301
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Watkins RR, David MZ, Salata RA. Current concepts on the virulence mechanisms of meticillin-resistant Staphylococcus aureus. J Med Microbiol 2012; 61:1179-1193. [PMID: 22745137 DOI: 10.1099/jmm.0.043513-0] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023] Open
Abstract
Meticillin-resistant Staphylococcus aureus (MRSA) strains are prevalent bacterial pathogens that cause both health care and community-associated infections. Increasing resistance to commonly prescribed antibiotics has made MRSA a serious threat to public health throughout the world. The USA300 strain of MRSA has been responsible for an epidemic of community-associated infections in the US, mostly involving skin and soft tissue but also more serious invasive syndromes such as pneumonia, severe sepsis and endocarditis. MRSA strains are particularly serious and potentially lethal pathogens that possess virulence mechanisms including toxins, adhesins, enzymes and immunomodulators. One of these is Panton-Valentine leukocidin (PVL), a toxin associated with abscess formation and severe necrotizing pneumonia. Earlier studies suggested that PVL was a major virulence factor in community-associated MRSA infections. However, some recent data have not supported this association while others have, leading to controversy. Therefore, investigators continue to search for additional mechanisms of pathogenesis. In this review, we summarize the current understanding of the biological basis of MRSA virulence and explore future directions for research, including potential vaccines and antivirulence therapies under development that might allow clinicians to more successfully treat and prevent MRSA infections.
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Affiliation(s)
- Richard R Watkins
- Division of Infectious Diseases, Akron General Medical Center, Akron, OH 44302, USA
| | - Michael Z David
- Departments of Medicine and Health Studies, The University of Chicago, Chicago, IL, USA
| | - Robert A Salata
- Division of Infectious Diseases and HIV Medicine, University Hospitals Case Medical Center, Cleveland, OH, USA
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302
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Host response signature to Staphylococcus aureus alpha-hemolysin implicates pulmonary Th17 response. Infect Immun 2012; 80:3161-9. [PMID: 22733574 DOI: 10.1128/iai.00191-12] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022] Open
Abstract
Staphylococcus aureus pneumonia causes significant morbidity and mortality. Alpha-hemolysin (Hla), a pore-forming cytotoxin of S. aureus, has been identified through animal models of pneumonia as a critical virulence factor that induces lung injury. In spite of considerable molecular knowledge of how this cytotoxin injures the host, the precise host response to Hla in the context of infection remains poorly understood. We employed whole-genome expression profiling of infected lungs to define the host response to wild-type S. aureus compared with the response to an Hla-deficient isogenic mutant in experimental pneumonia. These data provide a complete expression profile at 4 and at 24 h postinfection, revealing a unique response to the toxin-expressing strain. Gene ontogeny analysis revealed significant differences in the extracellular matrix and cardiomyopathy pathways, both of which govern cellular interactions in the tissue microenvironment. Evaluation of individual transcript responses to Hla-secreting staphylococci was notable for upregulation of host cytokine and chemokine genes, including the p19 subunit of interleukin-23. Consistent with this observation, the cellular immune response to infection was characterized by a prominent Th17 response to the wild-type pathogen. These findings define specific host mRNA responses to Hla-producing S. aureus, coupling the pulmonary Th17 response to the secretion of this cytotoxin. Expression profiling to define the host response to a single virulence factor proved to be a valuable tool in identifying pathways for further investigation in S. aureus pneumonia. This approach may be broadly applicable to the study of bacterial toxins, defining host pathways that can be targeted to mitigate toxin-induced disease.
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303
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Matrix metalloproteinase 9 contributes to gut microbe homeostasis in a model of infectious colitis. BMC Microbiol 2012; 12:105. [PMID: 22694805 PMCID: PMC3676156 DOI: 10.1186/1471-2180-12-105] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2011] [Accepted: 05/31/2012] [Indexed: 02/08/2023] Open
Abstract
BACKGROUND Inflammatory bowel diseases are associated with increased expression of zinc-dependent Matrix Metalloproteinase 9 (MMP-9). A stark dysregulation of intestinal mucosal homeostasis has been observed in patients with chronic inflammatory bowel diseases. We therefore sought to determine the contribution of MMP-9 to the pathogenesis of Citrobacter rodentium-induced colitis and its effects on gut microbiome homeostasis. RESULTS Wild-type and MMP-9-/- mice aged 5-6 weeks were challenged with C. rodentium by orogastric gavage and sacrificed either 10 or 30 days post-infection. Disease severity was assessed by histological analysis of colonic epithelial hyperplasia and by using an in vivo intestinal permeability assay. Changes in the inflammatory responses were measured by using qPCR, and the composition of the fecal microbiome evaluated with both qPCR and terminal restriction fragment length polymorphism. Activation and localization of MMP-9 to the apical surface of the colonic epithelium in response to C. rodentium infection was demonstrated by both zymography and immunocytochemistry. The pro-inflammatory response to infection, including colonic epithelial cell hyperplasia and barrier dysfunction, was similar, irrespective of genotype. Nonmetric multidimensional scaling of terminal restriction fragments revealed a different fecal microbiome composition and C. rodentium colonization pattern between genotypes, with MMP-9-/- having elevated levels of protective segmented filamentous bacteria and interleukin-17, and lower levels of C. rodentium. MMP-9-/- but not wild-type mice were also protected from reductions in fecal microbial diversity in response to the bacterial enteric infection. CONCLUSIONS These results demonstrate that MMP-9 expression in the colon causes alterations in the fecal microbiome and has an impact on the pathogenesis of bacterial-induced colitis in mice.
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304
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Lizak M, Yarovinsky TO. Phospholipid scramblase 1 mediates type i interferon-induced protection against staphylococcal α-toxin. Cell Host Microbe 2012; 11:70-80. [PMID: 22264514 DOI: 10.1016/j.chom.2011.12.004] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2011] [Revised: 11/10/2011] [Accepted: 12/19/2011] [Indexed: 10/14/2022]
Abstract
The opportunistic gram-positive pathogen Staphylococcus aureus is a leading cause of pneumonia and sepsis. Staphylococcal α-toxin, a prototypical pore-forming toxin, is a major virulence factor of S. aureus clinical isolates, and lung epithelial cells are highly sensitive to α-toxin's cytolytic activity. Type I interferon (IFN) signaling activated in response to S. aureus increases pulmonary cell resistance to α-toxin, but the underlying mechanisms are uncharacterized. We show that IFNα protects human lung epithelial cells from α-toxin-induced intracellular ATP depletion and cell death by reducing extracellular ATP leakage. This effect depends on protein palmitoylation and induction of phospholipid scramblase 1 (PLSCR1). IFNα-induced PLSCR1 associates with the cytoskeleton after exposure to α-toxin, and cellular depletion of PLSCR1 negates IFN-induced protection from α-toxin. PLSCR1-deficient mice display enhanced sensitivity to inhaled α-toxin and an α-toxin-producing S. aureus strain. These results uncover PLSCR1 activity as part of an innate protective mechanism to a bacterial pore-forming toxin.
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Affiliation(s)
- Miroslaw Lizak
- Section of Cardiovascular Medicine, Department of Internal Medicine, Yale University School of Medicine, New Haven, CT, USA
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305
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Anderson MJ, Lin YC, Gillman AN, Parks PJ, Schlievert PM, Peterson ML. Alpha-toxin promotes Staphylococcus aureus mucosal biofilm formation. Front Cell Infect Microbiol 2012; 2:64. [PMID: 22919655 PMCID: PMC3417397 DOI: 10.3389/fcimb.2012.00064] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2012] [Accepted: 04/20/2012] [Indexed: 02/01/2023] Open
Abstract
Staphylococcus aureus causes many diseases in humans, ranging from mild skin infections to serious, life-threatening, superantigen-mediated Toxic Shock Syndrome (TSS). S. aureus may be asymptomatically carried in the anterior nares or vagina or on the skin, serving as a reservoir for infection. Pulsed-field gel electrophoresis clonal type USA200 is the most widely disseminated colonizer and the leading cause of TSS. The cytolysin α-toxin (also known as α-hemolysin or Hla) is the major epithelial proinflammatory exotoxin produced by TSS S. aureus USA200 isolates. The current study aims to characterize the differences between TSS USA200 strains [high (hla+) and low (hla−) α-toxin producers] in their ability to disrupt vaginal mucosal tissue and to characterize the subsequent infection. Tissue viability post-infection and biofilm formation of TSS USA200 isolates CDC587 and MN8, which contain the α-toxin pseudogene (hla−), MNPE (hla+), and MNPE isogenic hla knockout (hlaKO), were observed via LIVE/DEAD® staining and confocal microscopy. All TSS strains grew to similar bacterial densities (1–5 × 108 CFU) on the mucosa and were proinflammatory over 3 days. However, MNPE formed biofilms with significant reductions in the mucosal viability whereas neither CDC587 (hla−), MN8 (hla−), nor MNPE hlaKO formed biofilms. The latter strains were also less cytotoxic than wild-type MNPE. The addition of exogenous, purified α-toxin to MNPE hlaKO restored the biofilm phenotype. We speculate that α-toxin affects S. aureus phenotypic growth on vaginal mucosa by promoting tissue disruption and biofilm formation. Further, α-toxin mutants (hla−) are not benign colonizers, but rather form a different type of infection, which we have termed high density pathogenic variants (HDPV).
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Affiliation(s)
- Michele J Anderson
- Department of Experimental and Clinical Pharmacology, University of Minnesota Minneapolis, MN, USA
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306
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Lo Sardo V, Zuccato C, Gaudenzi G, Vitali B, Ramos C, Tartari M, Myre MA, Walker JA, Pistocchi A, Conti L, Valenza M, Drung B, Schmidt B, Gusella J, Zeitlin S, Cotelli F, Cattaneo E. An evolutionary recent neuroepithelial cell adhesion function of huntingtin implicates ADAM10-Ncadherin. Nat Neurosci 2012; 15:713-21. [PMID: 22466506 DOI: 10.1038/nn.3080] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Accepted: 03/05/2012] [Indexed: 02/06/2023]
Abstract
The Huntington's disease gene product, huntingtin, is indispensable for neural tube formation, but its role is obscure. We studied neurulation in htt-null embryonic stem cells and htt-morpholino zebrafish embryos and found a previously unknown, evolutionarily recent function for this ancient protein. We found that htt was essential for homotypic interactions between neuroepithelial cells; it permitted neurulation and rosette formation by regulating metalloprotease ADAM10 activity and Ncadherin cleavage. This function was embedded in the N terminus of htt and was phenocopied by treatment of htt knockdown zebrafish with an ADAM10 inhibitor. Notably, in htt-null cells, reversion of the rosetteless phenotype occurred only with expression of evolutionarily recent htt heterologues from deuterostome organisms. Conversely, all of the heterologues that we tested, including htt from Drosophila melanogaster and Dictyostelium discoideum, exhibited anti-apoptotic activity. Thus, anti-apoptosis may have been one of htt’s ancestral function(s), but, in deuterostomes, htt evolved to acquire a unique regulatory activity for controlling neural adhesion via ADAM10-Ncadherin, with implications for brain evolution and development.
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Affiliation(s)
- Valentina Lo Sardo
- Department of Pharmacological Sciences and Centre for Stem Cell Research, Università degli Studi di Milano, Milano, Italy
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307
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Cheung GYC, Otto M. The potential use of toxin antibodies as a strategy for controlling acute Staphylococcus aureus infections. Expert Opin Ther Targets 2012; 16:601-12. [PMID: 22530584 DOI: 10.1517/14728222.2012.682573] [Citation(s) in RCA: 40] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022]
Abstract
INTRODUCTION The pandemic human pathogen, Staphylococcus aureus, displays high levels of antibiotic resistance and is a major cause of hospital- and community-associated infections. S. aureus disease manifestation is to a great extent due to the production of a large arsenal of virulence factors, which include a series of secreted toxins. Antibodies to S. aureus toxins are found in people who are infected or asymptomatically colonized with S. aureus. Immunotherapies consisting of neutralizing anti-toxin antibodies could provide immediate aid to patients with impaired immune systems or in advanced stages of disease. AREAS COVERED Important S. aureus toxins, their roles in pathogenesis, rationales for selecting S. aureus toxins for immunization efforts, and caveats associated with monoclonal antibody-based passive immunization are discussed. This review will focus on hyper-virulent community-associated methicillin-resistant S. aureus because of their recent surge and clinical importance. EXPERT OPINION Antibodies against genome-encoded toxins may be more broadly applicable than those directed against toxins found only in a sub-population of S. aureus isolates. Furthermore, there is substantial functional redundancy among S. aureus toxins. Thus, an optimal anti-S. aureus formulation may consist of multiple antibodies directed against a series of key S. aureus genome-encoded toxins.
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Affiliation(s)
- Gordon Y C Cheung
- Laboratory of Human Bacterial Pathogenesis, NIAID, NIH, 9000 Rockville Pike, Bethesda, MD 20892, USA
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308
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Fraunholz M, Sinha B. Intracellular Staphylococcus aureus: live-in and let die. Front Cell Infect Microbiol 2012; 2:43. [PMID: 22919634 PMCID: PMC3417557 DOI: 10.3389/fcimb.2012.00043] [Citation(s) in RCA: 261] [Impact Index Per Article: 21.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2012] [Accepted: 03/15/2012] [Indexed: 12/30/2022] Open
Abstract
Staphylococcus aureus uses a plethora of virulence factors to accommodate a diversity of niches in its human host. Aside from the classical manifestations of S. aureus-induced diseases, the pathogen also invades and survives within mammalian host cells.The survival strategies of the pathogen are as diverse as strains or host cell types used. S. aureus is able to replicate in the phagosome or freely in the cytoplasm of its host cells. It escapes the phagosome of professional and non-professional phagocytes, subverts autophagy, induces cell death mechanisms such as apoptosis and pyronecrosis, and even can induce anti-apoptotic programs in phagocytes. The focus of this review is to present a guide to recent research outlining the variety of intracellular fates of S. aureus.
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Affiliation(s)
- Martin Fraunholz
- Department of Microbiology, Biocenter, University of Würzburg, Würzburg, Germany.
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309
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Soong G, Chun J, Parker D, Prince A. Staphylococcus aureus activation of caspase 1/calpain signaling mediates invasion through human keratinocytes. J Infect Dis 2012; 205:1571-9. [PMID: 22457275 DOI: 10.1093/infdis/jis244] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
The USA300 strains of Staphylococcus aureus are the major cause of skin and soft tissue infection in the United States. Invasive USA300 infection has been attributed to several virulence factors, including protein A and the α-hemolysin (Hla), which cause pathology by activating host signaling cascades. Here we show that S. aureus exploits the proinflammatory bias of human keratinocytes to activate pyroptosis, a caspase 1-dependent form of inflammatory cell death, which was required for staphylococci to penetrate across a keratinocyte barrier. Keratinocyte necrosis was mediated by calpains, Ca(2+)-dependent intracellular proteases whose endogenous inhibitor, calpastatin, is targeted by Hla-induced caspase 1. Neither Panton-Valentine leukocidin nor protein A expression was essential, but inhibition of either calpain or caspase 1 activity was sufficient to prevent staphylococcal invasion across the keratinocytes. These studies suggest that pharmacological interruption of specific keratinocyte signaling cascades as well as targeting the Hla might prevent invasive skin infection by staphylococci.
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Affiliation(s)
- Grace Soong
- Department of Pediatrics, Columbia University, New York, New York 10032, USA
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310
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Narayanavari SA, Sritharan M, Haake DA, Matsunaga J. Multiple leptospiral sphingomyelinases (or are there?). MICROBIOLOGY-SGM 2012; 158:1137-1146. [PMID: 22422753 DOI: 10.1099/mic.0.057737-0] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Culture supernatants of leptospiral pathogens have long been known to haemolyse erythrocytes. This property is due, at least in part, to sphingomyelinase activity. Indeed, genome sequencing reveals that pathogenic Leptospira species are richly endowed with sphingomyelinase homologues: five genes have been annotated to encode sphingomyelinases in Leptospira interrogans. Such redundancy suggests that this class of genes is likely to benefit leptospiral pathogens in their interactions with the mammalian host. Surprisingly, sequence comparison with bacterial sphingomyelinases for which the crystal structures are known reveals that only one of the leptospiral homologues has the active site amino acid residues required for enzymic activity. Based on studies of other bacterial toxins, we propose that leptospiral sphingomyelinase homologues, irrespective of their catalytic activity, may possess additional molecular functions that benefit the spirochaete. Potential secretion pathways and roles in pathogenesis are discussed, including nutrient acquisition, dissemination, haemorrhage and immune evasion. Although leptospiral sphingomyelinase-like proteins are best known for their cytolytic properties, we believe that a better understanding of their biological role requires the examination of their sublytic properties as well.
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Affiliation(s)
| | - Manjula Sritharan
- Department of Animal Sciences, University of Hyderabad, Hyderabad, India
| | - David A Haake
- Department of Medicine, University of California at Los Angeles, Los Angeles, CA, USA.,Department of Urology, University of California at Los Angeles, Los Angeles, CA, USA.,Division of Infectious Diseases, VA Greater Los Angeles Healthcare System, Los Angeles, CA, USA.,Department of Microbiology, Immunology, and Molecular Genetics, University of California at Los Angeles, Los Angeles, CA, USA
| | - James Matsunaga
- Research Service, VA Greater Los Angeles Healthcare System, Los Angeles, CA, USA.,Department of Medicine, University of California at Los Angeles, Los Angeles, CA, USA
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311
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Perret M, Badiou C, Lina G, Burbaud S, Benito Y, Bes M, Cottin V, Couzon F, Juruj C, Dauwalder O, Goutagny N, Diep BA, Vandenesch F, Henry T. Cross-talk between Staphylococcus aureus leukocidins-intoxicated macrophages and lung epithelial cells triggers chemokine secretion in an inflammasome-dependent manner. Cell Microbiol 2012; 14:1019-36. [DOI: 10.1111/j.1462-5822.2012.01772.x] [Citation(s) in RCA: 89] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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312
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Inoshima N, Wang Y, Bubeck Wardenburg J. Genetic requirement for ADAM10 in severe Staphylococcus aureus skin infection. J Invest Dermatol 2012; 132:1513-6. [PMID: 22377761 PMCID: PMC3326222 DOI: 10.1038/jid.2011.462] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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313
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Vandenesch F, Lina G, Henry T. Staphylococcus aureus hemolysins, bi-component leukocidins, and cytolytic peptides: a redundant arsenal of membrane-damaging virulence factors? Front Cell Infect Microbiol 2012; 2:12. [PMID: 22919604 PMCID: PMC3417661 DOI: 10.3389/fcimb.2012.00012] [Citation(s) in RCA: 233] [Impact Index Per Article: 19.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/26/2011] [Accepted: 01/31/2012] [Indexed: 12/17/2022] Open
Abstract
One key aspect of the virulence of Staphylococcus aureus lies in its ability to target the host cell membrane with a large number of membrane-damaging toxins and peptides. In this review, we describe the hemolysins, the bi-component leukocidins (which include the Panton Valentine leukocidin, LukAB/GH, and LukED), and the cytolytic peptides (phenol soluble modulins). While at first glance, all of these factors might appear redundant, it is now clear that some of these factors play specific roles in certain S. aureus life stages and diseases or target specific cell types or species. In this review, we present an update of the literature on toxin receptors and their cell type and species specificities. Furthermore, we review epidemiological studies and animal models illustrating the role of these membrane-damaging factors in various diseases. Finally, we emphasize the interplay of these factors with the host immune system and highlight all their non-lytic functions.
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Affiliation(s)
- François Vandenesch
- Bacterial Pathogenesis and Innate Immunity Laboratory, INSERM U851 "Immunity, Infection and Vaccination," Lyon, France
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314
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Kebaier C, Chamberland RR, Allen IC, Gao X, Broglie PM, Hall JD, Jania C, Doerschuk CM, Tilley SL, Duncan JA. Staphylococcus aureus α-hemolysin mediates virulence in a murine model of severe pneumonia through activation of the NLRP3 inflammasome. J Infect Dis 2012; 205:807-17. [PMID: 22279123 DOI: 10.1093/infdis/jir846] [Citation(s) in RCA: 184] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Staphylococcus aureus is a dangerous pathogen that can cause necrotizing infections characterized by massive inflammatory responses and tissue destruction. Staphylococcal α-hemolysin is an essential virulence factor in severe S. aureus pneumonia. It activates the nucleotide-binding domain and leucine-rich repeat containing gene family, pyrin domain containing 3 (NLRP3) inflammasome to induce production of interleukin-1β and programmed necrotic cell death. We sought to determine the role of α-hemolysin-mediated activation of NLRP3 in the pathogenesis of S. aureus pneumonia. We show that α-hemolysin activates the NLRP3 inflammasome during S. aureus pneumonia, inducing necrotic pulmonary injury. Moreover, Nlrp3(-/-) mice have less-severe pneumonia. Pulmonary injury induced by isolated α-hemolysin or live S. aureus is independent of interleukin-1β signaling, implicating NLRP3-induced necrosis in the pathogenesis of severe infection. This work demonstrates the exploitation of host inflammatory signaling by S. aureus and suggests the NLRP3 inflammasome as a potential target for pharmacologic interventions in severe S. aureus infections.
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Affiliation(s)
- Chahnaz Kebaier
- Department of Medicine, Division of Infectious Diseases, University of North Carolina, Chapel Hill, USA
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315
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Identification of anti-alpha toxin monoclonal antibodies that reduce the severity of Staphylococcus aureus dermonecrosis and exhibit a correlation between affinity and potency. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2012; 19:377-85. [PMID: 22237895 DOI: 10.1128/cvi.05589-11] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Staphylococcus aureus alpha toxin (AT) is an important virulence determinant and may be a valid target for immunoprophylaxis against staphylococcal disease. Here we report the identification of potent inhibitory anti-AT monoclonal antibodies (MAbs) derived using B-cell hybridoma technology from VelocImmune mice engineered to produce IgG with a human variable domain. A small panel of inhibitory MAbs blocked AT-mediated lysis of rabbit red blood cells, A549 human lung epithelial cells, and THP-1 human monocytic cells, in a dose-dependent manner. Binding studies indicated that these MAbs recognize a similar epitope on AT and exhibit dissociation constants (K(D)) ranging from 0.50 to 15 nM. In an S. aureus dermonecrosis model, mice passively immunized with anti-AT inhibitory MAbs exhibited significant reductions of lesion size relative to mice treated with an irrelevant IgG control. Interestingly, there was a correlation between MAb affinity for a single epitope, the 50% inhibitory concentration (IC(50)) in the AT hemolytic assay, and lesion size reduction in the dermonecrosis model. A representative high-affinity MAb, 2A3.1, was demonstrated to significantly reduce lesion size following infection with three different clinical isolates (USA300, CC30, and CC5). Taken together, these results indicate that in vitro potency of anti-AT MAbs predicts in vivo potency in this model, supporting their continued preclinical evaluation as molecules for immunoprophylaxis against staphylococcal skin and soft tissue infections caused by diverse clinical isolates.
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316
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David R. Breaking the barrier. Nat Rev Microbiol 2011; 9:768. [DOI: 10.1038/nrmicro2672] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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