce massive production of cytokines.
GAS also secretes a plaminogen activator, streptokinase that is crucial for invasiveness. All together, secreted products
of this pathogen work in concert to pinpoint different targets in order to destroy and or to disable human defense system
and cause host damages.
Keywords: Streptococcus pyogenes, Secreted virulence factors, Bacterial colonization, Host damage
Abstrak
Streptococcus pyogenes atau streptokokus kelompok A (group A streptococcus, GAS) adalah pathogen yang hanya
menginfeksi manusia. Untuk menjadi pathogen yang berhasil, GAS dilengkapi dengan faktor virulensi, baik berupa
molekul permukaan maupun yang disekresikan. Faktor virulensi yang disekresikan mempunyai fungsi penting karena
berinteraksi dengan komponen inang untuk menyebabkan infeksi dan penyakit pada manusia. Faktor virulensi tersebut
mencakup sejumlah protease, DNase, superantigen dan aktivator plasminogen. Bagaimana faktor virulensi tersebut
berinteraksi dengan protein inang menentukan kemampuan pathogen untuk menyebabkan berbagai penyakit. Beberapa
protease bekerja secara independen untuk mentarget molekul imunoglobulin dengan tujuan menghindari sistem
pertahanan inang dan mengubah protein inang, sehingga menginduksi kerusakan yang diperantarai inang. Selain
menghasilkan protease, banyak galur GAS pathogenik juga menghasilkan DNase; tetapi, keterlibatannya dalam
pathogenesis inang masih belum dimengerti. Superantigen, protein lain yang disekresi, bertanggung jawab untuk
menimbulkan kerusakan inang yang parah dengan memotong jalur presentasi antigen sehingga menimbulkan produksi
sitokin dalam jumlah besar. GAS juga mensekresi aktivator plasminogen, streptokinase yang penting untuk invasi.
Secara bersama-sama, produk yang disekresi oleh pathogen ini bekerja bersama-sama untuk menyerang target berbeda
dengan tujuan menghancurkan dan atau melumpuhkan sistem pertahanan manusia dan menyebabkan kerusakan inang.
Kata kunci: Streptococcus pyogenes, disekresi faktor virulensi, bakteri penjajahan, Host kerusakan
mediated damages that are responsible for disease
manifestation. GAS is equipped by various surface
displayed and secreted virulence factors. Both virulence
factors collaborate to ensure pathogen establishment in
our body. Surface-associated virulence factors have
been discussed previously (Retnoningrum, 2006).
Culture supernatants of the GAS contain at
least 16 proteins with identifiable export sequence
(Lyon and Caparon, 2004). Mostly, their genes have
been cloned and their gene products were studied at
protein level for their in vitro and or in vivo activities
including their proven or putative role(s) in disease
pathogenesis using animal models or patients suffering
from GAS infections or sequelae. The secreted
1. Introduction
Streptococcus pyogenes or group A
streptococcus (GAS) is a Gram positive bacterium and
is the causative agent of numerous suppurative
infections, strep throat, impetigo (skin infection) and
soft tissues (impetigo, cellulitis, and necrotizing
fasciitis), as well as several systemic diseases that can
result toxigenic processes (scarlet fever and toxic shock
syndrome) and sequelae (rheumatic fever and
glomerulonephritis). To be a successful pathogen, GAS
should overcome or modify our host defense
mechanisms in order to colonize our body. After
colonization, this bacterium causes bacterial or host33
34
JURNAL MATEMATIKA DAN SAINS, JUNI 2009, VOL. 14 NO. 2
virulence factors play a vital role in streptococcal
colonization, invasion, dissemination and host damage.
This mini review focuses on several secreted virulence
factors of GAS and covers proteases, DNases,
plasminogen activators, and superantigens and will
discuss how these secreted products interact with
human components and their involvement in
streptococcal pathogenesis.
Virulence genes in genomes of GAS
To date, 13 genomes of GAS strain have been
completely sequenced, two of M1 serotypes (SF370
and MGAS5005), M2 (MGAS10270), two of M3
(MGAS315 and SSI-1), M4 (MGAS10750), M5
(Malfredo), M6 (MGAS10394), two of M12 serotypes
(MGAS2096 and MGAS9429), M18 (MGAS8232),
M28 (MGAS6180) and M49 (NZ131). The genome
size is varied in the range of 1,815,783 base pairs (bp)
for M49 and 1,937,111 bp for M4 (McShan et al.,
2008). By comparing genomes of four strains
(MGAS315, SF370, SSI-1 and MGAS8232), the
number of putative and predicted virulence genes are
between 42 and 43. They are classified as proteinases,
adhesins, hemolisins, enzymes involved capsule
synthesis and degradation, DNases, superantigens,
immunoreactive antigens, regulators, bacteriocins,
NADase, hyaluronidase, streptolysin S and secreted
inhibitor of complement (sic).
Most virulence genes are chromosomally
encoded; however some of them are located in phage
sequences, several to mention are some hyaluronidase
genes, mitogenic factor (MF)-like gene, and a number
of superantigen genes encoding for streptococcal
pyrogenic exotoxin A (SpeA), SpeC, SpeH, SpeI, SpeK
and streptococcal superantigen (SSA). The presence of
virulence genes are vary between serotypes, for
instance, gene encoding for DNases such as MF-like
gene are absent in M1 (SF370) and M5 (MGAS8232),
MF2 gene is not found in M3 (SSI-1 and MGAS315),
MF3 gene is not present in M3 and M5 and
streptodornase (sda) gene is missing in M1. With
regards to superantigen genes, so far ten different
superantigens are discovered in GAS and their presence
is also varied between serotypes. For instance, M1
serotype is lacking speA gene, M3 does not posses
speC gene, M3 and M5 is missing speH gene but speG
gene is present in M1, M3 and M5 serotypes
(Nakagawa et al., 2003; Ferreti et al., 2001).
Taken together this information, the genome
of GAS exhibits some plasticity especially in terms of
their virulence genes and this explains the diversity of
diseases they cause in human. The existence of gene
encoding for secreted virulence factors is also diverse
between strains and this explains unique strategy that
GAS strains to deal with our defense mechanism and to
cause host damage.
Evasion of host defense mechanisms
Some GAS strains, mostly M1 and M3 are
reported to be associated with systemic diseases. Their
survival and multiplication in human requires clever
strategy to combat innate and adaptive immunity. GAS
avoids innate immunity for example by inhibiting
leukocyte recruitment and complement activation as
well as killing immune cells. Moreover, this pathogen
develops mechanisms to cleave immunoglobulins (Igs)
to circumvent adaptive immunity. Here, a number of
strategies of GAS to avoid human defense mechanisms
by secreted virulence factors will be addressed.
From their genome information, it was
revealed that GAS evolves a number of secreted
proteinases with C3b and Ig degrading ability, and
some of them belong to serine or cysteine proteinase.
GAS must evade complement system which acts as
protective shield at early phase of infection. C3b is a
component produced upon complement activation and
acts as an opsonin that ultimately involved in C3bdriven phagocytosis which results in bacterial
elimination. GAS secretes virulence factors that interact
with these molecules. SpeB, a cysteine protease, is a
virulence factor that affects many proteins of immune
system. One recent investigation strongly indicated that
wild type GAS, but not GAS lacking SpeB production
had ability for C3b cleavage (Terao et al., 2008). By
cleaving C3b, GAS avoids C3b-mediated phagocytosis
and hence survives in human blood. The gene encoding
for SpeB is highly conserved and is present in all GAS
isolates (Yu and Ferretti, 1991). Our results showed
that at the amino acid level, SpeB in various strains
exhibits 97 –– 98% identity to SpeB from M49 strain
NZ131 indicating that its amino acid conservation is
required for its functions. Using motif searching tools
(NCBI, www.ncbi.nlm.nih.gov), SpeB contains a
putative conserved domain showing that it belongs to
peptidase C10 family.
This protease is secreted as a 371 amino acids
(40 kDa) zymogen, an inactive precursor at early
stationary phase and processed by autolytic cleavage to
remove its first 118 amino acid into a 28 kDa mature
protease that is accumulated at late stationary phase.
The precursor form of SpeB has been crystallized and
its three dimensional structure was determined at high
resolution by x-ray crystallography. This study revealed
that the folding of SpeB is similar to that of papain
which is also a cysteine protease (Kagawa et al., 2000).
Of the streptococcal secreted proteases, SpeB is the
most studied; therefore, this mini review discusses
SpeB more extensive than other proteases.
SpeB is also shown to have a broad human Igdegrading activity for all types of Ig. This protein is a
specific IgG-protease and partially or totally degrades
them. It is interesting to point out that SpeB cleaves
IgG in a similar manner to IgA protease produced by
Retnoningrum, Extracellular Products of Streptococcus Pyogenes and Their Involvement 35
Neisseria gonorhheae where IgG is cleaved at a
defined site in the hinge region into stable monomeric
Fab fragments and one Fc fragment. Although the
degradation pattern resembles that of papain, the
cleavage site is different. SpeB cleaves between two
glycines located between residues 236 and 237,
whereas papain cuts between residues histidines and
threonine at positions 224 –– 225 (Collins and Olsen,
2003). SpeB also cleaves the C-terminal part of the
heavy chain of IgA, IgM, and IgD into low-molecular
weight fragments, whereas the heavy chains of IgE are
completely degraded (Collin and Olsen, 2001).
Nevertheless, the role of Ig-degrading activity in
pathogenesis and disease manifestation in GAS awaits
further investigation.
SpeB is not the only enzyme that acts on
human Ig. Another enzyme also degrades IgG and is
designated as IgG-degrading enzyme of S. pyogenes or
IdeS (Åkesson et al., 2006). Like SpeB, IdeS is a
secreted cysteine protease that cleaves human IgG in
the hinge region at the same position as SpeB does.
Both cystein proteases cleave human IgG between two
glycine residues at positions 236 and 237 (Collin and
Olsen, 2003). This cleavage inhibits antibody-mediated
phagocytosis; therefore by expressing IdeS, GAS is
able to evade phagocytosis even in the presence of Ig.
Unlike SpeB that degrades all types of Ig, IdeS shows
high degree of specificity since it only cleaves IgG. The
IdeS genes are present in many isolates and the protein
is secreted by several serotypes. Patients infected with
GAS produce antibody against IdeS indicating that
IdeS is expressed in vivo during infection. Our in silico
study indicates that amino acid sequences of IdeS of
M49 (strain NZ131) has 99% identity to those of
MGAS315 and SSI-1, while only shows 84 –– 84%
identity to those of MGA92429, 10270, 6180 and
10394 (M6 serotype). The SpeB of NZ131 shows 63%
identity to IdeZ, an IgG-degrading protease of
Streptococcus equi subsp. zooepidemicus.
One recent research raised the question
whether specific IgG are able to neutralize IdeS and the
presence of neutralizing antibodies correlates with
disease manifestations. The investigation showed that
neutralizing antibodies against IdeS enzymatic activity
were detected in two-thirds of acute-phase sera. The
presence of neutralizing antibodies reduced IdeS ability
to mediate bacterial survival in immune human blood.
In patients with bacteremia, it was found that there was
no correlation between the presence of neutralizing
antibodies to severity or outcome of invasive
infections. The fact that the human immune response
targets the enzymatic activity of IdeS supports the view
that the enzyme plays an important role during
streptococcal infection (Åkesson et al., 2006).
Another protease that takes part in immune
modulation is EndoS. It is a big protein of various sizes
and from published sequences; their size is in the range
of 834 –– 953 amino acids. Due to its size variations, the
identity is rather low (41%) between different strains. It
has an endo-beta-N-acetylglucosaminidase activity and
specifically degrades native but not denatured IgG by
hydrolyzing the glycan moeity leaving an Nacetylglucosamine with a core fucose. It was reported
that EndoS does not remove any major glycans from
IgA and IgM. EndoS recognizes two identical N-linked
glycans attached to asparagine 297 in the heavy chain
of IgG and hydrolyzes the chitibiose core of the glycan
between 4 GlcNAc ȕ1 and 4 GlcNac, leaving the
intermost GlcNAc with a core fucose (Collins and
Olsen, 2001). By performing motif searching, it is
revealed that EndoS belongs to G18-chitinase-like
superfamily and the active site is located at the amino
terminus half of the protein. The significance of EndoS
size variation is currently unknown.
This evidence pointed out that GAS has
evolved three different proteases i.e SpeB, IdeS and
EndoS that targets Ig molecules (Figure 1). Both SpeB
and IdeS cleaves Ig at hinge region and SpeB cleaves
all five Igs, while IdeS specializes on IgG. On the other
hand, EndoS acts on the carbohydrate group of native
IgG. Carbohydrate moeity of Fc portion of Ig has been
accounted for complement activation, binding to Fc
receptor on macrophages and inducing antibodydependent cellular cytotoxicity. In addition, antibodycomplexes produced from carbohydrate-lacking Ig
failed to be rapidly cleared from the circulation system
(Nose and Wigzell, 1983). It is therefore removal of
carbohydrate moeity of Ig molecules has a profound
impact on their biological activity. IgG especially IgG1
and IgG3 has strong moderate ability for opsonization
and complement activation, consequently by removing
their carbohydrate group, EndoS secreted by GAS will
inactivate the function of IgG. They collaborate to
attack by different mechanisms and or speficity to
disable one of our humoral immunity. These findings
contribute to the understanding of the role of secreted
enzymes in the pathogenesis of GAS at molecular level.
The role of human proteins on SpeB production
Human serum albumin (HSA) is the most
abundant protein in the blood; therefore we expected
that HSA would affect the expression of virulence
gene(s). The effect of human serum and HSA to the
expression of speB gene was investigated using a GAS
CS101, an M49 strain carrying a luciferase (luc)
reporter gene located downstream of speB promoter.
36
JURNAL MATEMATIKA DAN SAINS, JUNI 2009, VOL. 14 NO. 2
it seems that HSA signals streptococcal cells to produce
more SpeB.
Modulation of host proteins by SpeB
Figure1. Interaction of several important secreted
products of GAS with human components and their
consequences in streptococcal pathogenesis.
Using this system, we were able to investigate the level
of speB gene transcription by measuring luciferase
(Luc) activity. Our result demonstrated that in the
presence of individual or pooled human plasma from
three different people in the growth medium, the Luc
activity produced by CS101 was significantly higher
than in its absence. The maximal Luc activity was
reached at 5 hours growth in Todd Hewith Broth Yeast Extract (THY) and O.D.600 nm ~ 1.2 (transition
from exponential to stationary phase). This result was
in agreement with previous work showing that SpeB
precursor was produced at early stationary phase
(Kagawa et al., 2000).
To determine the human plasma component(s)
responsible for speB upregulation, fractionated human
plasma (fractions < 3 kDa, 3 –– 10 kDa, and > 10 kDa)
was used in the experiment. Only fraction > 10 kDa,
but not other fractions increased the Luc activity and
the activity in the presence of > 10 kDa fraction was
considerably higher than that in the presence of pooled
human plasma. The Luc activity in the presence of
fraction < 3 kDa and 3 –– 10 kDa was similar as that in
THY and THY - NaCl solution as negative controls. It
is obvious that HSA with molecular weight of 65 kDa
was present in fraction > 10 kDa; however to ensure
that HSA is certainly responsible for speB upregulation,
the same experiment was performed in the presence of
HSA. The result showed that the addition of HSA in
growth medium, the Luc activity increased significantly
compared to the addition of NaCl solution as negative
control (Retnoningrum, 1999 unpublished data). This
evidence supports the notion that SpeB production is
regulated by human serum component, HSA in
particular. As previously discussed, SpeB has a number
of functions while GAS is present in human blood and
Our body consists of many different proteins
with unique functions. SpeB was demonstrated to affect
human proteins by activating or inactivating them.
SpeB activates a 66-kDa host matrix metalloproteinase
and this is proposed to contribute to the extensive soft
tissue destruction observed in many patients bearing
streptococcal infection. SpeB was first found to have
fibrinolytic activity in 1940 and found to cause
myocardial necrosis in rabbits and trigger apoptosis
(Elliot, 1945; Kagawa et al., 2000). How relevant this
finding with damage in human is uncertain since GAS
exclusively causes diseases in human. Most strains of
GAS associated with severe invasive disease such as
streptococcal toxic shock syndrome (STTS) and
necrotizing faciitis express a variant of SpeB with
integrin-binding activity, which may be linked to their
pathogenesis (Kagawa et al., 2000). Integrin-binding
activity has been shown to be essential in
internalization of host cells by GAS and this process
might be crucial in establishment of invasive diseases.
SpeB also has another immunomodulating
activity on several host molecules or cells. It was
shown to act on H-kininogen results in bradykinin
release and bradykinin causes vasodilatation that will
lower the blood pressure (Heward et al., 1996). SpeB
also activates a cytokine, IL-1ȕ which is an important
mediator of inflammatory response (Kapur et al.,
1993). Moreover, it causes histamine release from mast
cells and histamine is a protein that involves in many
allergic reactions (Watanabe et al., 2002). It is obvious
that by interacting with host proteins or cells, SpeB
causes host-mediated damages. Antibacterial peptide is
a component of innate immunity and it works mostly
by inserting bacterial membrane leading to cell leakage.
GAS defeats this human defense by degrading an
antibacterial peptide LL-37 and affecting decorin that
releases dermatan sulfate which is an inhibitor for
antibacterial peptides (Schmidtchen et al., 2002).
SpeB as a virulence factor: how good is the
evidence?
It is undoubltful that SpeB functions as an
important virulence factor and its production should
contribute to GAS pathogenesis. SpeB is found
predominantly in total secreted proteins (Kagawa et al.,
2000). The role of SpeB in virulence of GAS was
proven in a mouse model using a pair of isogenic
strains with speB gene inactivated by genetic approach.
Intraperitoneal challenge of isogenic speB mutant
strains was significantly less lethal to mice (Lukomski
et al., 1997) and subcutaneous infection caused less
mortality and tissue damage (Kuo et al., 1998;
Retnoningrum, Extracellular Products of Streptococcus Pyogenes and Their Involvement 37
Lukomski et al., 1997). Another study showed that
GAS mutants lacking SpeB were less resistant to
phagocytosis possibly due to SpeB-mediated cleavage
of M protein and did not spread into internal organs as
the wild-type bacteria did (Lukomski et al., 1998).
Animal studies have suggested that SpeB plays an
important role in the balance of the host-pathogen
interaction. SpeB also plays a role in host tissue
tropism, since SpeB increased the bacterial
reproduction in mouse impetigo model an acts
synergistically with cell wall antigens and streptolysin
O (SLO) to induce injury in rats (Shanley et al., 1996).
Relevance of animal model is questionable,
since GAS only infects human. However, there is
ample evidence supporting the role of SpeB in
pathogenesis in human. Patients with invasive disease
caused by different serotypes of GAS seroconverted to
SpeB indicating that SpeB is produced in vivo during
infections (Terao et al., 2008). Patients suffering from
severe invasive disease have low antibody titer against
SpeB, suggesting that these patients failed to produce
Spe-specific antibody which is supposed to neutralize
SpeB and this contributes to the development of serious
condition. Highly invasive M1 strains from STSS
patients are associated with the production of SpeB.
Another study showed that there is an inverse
relationship between SpeB production and disease
severity, possibly due to a sparing of the M protein on
the surface. SpeB has been suggested to play a role in
the development of Acute Poststreptococcal
Glomerulonephritis and these patients have elevated
antibody levels against SpeB, and SpeB can be detected
in glomerulonephritis biopsies (Kuo et al., 2004).
These data undoubtedly demonstrated that SpeB
involves in streptococcal pathogenesis.
How does serine protease contribute to other
virulence factors?
GAS produces another type of protease, a
serine protease. In Gram negative bacteria, serine
proteases have been demonstrated to involve in the
degradation of misfolded or aggregated exported
proteins. However, numerous investigations have
provided significant finding about the importance of
HtrA, a serine protease in bacterial pathogenesis. GAS
serine protease is a 407 amino acid polypeptide, and is
high conserved with identity of 99% at their amino acid
level to serine protease of M49 NZ131. It has been
reported that GAS lacking HtrA reduced its virulence
in a mouse model of systemic infection. This strongly
indicates a possible role for HtrA in the biogenesis of
secreted virulence factors. Two important secreted
virulence factors, SpeB and the hemolysin streptolysin
S (SLS) need extensive processing for the generation of
their active forms. One recent study showed that
mutation in gene encoding for HtrA affects the
production of at least two secreted virulence factors,
SpeB and SLS. Mutant lacking HtrA is unable to
secrete active form of SpeB. On the other hand, the
mutant increases the hemolytic activity caused by SLS.
Interestingly, mutation in gene encoding for HtrA did
not result in attenuation of GAS in a murine model of
subcutaneous infection (Lyon and Caparon, 2004). This
finding pointed out that HtrA is vital for systemic, but
not for subcutaneous infections in animal model. The
relevance of this finding to human is unclear.
What is the role of DNase in GAS pathogenesis?
Besides secreting enzymes that attack protein,
GAS also produces DNase. Many pathogenic bacteria
produce extracellular DNase, but the role of this
enzyme in the pathogenesis is unknown. GAS has been
reported to produce four types of DNase: DNase A, B,
C and D. Of the four DNases, DNaseB is the dominant
DNase produced in many strains (Matsumoko et al.,
2005). All GAS genomes sequenced contain several
genes encoding putative or proven secreted DNases.
For example, an M1 strain, MGAS5005 has three genes
that encode for putative secreted DNases. Two of these
genes (spd3 and sdaD2) are encoded by prophages and
one is chromosomally encoded (spd). Three indirect
lines of evidence indicate the role of DNase in GAS
pathogenesis. First, all strains of the GAS produce at
least one secreted DNase, and most strains make
several different enzymes. Second, DNase is produced
more when GAS interacts with human epithelial cells,
polymorphonuclear leukocytes, and oropharyngeal
cells. Third, patients with GAS infections generate
antibody againts DNases, indicating that these enzymes
are immunogenic and produced in vivo during
infections.
To provide direct evidence on the role of
DNase in GAS pathogenesis, a DNase-lacking mutant
strain was generated using genetic approach and this
mutant showed significantly less virulent in mouse
models. Compared to the wild-type strain, the mutant
strain was eliminated from the skin injection site
considerably faster. The mutant strain has significantly
less ability to cause experimental pharyngeal disease in
cynomolgus macaques. Another result strongly
suggested that the prophage-encoded SdaD2 enzyme is
the major DNase that contributes to virulence.
Extracellular DNases produced by GAS play role in
disease progression, although the association between
their ability to hydrolyze DNA and GAS pathogenesis
is unclear (Sumby et al., 2005). Whether activity to
hydrolyze DNA or other unrelated activity of DNAse
indeed contributes to pathogenesis is presently
unknown.
38
JURNAL MATEMATIKA DAN SAINS, JUNI 2009, VOL. 14 NO. 2
How do streptococcal superantigens damage our
body?
Certain strains of GAS produce a number of
secreted virulence factors that enable them to cause
host damage (Fig. 1). Among these are exotoxins
designated collectively as superantigens (SSA). These
molecules belong to a protein family that bypasses
normal route of T cell activation. These molecules bind
to major histocompatibility complex class II molecules
and outside part of T-cell receptor. This nonspecific
binding results in the activation of a large proportion of
antigen-presenting cells and T cells, with subsequent
release of high level of cytokines in the blood that is
responsible for undesirable effects in human and can
lead to death due to multiorgan failure (Nooh et al.,
2006).
A number of SSA such as SpeA, SpeC, SpeH,
and SpeG are produced by GAS. These SSA have been
associated in STSS and the involvement of multiorgan
failure in this syndrome suggests that toxins might be
involved in pathogenesis. However, other virulence
factors such as streptolysin O and various cell wall
antigens can also cause toxic shock. Some reports
indicated that SpeB also functions as a SSA and this
activity is independent of its proteolytic activity
(Erikson and Norgren, 1999; Leonard et al., 1991).
Other reports on the contrary found that SpeB does not
have any superantigenic property and the observed
activity originates from contaminating SSA such as
SpeA, SpeC or other unknown mitogens (Gerlach et al.,
1994).
A number novel SSAs have been identified,
including streptococcal mitogenic exotoxin Z (SmeZ,
SmeZ-2), SpeG, SpeH, SpeJ, and Spe-I. They share
typical SSA features and are highly mitogenic on T
cells. These findings strongly indicate that, in addition
to SpeA and SpeC, one or more of these novel SSAs
might be involved in STSS. Recently, SpeB was
reported to completely degrade SmeZ. SpeG was more
resistant to SpeB cleavage, while SpeA was not
affected by SpeB (Nooh et al., 2006). This evidence
supports previous finding that SpeB is not an SSA, but
it affects the degradation of several SAgs.
Plasminogen activator is an important virulence
factor for streptococcal invasiveness
GAS has been long known to activate
plasminogen (Pg) and this ability has been suggested as
a critical component in the establishment of invasive
streptococcal infections. A virulence factor that
activates Pg is streptokinase (SK). SK is a secreted
protein produced by many GAS strains. It facilitates
lyses of blood clots by activating Pg to plasmin, the
fibrinolytic enzyme.
SK is a 414 amino acids long polypeptide with
three domains, Į domain ranging from amino acids 1 ––
150, ȕ domain from 151 –– 287 and Ȗ domain 288 –– 414.
The Į and Ȗ domains show the highest conservation
among SK with • 85% sequence identity and these two
domains provide most of the contact sites with the
plasmin and exhibit a synergistic effect on Pg
activation. The ȕ domain provides no direct contact
sites with the plasmin active-site, although it is required
to place Pg in a region located from amino acids 251
and 262. A region between amino acids 144 and 218
which spans the second structural loop of the ȕ domain
is the most diverse sequence, and contains a region of
sequence diversity associated with infection and
disease in GAS. One study reported that mutagenesis of
this polymorphic region does not alter Pg activation,
which suggests an alternative function for this
molecular motif in streptococcal disease (Lizano and
Johnston, 2005). GAS shows preference for human Pg.
Previous studies have shown that streptococcal isolates
that can activate mouse Pg are more invasive when
injected into the skin. SK and Pg are suggested to play
a key role in invasion process.
2. Conclusions
GAS has evolved several strategies to
overcome our human defense and cause host damages
by expressing a number of secreted virulence factors.
Three secreted proteases i.e. SpeB, IdeS and EndoS by
using different mechanisms target immune proteins, Ig
molecules to enhance streptococal blood survival. SpeB
modulates several non-immune host proteins and all
together this interaction results in host-mediated
damages. SSA on the other hand specializes on T cell
and activates large population of them in order to cause
severe host damage that may lead to mortality. SK
helps streptococcal dissemination by increasing
invasion. By putting the information together, secreted
products involve in bacterial colonization and host
damage.
References
Åkesson, P.
L. Moritz,
M. Truedsson, B.
Christensson, and U. P. -Rammingen, 2006,
IdeS, a Highly Specific Immunoglobulin G
(IgG)-Cleaving Enzyme from Streptococcus
pyogenes, Is Inhibited by Specific IgG
Antibodies Generated during Infection, Infect.
Immun., 74:1, 497-503.
Collin, M., and A. Olsen, 2001, Effect of SpeB and
EndoS from Streptococcus pyogenes on
Human Immunoglobulins, Infect. Immun.
69:11, 7187-7189.
Collin, M,. and A. Olsen, 2003, Extracellular Enzymes
with Immunomodulating Activities: Variations
Retnoningrum, Extracellular Products of Streptococcus Pyogenes and Their Involvement 39
on a Theme in Streptococcus Pyogenes, Infect.
Immun. 71:6, 2983-2992.
Elliot, SD, 1945, A proteolytic Enzyme Produced by
Group a Streptococci with Special Reference
to its Effect on the Type-specific M Antigen.
J. Exp. Med. 81,573-592.
Erikson, A., and M. Norgren. 1999. The Superantigenic
Activity of Streptococcal Pyrogenic Exotoxin
B is Independent of the Protease Activity.
FEMS Immunol. Med. Microbol. 25, 355-363.
Ferretti, J. J., W. M. McShan, D. Ajdic, D. J. Savic, G.
Savic, K. Lyon, C. Primeaux, S. Sezate, A. N.
Suvorov, S. Kenton, H. S. Lai, S. P. Lin, Y.
Qian, H. G. Jia, F. Z. Najar, Q. Ren, H. Zhu,
L. Song, J. White, X. Yuan, S. W. Clifton, B.
A. Roe, and R. McLaughlin, 2001, Complete
Genome Sequence of an M1 Strain of
Streptococcus pyogenes, Proc. Natl. Acad.
Sci., 98:8, 4658-4663.
Gerlach, D., W. Reichardt, B. Fleicher, and K. H.
Schmidt. 1994. Separation of Mitogenic and
Pyrogenic
Activities
from
So-called
Erythrogenic Toxin Type B (streptococcal
proteinase). Zenth. Bakteriol. 280, 507-514.
Heward, H. M. Collin, W. Muller-Esterl, and L. Bjork,
1996, Streptococcal Cysteine Proteinase
Releases Kinins: a Novel Virulence
Mechanism. J. Exp. Med. 184, 665-673.
Kagawa, T. F, J. C. Cooney, H. M. Baker, S.
McSweeney, M. Liu, S. Gubba, J. M. Musser,
and E. N. Baker, 2000, Crystal Structure of
the Zymogen form of the Group A
Streptococcus Virulence Factor SpeB: An
Integrin-binding Cysteine Protease, Proc Natl.
Acad Sci., 97:5, 2235-2240.
Kapur. V. M., W. Malesky, L. -L. Li, R. A. Black, and
J. M. Muller, 1993, Cleavage of Interleukin 1ȕ
(Il-1ȕ) Precursor to Produce Acive IL-1ȕ by a
Conserved Extracellular Cysteine Proteinase
from Streptococcus pyogenes, Proc. Natl.
Acad. Sci. USA, 90, 7676-7680.
Kuo, C-F., Y-H. Luo, H-Y. Lin, K-J. Huang, J-J. Wu,
H-Y. Lei, M. T. Lin, W-J. Chuang, C-C. Liu,
Y-T. Jin and Y-S. Lin, 2004, Histopathologic
Changes in Kidney and Liver Correlate with
Streptococcal
Pyrogenic
Exotoxin
B
Production in the Mouse Model of Group A
Streptococcal
Infection,
Microbial
Pathogenesis, 36:5, 273-285
Lizano, S., and K. H. Johnston, 2005, Structural
Diversity of Streptokinase and Activation of
Human Plasminogen, Infect. Immun., 73:7,
4451-4453
Loenard, B. A. B., P. K. Lee, M. K. Jenkins, and P. M.
Schlievert. 1991. Cell and Receptor
Requirements for Streptococcal Pyrogenic
Exotoxin T-cell Mitogenicity. Infect. Immun.
59, 1210-1214.
Lukomski, S., S. Sreevatsan, A. Amberg, W. Reichardt,
M. Woichnik, A., Podbielski, and J. M.
Musser. 1997. Incativation of Streptococcus
pyogenes Extracellular Cysteine Protease
Significantly Decreases Mouse Lethality of
Serotype M3 and M49 Strains. J. Clin.
Investig. 99, 2574-2580.
Lyon, W. R., and M. G. Caparon. 2004. Role for Serine
Protease HtrA (DegP) of Streptococcus
pyogenes in the Biogenesis of Virulence
Factors SpeB and the Hemolysin Streptolysin
S. Infect. Immun, 72:3,1618-1625.
Matsumoko, M., K. Sakae, S. Hashikawa, K. Torii, T.
Hasegawa, T. Horii, M. Endo, R. Ukono, S.
Murayama, K. Hirasawa, R. Suzuki, J. Isobe,
D. Tanaka, C. Katsukawa, A. Tamaru, M.
Tomita, K. Ogata, T. Ikebe, and H. Watanabe,
2005, Close Correlation of Streptococcal
DnaseB (sdaB) Alleles with emm Genotypes
in Streptococcus pyogenes, Microbiol.
Immunol. 49:10, 925-929.
McShan, W. M., J. J. Ferretti, T. Karasawa, A. N.
Suvorov, S. Lin, B. Qin, H. Jia, S. Kenton, F.
Najar, H. Wu, J. Scott, B. A. Roe, and D. J.
Savic, 2008, Genome Sequence of a
Nephritogenic and Highly Transformable M49
Strain of Streptococcus pyogenes, J. Bacteriol.
190:23, 7773-7785.
Nakagawa, I., K. Kurokawa, A. Yamashita, M. Nakata,
Y. Tomiyasu, N. Okahashi, S. Kawabata, K.
Yamazaki, T. Shiba, T. Yasunaga, H. Hayashi,
M. Hattori, and S. Hamada, 2003, Genome
Sequence of an M3 Strain of Streptococcus
pyogenes Reveals a Large-Scale Genomic
Rearrangement in Invasive Strains and New
Insights into Phage Evolution, Genome
Research, 13,1042-1055
Nooh, M. M., R. K. Aziz, M. Kotb, A. Eroshkin, W.-J.
Chuang, T. Proft, and R. Kansal, 2006,
Streptococcal Mitogenic Exotoxin, SmeZ, Is
the Most Susceptible M1T1 Streptococcal
Superantigen to Degradation by the
Streptococcal Cysteine Protease, SpeB, J.
Biol. Chem. 281:46, 35281-35288.
Nose. M., and H. Wigzell, 1983, Biological
Significance of Carbohydrate Chains on
Monoclonal Antibodies. Proc Natl. Acad. Sci.,
USA. 80:21,6632-6636.
Retnoningrum, D. S, 2006, Molecular Mechanisms of
Virulence Mediated by Surface-Associated
Proteins in Streptococcus pyogenes: a Short
Review. J Mikrobiol Indonesia. 11:2,51-56.
Schmidtchen, A., I. ––M. Frick, and L. Bjorck. 2001.
Dermatan Sulphate is Released by Proteinases
40
JURNAL MATEMATIKA DAN SAINS, JUNI 2009, VOL. 14 NO. 2
of Common Pathogenic Bacteria and
Inactivates Antibacterial Į-defensin. Mol.
Microbiol. 39,57-168.
Shanley, T. P., D. Schrier, V. Kapur, M. Kehoe, J. M.
Musser, and P.A. Ward. 1996. Streptococcal
Cysteine Protease Augments Lung Injury
Induced by Products of Group a Streptococci.
Infect. Immun. 64,870-877.
Sumby, P., K. D. Barbian, D. J. Gardner, A. R.
Whitney, D. M. Welty, R. D. Long, J. R.
Bailey, M. J. Parnell, N. P. Hoe, G. G. Adams,
F. R. DeLeo, and J. M. Musser. 2005.
Extracellular Deoxyribonuclease Made by
Group a Streptococcus Assists Pathogenesis
by Enhancing Evasion of the Innate Immune
Response. Proc Natl. Acad Sci., 102:5,16791684.
Terao Y., Y. Mori, M. Yamaguchi, Y. Shimizu, K.
Ooe, S. Hamada, and S. Kawabata, 2008,
Group a Streptococcal Cysteine Protease
Degrades C3 (C3b) and Contributes to
Evasion of Innate Immunity, J. Biol. Chem.
283:10,6253-6260.
Yu, C., and J. J. Ferretti, 1991, Frequency of the
Erythrogenic Toxin B and C Genes (speB and
speC) among Clinical Isolates of Group A
Streptococci, Infect. Immun., 59:1,211-215.
Watanabe, Y., Y. Todome, H. Ohkuni, S. Sakurada, T.
Ishikawa, T. Yutsudo, V. A. Fischetti, and J.
B. Zabriskie. 2002. Cysteins Protease Activity
and Histamine Release from the Human Mast
Cell Line HMC-1 Stimulated by Recombinant
Streptococcal
Pyrogenic
Exotoxin
B/streptococal Cysteine Protease. Infect.
Immun., 70,3844-3947.