51
|
Los FCO, Randis TM, Aroian RV, Ratner AJ. Role of pore-forming toxins in bacterial infectious diseases. Microbiol Mol Biol Rev 2013; 77:173-207. [PMID: 23699254 PMCID: PMC3668673 DOI: 10.1128/mmbr.00052-12] [Citation(s) in RCA: 299] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Pore-forming toxins (PFTs) are the most common bacterial cytotoxic proteins and are required for virulence in a large number of important pathogens, including Streptococcus pneumoniae, group A and B streptococci, Staphylococcus aureus, Escherichia coli, and Mycobacterium tuberculosis. PFTs generally disrupt host cell membranes, but they can have additional effects independent of pore formation. Substantial effort has been devoted to understanding the molecular mechanisms underlying the functions of certain model PFTs. Likewise, specific host pathways mediating survival and immune responses in the face of toxin-mediated cellular damage have been delineated. However, less is known about the overall functions of PFTs during infection in vivo. This review focuses on common themes in the area of PFT biology, with an emphasis on studies addressing the roles of PFTs in in vivo and ex vivo models of colonization or infection. Common functions of PFTs include disruption of epithelial barrier function and evasion of host immune responses, which contribute to bacterial growth and spreading. The widespread nature of PFTs make this group of toxins an attractive target for the development of new virulence-targeted therapies that may have broad activity against human pathogens.
Collapse
Affiliation(s)
| | - Tara M. Randis
- Department of Pediatrics, Columbia University, New York, New York, USA
| | - Raffi V. Aroian
- Division of Biological Sciences, Section of Cell and Developmental Biology, University of California San Diego, La Jolla, California, USA
| | - Adam J. Ratner
- Department of Pediatrics, Columbia University, New York, New York, USA
| |
Collapse
|
52
|
Asam D, Mauerer S, Walheim E, Spellerberg B. Identification of β-haemolysin-encoding genes inStreptococcus anginosus. Mol Oral Microbiol 2013; 28:302-15. [DOI: 10.1111/omi.12026] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/21/2013] [Indexed: 11/30/2022]
Affiliation(s)
- D. Asam
- Institute of Medical Microbiology and Hospital Hygiene; University of Ulm; Ulm; Germany
| | - S. Mauerer
- Institute of Medical Microbiology and Hospital Hygiene; University of Ulm; Ulm; Germany
| | | | - B. Spellerberg
- Institute of Medical Microbiology and Hospital Hygiene; University of Ulm; Ulm; Germany
| |
Collapse
|
53
|
Cassidy SKB, O'Riordan MXD. More than a pore: the cellular response to cholesterol-dependent cytolysins. Toxins (Basel) 2013; 5:618-36. [PMID: 23584137 PMCID: PMC3705283 DOI: 10.3390/toxins5040618] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2013] [Revised: 04/07/2013] [Accepted: 04/07/2013] [Indexed: 12/15/2022] Open
Abstract
Targeted disruption of the plasma membrane is a ubiquitous form of attack used in all three domains of life. Many bacteria secrete pore-forming proteins during infection with broad implications for pathogenesis. The cholesterol-dependent cytolysins (CDC) are a family of pore-forming toxins expressed predominately by Gram-positive bacterial pathogens. The structure and assembly of some of these oligomeric toxins on the host membrane have been described, but how the targeted cell responds to intoxication by the CDCs is not as clearly understood. Many CDCs induce lysis of their target cell and can activate apoptotic cascades to promote cell death. However, the extent to which intoxication causes cell death is both CDC- and host cell-dependent, and at lower concentrations of toxin, survival of intoxicated host cells is well documented. Additionally, the effect of CDCs can be seen beyond the plasma membrane, and it is becoming increasingly clear that these toxins are potent regulators of signaling and immunity, beyond their role in intoxication. In this review, we discuss the cellular response to CDC intoxication with emphasis on the effects of pore formation on the host cell plasma membrane and subcellular organelles and whether subsequent cellular responses contribute to the survival of the affected cell.
Collapse
Affiliation(s)
- Sara K B Cassidy
- Department of Microbiology and Immunology, University of Michigan Medical School, 1150 W. Medical Center Dr., Ann Arbor, MI 48109, USA.
| | | |
Collapse
|
54
|
Horst SA, Linnér A, Beineke A, Lehne S, Höltje C, Hecht A, Norrby-Teglund A, Medina E, Goldmann O. Prognostic value and therapeutic potential of TREM-1 in Streptococcus pyogenes- induced sepsis. J Innate Immun 2013; 5:581-90. [PMID: 23571837 DOI: 10.1159/000348283] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2012] [Accepted: 01/21/2013] [Indexed: 12/31/2022] Open
Abstract
TREM-1 (triggering receptor expressed on myeloid cells) is a surface molecule expressed on neutrophils and macrophages which has been implicated in the amplification of inflammatory responses triggered during infection. In the present study, we have investigated the clinical significance of TREM-1 in Streptococcus pyogenes-induced severe sepsis in both experimentally infected mice as well as in patients with streptococcal toxic shock. We found that S. pyogenes induced a dose-dependent upregulation of TREM-1 in in vitro cultured phagocytic cells and in the organs of S. pyogenes-infected mice. Furthermore, we reported a positive correlation between serum levels of soluble TREM-1 (sTREM-1) and disease severity in infected patients as well as in experimentally infected mice. Hence, sTREM-1 may represent a useful surrogate marker for streptococcal sepsis. We found that modulation of TREM-1 by administration of the TREM-1 decoy receptor rTREM-1/Fc substantially attenuated the synthesis of inflammatory cytokines. More importantly, treatment of S. pyogenes-infected septic mice with rTREM-1/Fc or the synthetically produced conserved extracellular domain LP17 significantly improved disease outcome. In summary, our data suggest that TREM-1 may not only represent a valuable marker for S. pyogenes infection severity but it may also be an attractive target for the treatment of streptococcal sepsis.
Collapse
Affiliation(s)
- Sarah A Horst
- Infection Immunology Research Group, Department of Microbial Pathogenesis, Helmholtz Center for Infection Research, Braunschweig, Germany
| | | | | | | | | | | | | | | | | |
Collapse
|
55
|
Remuzgo-Martínez S, Aranzamendi-Zaldunbide M, Pilares-Ortega L, Icardo JM, Acosta F, Martínez-Martínez L, Ramos-Vivas J. Interaction of macrophages with a cytotoxic Serratia liquefaciens human isolate. Microbes Infect 2013; 15:480-90. [PMID: 23524146 DOI: 10.1016/j.micinf.2013.03.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2012] [Revised: 03/07/2013] [Accepted: 03/11/2013] [Indexed: 11/18/2022]
Abstract
Macrophages play key roles in host defense by recognizing, engulfing, and killing microorganisms. Understanding the response of macrophages to pathogens may provide insights into host defenses and the tactics used by pathogens to circumvent these defenses. In the present study, we investigated the interaction between a clinical isolate of Serratia liquefaciens and macrophages. S. liquefaciens strain HUMV-3250 triggers a fast and potent cytotoxic effect upon infection. This process requires the presence of live bacteria, adherence, and protein synthesis but not phagocytosis/bacterial internalization. Moreover, cytotoxicity assays, analysis of DNA integrity, immunofluorescence, and confocal, scanning, and time-lapse microscopy revealed that macrophage viability decreased rapidly with time upon challenge, and depends on the MOI used. Treatment of macrophages with caspase-1 inhibitors, or with specific inhibitors of phagocytosis, did not alter the infection outcome. Moreover, human macrophages exhibited similar cytotoxic changes after infection with this strain. Macrophages responded to this cytotoxic strain with a robust pattern of pro-inflammatory gene expression. However, phagocytosis attempts to engulf live bacteria were unsuccessful, and the phagocytes were unable to kill the bacteria. We conclude that macrophage cell death occurs rapidly as a result of necrotic events after close contact with S. liquefaciens. These results likely have important implications for understanding Serratia pathogenesis and host response to infection.
Collapse
Affiliation(s)
- Sara Remuzgo-Martínez
- Servicio de Microbiología, Hospital Universitario Marqués de Valdecilla-IFIMAV, Santander, Cantabria, Spain
| | | | | | | | | | | | | |
Collapse
|
56
|
Vitamin D and the human antimicrobial peptide LL-37 enhance group a streptococcus resistance to killing by human cells. mBio 2012; 3:mBio.00394-12. [PMID: 23093388 PMCID: PMC3482505 DOI: 10.1128/mbio.00394-12] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
The CsrRS two-component regulatory system of group A Streptococcus (GAS; Streptococcus pyogenes) responds to subinhibitory concentrations of the human antimicrobial peptide LL-37. LL-37 signaling through CsrRS results in upregulation of genes that direct synthesis of virulence factors, including the hyaluronic acid capsule and streptolysin O (SLO). Here, we demonstrate that a consequence of this response is augmented GAS resistance to killing by human oropharyngeal keratinocytes, neutrophils, and macrophages. LL-37-induced upregulation of SLO and hyaluronic acid capsule significantly reduced internalization of GAS by keratinocytes and phagocytic killing by neutrophils and macrophages. Because vitamin D induces LL-37 production by macrophages, we tested its effect on macrophage killing of GAS. In contrast to the reported enhancement of macrophage function in relation to other pathogens, treatment of macrophages with 1α,25-dihydroxy-vitamin D3 paradoxically reduced the ability of macrophages to control GAS infection. These observations demonstrate that LL-37 signals through CsrRS to induce a virulence phenotype in GAS characterized by heightened resistance to ingestion and killing by both epithelial cells and phagocytes. By inducing LL-37 production in macrophages, vitamin D may contribute to this paradoxical exacerbation of GAS infection. IMPORTANCE It remains poorly understood why group A Streptococcus (GAS) causes asymptomatic colonization or localized throat inflammation in most individuals but rarely progresses to invasive infection. The human antimicrobial peptide LL-37, which is produced as part of the innate immune response to GAS infection, signals through the GAS CsrRS two-component regulatory system to upregulate expression of multiple virulence factors. This study reports that two CsrRS-regulated GAS virulence factors-streptolysin O and the hyaluronic acid capsule-are critical in LL-37-induced resistance of GAS to killing by human throat epithelial cells and by neutrophils and macrophages. Vitamin D, which increases LL-37 production in macrophages, has the paradoxical effect of increasing GAS resistance to macrophage-mediated killing. In this way, the human innate immune response may promote the transition from GAS colonization to invasive infection.
Collapse
|
57
|
Agarwal S, Agarwal S, Jin H, Pancholi P, Pancholi V. Serine/threonine phosphatase (SP-STP), secreted from Streptococcus pyogenes, is a pro-apoptotic protein. J Biol Chem 2012; 287:9147-67. [PMID: 22262847 DOI: 10.1074/jbc.m111.316554] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023] Open
Abstract
This investigation illustrates an important property of eukaryote-type serine/threonine phosphatase (SP-STP) of group A Streptococcus (GAS) in causing programmed cell death of human pharyngeal cells. The secretory nature of SP-STP, its elevated expression in the intracellular GAS, and the ability of wild-type GAS but not the GAS mutant devoid of SP-STP to cause apoptosis of the host cell both in vitro and in vivo suggest that GAS deploys SP-STP as an important virulence determinant to exploit host cell machinery for its own advantage during infection. The exogenously added SP-STP is able to enter the cytoplasm and subsequently traverses into the nucleus in a temporal fashion to cause apoptosis of the pharyngeal cells. The programmed cell death induced by SP-STP, which requires active transcription and de novo protein synthesis, is also caspase-dependent. Furthermore, the entry of SP-STP into the cytoplasm is dependent on its secondary structure as the catalytically inactive SP-STP with an altered structure is unable to internalize and cause apoptosis. The ectopically expressed wild-type SP-STP was found to be in the nucleus and conferred apoptosis of Detroit 562 pharyngeal cells. However, the catalytically inactive SP-STP was unable to cause apoptosis even when intracellularly expressed. The ability of SP-STP to activate pro-apoptotic signaling cascades both in the cytoplasm and in the nucleus resulted in mitochondrial dysfunctioning and perturbation in the phosphorylation status of histones in the nucleus. SP-STP thus not only functions as a virulence regulator but also as an important factor responsible for host-related pathogenesis.
Collapse
Affiliation(s)
- Shivani Agarwal
- Department of Pathology, Ohio State University College of Medicine, Columbus, Ohio 43210-1214, USA
| | | | | | | | | |
Collapse
|
58
|
Lai Y, Riley K, Cai A, Leong JM, Herman IM. Calpain mediates epithelial cell microvillar effacement by enterohemorrhagic Escherichia coli. Front Microbiol 2011; 2:222. [PMID: 22073041 PMCID: PMC3210503 DOI: 10.3389/fmicb.2011.00222] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2011] [Accepted: 10/20/2011] [Indexed: 11/13/2022] Open
Abstract
A member of the attaching and effacing (AE) family of pathogens, enterohemorrhagic Escherichia coli (EHEC) induces dramatic changes to the intestinal cell cytoskeleton, including effacement of microvilli. Effacement by the related pathogen enteropathogenic E. coli (EPEC) requires the activity of the Ca+2-dependent host protease, calpain, which participates in a variety of cellular processes, including cell adhesion and motility. We found that EHEC infection results in an increase in epithelial (CaCo-2a) cell calpain activity and that EHEC-induced microvillar effacement was blocked by ectopic expression of calpastatin, an endogenous calpain inhibitor, or by pretreatment of intestinal cells with a cell-penetrating version of calpastatin. In addition, ezrin, a known calpain substrate that links the plasma membrane to axial actin filaments in microvilli, was cleaved in a calpain-dependent manner during EHEC infection and lost from its normal locale within microvilli. Calpain may be a central conduit through which EHEC and other AE pathogens induce enterocyte cytoskeletal remodeling and exert their pathogenic effects.
Collapse
Affiliation(s)
- Yushuan Lai
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School Worcester, MA, USA
| | | | | | | | | |
Collapse
|
59
|
Molloy EM, Cotter PD, Hill C, Mitchell DA, Ross RP. Streptolysin S-like virulence factors: the continuing sagA. Nat Rev Microbiol 2011; 9:670-81. [PMID: 21822292 DOI: 10.1038/nrmicro2624] [Citation(s) in RCA: 107] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Streptolysin S (SLS) is a potent cytolytic toxin and virulence factor that is produced by nearly all Streptococcus pyogenes strains. Despite a 100-year history of research on this toxin, it has only recently been established that SLS is just one of an extended family of post-translationally modified virulence factors (the SLS-like peptides) that are produced by some streptococci and other Gram-positive pathogens, such as Listeria monocytogenes and Clostridium botulinum. In this Review, we describe the identification, genetics, biochemistry and various functions of SLS. We also discuss the shared features of the virulence-associated SLS-like peptides, as well as their place within the rapidly expanding family of thiazole/oxazole-modified microcins (TOMMs).
Collapse
Affiliation(s)
- Evelyn M Molloy
- Department of Microbiology, University College Cork, Cork, Ireland
| | | | | | | | | |
Collapse
|
60
|
Medina E, Goldmann O. In vivo and ex vivo protocols for measuring the killing of extracellular pathogens by macrophages. ACTA ACUST UNITED AC 2011; Chapter 14:Unit 14.19.1-17. [PMID: 21400679 DOI: 10.1002/0471142735.im1419s92] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
This unit describes a series of in vivo/ex vivo combined protocols for investigating the interactions (adhesion, phagocytosis, and killing) of extracellular bacteria with peritoneal murine macrophages. It includes steps needed for in vivo infection of murine peritoneal macrophages after intraperitoneal inoculation with the pathogen of interest, as well as the measurement of bacteria associated with or truly internalized by these phagocytic cells. Several protocols for the ex vivo measurement of the ability of peritoneal macrophages to kill the microorganisms that have been ingested during the in vivo infection assay are included.
Collapse
Affiliation(s)
- Eva Medina
- Infection Immunology Research Group, Helmholtz Centre for Infection Research, Braunschweig, Germany
| | | |
Collapse
|
61
|
Siemens N, Patenge N, Otto J, Fiedler T, Kreikemeyer B. Streptococcus pyogenes M49 plasminogen/plasmin binding facilitates keratinocyte invasion via integrin-integrin-linked kinase (ILK) pathways and protects from macrophage killing. J Biol Chem 2011; 286:21612-22. [PMID: 21521694 DOI: 10.1074/jbc.m110.202671] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
The entry into epithelial cells and the prevention of primary immune responses are a prerequisite for a successful colonization and subsequent infection of the human host by Streptococcus pyogenes (group A streptococci, GAS). Here, we demonstrate that interaction of GAS with plasminogen promotes an integrin-mediated internalization of the bacteria into keratinocytes, which is independent from the serine protease activity of potentially generated plasmin. α(1)β(1)- and α(5)β(1)-integrins were identified as the major keratinocyte receptors involved in this process. Inhibition of integrin-linked kinase (ILK) expression by siRNA silencing or blocking of PI3K and Akt with specific inhibitors, reduced the GAS M49-plasminogen/plasmin-mediated invasion of keratinocytes. In addition, blocking of actin polymerization significantly reduced GAS internalization into keratinocytes. Altogether, these results provide a first model of plasminogen-mediated GAS invasion into keratinocytes. Furthermore, we demonstrate that plasminogen binding protects the bacteria against macrophage killing.
Collapse
Affiliation(s)
- Nikolai Siemens
- Institute of Medical Microbiology, Virology and Hygiene, Rostock University Hospital, Schillingallee 70, 18057 Rostock, Germany
| | | | | | | | | |
Collapse
|
62
|
Connolly KL, Roberts AL, Holder RC, Reid SD. Dispersal of Group A streptococcal biofilms by the cysteine protease SpeB leads to increased disease severity in a murine model. PLoS One 2011; 6:e18984. [PMID: 21547075 PMCID: PMC3081844 DOI: 10.1371/journal.pone.0018984] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2011] [Accepted: 03/18/2011] [Indexed: 12/19/2022] Open
Abstract
Group A Streptococcus (GAS) is a Gram-positive human pathogen best known for causing pharyngeal and mild skin infections. However, in the 1980's there was an increase in severe GAS infections including cellulitis and deeper tissue infections like necrotizing fasciitis. Particularly striking about this elevation in the incidence of severe disease was that those most often affected were previously healthy individuals. Several groups have shown that changes in gene content or regulation, as with proteases, may contribute to severe disease; yet strains harboring these proteases continue to cause mild disease as well. We and others have shown that group A streptococci (MGAS5005) reside within biofilms both in vitro and in vivo. That is to say that the organism colonizes a host surface and forms a 3-dimensional community encased in a protective matrix of extracellular protein, DNA and polysaccharide(s). However, the mechanism of assembly or dispersal of these structures is unclear, as is the relationship of these structures to disease outcome. Recently we reported that allelic replacement of the streptococcal regulator srv resulted in constitutive production of the streptococcal cysteine protease SpeB. We further showed that the constitutive production of SpeB significantly decreased MGAS5005Δsrv biofilm formation in vitro. Here we show that mice infected with MGAS5005Δsrv had significantly larger lesion development than wild-type infected animals. Histopathology, Gram-staining and immunofluorescence link the increased lesion development with lack of disease containment, lack of biofilm formation, and readily detectable levels of SpeB in the tissue. Treatment of MGAS5005Δsrv infected lesions with a chemical inhibitor of SpeB significantly reduced lesion formation and disease spread to wild-type levels. Furthermore, inactivation of speB in the MGAS5005Δsrv background reduced lesion formation to wild-type levels. Taken together, these data suggest a mechanism by which GAS disease may transition from mild to severe through the Srv mediated dispersal of GAS biofilms.
Collapse
Affiliation(s)
- Kristie L. Connolly
- Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States of America
| | - Amity L. Roberts
- Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States of America
| | - Robert C. Holder
- Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States of America
| | - Sean D. Reid
- Department of Microbiology and Immunology, Wake Forest University School of Medicine, Winston-Salem, North Carolina, United States of America
- * E-mail:
| |
Collapse
|
63
|
Interactions between bacterial pathogens and mitochondrial cell death pathways. Nat Rev Microbiol 2010; 8:693-705. [PMID: 20818415 DOI: 10.1038/nrmicro2421] [Citation(s) in RCA: 123] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The modulation of host cell death pathways by bacteria has been recognized as a major pathogenicity mechanism. Among other strategies, bacterial pathogens can hijack the cell death machinery of host cells by influencing the signalling pathways that converge on the mitochondria. In particular, many bacterial proteins have evolved to interact in a highly specific manner with host mitochondria, thereby modulating the decision between cell life and death. In this Review, we explore the intimate interactions between bacterial pathogens and mitochondrial cell death pathways.
Collapse
|
64
|
M protein and hyaluronic acid capsule are essential for in vivo selection of covRS mutations characteristic of invasive serotype M1T1 group A Streptococcus. mBio 2010; 1. [PMID: 20827373 PMCID: PMC2934611 DOI: 10.1128/mbio.00191-10] [Citation(s) in RCA: 109] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/16/2010] [Accepted: 07/29/2010] [Indexed: 12/14/2022] Open
Abstract
The initiation of hyperinvasive disease in group A Streptococcus (GAS) serotype M1T1 occurs by mutation within the covRS two-component regulon (named covRS for control of virulence regulatory sensor kinase), which promotes resistance to neutrophil-mediated killing through the upregulation of bacteriophage-encoded Sda1 DNase. To determine whether other virulence factors contribute to this phase-switching phenomenon, we studied a panel of 10 isogenic GAS serotype M1T1 virulence gene knockout mutants. While loss of several individual virulence factors did not prevent GAS covRS switching in vivo, we found that M1 protein and hyaluronic acid capsule are indispensable for the switching phenotype, a phenomenon previously attributed uniquely to the Sda1 DNase. We demonstrate that like M1 protein and Sda1, capsule expression enhances survival of GAS serotype M1T1 within neutrophil extracellular traps. Furthermore, capsule shares with M1 protein a role in GAS resistance to human cathelicidin antimicrobial peptide LL-37. We conclude that a quorum of GAS serotype M1T1 virulence genes with cooperative roles in resistance to neutrophil extracellular killing is essential for the switch to a hyperinvasive phenotype in vivo. The pathogen group A Streptococcus (GAS) causes a wide range of human infections ranging from the superficial “strep throat” to potentially life-threatening conditions, such as necrotizing fasciitis, also known as “flesh-eating disease.” A marked increase in the number of cases of severe invasive GAS infection during the last 30 years has been traced to the emergence and spread of a single clone of the M1T1 serotype. Recent studies have shown that GAS serotype M1T1 bacteria undergo a genetic “switch” in vivo to a hypervirulent state that allows dissemination into the bloodstream. The present study was undertaken to identify specific GAS serotype M1T1 virulence factors required for this switch to hypervirulence. The surface-anchored GAS M1 protein and hyaluronic acid capsule are found to be essential for the switching phenotype, and a novel role for capsule in GAS resistance to host defense peptides and neutrophil extracellular killing is revealed.
Collapse
|
65
|
Cao X, Zhang Y, Zou L, Xiao H, Chu Y, Chu X. Persistent oxygen-glucose deprivation induces astrocytic death through two different pathways and calpain-mediated proteolysis of cytoskeletal proteins during astrocytic oncosis. Neurosci Lett 2010; 479:118-22. [DOI: 10.1016/j.neulet.2010.05.040] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2010] [Revised: 05/04/2010] [Accepted: 05/13/2010] [Indexed: 10/19/2022]
|
66
|
Goldmann O, Lehne S, Medina E. Age-related susceptibility to Streptococcus pyogenes infection in mice: underlying immune dysfunction and strategy to enhance immunity. J Pathol 2010; 220:521-9. [PMID: 20020512 DOI: 10.1002/path.2664] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Epidemiological studies have shown that the elderly are at higher risk of severe Streptococcus pyogenes infections. In this study, we used a mouse model that displays the age-related loss of resistance to S. pyogenes infection seen in humans to investigate the impaired immune mechanism underlying the age-associated susceptibility to this pathogen. Young (2-3 months old) and aged (>20 months old) BALB/c mice were subcutaneously or intravenously inoculated with S. pyogenes and their capacity to control infection was compared. Aged mice showed faster progression of disease, earlier morbidity, and increased mortality when compared with young animals. Since macrophages are critical for host defence against S. pyogenes, we investigated whether susceptibility of aged mice may be due to an age-associated decline in the functionality of these cells. Our results showed that macrophages from aged mice were as capable as those from young animals to uptake and kill S. pyogenes, but the number of resident tissue macrophages was significantly reduced in the aged host. Treatment of aged mice with macrophage colony-stimulating factor (M-CSF) significantly increased the number of resident macrophages and improved their response to infection. Our results indicate that treatment with M-CSF can restore, at least in part, the mechanisms affected by immunosenescence and enhance the natural resistance of aged mice to infection with S. pyogenes.
Collapse
Affiliation(s)
- Oliver Goldmann
- Infection Immunology Research Group, Department of Microbial Pathogenesis, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, D-38124 Braunschweig, Germany
| | | | | |
Collapse
|
67
|
Loof TG, Goldmann O, Gessner A, Herwald H, Medina E. Aberrant inflammatory response to Streptococcus pyogenes in mice lacking myeloid differentiation factor 88. THE AMERICAN JOURNAL OF PATHOLOGY 2009; 176:754-63. [PMID: 20019195 DOI: 10.2353/ajpath.2010.090422] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Several in vitro studies have emphasized the importance of toll-like receptor/myeloid differentiation factor 88 (MyD88) signaling in the inflammatory response to Streptococcus pyogenes. Since the extent of inflammation has been implicated in the severity of streptococcal diseases, we have examined here the role of toll-like receptor/MyD88 signaling in the pathophysiology of experimental S. pyogenes infection. To this end, we compared the response of MyD88-knockout (MyD88(-/-)) after subcutaneous inoculation with S. pyogenes with that of C57BL/6 mice. Our results show that MyD88(-/-) mice harbored significantly more bacteria in the organs and succumbed to infection much earlier than C57BL/6 animals. Absence of MyD88 resulted in diminished production of inflammatory cytokines such as interleukin-12, interferon-gamma, and tumor necrosis factor-alpha as well as chemoattractants such as monocyte chemotactic protein-1 (MCP-1) and Keratinocyte-derived chemokine (KC), and hampered recruitment of effector cells involved in bacterial clearance (macrophages and neutrophils) to the infection site. Furthermore, MyD88(-/-) but not C57BL/6 mice exhibited a massive infiltration of eosinophils in infected organs, which can be explained by an impaired production of the regulatory chemokines, gamma interferon-induced monokine (MIG/CXCL9) and interferon-induced protein 10 (IP-10/CXCL10), which can inhibit transmigration of eosinophils. Our results indicate that MyD88 signaling targets effector cells to the site of streptococcal infection and prevents extravasation of cells that can induce tissue damage. Therefore, MyD88 signaling may be important for shaping the quality of the inflammatory response elicited during infection to ensure optimal effector functions.
Collapse
Affiliation(s)
- Torsten G Loof
- Department of Microbial Pathogenesis, Infection Immunology Research Group, Helmholtz Centre for Infection Research, D-38124 Braunschweig, Germany
| | | | | | | | | |
Collapse
|
68
|
The role of mitochondria in cellular defense against microbial infection. Semin Immunol 2009; 21:223-32. [PMID: 19535268 DOI: 10.1016/j.smim.2009.05.009] [Citation(s) in RCA: 76] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/16/2009] [Accepted: 05/07/2009] [Indexed: 12/31/2022]
Abstract
Mitochondria have been long recognized for their key role in the modulation of cell death pathways. Thus, it is therefore not surprising that this organelle represents a recurrent target for pathogenic microbes, aiming to manipulate the fate of the infected host cell. More recently, mitochondria have been shown to serve as a crucial platform for innate immune signaling, as illustrated by the identification of MAVS (also known as IPS-1, VISA and Cardif), NLRX1 and STING as mitochondrial proteins. This review discusses the tight interplay between microbial infection, innate immune signaling and mitochondria.
Collapse
|
69
|
Cell death during sepsis: integration of disintegration in the inflammatory response to overwhelming infection. Apoptosis 2009; 14:509-21. [DOI: 10.1007/s10495-009-0320-3] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
|