Neutrophils Select Hypervirulent CovRS Mutants of M1T1 Group A Streptococcus during Subcutaneous Infection of Mice

Li, Jinquan; Liu, Guanghui; Feng, Wenchao; Zhou, Yang; Liu, Mengyao; Wiley, James; Lei, Benfang

doi:10.1128/iai.01458-13

Cited by 38 publications

(77 citation statements)

References 63 publications

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“…Invasive deep tissue infections are responsible for significant mortality, particularly in the very young, the elderly, and in those with chronic diseases (2)(3)(4). Organisms with a mutation in their cluster of virulence responder/ sensor (CovR/S) are responsible for a disproportionate number of such infections (5)(6)(7). The mutated regulon results in upregulation of numerous GAS virulence factors, including the cell wall-attached and -shed serine protease, S. pyogenes cell envelope proteinase (SpyCEP) (8,9).…”

Section: S Treptococcus Pyogenes (Group a Streptococcus [Gas]mentioning

confidence: 99%

Combinatorial Synthetic Peptide Vaccine Strategy Protects against Hypervirulent CovR/S Mutant Streptococci

Pandey

Mortensen

Calcutt

et al. 2016

The Journal of Immunology

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Cluster of virulence responder/sensor (CovR/S) mutant group A streptococci (GAS) are serious human pathogens of multiple M protein strains that upregulate expression of virulence factors, including the IL-8 protease Streptococcus pyogenes cell envelope proteinase (SpyCEP), thus blunting neutrophil-mediated killing and enabling ingress of bacteria from a superficial wound to deep tissue. We previously showed that a combination vaccine incorporating J8-DT (conserved peptide vaccine from the M protein) and a recombinant SpyCEP fragment protects against CovR/S mutants. To enhance the vaccine’s safety profile, we identified a minimal epitope (S2) that was the target for anti-SpyCEP Abs that could protect IL-8 from SpyCEP-mediated proteolysis. Abs from healthy humans and from mice experimentally infected with GAS also recognized S2, albeit at low titers. Native SpyCEP may be poorly immunogenic (cryptic or subdominant), and it would be to the organism’s advantage if the host did not induce a strong Ab response against it. However, S2 conjugated to diphtheria toxoid is highly immunogenic and induces Abs that recognize and neutralize SpyCEP. Hence, we describe a two-component peptide vaccine that induces Abs (anti-S2) that protect IL-8 from proteolysis and other Abs (anti-J8) that cause strain-independent killing in the presence of neutrophils. We show that either component alone is ineffectual in preventing skin infection and bacteremia due to CovR/S mutants but that the combination induces complete protection. This protection correlated with a significant influx of neutrophils to the infection site. The data strongly suggest that the lack of natural immunity to hypervirulent GAS strains in humans could be rectified by this combination vaccine.

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Section: S Treptococcus Pyogenes (Group a Streptococcus [Gas]mentioning

confidence: 99%

Combinatorial Synthetic Peptide Vaccine Strategy Protects against Hypervirulent CovR/S Mutant Streptococci

Pandey

Mortensen

Calcutt

et al. 2016

The Journal of Immunology

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“…Most relevant to immune cell resistance was the induced set of known virulence factors of GAS (i.e., speB, spd, nga [spn], prtS [SpyCEP], and sse). Expression of the SpeB cysteine protease promotes colonization and aids in immune cell evasion (44)(45)(46), whereas downregulation of SpeB expression is linked to neutrophil-dependent selection of invasive GAS strains (47)(48)(49). Streptococcal nucleases like the one encoded by spd enhance GAS evasion of the innate immune response (50) by degrading neutrophil extracellular traps (NETs) (51).…”

Section: Discussionmentioning

confidence: 99%

The Transcriptional Regulator CpsY Is Important for Innate Immune Evasion in Streptococcus pyogenes

et al. 2017

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As an exclusively human pathogen, Streptococcus pyogenes (the group A streptococcus [GAS]) has specifically adapted to evade host innate immunity and survive in multiple tissue niches, including blood. GAS can overcome the metabolic constraints of the blood environment and expresses various immunomodulatory factors necessary for survival and immune cell resistance. Here we present our investigation of one such factor, the predicted LysR family transcriptional regulator CpsY. The encoding gene, cpsY, was initially identified as being required for GAS survival in a transposon-site hybridization (TraSH) screen in whole human blood. CpsY is homologous with transcriptional regulators of Streptococcus mutans (MetR), Streptococcus iniae (CpsY), and Streptococcus agalactiae (MtaR) that regulate methionine transport, amino acid metabolism, resistance to neutrophil-mediated killing, and survival in vivo. Our investigation indicated that CpsY is involved in GAS resistance to innate immune cells of its human host. However, GAS CpsY does not manifest the in vitro phenotypes of its homologs in other streptococcal species. GAS CpsY appears to regulate a small set of genes that is markedly different from the regulons of its homologs. The differential expression of these genes depends on the growth medium, and CpsY modestly influences their expression. The GAS CpsY regulon includes known virulence factors (mntE, speB, spd, nga [spn], prtS [SpyCEP], and sse) and cell surface-associated factors of GAS (emm1, mur1.2, sibA [cdhA], and M5005_Spy0500). Intriguingly, the loss of CpsY in GAS does not result in virulence defects in murine models of infection, suggesting that CpsY function in immune evasion is specific to the human host.

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“…The parental strain used in this study was the serotype M1 GAS strain MGAS2221, which we and others have characterized extensively (23,35,36). A list of all GAS strains used in this study is presented in Table 1.…”

Section: Methodsmentioning

confidence: 99%

Multimerization of the Virulence-Enhancing Group A Streptococcus Transcription Factor RivR Is Required for Regulatory Activity

et al. 2017

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Group A Streptococcus (GAS) (Streptococcus pyogenes) causes more than 700 million human infections each year. The significant morbidity and mortality rates associated with GAS infections are in part a consequence of the ability of this pathogen to coordinately regulate virulence factor expression during infection. RofA-like protein IV (RivR) is a member of the Mga-like family of transcriptional regulators, and previously we reported that RivR negatively regulates transcription of the hasA and grab virulence factor-encoding genes. Here, we determined that RivR inhibits the ability of GAS to survive and to replicate in human blood. To begin to assess the biochemical basis of RivR activity, we investigated its ability to form multimers, which is a characteristic of Mga-like proteins. We found that RivR forms both dimers and a higher-molecular-mass multimer, which we hypothesize is a tetramer. As cysteine residues are known to contribute to the ability of proteins to dimerize, we created a library of expression plasmids in which each of the four cysteines in RivR was converted to serine. While the C68S RivR protein was essentially unaffected in its ability to dimerize, the C32S and C377S proteins were attenuated, while the C470S protein completely lacked the ability to dimerize. Consistent with dimerization being required for regulatory activity, the C470S RivR protein was unable to repress hasA and grab gene expression in a rivR mutant. Thus, multimer formation is a prerequisite for RivR activity, which supports recent data obtained for other Mga-like family members, suggesting a common regulatory mechanism.IMPORTANCE The modulation of gene transcription is key to the ability of bacterial pathogens to infect hosts to cause disease. Here, we discovered that the group A Streptococcus transcription factor RivR negatively regulates the ability of this pathogen to survive in human blood, and we also began biochemical characterization of this protein. We determined that, in order for RivR to function, it must self-associate, forming both dimers (consisting of two RivR proteins) and higher-order complexes (consisting of more than two RivR proteins). This functional requirement for RivR is shared by other regulators in the same family of proteins, suggesting a common regulatory mechanism. Insight into how these transcription factors function may facilitate the development of novel therapeutic agents targeting their activity.KEYWORDS multimer, transcription factor, virulence regulation, Streptococcus pyogenes T he human bacterial pathogen group A Streptococcus (GAS) causes a diverse range of infections, from the superficial, such as pharyngitis, to the severely invasive, such as necrotizing fasciitis (1-3). In addition, failure to adequately treat individuals with skin

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Neutrophils Select Hypervirulent CovRS Mutants of M1T1 Group A Streptococcus during Subcutaneous Infection of Mice

Cited by 38 publications

References 63 publications

Combinatorial Synthetic Peptide Vaccine Strategy Protects against Hypervirulent CovR/S Mutant Streptococci

Combinatorial Synthetic Peptide Vaccine Strategy Protects against Hypervirulent CovR/S Mutant Streptococci

The Transcriptional Regulator CpsY Is Important for Innate Immune Evasion in Streptococcus pyogenes

Multimerization of the Virulence-Enhancing Group A Streptococcus Transcription Factor RivR Is Required for Regulatory Activity

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