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Abstract
Given their small size, platelets are emerging as being one of the most important entities in the bloodstream. Not only do they play a key role in maintaining thrombosis and haemostasis, platelets also play a critical role in orchestrating the immune response. Being the first cell at the site of injury, they are perfectly placed to assess the extent of the damage and recruit immune cells as is necessary. As a first line of defence, platelets can act as primitive immune cells themselves by interacting with invading pathogens. A number of platelet receptors have been shown to interact with bacteria either directly or indirectly, involving a plasma protein bridge. This review will discuss the molecular mechanisms that exist between platelets and bacteria and the functional response to the interaction. We will also discuss the importance of considering animal models of disease and the use of physiological shear when studying platelet-bacterial interactions.
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Affiliation(s)
- Steven W Kerrigan
- School of Pharmacy & Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland , Dublin , Ireland
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52
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Suzuki N, Ohtaguro N, Yoshida Y, Hirai M, Matsuo H, Yamada Y, Imamura N, Tsuchiya T. A Compound Inhibits Biofilm Formation of Staphylococcus aureus from Streptomyces. Biol Pharm Bull 2015; 38:889-92. [DOI: 10.1248/bpb.b15-00053] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Affiliation(s)
- Naomoto Suzuki
- College of Pharmaceutical Sciences, Ritsumeikan University
| | | | | | - Motoshi Hirai
- College of Pharmaceutical Sciences, Ritsumeikan University
| | | | - Yoichi Yamada
- College of Pharmaceutical Sciences, Ritsumeikan University
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53
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The effect of skin fatty acids on Staphylococcus aureus. Arch Microbiol 2014; 197:245-67. [PMID: 25325933 PMCID: PMC4326651 DOI: 10.1007/s00203-014-1048-1] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Revised: 09/19/2014] [Accepted: 10/06/2014] [Indexed: 12/14/2022]
Abstract
Staphylococcus aureus is a commensal of the human nose and skin. Human skin fatty acids, in particular cis-6-hexadecenoic acid (C-6-H), have high antistaphylococcal activity and can inhibit virulence determinant production. Here, we show that sub-MIC levels of C-6-H result in induction of increased resistance. The mechanism(s) of C-6-H activity was investigated by combined transcriptome and proteome analyses. Proteome analysis demonstrated a pleiotropic effect of C-6-H on virulence determinant production. In response to C-6-H, transcriptomics revealed altered expression of over 500 genes, involved in many aspects of virulence and cellular physiology. The expression of toxins (hla, hlb, hlgBC) was reduced, whereas that of host defence evasion components (cap, sspAB, katA) was increased. In particular, members of the SaeRS regulon had highly reduced expression, and the use of specific mutants revealed that the effect on toxin production is likely mediated via SaeRS.
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54
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Inactivation of sortase A mediated by metal ATCUN complexes. J Biol Inorg Chem 2014; 19:1327-39. [PMID: 25217034 DOI: 10.1007/s00775-014-1190-x] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2014] [Accepted: 08/24/2014] [Indexed: 02/07/2023]
Abstract
Catalytic metallopeptides that target the membrane-associated sortase A transpeptidase have been developed and evaluated as irreversible inactivators of SrtA∆N59 (sortase A, lacking the initial membrane-binding domain). The copper-binding GGH tripeptide ATCUN motif was linked to amidated forms of the cell wall sorting signal, LPET and LPETG, as sortase-targeting moieties. The resulting metallopeptides were used to determine half maximal inhibitory concentrations (IC₅₀) and rate constants for time-dependent sortase A inactivation. Michaelis-Menten behavior was observed for the catalytic metallopeptides, and k(cat), K(M) and k(cat)/K(M) parameters were obtained as 0.080 ± 0.002 min⁻¹, 23 ± 2 μM and 0.0035 ± 0.0003 μM⁻¹ min⁻¹, respectively. Concentration-dependent inhibition of SrtA∆N59 by the metallopeptides revealed IC₅₀ values ranging from 570 to 700 µM, while Cu-GGH, which lacked a targeting motif, had no measurable IC₅₀ value (>2,000 µM). Time-dependent inactivation of SrtA revealed a range of catalytic activities, with Cu-GGHGLPETG-NH2 demonstrating the fastest rate of inactivation in the presence of ascorbate and hydrogen peroxide coreactants. The active site of the enzyme comprises residues Cys-184, Arg-197 and His-120. LC-MS/MS analysis of the reaction products demonstrated modification of Cys-184 to cysteine sulfonic acid (+48 amu). Results obtained from a DTNB assay support oxidation of the Cys-184 residue. LC-MS/MS also suggested oxidation of the Arg-197 containing peptide. 2D NMR analysis was performed to assess the possible oxidation of His-120, however, none was observed. These compounds possess the potential for irreversible inactivation of SrtA through oxidative modification of essential residues required for substrate binding.
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55
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Hoppe B. Fibrinogen and factor XIII at the intersection of coagulation, fibrinolysis and inflammation. Thromb Haemost 2014; 112:649-58. [PMID: 25182841 DOI: 10.1160/th14-01-0085] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2014] [Accepted: 07/09/2014] [Indexed: 01/07/2023]
Abstract
Fibrinogen and factor XIII are two essential proteins that are involved directly in fibrin gel formation as the final step of a sequence of reactions triggered by a procoagulant stimulus. Haemostasis is the most obvious function of the resulting fibrin clot. Different variables affect the conversion of fibrinogen to fibrin as well as the mode of fibrin polymerisation and fibrin crosslinking, hereby, critically influencing the architecture of the resulting fibrin network and consequently determining its mechanical strength and resistance against fibrinolysis. Due to fibrinogen's structure with a multitude of domains and binding motifs the fibrin gel allows for complex interactions with other coagulation factors, with profibrinolytic as well as antifibrinolyic proteins, with complement factors and with various cellular receptors. These interactions enable the fibrin network to control its own further state (i. e. expansion or degradation), to influence innate immunity, and to function as a scaffold for cell migration processes. During the whole process of fibrin gel formation biologically active peptides and protein fragments are released that additionally influence cellular processes via chemotaxis or by modulating cell-cell interactions. Thus, it is not surprising that fibrinogen and factor XIII in addition to their haemostatic function influence innate immunity as well as cell-mediated reactions like wound healing, response to tissue injury or inflammatory processes. The present review summarises current knowledge of fibrinogen's and factor XIII's function in coagulation and fibrinolysis giving special emphasis on their relation to inflammation control.
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Affiliation(s)
- Berthold Hoppe
- PD Dr. Berthold Hoppe, Institute of Laboratory Medicine and Pathobiochemistry, Charité - Universitätsmedizin Berlin, Campus Virchow-Klinikum, Augustenburger Platz 1, 13353 Berlin, Germany, Tel.: +49 30 40 50 26 209, Fax: +49 30 40 50 26 77 209, E-mail:
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56
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Kim HK, Missiakas D, Schneewind O. Mouse models for infectious diseases caused by Staphylococcus aureus. J Immunol Methods 2014; 410:88-99. [PMID: 24769066 PMCID: PMC6211302 DOI: 10.1016/j.jim.2014.04.007] [Citation(s) in RCA: 106] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2014] [Revised: 04/16/2014] [Accepted: 04/16/2014] [Indexed: 12/13/2022]
Abstract
Staphylococcus aureus - a commensal of the human skin, nares and gastrointestinal tract - is also a leading cause of bacterial skin and soft tissue infection (SSTIs), bacteremia, sepsis, peritonitis, pneumonia and endocarditis. Antibiotic-resistant strains, designated MRSA (methicillin-resistant S. aureus), are common and represent a therapeutic challenge. Current research and development efforts seek to address the challenge of MRSA infections through vaccines and immune therapeutics. Mice have been used as experimental models for S. aureus SSTI, bacteremia, sepsis, peritonitis and endocarditis. This work led to the identification of key virulence factors, candidate vaccine antigens or immune-therapeutics that still require human clinical testing to establish efficacy. Past failures of human clinical trials raised skepticism whether the mouse is an appropriate model for S. aureus disease in humans. S. aureus causes chronic-persistent infections that, even with antibiotic or surgical intervention, reoccur in humans and in mice. Determinants of S. aureus evasion from human innate and adaptive immune responses have been identified, however only some of these are relevant in mice. Future research must integrate these insights and refine the experimental mouse models for specific S. aureus diseases to accurately predict the failure or success for candidate vaccines and immune-therapeutics.
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Affiliation(s)
- Hwan Keun Kim
- Department of Microbiology, University of Chicago, 920 East 58th Street, Chicago, IL 60637, United States
| | - Dominique Missiakas
- Department of Microbiology, University of Chicago, 920 East 58th Street, Chicago, IL 60637, United States
| | - Olaf Schneewind
- Department of Microbiology, University of Chicago, 920 East 58th Street, Chicago, IL 60637, United States
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57
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Baumstummler A, Lehmann D, Janjic N, Ochsner UA. Specific capture and detection of Staphylococcus aureus with high-affinity modified aptamers to cell surface components. Lett Appl Microbiol 2014; 59:422-31. [PMID: 24935714 PMCID: PMC4299505 DOI: 10.1111/lam.12295] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2014] [Revised: 06/10/2014] [Accepted: 06/11/2014] [Indexed: 01/15/2023]
Abstract
Slow off-rate modified aptamer (SOMAmer) reagents were generated to several Staphylococcus aureus cell surface-associated proteins via SELEX with multiple modified DNA libraries using purified recombinant or native proteins. High-affinity binding agents with sub-nanomolar Kd 's were obtained for staphylococcal protein A (SpA), clumping factors (ClfA, ClfB), fibronectin-binding proteins (FnbA, FnbB) and iron-regulated surface determinants (Isd). Further screening revealed several SOMAmers that specifically bound to Staph. aureus cells from all strains that were tested, but not to other staphylococci or other bacteria. SpA and ClfA SOMAmers proved useful for the selective capture and enrichment of Staph. aureus cells, as shown by culture and PCR, leading to improved limits of detection and efficient removal of PCR inhibitors. Detection of Staph. aureus cells was enhanced by several orders of magnitude when the bacterial cell surface was coated with SOMAmers followed by qPCR of the SOMAmers. Furthermore, fluorescence-labelled SpA SOMAmers demonstrated their utility as direct detection agents in flow cytometry. Significance and impact of the study: Monitoring for microbial contamination of food, water, nonsterile products or the environment is typically based on culture, PCR or antibodies. Aptamers that bind with high specificity and affinity to well-conserved cell surface epitopes represent a promising novel type of reagents to detect bacterial cells without the need for culture or cell lysis, including for the capture and enrichment of bacteria present at low cell densities and for the direct detection via qPCR or fluorescent staining.
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Affiliation(s)
- A Baumstummler
- Merck Millipore, Lab Solutions, BioMonitoring, Molsheim, France
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58
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Stemberk V, Jones RPO, Moroz O, Atkin KE, Edwards AM, Turkenburg JP, Leech AP, Massey RC, Potts JR. Evidence for steric regulation of fibrinogen binding to Staphylococcus aureus fibronectin-binding protein A (FnBPA). J Biol Chem 2014; 289:12842-51. [PMID: 24627488 PMCID: PMC4007472 DOI: 10.1074/jbc.m113.543546] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The adjacent fibrinogen (Fg)- and fibronectin (Fn)-binding sites on Fn-binding protein A (FnBPA), a cell surface protein from Staphylococcus aureus, are implicated in the initiation and persistence of infection. FnBPA contains a single Fg-binding site (that also binds elastin) and multiple Fn-binding sites. Here, we solved the structure of the N2N3 domains containing the Fg-binding site of FnBPA in the apo form and in complex with a Fg peptide. The Fg binding mechanism is similar to that of homologous bacterial proteins but without the requirement for "latch" strand residues. We show that the Fg-binding sites and the most N-terminal Fn-binding sites are nonoverlapping but in close proximity. Although Fg and a subdomain of Fn can form a ternary complex on an FnBPA protein construct containing a Fg-binding site and single Fn-binding site, binding of intact Fn appears to inhibit Fg binding, suggesting steric regulation. Given the concentrations of Fn and Fg in the plasma, this mechanism might result in targeting of S. aureus to fibrin-rich thrombi or elastin-rich tissues.
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Affiliation(s)
| | | | - Olga Moroz
- Chemistry, University of York, York YO10 5DD, United Kingdom and
| | | | - Andrew M. Edwards
- the Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom
| | | | | | - Ruth C. Massey
- the Department of Biology and Biochemistry, University of Bath, Bath BA2 7AY, United Kingdom
| | - Jennifer R. Potts
- From the Departments of Biology and , Recipient of British Heart Foundation Senior Basic Science Research Fellowship FS/12/36/29588. To whom correspondence should be addressed. Tel.: 44-1904-328679; E-mail:
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59
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Scully IL, Liberator PA, Jansen KU, Anderson AS. Covering all the Bases: Preclinical Development of an Effective Staphylococcus aureus Vaccine. Front Immunol 2014; 5:109. [PMID: 24715889 PMCID: PMC3970019 DOI: 10.3389/fimmu.2014.00109] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2014] [Accepted: 03/04/2014] [Indexed: 01/19/2023] Open
Abstract
A key aspect of the pathogenesis of the Gram positive bacterium Staphylococcus aureus is its ability to rapidly adapt to the host environment during the course of an infection. To successfully establish infection, the organism deploys a variety of survival and immune evasion strategies, ranging from the acquisition of essential nutrients and expression of adhesins, which promote colonization and survival, to the elaboration of virulence factors such as capsule, which aids host immune evasion. The ability of S. aureus to deploy different virulence factors must be taken into account for S. aureus vaccine design. Here, we present a strategy for designing an effective vaccine against S. aureus disease by evaluating vaccine candidate performance in multiple in vivo models targeted to mimic aspects of human disease, and by co-development of functional in vitro immunoassays that measure the neutralization of relevant S. aureus virulence factors.
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Affiliation(s)
- Ingrid L Scully
- Pfizer Vaccine Research and Development Unit , Pearl River, NY , USA
| | - Paul A Liberator
- Pfizer Vaccine Research and Development Unit , Pearl River, NY , USA
| | - Kathrin U Jansen
- Pfizer Vaccine Research and Development Unit , Pearl River, NY , USA
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60
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McCormack N, Foster TJ, Geoghegan JA. A short sequence within subdomain N1 of region A of the Staphylococcus aureus MSCRAMM clumping factor A is required for export and surface display. MICROBIOLOGY-SGM 2014; 160:659-670. [PMID: 24464799 DOI: 10.1099/mic.0.074724-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
Clumping factor A (ClfA) is the archetypal fibrinogen-binding surface protein of Staphylococcus aureus and a member of the microbial surface component recognizing adhesive matrix molecules (MSCRAMM) family. An N-terminal signal sequence directs export of the MSCRAMM by the Sec pathway and the C-terminal cell wall-anchoring domain allows covalent attachment of ClfA to peptidoglycan by sortase. Region A of ClfA comprises three independently folded subdomains N1, N2 and N3. Subdomains N2N3 comprise IgG-like folds and promote fibrinogen binding. Nothing is known about the structure or function of subdomain N1. Here we demonstrate an unexpected role for N1 in the export and surface localization of ClfA. Attempted expression of a ClfA variant lacking subdomain N1 resulted in impaired growth of S. aureus and accumulation of ClfA protein in the cytoplasm and cytoplasmic membrane. The presence of residues 211-228 of N1 was required to allow display of ClfA on the bacterial surface. The importance of this region was confirmed when a ClfA variant lacking residues 211-220 was also mislocalized to the cytoplasm and cytoplasmic membrane. However, these residues were not required for export of ClfA lacking the Ser-Asp repeats that link region A to the wall-anchoring domain. Similarly, subdomain N1 of a related MSCRAMM fibronectin-binding protein B was required for export and surface display of the full-length protein, but not a derivative lacking fibronectin-binding repeats. In summary, we demonstrate that residues in the N1 subdomain are required for export and cell wall localization of S. aureus MSCRAMM proteins.
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Affiliation(s)
- Niamh McCormack
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland
| | - Timothy J Foster
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland
| | - Joan A Geoghegan
- Department of Microbiology, Moyne Institute of Preventive Medicine, School of Genetics and Microbiology, Trinity College Dublin, Dublin 2, Ireland
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61
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Emergence of the epidemic methicillin-resistant Staphylococcus aureus strain USA300 coincides with horizontal transfer of the arginine catabolic mobile element and speG-mediated adaptations for survival on skin. mBio 2013; 4:e00889-13. [PMID: 24345744 PMCID: PMC3870260 DOI: 10.1128/mbio.00889-13] [Citation(s) in RCA: 98] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
UNLABELLED The arginine catabolic mobile element (ACME) is the largest genomic region distinguishing epidemic USA300 strains of methicillin-resistant Staphylococcus aureus (MRSA) from other S. aureus strains. However, the functional relevance of ACME to infection and disease has remained unclear. Using phylogenetic analysis, we have shown that the modular segments of ACME were assembled into a single genetic locus in Staphylococcus epidermidis and then horizontally transferred to the common ancestor of USA300 strains in an extremely recent event. Acquisition of one ACME gene, speG, allowed USA300 strains to withstand levels of polyamines (e.g., spermidine) produced in skin that are toxic to other closely related S. aureus strains. speG-mediated polyamine tolerance also enhanced biofilm formation, adherence to fibrinogen/fibronectin, and resistance to antibiotic and keratinocyte-mediated killing. We suggest that these properties gave USA300 a major selective advantage during skin infection and colonization, contributing to the extraordinary evolutionary success of this clone. IMPORTANCE Over the past 15 years, methicillin-resistant Staphylococcus aureus (MRSA) has become a major public health problem. It is likely that adaptations in specific MRSA lineages (e.g., USA300) drove the spread of MRSA across the United States and allowed it to replace other, less-virulent S. aureus strains. We suggest that one major factor in the evolutionary success of MRSA may have been the acquisition of a gene (speG) that allows S. aureus to evade the toxicity of polyamines (e.g., spermidine and spermine) that are produced in human skin. Polyamine tolerance likely gave MRSA multiple fitness advantages, including the formation of more-robust biofilms, increased adherence to host tissues, and resistance to antibiotics and killing by human skin cells.
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62
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Thomer L, Becker S, Emolo C, Quach A, Kim HK, Rauch S, Anderson M, Leblanc JF, Schneewind O, Faull KF, Missiakas D. N-acetylglucosaminylation of serine-aspartate repeat proteins promotes Staphylococcus aureus bloodstream infection. J Biol Chem 2013; 289:3478-86. [PMID: 24344128 DOI: 10.1074/jbc.m113.532655] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Staphylococcus aureus secretes products that convert host fibrinogen to fibrin and promote its agglutination with fibrin fibrils, thereby shielding bacteria from immune defenses. The agglutination reaction involves ClfA (clumping factor A), a surface protein with serine-aspartate (SD) repeats that captures fibrin fibrils and fibrinogen. Pathogenic staphylococci express several different SD proteins that are modified by two glycosyltransferases, SdgA and SdgB. Here, we characterized three genes of S. aureus, aggA, aggB (sdgA), and aggC (sdgB), and show that aggA and aggC contribute to staphylococcal agglutination with fibrin fibrils in human plasma. We demonstrate that aggB (sdgA) and aggC (sdgB) are involved in GlcNAc modification of the ClfA SD repeats. However, only sdgB is essential for GlcNAc modification, and an sdgB mutant is defective in the pathogenesis of sepsis in mice. Thus, GlcNAc modification of proteins promotes S. aureus replication in the bloodstream of mammalian hosts.
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Affiliation(s)
- Lena Thomer
- From the Department of Microbiology, The University of Chicago, Chicago, Illinois 60637 and
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63
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Momtaz H, Dehkordi FS, Rahimi E, Asgarifar A, Momeni M. Virulence genes and antimicrobial resistance profiles of Staphylococcus aureus isolated from chicken meat in Isfahan province, Iran. J APPL POULTRY RES 2013. [DOI: 10.3382/japr.2012-00673] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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64
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Nichols SP, Schoenfisch MH. Nitric oxide-flux dependent bacterial adhesion and viability at fibrinogen-coated surfaces. Biomater Sci 2013; 1:10.1039/C3BM60130G. [PMID: 24288588 PMCID: PMC3839865 DOI: 10.1039/c3bm60130g] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Nitric oxide (NO) is an endogenous antibacterial agent produced by immune cells in response to pathogens. Herein, the NO fluxes necessary to reduce bacterial adhesion of different bacteria (S. aureus, methicillin-resistant S. aureus, S. epidermidis, E. faecalis, E. coli, and P. aeruginosa) were investigated to ascertain the sensitivity of these bacteria to NO. S-nitrosothiol NO donor-modified xerogels were selected as a model NO-release surface due to their extended NO-release kinetics relative to other NO donor systems. The xerogels were coated with poly(vinyl chloride) (PVC) to achieve consistent surface energy between NO-releasing and control substrates. Fibrinogen was pre-adsorbed to these materials to more accurately mimic conditions encountered in blood and promote bacteria adhesion. Nitric oxide fluxes ranging from 20-50 pmol cm-2 s-1 universally inhibited the bacterial adhesion by >80% for each strain studied. Maximum bacteria killing activity (reduced viability by 85-98%) was observed at the greatest NO payload (1700 nmol cm-2).
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Affiliation(s)
- Scott P. Nichols
- Department of Chemistry, Caudill Laboratories, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
| | - Mark H. Schoenfisch
- Department of Chemistry, Caudill Laboratories, University of North Carolina at Chapel Hill, Chapel Hill, NC 27599
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65
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Seo HS, Minasov G, Seepersaud R, Doran KS, Dubrovska I, Shuvalova L, Anderson WF, Iverson TM, Sullam PM. Characterization of fibrinogen binding by glycoproteins Srr1 and Srr2 of Streptococcus agalactiae. J Biol Chem 2013; 288:35982-96. [PMID: 24165132 PMCID: PMC3861647 DOI: 10.1074/jbc.m113.513358] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The serine-rich repeat glycoproteins of Gram-positive bacteria comprise a large family of cell wall proteins. Streptococcus agalactiae (group B streptococcus, GBS) expresses either Srr1 or Srr2 on its surface, depending on the strain. Srr1 has recently been shown to bind fibrinogen, and this interaction contributes to the pathogenesis of GBS meningitis. Although strains expressing Srr2 appear to be hypervirulent, no ligand for this adhesin has been described. We now demonstrate that Srr2 also binds human fibrinogen and that this interaction promotes GBS attachment to endothelial cells. Recombinant Srr1 and Srr2 bound fibrinogen in vitro, with affinities of KD = 2.1 × 10−5 and 3.7 × 10−6m, respectively, as measured by surface plasmon resonance spectroscopy. The binding site for Srr1 and Srr2 was localized to tandem repeats 6–8 of the fibrinogen Aα chain. The structures of both the Srr1 and Srr2 binding regions were determined and, in combination with mutagenesis studies, suggest that both Srr1 and Srr2 interact with a segment of these repeats via a “dock, lock, and latch” mechanism. Moreover, properties of the latch region may account for the increased affinity between Srr2 and fibrinogen. Together, these studies identify how greater affinity of Srr2 for fibrinogen may contribute to the increased virulence associated with Srr2-expressing strains.
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Affiliation(s)
- Ho Seong Seo
- From the Division of Infectious Diseases, Veterans Affairs Medical Center, University of California at San Francisco and the Northern California Institute for Research and Education, San Francisco, California 94121
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Garnett JA, Matthews S. Interactions in bacterial biofilm development: a structural perspective. Curr Protein Pept Sci 2013; 13:739-55. [PMID: 23305361 PMCID: PMC3601411 DOI: 10.2174/138920312804871166] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2012] [Revised: 07/16/2012] [Accepted: 08/03/2012] [Indexed: 11/24/2022]
Abstract
A community-based life style is the normal mode of growth and survival for many bacterial species. These cellular accretions or biofilms are initiated upon recognition of solid phases by cell surface exposed adhesive moieties. Further cell-cell interactions, cell signalling and bacterial replication leads to the establishment of dense populations encapsulated in a mainly self-produced extracellular matrix; this comprises a complex mixture of macromolecules. These fascinating architectures protect the inhabitants from radiation damage, dehydration, pH fluctuations and antimicrobial compounds. As such they can cause bacterial persistence in disease and problems in industrial applications. In this review we discuss the current understandings of these initial biofilm-forming processes based on structural data. We also briefly describe latter biofilm maturation and dispersal events, which although lack high-resolution insights, are the present focus for many structural biologists working in this field. Finally we give an overview of modern techniques aimed at preventing and disrupting problem biofilms.
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Affiliation(s)
- James A Garnett
- Centre for Structural Biology, Department of Life Sciences, Imperial College London, South Kensington, London SW7 2AZ, UK
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67
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Chen M, Yu Q, Sun H. Novel strategies for the prevention and treatment of biofilm related infections. Int J Mol Sci 2013; 14:18488-501. [PMID: 24018891 PMCID: PMC3794791 DOI: 10.3390/ijms140918488] [Citation(s) in RCA: 242] [Impact Index Per Article: 22.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2013] [Revised: 08/28/2013] [Accepted: 08/30/2013] [Indexed: 02/06/2023] Open
Abstract
Biofilm formation by human bacterial pathogens on implanted medical devices causes major morbidity and mortality among patients, and leads to billions of dollars in healthcare cost. Biofilm is a complex bacterial community that is highly resistant to antibiotics and human immunity. As a result, novel therapeutic solutions other than the conventional antibiotic therapies are in urgent need. In this review, we will discuss the recent research in discovery of alternative approaches to prevent or treat biofilms. Current anti-biofilm technologies could be divided into two groups. The first group focuses on targeting the biofilm forming process of bacteria based on our understanding of the molecular mechanism of biofilm formation. Small molecules and enzymes have been developed to inhibit or disrupt biofilm formation. Another group of anti-biofilm technologies focuses on modifying the biomaterials used in medical devices to make them resistant to biofilm formation. While these novel anti-biofilm approaches are still in nascent phases of development, efforts devoted to these technologies could eventually lead to anti-biofilm therapies that are superior to the current antibiotic treatment.
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Affiliation(s)
- Meng Chen
- Nanova, Inc. Columbia, MO 65211, USA; E-Mail: or
| | - Qingsong Yu
- Department of Mechanical and Aerospace Engineering, University of Missouri, Columbia, MO 65211, USA; E-Mail:
| | - Hongmin Sun
- Division of Cardiovascular Medicine, Department of Internal Medicine, University of Missouri, Columbia, MO 65212, USA
- Author to whom correspondence should be addressed; E-Mail: ; Tel.: +1-573-884-1964; Fax: +1-573-884-7743
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Pietrocola G, Geoghegan JA, Rindi S, Di Poto A, Missineo A, Consalvi V, Foster TJ, Speziale P. Molecular Characterization of the Multiple Interactions of SpsD, a Surface Protein from Staphylococcus pseudintermedius, with Host Extracellular Matrix Proteins. PLoS One 2013; 8:e66901. [PMID: 23805283 PMCID: PMC3689669 DOI: 10.1371/journal.pone.0066901] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Accepted: 05/12/2013] [Indexed: 12/03/2022] Open
Abstract
Staphylococcus pseudintermedius, a commensal and pathogen of dogs and occasionally of humans, expresses surface proteins potentially involved in host colonization and pathogenesis. Here, we describe the cloning and characterization of SpsD, a surface protein of S. pseudintermedius reported as interacting with extracellular matrix proteins and corneocytes. A ligand screen and Western immunoblotting revealed that the N-terminal A domain of SpsD bound fibrinogen, fibronectin, elastin and cytokeratin 10. SpsD also interfered with thrombin-induced fibrinogen coagulation and blocked ADP-induced platelet aggregation. The binding site for SpsD was mapped to residues 395–411 in the fibrinogen γ-chain, while binding sites in fibronectin were localized to the N- and C-terminal regions. SpsD also bound to glycine- and serine-rich omega loops within the C-terminal tail region of cytokeratin 10. Ligand binding studies using SpsD variants lacking the C-terminal segment or containing an amino-acid substitution in the putative ligand binding site provided insights into interaction mechanism of SpsD with the different ligands. Together these data demonstrate the multi-ligand binding properties of SpsD and illustrate some interesting differences in the variety of ligands bound by SpsD and related proteins from S. aureus.
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Affiliation(s)
| | - Joan A. Geoghegan
- Department Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin, Ireland
| | - Simonetta Rindi
- Department of Molecular Medicine, Institute of Biochemistry, Pavia, Italy
| | - Antonella Di Poto
- Department of Molecular Medicine, Institute of Biochemistry, Pavia, Italy
| | - Antonino Missineo
- Department of Molecular Medicine, Institute of Biochemistry, Pavia, Italy
| | - Valerio Consalvi
- Department of Biochemical Sciences “A. Rossi Fanelli”, University of Rome “La Sapienza”, Roma, Italy
| | - Timothy J. Foster
- Department Microbiology, Moyne Institute of Preventive Medicine, Trinity College, Dublin, Ireland
| | - Pietro Speziale
- Department of Molecular Medicine, Institute of Biochemistry, Pavia, Italy
- * E-mail:
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69
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Jansen KU, Girgenti DQ, Scully IL, Anderson AS. Vaccine review: "Staphyloccocus aureus vaccines: problems and prospects". Vaccine 2013; 31:2723-30. [PMID: 23624095 DOI: 10.1016/j.vaccine.2013.04.002] [Citation(s) in RCA: 104] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/28/2013] [Accepted: 04/01/2013] [Indexed: 12/18/2022]
Abstract
Staphylococcus aureus is a leading cause of both healthcare- and community-associated infections globally. S. aureus exhibits diverse clinical presentations, ranging from benign carriage and superficial skin and soft tissue infections to deep wound and organ/space infections, biofilm-related prosthesis infections, life-threatening bacteremia and sepsis. This broad clinical spectrum, together with the high incidence of these disease manifestations and magnitude of the diverse populations at risk, presents a high unmet medical need and a substantial burden to the healthcare system. With the increasing propensity of S. aureus to develop resistance to essentially all classes of antibiotics, alternative strategies, such as prophylactic vaccination to prevent S. aureus infections, are actively being pursued in healthcare settings. Within the last decade, the S. aureus vaccine field has witnessed two major vaccine failures in phase 3 clinical trials designed to prevent S. aureus infections in either patients undergoing cardiothoracic surgery or patients with end-stage renal disease undergoing hemodialysis. This review summarizes the potential underlying reasons why these two approaches may have failed, and proposes avenues that may provide successful vaccine approaches to prevent S. aureus disease in the future.
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70
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Franks Z, Campbell RA, Vieira de Abreu A, Holloway JT, Marvin JE, Kraemer BF, Zimmerman GA, Weyrich AS, Rondina MT. Methicillin-resistant Staphylococcus aureus-induced thrombo-inflammatory response is reduced with timely antibiotic administration. Thromb Haemost 2013; 109:684-95. [PMID: 23348831 DOI: 10.1160/th12-08-0543] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2013] [Accepted: 12/15/2012] [Indexed: 11/05/2022]
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) induces a pro-thrombotic and pro-inflammatory milieu. Although timely antibiotic administration in MRSAsepsis may improve outcomes by arresting bacterial growth, the effects of antibiotics on mitigating injurious thrombo-inflammatory cellular responses remains unexplored. Using a newly developed human whole blood model and an in vivo mouse model of MRSAinfection, we examined how antibiotics inhibit MRSAinduced thrombo-inflammatory pathways. Human whole blood was inoculated with MRSA. Thrombin generation and inflammatory cytokine synthesis was measured in the presence or absence of linezolid and vancomycin. C57BL/6 mice were injected with MRSA and the effect of vancomycin administration was examined. MRSAaccelerated thrombin generation in a time- and concentration-dependent manner andinduced the release of cytokines, including interleukin (IL)-6, IL-8, and monocyte chemotactic protein (MCP)-1. The increase in thrombin generation and inflammatory responses was mediated through the synthesis of tissue factor and cytokines, respectively, and the release of microparticles. The early administration of antibiotics restored normal thrombin generation patterns and significantly reduced the synthesis of cytokines. In contrast, when antibiotic administration was delayed, thrombin generation and cytokine synthesis were not significantly reduced. In mice infected with MRSA, early antibiotic administration reduced thrombin anti-thrombin complexes and cytokine synthesis, whereas delayed antibiotic administration did not. These data provide novel mechanistic evidence of the importance of prompt antibiotic administration in infectious syndromes.
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Affiliation(s)
- Zechariah Franks
- University of Utah, Department of Internal Medicine, 50 North Medical Drive, Room 4B120, SLC, Utah 84132, USA
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71
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Genetic elimination of the binding motif on fibrinogen for the S. aureus virulence factor ClfA improves host survival in septicemia. Blood 2013; 121:1783-94. [PMID: 23299312 DOI: 10.1182/blood-2012-09-453894] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Fibrinogen can support host antimicrobial containment/clearance mechanisms, yet selected pathogens appear to benefit from host procoagulants to drive bacterial virulence. Here, we explored the hypothesis that host fibrin(ogen), on balance, supports Staphylococcus aureus infection in the context of septicemia. Survival studies following intravenous infection in control and fibrinogen-deficient mice established the overall utility of host fibrin(ogen) to S. aureus virulence. Complementary studies in mice expressing mutant forms of fibrinogen-retaining clotting function, but lacking either the bacterial ClfA (Fibγ(Δ5)) binding motif or the host leukocyte integrin receptor αMβ2 (Fibγ(390-396A)) binding motif, revealed the preeminent importance of the bacterial ClfA-fibrin(ogen) interaction in determining host survival. Studies of mice lacking platelets or the platelet integrin receptor subunit αIIb established that the survival benefits observed in Fibγ(Δ5) mice were largely independent of platelet αIIbβ3-mediated engagement of fibrinogen. Fibγ(Δ5) mice exhibited reduced bacterial burdens in the hearts and kidneys, a blunted host proinflammatory cytokine response, diminished microscopic tissue damage, and significantly diminished plasma markers of cardiac and other organ damage. These findings indicate that host fibrin(ogen) and bacterial ClfA are dual determinants of virulence and that therapeutic interventions at the level of fibrinogen could be advantageous in S. aureus septicemia.
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72
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Factores de virulencia de Staphylococcus aureus asociados con infecciones mamarias en bovinos: relevancia y rol como agentes inmunógenos. Rev Argent Microbiol 2013; 45:119-30. [DOI: 10.1016/s0325-7541(13)70011-7] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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73
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Anderson AS, Miller AA, Donald RGK, Scully IL, Nanra JS, Cooper D, Jansen KU. Development of a multicomponent Staphylococcus aureus vaccine designed to counter multiple bacterial virulence factors. Hum Vaccin Immunother 2012; 8:1585-94. [PMID: 22922765 PMCID: PMC3601133 DOI: 10.4161/hv.21872] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022] Open
Abstract
Staphylococcus aureus is a major cause of healthcare-associated infections and is responsible for a substantial burden of disease in hospitalized patients. Despite increasingly rigorous infection control guidelines, the prevalence and corresponding negative impact of S. aureus infections remain considerable. Difficulties in controlling S. aureus infections as well as the associated treatment costs are exacerbated by increasing rates of resistance to available antibiotics. Despite ongoing efforts over the past 20 years, no licensed S. aureus vaccine is currently available. However, learnings from past clinical failures of vaccine candidates and a better understanding of the immunopathology of S. aureus colonization and infection have aided in the design of new vaccine candidates based on multiple important bacterial pathogenesis mechanisms. This review outlines important considerations in designing a vaccine for the prevention of S. aureus disease in healthcare settings.
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74
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A recombinant clumping factor A-containing vaccine induces functional antibodies to Staphylococcus aureus that are not observed after natural exposure. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2012; 19:1641-50. [PMID: 22896688 DOI: 10.1128/cvi.00354-12] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Staphylococcus aureus is a Gram-positive pathogen that causes devastating disease and whose pathogenesis is dependent on interactions with host cell factors. Staphylococcal clumping factor A (ClfA) is a highly conserved fibrinogen (Fg)-binding protein and virulence factor that contributes to host tissue adhesion and initiation of infection. ClfA is being investigated as a possible component of a staphylococcal vaccine. We report the development of an Fg-binding assay that is specific for ClfA-mediated binding. Using the assay, we show that despite the presence of anti-ClfA antibodies, human sera from unvaccinated subjects are unable to prevent the binding of S. aureus to an Fg-coated surface. In contrast, antibodies elicited by a recombinant ClfA-containing vaccine were capable of blocking the ClfA-dependent binding of a diverse and clinically relevant collection of staphylococcal strains to Fg. These functional antibodies were also able to displace S. aureus already bound to Fg, suggesting that the ligand-binding activity of ClfA can be effectively neutralized through vaccination.
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75
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Xiang H, Feng Y, Wang J, Liu B, Chen Y, Liu L, Deng X, Yang M. Crystal structures reveal the multi-ligand binding mechanism of Staphylococcus aureus ClfB. PLoS Pathog 2012; 8:e1002751. [PMID: 22719251 PMCID: PMC3375286 DOI: 10.1371/journal.ppat.1002751] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 04/30/2012] [Indexed: 01/07/2023] Open
Abstract
Staphylococcus aureus (S. aureus) pathogenesis is a complex process involving a diverse array of extracellular and cell wall components. ClfB, an MSCRAMM (Microbial Surface Components Recognizing Adhesive Matrix Molecules) family surface protein, described as a fibrinogen-binding clumping factor, is a key determinant of S. aureus nasal colonization, but the molecular basis for ClfB-ligand recognition remains unknown. In this study, we solved the crystal structures of apo-ClfB and its complexes with fibrinogen α (Fg α) and cytokeratin 10 (CK10) peptides. Structural comparison revealed a conserved glycine-serine-rich (GSR) ClfB binding motif (GSSGXGXXG) within the ligands, which was also found in other human proteins such as Engrailed protein, TCF20 and Dermokine proteins. Interaction between Dermokine and ClfB was confirmed by subsequent binding assays. The crystal structure of ClfB complexed with a 15-residue peptide derived from Dermokine revealed the same peptide binding mode of ClfB as identified in the crystal structures of ClfB-Fg α and ClfB-CK10. The results presented here highlight the multi-ligand binding property of ClfB, which is very distinct from other characterized MSCRAMMs to-date. The adherence of multiple peptides carrying the GSR motif into the same pocket in ClfB is reminiscent of MHC molecules. Our results provide a template for the identification of other molecules targeted by S. aureus during its colonization and infection. We propose that other MSCRAMMs like ClfA and SdrG also possess multi-ligand binding properties.
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Affiliation(s)
- Hua Xiang
- Key Laboratory for Protein Sciences of Ministry of Education, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
- Department of Veterinary Pharmacology, College of Animal Science and Veterinary Medicine, Jilin University, Changchun, China
| | - Yue Feng
- Key Laboratory for Protein Sciences of Ministry of Education, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Jiawei Wang
- Key Laboratory for Protein Sciences of Ministry of Education, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Bao Liu
- Department of Vascular Surgery, Peking Union Medical College Hospital, Beijing, China
| | - Yeguang Chen
- Key Laboratory for Protein Sciences of Ministry of Education, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
| | - Lei Liu
- Key Laboratory for Protein Sciences of Ministry of Education, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
- Department of Chemistry, Tsinghua University, Beijing, China
| | - Xuming Deng
- Department of Veterinary Pharmacology, College of Animal Science and Veterinary Medicine, Jilin University, Changchun, China
- * E-mail: (XD); (MY)
| | - Maojun Yang
- Key Laboratory for Protein Sciences of Ministry of Education, Tsinghua-Peking Center for Life Sciences, School of Life Sciences, Tsinghua University, Beijing, China
- * E-mail: (XD); (MY)
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76
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[Inhibition of Staphylococcus epidermidis adhesion on titanium surface with bioactive water-soluble copolymers bearing sulfonate, phosphate or carboxylate functions]. ACTA ACUST UNITED AC 2012; 60:84-90. [PMID: 22406062 DOI: 10.1016/j.patbio.2010.07.004] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2009] [Accepted: 07/01/2010] [Indexed: 11/21/2022]
Abstract
Implanted prostheses are sometimes subject to bacterial infections, which can threat their benefit rule on a long-term basis. Various methods are studied to fight against these infections. Among them, the grafting of bioactive polymers onto the prosthesis surface shows up as a promising way to the problem of infections. This work presents the influence of various water-soluble bioactive polymers on the inhibition of the Staphylococcus epidermidis adhesion on the titanium samples surfaces initially preadsorbed with various proteins. Whatever the studied protein is, it is shown that the bioactive polymer containing sulfonate functions generates an inhibition of the adhesion of Staphylococcus epidermidis. For a plasma preadsorption, the inhibition rate rises up to 68% when the concentration of sulfonate function is 2.5μmol/L. Titanium surfaces grafted with the bioactive polymer were also tested. We find an inhibitive activity of the adhesion close to that of the previous case. These preliminary results can point up a clinical interest in the fight against the medical devices infection, because they highlight a clear local effect of S. epidermidis adhesion inhibition. Copolymers containing other functional groups (phosphate or carboxylate) were dissolved in a bacterial suspension to monitor the influence of the composition on the adhesion inhibition. Their inhibition rates are not significantly lower than those of pNaSS homopolymers, as much as the sulfonate function proportion remains higher than 50%. Thus, the sulfonate function is the main responsible for the inhibition of the S. epidermidis adhesion.
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77
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DeDent A, Kim HK, Missiakas D, Schneewind O. Exploring Staphylococcus aureus pathways to disease for vaccine development. Semin Immunopathol 2012; 34:317-33. [PMID: 22130613 PMCID: PMC3539746 DOI: 10.1007/s00281-011-0299-z] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2011] [Accepted: 10/28/2011] [Indexed: 12/21/2022]
Abstract
Staphylococcus aureus is a commensal of the human skin or nares and a pathogen that frequently causes skin and soft tissue infections as well as bacteremia and sepsis. Recent efforts in understanding the molecular mechanisms of pathogenesis revealed key virulence strategies of S. aureus in host tissues: bacterial scavenging of iron, induction of coagulation pathways to promote staphylococcal agglutination in the vasculature, and suppression of innate and adaptive immune responses. Advances in all three areas have been explored for opportunities in vaccine design in an effort to identify the critical protective antigens of S. aureus. Human clinical trials with specific subunit vaccines have failed, yet provide important insights for the design of future trials that must address the current epidemic of S. aureus infections with drug-resistant isolates (MRSA, methicillin-resistant S. aureus).
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Affiliation(s)
- Andrea DeDent
- Department of Microbiology, University of Chicago, 920 East 58th Street, Chicago, IL 60637, USA
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78
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Smith EJ, Corrigan RM, van der Sluis T, Gründling A, Speziale P, Geoghegan JA, Foster TJ. The immune evasion protein Sbi of Staphylococcus aureus occurs both extracellularly and anchored to the cell envelope by binding lipoteichoic acid. Mol Microbiol 2012; 83:789-804. [PMID: 22256861 PMCID: PMC3378709 DOI: 10.1111/j.1365-2958.2011.07966.x] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The Sbi protein of Staphylococcus aureus comprises two IgG-binding domains similar to those of protein A and a region that triggers the activation of complement C3. Sbi is expressed on the cell surface but its C-terminal domain lacks motifs associated with wall or membrane anchoring of proteins in Gram-positive bacteria. Cell-associated Sbi fractionates with the cytoplasmic membrane and is not solubilized during protoplast formation. S. aureus expressing Sbi truncates of the C-terminal Y domain allowed identification of residues that are required for association of Sbi with the membrane. Recombinant Sbi bound to purified cytoplasmic membrane material in vitro and to purified lipoteichoic acid. This explains how Sbi partitions with the membrane in fractionation experiments yet is partially exposed on the cell surface. An LTA-defective mutant of S. aureus had reduced levels of Sbi in the cytoplasmic membrane.
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Affiliation(s)
- Emma Jane Smith
- Microbiology Department, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland
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79
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Vanassche T, Verhaegen J, Peetermans WE, VAN Ryn J, Cheng A, Schneewind O, Hoylaerts MF, Verhamme P. Inhibition of staphylothrombin by dabigatran reduces Staphylococcus aureus virulence. J Thromb Haemost 2011; 9:2436-46. [PMID: 22040101 DOI: 10.1111/j.1538-7836.2011.04529.x] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
BACKGROUND Staphylocoagulase and von Willebrand binding protein (VWbp) bind to prothrombin to form the staphylothrombin complex that converts fibrinogen into fibrin. OBJECTIVES To study the role of staphylothrombin and its inhibition by dabigatran on Staphylococcus aureus virulence. METHODS We studied the effect of staphylothrombin inhibition on bacterial attachment to polystyrene surfaces, leukocyte activation and bactericidal activity for S. aureus ATCC 25923, S. aureus Newman, and staphylocoagulase- and VWbp-negative S. aureus Newman mutants in the presence or absence of prothrombin and fibrinogen. We measured the abscess size after subcutaneous (s.c.) injection of S. aureus ATCC 25923 and S. aureus Newman, as well as an S. aureus Newman mutant strain lacking staphylocoagulase and VWbp, in mice treated with either dabigatran or placebo. RESULTS Staphylothrombin-mediated fibrin increased the association of S. aureus to polystyrene surfaces and reduced the bactericidal activity of leukocytes. The absence or inhibition of staphylothrombin decreased the bacterial association, enhanced leukocyte activation and reduced bacterial survival in vitro. Abscess size was smaller in mice treated with dabigatran or infected with a coagulase-negative mutant. CONCLUSION Inhibition or the absence of staphylothrombin reduced S. aureus virulence in in vitro and in vivo models.
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Affiliation(s)
- T Vanassche
- Center for Molecular and Vascular Biology, University of Leuven, Leuven, Belgium.
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80
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McAdow M, Kim HK, DeDent AC, Hendrickx APA, Schneewind O, Missiakas DM. Preventing Staphylococcus aureus sepsis through the inhibition of its agglutination in blood. PLoS Pathog 2011; 7:e1002307. [PMID: 22028651 PMCID: PMC3197598 DOI: 10.1371/journal.ppat.1002307] [Citation(s) in RCA: 170] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2011] [Accepted: 08/25/2011] [Indexed: 12/15/2022] Open
Abstract
Staphylococcus aureus infection is a frequent cause of sepsis in humans, a disease associated with high mortality and without specific intervention. When suspended in human or animal plasma, staphylococci are known to agglutinate, however the bacterial factors responsible for agglutination and their possible contribution to disease pathogenesis have not yet been revealed. Using a mouse model for S. aureus sepsis, we report here that staphylococcal agglutination in blood was associated with a lethal outcome of this disease. Three secreted products of staphylococci--coagulase (Coa), von Willebrand factor binding protein (vWbp) and clumping factor (ClfA)--were required for agglutination. Coa and vWbp activate prothrombin to cleave fibrinogen, whereas ClfA allowed staphylococci to associate with the resulting fibrin cables. All three virulence genes promoted the formation of thromboembolic lesions in heart tissues. S. aureus agglutination could be disrupted and the lethal outcome of sepsis could be prevented by combining dabigatran-etexilate treatment, which blocked Coa and vWbp activity, with antibodies specific for ClfA. Together these results suggest that the combined administration of direct thrombin inhibitors and ClfA-antibodies that block S. aureus agglutination with fibrin may be useful for the prevention of staphylococcal sepsis in humans.
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Affiliation(s)
- Molly McAdow
- Department of Microbiology, University of Chicago, Chicago, Illinois, United States of America
| | - Hwan Keun Kim
- Department of Microbiology, University of Chicago, Chicago, Illinois, United States of America
| | - Andrea C. DeDent
- Department of Microbiology, University of Chicago, Chicago, Illinois, United States of America
| | - Antoni P. A. Hendrickx
- Department of Microbiology, University of Chicago, Chicago, Illinois, United States of America
| | - Olaf Schneewind
- Department of Microbiology, University of Chicago, Chicago, Illinois, United States of America
- * E-mail:
| | - Dominique M. Missiakas
- Department of Microbiology, University of Chicago, Chicago, Illinois, United States of America
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81
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Santos AP, Guimaraes AMS, do Nascimento NC, Sanmiguel PJ, Martin SW, Messick JB. Genome of Mycoplasma haemofelis, unraveling its strategies for survival and persistence. Vet Res 2011; 42:102. [PMID: 21936946 PMCID: PMC3196708 DOI: 10.1186/1297-9716-42-102] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2011] [Accepted: 09/21/2011] [Indexed: 02/08/2023] Open
Abstract
Mycoplasma haemofelis is a mycoplasmal pathogen (hemoplasma) that attaches to the host's erythrocytes. Distributed worldwide, it has a significant impact on the health of cats causing acute disease and, despite treatment, establishing chronic infection. It might also have a role as a zoonotic agent, especially in immunocompromised patients. Whole genome sequencing and analyses of M. haemofelis strain Ohio2 was undertaken as a step toward understanding its survival and persistence. Metabolic pathways are reduced, relying on the host to supply many of the nutrients and metabolites needed for survival. M. haemofelis must import glucose for ATP generation and ribose derivates for RNA/DNA synthesis. Hypoxanthine, adenine, guanine, uracil and CMP are scavenged from the environment to support purine and pyrimidine synthesis. In addition, nicotinamide, amino acids and any vitamins needed for growth, must be acquired from its environment. The core proteome of M. haemofelis contains an abundance of paralogous gene families, corresponding to 70.6% of all the CDSs. This "paralog pool" is a rich source of different antigenic epitopes that can be varied to elude the host's immune system and establish chronic infection. M. haemofelis also appears to be capable of phase variation, which is particularly relevant to the cyclic bacteremia and persistence, characteristics of the infection in the cat. The data generated herein should be of great use for understanding the mechanisms of M. haemofelis infection. Further, it will provide new insights into its pathogenicity and clues needed to formulate media to support the in vitro cultivation of M. haemofelis.
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Affiliation(s)
- Andrea P Santos
- Department of Comparative Pathobiology, Purdue University, 725 Harrison Street, West Lafayette, IN 47907, USA.
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82
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Pyburn TM, Bensing BA, Xiong YQ, Melancon BJ, Tomasiak TM, Ward NJ, Yankovskaya V, Oliver KM, Cecchini G, Sulikowski GA, Tyska MJ, Sullam PM, Iverson TM. A structural model for binding of the serine-rich repeat adhesin GspB to host carbohydrate receptors. PLoS Pathog 2011; 7:e1002112. [PMID: 21765814 PMCID: PMC3131266 DOI: 10.1371/journal.ppat.1002112] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2011] [Accepted: 04/25/2011] [Indexed: 11/18/2022] Open
Abstract
GspB is a serine-rich repeat (SRR) adhesin of Streptococcus gordonii that mediates binding of this organism to human platelets via its interaction with sialyl-T antigen on the receptor GPIbα. This interaction appears to be a major virulence determinant in the pathogenesis of infective endocarditis. To address the mechanism by which GspB recognizes its carbohydrate ligand, we determined the high-resolution x-ray crystal structure of the GspB binding region (GspB(BR)), both alone and in complex with a disaccharide precursor to sialyl-T antigen. Analysis of the GspB(BR) structure revealed that it is comprised of three independently folded subdomains or modules: 1) an Ig-fold resembling a CnaA domain from prokaryotic pathogens; 2) a second Ig-fold resembling the binding region of mammalian Siglecs; 3) a subdomain of unique fold. The disaccharide was found to bind in a pocket within the Siglec subdomain, but at a site distinct from that observed in mammalian Siglecs. Confirming the biological relevance of this binding pocket, we produced three isogenic variants of S. gordonii, each containing a single point mutation of a residue lining this binding pocket. These variants have reduced binding to carbohydrates of GPIbα. Further examination of purified GspB(BR)-R484E showed reduced binding to sialyl-T antigen while S. gordonii harboring this mutation did not efficiently bind platelets and showed a significant reduction in virulence, as measured by an animal model of endocarditis. Analysis of other SRR proteins revealed that the predicted binding regions of these adhesins also had a modular organization, with those known to bind carbohydrate receptors having modules homologous to the Siglec and Unique subdomains of GspB(BR). This suggests that the binding specificity of the SRR family of adhesins is determined by the type and organization of discrete modules within the binding domains, which may affect the tropism of organisms for different tissues.
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Affiliation(s)
- Tasia M. Pyburn
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Vanderbilt Institute of Chemical Biology, Nashville, Tennessee, United States of America
| | - Barbara A. Bensing
- Department of Medicine, Veterans Affairs Medical Center and the University of California, San Francisco, California, United States of America
| | - Yan Q. Xiong
- Department of Medicine, Harbor-UCLA Medical Center, Torrance, California, United States of America
| | - Bruce J. Melancon
- Vanderbilt Institute of Chemical Biology, Nashville, Tennessee, United States of America
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Thomas M. Tomasiak
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Vanderbilt Institute of Chemical Biology, Nashville, Tennessee, United States of America
| | - Nicholas J. Ward
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Victoria Yankovskaya
- Molecular Biology Division, Veterans Affairs Medical Center, San Francisco, California, United States of America
| | - Kevin M. Oliver
- Vanderbilt Institute of Chemical Biology, Nashville, Tennessee, United States of America
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Gary Cecchini
- Molecular Biology Division, Veterans Affairs Medical Center, San Francisco, California, United States of America
- Department of Biochemistry & Biophysics University of California, San Francisco, California, United States of America
| | - Gary A. Sulikowski
- Vanderbilt Institute of Chemical Biology, Nashville, Tennessee, United States of America
- Department of Chemistry, Vanderbilt University, Nashville, Tennessee, United States of America
| | - Matthew J. Tyska
- Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
| | - Paul M. Sullam
- Department of Medicine, Veterans Affairs Medical Center and the University of California, San Francisco, California, United States of America
| | - T. M. Iverson
- Department of Pharmacology, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- Vanderbilt Institute of Chemical Biology, Nashville, Tennessee, United States of America
- Department of Biochemistry, Vanderbilt University Medical Center, Nashville, Tennessee, United States of America
- * E-mail:
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83
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The Sbi protein is a multifunctional immune evasion factor of Staphylococcus aureus. Infect Immun 2011; 79:3801-9. [PMID: 21708997 DOI: 10.1128/iai.05075-11] [Citation(s) in RCA: 97] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023] Open
Abstract
The second immunoglobulin-binding protein (Sbi) of Staphylococcus aureus has two N-terminal domains that bind the Fc region of IgG in a fashion similar to that of protein A and two domains that can bind to the complement protein C3 and promote its futile consumption in the fluid phase. It has been proposed that Sbi helps bacteria to avoid innate immune defenses. By comparing a mutant defective in Sbi with mutants defective in protein A, clumping factor A, iron-regulated surface determinant H, and capsular polysaccharide, it was shown that Sbi is indeed an immune evasion factor that promotes bacterial survival in whole human blood and the avoidance of neutrophil-mediated opsonophagocytosis. Sbi is present in the culture supernatant and is also associated with the cell envelope. S. aureus strains that expressed truncates of Sbi lacking N-terminal domains D1 and D2 (D1D2) or D3 and D4 (D3D4) or a C-terminal truncate that was no longer retained in the cell envelope were analyzed. Both the secreted and envelope-associated forms of Sbi contributed to immune evasion. The IgG-binding domains contributed only when Sbi was attached to the cell, while only the secreted C3-binding domains were biologically active.
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84
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Dreisbach A, van der Kooi-Pol MM, Otto A, Gronau K, Bonarius HPJ, Westra H, Groen H, Becher D, Hecker M, van Dijl JM. Surface shaving as a versatile tool to profile global interactions between human serum proteins and the Staphylococcus aureus cell surface. Proteomics 2011; 11:2921-30. [PMID: 21674804 DOI: 10.1002/pmic.201100134] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2011] [Revised: 04/01/2011] [Accepted: 05/03/2011] [Indexed: 11/09/2022]
Abstract
The human commensal bacterium Staphylococcus aureus is renowned as a causative agent of severe invasive diseases. Upon entering the bloodstream, S. aureus can infect almost every tissue and organ system in the human body. To withstand insults from the immune system upon invasion, several immune-evasive mechanisms have evolved in S. aureus, such as complement inhibition by secreted proteins and IgG-binding by surface-exposed protein A. While it is generally accepted that S. aureus cells bind a range of host factors for various purposes, no global analyses to profile staphylococcal host factor binding have so far been performed. Therefore, we explored the possibility to profile the binding of human serum proteins to S. aureus cells by "surface shaving" with trypsin and subsequent MS analysis of liberated peptides. This resulted in the identification of several components of the complement system, the platelet factor 4 and the isoform 1 of the inter-α-trypsin inhibitor heavy chain H4 on the staphylococcal cell surface. We conclude that surface shaving is a versatile tool to profile global interactions between human serum proteins and the S. aureus cell surface.
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Affiliation(s)
- Annette Dreisbach
- Department of Medical Microbiology, University Medical Center Groningen and University of Groningen, Hanzeplein 1, Groningen, The Netherlands
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85
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Vazquez V, Liang X, Horndahl JK, Ganesh VK, Smeds E, Foster TJ, Hook M. Fibrinogen is a ligand for the Staphylococcus aureus microbial surface components recognizing adhesive matrix molecules (MSCRAMM) bone sialoprotein-binding protein (Bbp). J Biol Chem 2011; 286:29797-805. [PMID: 21642438 DOI: 10.1074/jbc.m110.214981] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Microbial surface components recognizing adhesive matrix molecules (MSCRAMMs) are bacterial surface proteins mediating adherence of the microbes to components of the extracellular matrix of the host. On Staphylococci, the MSCRAMMs often have multiple ligands. Consequently, we hypothesized that the Staphylococcus aureus MSCRAMM bone sialoprotein-binding protein (Bbp) might recognize host molecules other than the identified bone protein. A ligand screen revealed that Bbp binds human fibrinogen (Fg) but not Fg from other mammals. We have characterized the interaction between Bbp and Fg. The binding site for Bbp was mapped to residues 561-575 in the Fg Aα chain using recombinant Fg chains and truncation mutants in Far Western blots and solid-phase binding assays. Surface plasmon resonance was used to determine the affinity of Bbp for Fg. The interaction of Bbp with Fg peptides corresponding to the mapped residues was further characterized using isothermal titration calorimetry. In addition, Bbp expressed on the surface of bacteria mediated adherence to immobilized Fg Aα. Also, Bbp interferes with thrombin-induced Fg coagulation. Together these data demonstrate that human Fg is a ligand for Bbp and that Bbp can manipulate the biology of the Fg ligand in the host.
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Affiliation(s)
- Vanessa Vazquez
- Center for Infectious and Inflammatory Diseases, Institute of Biosciences and Technology, Texas A&M University System Health Science Center, Houston, Texas 77030, USA
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86
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Fry DE, Barie PS. The Changing Face ofStaphylococcus aureus:A Continuing Surgical Challenge. Surg Infect (Larchmt) 2011; 12:191-203. [DOI: 10.1089/sur.2011.068] [Citation(s) in RCA: 53] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Affiliation(s)
- Donald E. Fry
- Department of Surgery, Northwestern University Feinberg School of Medicine, Chicago, Illinois, and Department of Surgery, University of New Mexico School of Medicine, Albuquerque, New Mexico
| | - Philip S. Barie
- Department of Surgery and Department of Public Health, Weill Cornell Medical College, New York, New York
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87
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Choy HA, Kelley MM, Croda J, Matsunaga J, Babbitt JT, Ko AI, Picardeau M, Haake DA. The multifunctional LigB adhesin binds homeostatic proteins with potential roles in cutaneous infection by pathogenic Leptospira interrogans. PLoS One 2011; 6:e16879. [PMID: 21347378 PMCID: PMC3036719 DOI: 10.1371/journal.pone.0016879] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2010] [Accepted: 01/05/2011] [Indexed: 01/10/2023] Open
Abstract
Leptospirosis is a potentially fatal zoonotic disease in humans and animals caused by pathogenic spirochetes, such as Leptospira interrogans. The mode of transmission is commonly limited to the exposure of mucous membrane or damaged skin to water contaminated by leptospires shed in the urine of carriers, such as rats. Infection occurs during seasonal flooding of impoverished tropical urban habitats with large rat populations, but also during recreational activity in open water, suggesting it is very efficient. LigA and LigB are surface localized proteins in pathogenic Leptospira strains with properties that could facilitate the infection of damaged skin. Their expression is rapidly induced by the increase in osmolarity encountered by leptospires upon transition from water to host. In addition, the immunoglobulin-like repeats of the Lig proteins bind proteins that mediate attachment to host tissue, such as fibronectin, fibrinogen, collagens, laminin, and elastin, some of which are important in cutaneous wound healing and repair. Hemostasis is critical in a fresh injury, where fibrinogen from damaged vasculature mediates coagulation. We show that fibrinogen binding by recombinant LigB inhibits fibrin formation, which could aid leptospiral entry into the circulation, dissemination, and further infection by impairing healing. LigB also binds fibroblast fibronectin and type III collagen, two proteins prevalent in wound repair, thus potentially enhancing leptospiral adhesion to skin openings. LigA or LigB expression by transformation of a nonpathogenic saprophyte, L. biflexa, enhances bacterial adhesion to fibrinogen. Our results suggest that by binding homeostatic proteins found in cutaneous wounds, LigB could facilitate leptospirosis transmission. Both fibronectin and fibrinogen binding have been mapped to an overlapping domain in LigB comprising repeats 9-11, with repeat 11 possibly enhancing binding by a conformational effect. Leptospirosis patient antibodies react with the LigB domain, suggesting applications in diagnosis and vaccines that are currently limited by the strain-specific leptospiral lipopolysaccharide coats.
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Affiliation(s)
- Henry A Choy
- Department of Medicine, David Geffen School of Medicine at University of California Los Angeles, Los Angeles, California, United States of America.
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88
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Lin YP, McDonough SP, Sharma Y, Chang YF. Leptospira immunoglobulin-like protein B (LigB) binding to the C-terminal fibrinogen αC domain inhibits fibrin clot formation, platelet adhesion and aggregation. Mol Microbiol 2011; 79:1063-76. [PMID: 21219469 DOI: 10.1111/j.1365-2958.2010.07510.x] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Leptospira immunoglobulin-like (Lig) proteins including LigA and LigB are adhesins that bind to fibronectin, collagen, laminin and elastin. In addition, Lig proteins are fibrinogen (Fg)-binding proteins, although the physiological role of the Lig-Fg interaction is unclear. In this study, a previously identified Fg-binding region, LigBCen2 (amino acids 1014-1165 of LigB), has been further localized to LigBCen2R, which consists of the partial 11th and entire 12th Ig-like domain (amino acids 1014-1119). LigBCen2R was found to bind to the C-terminal αC domain of Fg (FgαCC; amino acids 392-644 in Fg α chain; isothermal titration calorimetry, K(D) = 0.375 µM; fluorescence spectrometry, K(D) = 0.364 µM). The quenching and blue shift observed for the maximum wavelength intensities of the tryptophan fluorescence spectra for FgαCCY570W upon LigBCen2RW1073C binding suggested an RGD motif close to the sole tryptophan on FgαCCY570W was buried in LigBCen2R upon saturation with FgαCC. A conformational change in LigBCen2R when bound to the FgαCC RGD motif blocked further binding to integrin α(IIb) β3 on platelets, thus preventing their aggregation. LigBCen2R binding to FgαCC reduced clot formation but did not affect plasminogen and tissue-type plasminogen activator interactions with FgαCC. This study is the first to report that a spirochaetal protein binds to the C-terminal αC domain of Fg, which regulates thrombosis and fibrinolysis, and may help explain the pulmonary haemorrhage and thrombocytopenia seen in clinical cases of leptospirosis.
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Affiliation(s)
- Yi-Pin Lin
- Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, Ithaca, New York, NY, USA
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89
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Heilmann C. Adhesion mechanisms of staphylococci. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2011; 715:105-23. [PMID: 21557060 DOI: 10.1007/978-94-007-0940-9_7] [Citation(s) in RCA: 132] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
Abstract
Staphylococcal adherence to an either biotic or abiotic surface is the critical first event in the establishment of an infection with these serious pathogens. Especially Staphylococcus aureus harbours a variety of proteinaceous and non-proteinaceous adhesins that mediate attachment to a multitude of host factors, such as extracellular matrix and plasma proteins and human host cells, or intercellular adhesion, which is essential for biofilm accumulation. Proteinaceous adhesins may be classified in covalently surface-anchored proteins of the MSCRAMM (microbial surface components recognizing adhesive matrix molecules) family or in proteins that are surface-associated by different means, such as ionic or hydrophobic interactions. Non-covalently surface-associated proteins include the autolysin/adhesins, proteins of the SERAM (secretable expanded repertoire adhesive molecules) family, or membrane-spanning proteins. Non-proteinaceous adhesins comprise the polysaccharide PIA (polysaccharide intercellular adhesin) and wall teichoic and lipoteichoic acids. The features and functions of surface and surface-associated protein adhesins as well as of non-proteinaceous adhesins are discussed.
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Affiliation(s)
- Christine Heilmann
- Institute for Medical Microbiology, University Hospital of Münster, 48149, Münster, Germany.
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90
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Ohbayashi T, Irie A, Murakami Y, Nowak M, Potempa J, Nishimura Y, Shinohara M, Imamura T. Degradation of fibrinogen and collagen by staphopains, cysteine proteases released from Staphylococcus aureus. MICROBIOLOGY-SGM 2010; 157:786-792. [PMID: 21081759 DOI: 10.1099/mic.0.044503-0] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Staphylococcus aureus is the most frequently isolated pathogen in gram-positive sepsis often complicated by a blood clotting disorder, and is the leading cause of infective endocarditis induced by bacterial destruction of endocardial tissues. The bacterium secretes cysteine proteases referred to as staphopain A (ScpA) and staphopain B (SspB). To investigate virulence activities of staphopains pertinent to clotting disorders and tissue destruction, we examined their effects on collagen, one of the major tissue components, and on plasma clotting. Both staphopains prolonged the partial thromboplastin time of plasma in a dose- and activity-dependent manner, with SspB being threefold more potent than ScpA. Staphopains also prolonged the thrombin time of both plasma and fibrinogen, indicating that these enzymes can cause impaired plasma clotting through fibrinogen degradation. Whereas SspB cleaved the fibrinogen Aα-chain at the C-terminal region very efficiently, ScpA degraded it rather slowly. This explains the superior ability of the former enzyme to impair fibrinogen clottability. Enzymically active staphopains, at concentrations as low as 10 nM, degraded collagen with comparable efficiency. These results show novel virulence activities of staphopains in degrading fibrinogen and collagen, and suggest an involvement of staphopains in the clotting impairment and tissue destruction caused by staphylococcal infection.
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Affiliation(s)
- Takehisa Ohbayashi
- Department of Oral and Maxillo-Facial Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Atsushi Irie
- Department of Immunogenetics, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan
| | - Yoji Murakami
- Department of Molecular Pathology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan.,Department of Urology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Magdalena Nowak
- Department of Microbiology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland
| | - Jan Potempa
- Department of Periodontics, Endodontics and Dental Hygiene, University of Louisville School of Dentistry, Louisville, KY 40202, USA.,Department of Microbiology, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Kraków, Poland
| | - Yasuharu Nishimura
- Department of Immunogenetics, Graduate School of Medical Sciences, Kumamoto University, Kumamoto, Japan
| | - Masanori Shinohara
- Department of Oral and Maxillo-Facial Surgery, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
| | - Takahisa Imamura
- Department of Molecular Pathology, Faculty of Life Sciences, Kumamoto University, Kumamoto, Japan
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91
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Evaluation of clumping factor A binding region A in a subunit vaccine against Staphylococcus aureus-induced mastitis in mice. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2010; 17:1746-52. [PMID: 20826613 DOI: 10.1128/cvi.00162-10] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
The present study evaluated the potential of recombinant binding region A of clumping factor A (rClfA-A) to be an effective component of a vaccine against mastitis induced by Staphylococcus aureus in the mouse. rClfA-A and inactivated S. aureus were each emulsified in Freund's adjuvant, mineral oil adjuvant, and Seppic adjuvant; phosphate-buffered saline was used as a control. Seven groups of 12 mice each were immunized intraperitoneally three times at 2-week intervals. The titers of IgG and subtypes thereof (IgG1 and IgG2a) in the rClfA-A-immunized group were more than 1,000-fold higher than those in the killed-bacteria-immunized group (P < 0.01). Of the three adjuvants used, mineral oil adjuvant induced the highest antibody levels for both antigens (P < 0.001). Furthermore, the anti-rClfA-A antibody capacities for bacterial adhesion and opsonizing phagocytosis were significantly greater in the rClfA-A-immunized group than in the killed-bacteria-immunized group (P < 0.05). Lactating mice immunized with either rClfA-A or inactivated vaccine were challenged with S. aureus via the intramammary route. The numbers of bacteria recovered from the murine mammary glands 24 h after inoculation were significantly lower in the rClfA-A group than in the killed-bacteria-immunized group (P < 0.001). Histologic examination of the mammary glands showed that rClfA-A immunization effectively preserved tissue integrity. Thus, rClfA-A emulsified in an oil adjuvant provides strong immune protection against S. aureus-induced mastitis in the mouse.
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92
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Seo HS, Xiong YQ, Mitchell J, Seepersaud R, Bayer AS, Sullam PM. Bacteriophage lysin mediates the binding of streptococcus mitis to human platelets through interaction with fibrinogen. PLoS Pathog 2010; 6:e1001047. [PMID: 20714354 PMCID: PMC2920869 DOI: 10.1371/journal.ppat.1001047] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2010] [Accepted: 07/15/2010] [Indexed: 12/02/2022] Open
Abstract
The binding of bacteria to human platelets is a likely central mechanism in the pathogenesis of infective endocarditis. We have previously found that platelet binding by Streptococcus mitis SF100 is mediated by surface components encoded by a lysogenic bacteriophage, SM1. We now demonstrate that SM1-encoded lysin contributes to platelet binding via its direct interaction with fibrinogen. Far Western blotting of platelets revealed that fibrinogen was the major membrane-associated protein bound by lysin. Analysis of lysin binding with purified fibrinogen in vitro confirmed that these proteins could bind directly, and that this interaction was both saturable and inhibitable. Lysin bound both the Aα and Bβ chains of fibrinogen, but not the γ subunit. Binding of lysin to the Bβ chain was further localized to a region within the fibrinogen D fragment. Disruption of the SF100 lysin gene resulted in an 83±3.1% reduction (mean ± SD) in binding to immobilized fibrinogen by this mutant strain (PS1006). Preincubation of this isogenic mutant with purified lysin restored fibrinogen binding to wild type levels. When tested in a co-infection model of endocarditis, loss of lysin expression resulted in a significant reduction in virulence, as measured by achievable bacterial densities (CFU/g) within vegetations, kidneys, and spleens. These results indicate that bacteriophage-encoded lysin is a multifunctional protein, representing a new class of fibrinogen-binding proteins. Lysin appears to be cell wall-associated through its interaction with choline. Once on the bacterial surface, lysin can bind fibrinogen directly, which appears to be an important interaction for the pathogenesis of endocarditis. The binding of bacteria to human platelets is thought to be a central event in the development of endocarditis (a life-threatening cardiovascular infection). We have previously found that platelet binding by Streptococcus mitis is mediated by surface components encoded by a bacteriophage contained within the host bacterium. We now show that lysin (an enzyme of bacteriophage origin) contributes to platelet binding via its direct interaction with fibrinogen on the platelet surface. Lysin bound to purified fibrinogen in vitro, and this interaction specifically involved the Aα and Bβ chains of fibrinogen. Binding of lysin to the Bβ chain was further localized to a region within the fibrinogen D fragment. Disruption of the gene encoding lysin gene resulted in a significant reduction in binding to fibrinogen by S. mitis, as well as a major reduction in virulence, as measured by a rat model of endocarditis. These results indicate that lysin is a multifunctional protein, representing a new class of fibrinogen-binding molecules. Lysin is localized to the bacterial surface via its interaction with cell wall choline, where it then can bind fibrinogen directly. Cell surface lysin apparently also contributes to the development of endovascular infections via its previously unrecognized fibrinogen binding activity.
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Affiliation(s)
- Ho Seong Seo
- Division of Infectious Diseases, Veterans Affairs Medical Center and the University of California, San Francisco, California, United States of America
| | - Yan Q. Xiong
- Division of Infectious Diseases, Harbor-UCLA Medical Center, Torrance, California, United States of America
| | | | - Ravin Seepersaud
- Division of Infectious Diseases, Veterans Affairs Medical Center and the University of California, San Francisco, California, United States of America
| | - Arnold S. Bayer
- Division of Infectious Diseases, Harbor-UCLA Medical Center, Torrance, California, United States of America
| | - Paul M. Sullam
- Division of Infectious Diseases, Veterans Affairs Medical Center and the University of California, San Francisco, California, United States of America
- * E-mail:
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93
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Genetic variation in Staphylococcus aureus surface and immune evasion genes is lineage associated: implications for vaccine design and host-pathogen interactions. BMC Microbiol 2010; 10:173. [PMID: 20550675 PMCID: PMC2905362 DOI: 10.1186/1471-2180-10-173] [Citation(s) in RCA: 163] [Impact Index Per Article: 11.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2010] [Accepted: 06/15/2010] [Indexed: 01/22/2023] Open
Abstract
Background S. aureus is a coloniser and pathogen of humans and mammals. Whole genome sequences of 58 strains of S. aureus in the public domain and data from multi-strain microarrays were compared to assess variation in the sequence of proteins known or putatively interacting with host. Results These included 24 surface proteins implicated in adhesion (ClfA, ClfB, Cna, Eap, Ebh, EbpS, FnBPA, FnBPB, IsaB, IsdA, IsdB, IsdH, SasB, SasC, SasD, SasF, SasG, SasH, SasK, SdrC, SdrD, SdrE, Spa and SraP) and 13 secreted proteins implicated in immune response evasion (Coa, Ecb, Efb, Emp, EsaC, EsxA, EssC, FLIPr, FLIPr like, Sbi, SCIN-B, SCIN-C, VWbp) located on the stable core genome. Many surface protein genes were missing or truncated, unlike immune evasion genes, and several distinct variants were identified. Domain variants were lineage specific. Unrelated lineages often possess the same sequence variant domains proving that horizontal transfer and recombination has contributed to their evolution. Surprisingly, sequenced strains from four animal S. aureus strains had surface and immune evasion proteins remarkably similar to those found in human strains, yet putative targets of these proteins vary substantially between different hosts. This suggests these proteins are not essential for virulence. However, the most variant protein domains were the putative functional regions and there is biological evidence that variants can be functional, arguing they do play a role. Conclusion Surface and immune evasion genes are candidates for S. aureus vaccines, and their distribution and functionality is key. Vaccines should contain cocktails of antigens representing all variants or they will not protect against naturally occurring S. aureus populations.
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94
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Foster TJ. Colonization and infection of the human host by staphylococci: adhesion, survival and immune evasion. Vet Dermatol 2010; 20:456-70. [PMID: 20178484 DOI: 10.1111/j.1365-3164.2009.00825.x] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
The natural habitat of Staphylococcus aureus in humans is the moist squamous epithelium of the anterior nares. Several bacterial surface proteins are implicated in promoting adhesion to desquamated epithelial cells. Clumping factor B (ClfB) and iron-regulated surface determinant A both promote nasal colonization in rodent models, and in the case of ClfB, humans. One of the ligands involved in adhesion is cytokeratin 10. Reduction in nasal colonization can be achieved by active and passive immunization. S. aureus is well endowed with secreted and surface components that compromise innate immune responses, particularly the function of neutrophils. S. aureus secretes proteins that reduce migration of neutrophils from the bloodstream to the site of infection by impeding diapedesis and receptors for chemotactic molecules. Several secreted proteins interfere with complement C3 and C5 convertases, thus reducing the level of C3b opsonin and the chemotactic peptide C5a. Host proteases are recruited to the cell surface to enhance destruction of opsonic C3b and IgG. Surface components ClfA, protein A and polysaccharide capsule compromise the recognition of opsonins on the bacterial cell surface. If engulfed by neutrophils the intracellular bacterium can resist reactive oxygen intermediates, nitric oxide radicals, defensin peptides and bactericidal proteins. A prior infection by S. aureus does not induce complete protective immunity. This could be due to immunosuppression caused by expression of superantigen proteins that disrupt normal activation of T cells and B cells during antigen presentation. By studying the molecular pathogenesis of S. aureus infections markers might be found for investigating S. pseudintermedius infections of dogs.
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Affiliation(s)
- Timothy J Foster
- Microbiology Department, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland.
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95
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Burke FM, McCormack N, Rindi S, Speziale P, Foster TJ. Fibronectin-binding protein B variation in Staphylococcus aureus. BMC Microbiol 2010; 10:160. [PMID: 20515471 PMCID: PMC2894786 DOI: 10.1186/1471-2180-10-160] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2009] [Accepted: 06/01/2010] [Indexed: 12/28/2022] Open
Abstract
Background Fibronectin binding proteins A and B (FnBPA and FnBPB) mediate adhesion of S. aureus to fibrinogen, elastin and fibronectin. We previously identified seven different isotypes of FnBPA based on divergence in the fibrinogen- and elastin-binding A domains. The variation created differences in antigenicity while ligand binding functions were retained. Here, FnBPB variation was examined in both human and bovine isolates and compared to that of FnBPA. Results Seven different fnbB allelic variants were identified. Some strains that cluster by phylogenetic analysis contain different fnbB variants, whereas more divergent strains contain the same fnbB variant. The phylogeny of fnbB alleles does not match the phylogeny of fnbA alleles. Some FnBPA and FnBPB isotypes that are specified by human S. aureus strains are also found in bovine strains. The seven fnbB allelic variants encode seven distinct isotypes of the FnBPB A domain that are 61 to 85% identical in amino acid sequence. Variant amino acid residues were mapped on a three-dimensional model of the FnBPB A domain and were predicted to be surface-exposed. They are responsible for the antigenic diversity detected with polyclonal antibody and a monoclonal antibody raised against isotype I. Ligand binding by recombinant FnBPB N23 isotypes was compared by ELISA-based solid phase assays and surface plasmon resonance. Each bound to immobilized fibrinogen, elastin and fibronectin dose-dependently and saturably with similar affinities. Binding to fibronectin was surprising because the A domains do not contain any known motifs that mediate binding to fibronectin. This raises the possibility that the A domain of FnBPB contains a novel fibronectin binding motif that binds fibronectin by a novel mechanism. Conclusions Seven different isoforms of FnBPB A domain retain ligand-binding functions but are antigenically distinct. The variation in FnBPA and FnBPB occurs in human and bovine S. aureus strains and may act as an immune evasion mechanism. All seven isotypes of FnBPB are capable of binding fibronectin though none contain any known fibronectin-binding motifs. These results have implications for the development of vaccines or immunotherapeutics that target FnBPB
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Affiliation(s)
- Fiona M Burke
- Department of Microbiology, Moyne Institute of Preventive Medicine, University of Dublin, Trinity College, Dublin, Ireland
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96
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Said KB, Zhu G, Zhao X. Organ- and Host-Specific Clonal Groups ofStaphylococcus aureusfrom Human Infections and Bovine Mastitis Revealed by the Clumping Factor A Gene. Foodborne Pathog Dis 2010; 7:111-9. [DOI: 10.1089/fpd.2009.0334] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Affiliation(s)
| | - Guoqiang Zhu
- Department of Microbiology, College of Veterinary Science, Yanzhou University, Yanzhou, China
| | - Xin Zhao
- Department of Animal Science, McGill University, Quebec, Canada
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Geoghegan JA, Ganesh VK, Smeds E, Liang X, Höök M, Foster TJ. Molecular characterization of the interaction of staphylococcal microbial surface components recognizing adhesive matrix molecules (MSCRAMM) ClfA and Fbl with fibrinogen. J Biol Chem 2009; 285:6208-16. [PMID: 20007717 DOI: 10.1074/jbc.m109.062208] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The ligand-binding domain of Fbl (the fibrinogen binding protein from Staphylococcus lugdunensis) shares 60% sequence identity with ClfA (clumping factor A) of Staphylococcus aureus. Recombinant Fbl corresponding to the minimum fibrinogen-binding region (subdomains N2N3) was compared with ClfA for binding to fibrinogen. Fbl and ClfA had very similar affinities for fibrinogen by surface plasmon resonance. The binding site for Fbl in fibrinogen was localized to the extreme C terminus of the fibrinogen gamma-chain at the same site recognized by ClfA. Isothermal titration calorimetry showed that Fbl and ClfA had very similar affinities for a peptide mimicking the C-terminal segment of the fibrinogen gamma-chain. The peptide also inhibited binding of Fbl and ClfA to fibrinogen. A series of substituted gamma-chain variant peptides behaved very similarly when used to inhibit ClfA and Fbl binding to immobilized fibrinogen. Both ClfA and Fbl bound to bovine fibrinogen with a lower affinity compared with human fibrinogen and did not bind detectably to ovine fibrinogen. The structure of the N2N3 subdomains of Fbl in complex with the fibrinogen gamma-chain peptide was modeled based on the crystal structure of the N2N3 subdomains of the ClfA-gamma-chain peptide complex. Residues in the putative binding trench likely to be involved in fibrinogen binding were identified. Fbl variant proteins with alanine substitutions in key residues had reduced affinities for fibrinogen. Thus Fbl and ClfA bind the same site in fibrinogen by similar mechanisms.
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Affiliation(s)
- Joan A Geoghegan
- Microbiology Department, Moyne Institute of Preventive Medicine, Trinity College, Dublin 2, Ireland
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Speziale P, Pietrocola G, Rindi S, Provenzano M, Provenza G, Di Poto A, Visai L, Arciola CR. Structural and functional role of Staphylococcus aureus surface components recognizing adhesive matrix molecules of the host. Future Microbiol 2009; 4:1337-52. [DOI: 10.2217/fmb.09.102] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022] Open
Abstract
Staphylococcus aureus is a versatile and harmful human pathogen in both hospital- and community-acquired infections. S. aureus can initiate host infection by adhering to components of the extracellular matrix. Adherence is mediated by a variety of protein adhesins of the microbial surface component recognizing adhesive matrix molecule (MSCRAMM) family. In this article, we describe these MSCRAMMs in terms of structural organization and ligand-binding capacity and discuss their role as a possible target for immunotherapy.
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Affiliation(s)
- Pietro Speziale
- Department of Biochemistry, Viale Taramelli 3/b 27100 Pavia, Italy
| | | | - Simonetta Rindi
- Department of Biochemistry, Viale Taramelli 3/b 27100 Pavia, Italy
| | - Maria Provenzano
- Department of Biochemistry, Viale Taramelli 3/b 27100 Pavia, Italy
| | - Giulio Provenza
- Department of Biochemistry, Viale Taramelli 3/b 27100 Pavia, Italy
| | | | - Livia Visai
- Department of Biochemistry, Viale Taramelli 3/b 27100 Pavia, Italy and Center for Tissue Engineering (CIT), Via Ferrata 1, 27100 Pavia, Italy
| | - Carla Renata Arciola
- Research Unit on Implant Infections, Rizzoli Orthopaedic Institute, Via di Barbiano 1/10, 40136 Bologna, Italy and Experimental Pathology Department, University of Bologna, Via S. Giacomo 14, 40126 Bologna, Italy
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COMPARISON OF THE PREVALENCE OF GENES CODING FOR ENTEROTOXINS, EXFOLIATINS, PANTON-VALENTINE LEUKOCIDIN AND TSST-1 BETWEEN METHICILLIN-RESISTANT AND METHICILLIN-SUSCEPTIBLE ISOLATES OF STAPHYLOCOCCUS AUREUS AT THE UNIVERSITY HOSPITAL IN OLOMOUC. Biomed Pap Med Fac Univ Palacky Olomouc Czech Repub 2009; 153:215-8. [DOI: 10.5507/bp.2009.036] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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100
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Brennan MP, Loughman A, Devocelle M, Arasu S, Chubb AJ, Foster TJ, Cox D. Elucidating the role of Staphylococcus epidermidis serine-aspartate repeat protein G in platelet activation. J Thromb Haemost 2009; 7:1364-72. [PMID: 19486275 DOI: 10.1111/j.1538-7836.2009.03495.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023]
Abstract
BACKGROUND Staphylococcus epidermidis is a commensal of the human skin that has been implicated in infective endocarditis and infections involving implanted medical devices. S. epidermidis induces platelet aggregation by an unknown mechanism. The fibrinogen-binding protein serine-aspartate repeat protein G (SdrG) is present in 67-91% of clinical strains. OBJECTIVES To determine whether SdrG plays a role in platelet activation, and if so to investigate the role of fibrinogen in this mechanism. METHODS SdrG was expressed in a surrogate host, Lactococcus lactis, in order to investigate its role in the absence of other staphylococcal components. Platelet adhesion and platelet aggregation assays were employed. RESULTS L. lactis expressing SdrG stimulated platelet aggregation (lag time: 2.9 +/- 0.5 min), whereas the L. lactis control did not. L. lactis SdrG-induced aggregation was inhibited by alpha(IIb)beta3 antagonists and aspirin. Aggregation was dependent on both fibrinogen and IgG, and the platelet IgG receptor FcgammaRIIa. Preincubation of the bacteria with Bbeta-chain fibrinopeptide inhibited aggregation (delaying the lag time six-fold), suggesting that fibrinogen acts as a bridging molecule. Platelets adhered to L. lactis SdrG in the absence of fibrinogen. Adhesion was inhibited by alpha(IIb)beta3 antagonists, suggesting that this direct interaction involves alpha(IIb)beta3. Investigation using purified fragments of SdrG revealed a direct interaction with the B-domains. Adhesion to the A-domain involved both a fibrinogen and an IgG bridge. CONCLUSION SdrG alone is sufficient to support platelet adhesion and aggregation through both direct and indirect mechanisms.
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Affiliation(s)
- M P Brennan
- Molecular and Cellular Therapeutics, Royal College of Surgeons in Ireland, Dublin, Ireland
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