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Updated: Jun 6, 2026

Isolation of Salmonella typhimurium-containing Phagosomes from Macrophages
Published on: October 25, 2017
The Vi capsular polysaccharide prevents complement receptor 3-mediated clearance of Salmonella enterica serotype
R Paul Wilson1, Sebastian E Winter, Alanna M Spees
1Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, One Shields Ave., Davis, CA 95616-8645, USA.
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.
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