title: The Vi capsular polysaccharide prevents complement receptor 3-mediated clearance of Salmonella enterica serotype Typhi.
abstract: Capsular polysaccharides are important virulence factors of invasive bacterial pathogens. Here we studied the role of the virulence (Vi) capsular polysaccharide of Salmonella enterica serotype Typhi (S. Typhi) in preventing innate immune recognition by complement. Comparison of capsulated S. Typhi with a noncapsulated mutant (ΔtviBCDE vexABCDE mutant) revealed that the Vi capsule interfered with complement component 3 (C3) deposition. Decreased complement fixation resulted in reduced bacterial binding to complement receptor 3 (CR3) on the surface of murine macrophages in vitro and decreased CR3-dependent clearance of Vi capsulated S. Typhi from the livers and spleens of mice. Opsonization of bacteria with immune serum prior to intraperitoneal infection increased clearance of capsulated S. Typhi from the liver. Our data suggest that the Vi capsule prevents CR3-dependent clearance, which can be overcome in part by a specific antibody response.
authors.affiliation: Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, One Shields Ave., Davis, CA 95616-8645, USA.
authors.forename: R Paul
authors.initials: RP
authors.lastname: Wilson
authors.forename: Sebastian E
authors.initials: SE
authors.lastname: Winter
authors.forename: Alanna M
authors.initials: AM
authors.lastname: Spees
authors.forename: Maria G
authors.initials: MG
authors.lastname: Winter
authors.forename: Jessalyn H
authors.initials: JH
authors.lastname: Nishimori
authors.forename: Jesus F
authors.initials: JF
authors.lastname: Sanchez
authors.forename: Sean-Paul
authors.initials: SP
authors.lastname: Nuccio
authors.forename: Robert W
authors.initials: RW
authors.lastname: Crawford
authors.forename: Çagla
authors.initials: Ç
authors.lastname: Tükel
authors.forename: Andreas J
authors.initials: AJ
authors.lastname: Bäumler
mesh_terms: D000818:Animals; D002236:Carbohydrate Conformation; D003176:Complement C3 / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial; D007074:Immunoglobulin G / Q000378:metabolism; D008070:Lipopolysaccharides / Q000737:chemistry; D008099:Liver / Q000382:microbiology; D008264:Macrophages; D051379:Mice; D008810:Mice, Inbred C57BL; D019081:O Antigens / Q000737:chemistry; D011135:Polysaccharides, Bacterial / Q000235:genetics / Q000378:metabolism*; D011485:Protein Binding; D011951:Receptors, Complement / Q000378:metabolism*; D012481:Salmonella Infections, Animal / Q000276:immunology*; D012485:Salmonella typhi / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D013154:Spleen / Q000382:microbiology
chemical_list: D003176:Complement C3; D007074:Immunoglobulin G; D008070:Lipopolysaccharides; D019081:O Antigens; D011135:Polysaccharides, Bacterial; D011951:Receptors, Complement; C054154:capsular polysaccharide, Salmonella