The binding of streptococci to human platelets is a postulated central mechanism in the pathogenesis of infective endocarditis. Bacterium-platelet binding may be important both for the initial attachment of blood-borne organisms to the valve surface, and for the subsequent formation of macroscopic vegetations. Our previous research has shown that platelet binding by Streptococcus mitis strain SF100 is mediated in part by two cell wall-associated proteins (PblA and PblB) that are encoded by a temperate bacteriophage (SM1). Expression of both proteins on the bacterial surface is required for maximum levels of platelet binding by SF100. The overall goal of this proposal is to delineate further the mechanisms by which these proteins contribute to platelet binding, and to determine the role of PblA and PblB mediated binding in the pathogenesis of endocarditis. We will first purify PblA and PblB, and examine the binding properties of each protein with human platelets in vitro, to determine whether either or both proteins can bind human platelets directly in vitro. Formal binding analysis will be done to determine whether binding resembles a receptor-ligand interaction. Purified PblA and PblB will also be used to identify their respective platelet binding sites, by far western blotting and by immunoprecipitation or affinity chromatography. Platelet membrane proteins bound by either PblA or PblB will then be identified by several methods as needed (e.g., N-terminal sequencing, or mass spectroscopy). We will also assess the mechanisms for the export of PblA and PblB to the bacterial surface, and whether these proteins form platelet-binding complexes with other phage structural proteins. To address the role of these adhesins in the pathogenesis of endocarditis, we will compare the virulence of SF100 and selected mutants in a rabbit model of endocardial infection. By characterizing streptococcal adhesins for platelets, this research will further define the role of platelet binding in the pathogenesis of endocarditis. In addition, it may identify novel targets for new preventative or therapeutic strategies.

Agency
National Institute of Health (NIH)
Institute
National Institute of Allergy and Infectious Diseases (NIAID)
Type
Research Project (R01)
Project #
5R01AI057433-04
Application #
7174307
Study Section
Bacteriology and Mycology Subcommittee 2 (BM)
Program Officer
Rubin, Fran A
Project Start
2004-08-01
Project End
2009-01-31
Budget Start
2007-02-01
Budget End
2008-01-31
Support Year
4
Fiscal Year
2007
Total Cost
$391,124
Indirect Cost
Name
Northern California Institute Research & Education
Department
Type
DUNS #
613338789
City
San Francisco
State
CA
Country
United States
Zip Code
94121
Wang, Nai-Yu; Patras, Kathryn A; Seo, Ho Seong et al. (2014) Group B streptococcal serine-rich repeat proteins promote interaction with fibrinogen and vaginal colonization. J Infect Dis 210:982-91
Seo, Ho Seong; Minasov, George; Seepersaud, Ravin et al. (2013) Characterization of fibrinogen binding by glycoproteins Srr1 and Srr2 of Streptococcus agalactiae. J Biol Chem 288:35982-96
Yen, Yihfen T; Cameron, Todd A; Bensing, Barbara A et al. (2013) Differential localization of the streptococcal accessory sec components and implications for substrate export. J Bacteriol 195:682-95
Seo, Ho Seong; Xiong, Yan Q; Sullam, Paul M (2013) Role of the serine-rich surface glycoprotein Srr1 of Streptococcus agalactiae in the pathogenesis of infective endocarditis. PLoS One 8:e64204
Seo, Ho Seong; Mu, Rong; Kim, Brandon J et al. (2012) Binding of glycoprotein Srr1 of Streptococcus agalactiae to fibrinogen promotes attachment to brain endothelium and the development of meningitis. PLoS Pathog 8:e1002947
Seepersaud, Ravin; Bensing, Barbara A; Yen, Yihfen T et al. (2012) The accessory Sec protein Asp2 modulates GlcNAc deposition onto the serine-rich repeat glycoprotein GspB. J Bacteriol 194:5564-75
Seo, Ho Seong; Sullam, Paul M (2011) Characterization of the fibrinogen binding domain of bacteriophage lysin from Streptococcus mitis. Infect Immun 79:3518-26
Nallapareddy, Sreedhar R; Sillanpaa, Jouko; Mitchell, Jennifer et al. (2011) Conservation of Ebp-type pilus genes among Enterococci and demonstration of their role in adherence of Enterococcus faecalis to human platelets. Infect Immun 79:2911-20
Pyburn, Tasia M; Bensing, Barbara A; Xiong, Yan Q et al. (2011) A structural model for binding of the serine-rich repeat adhesin GspB to host carbohydrate receptors. PLoS Pathog 7:e1002112
Yen, Yihfen T; Seepersaud, Ravin; Bensing, Barbara A et al. (2011) Asp2 and Asp3 interact directly with GspB, the export substrate of the Streptococcus gordonii accessory Sec System. J Bacteriol 193:3165-74

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