The Vi capsular polysaccharide prevents complement receptor 3-mediated clearance of Salmonella enterica serotype Typhi

Infect Immun. 2011 Feb;79(2):830-7. doi: 10.1128/IAI.00961-10. Epub 2010 Nov 22.

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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Carbohydrate Conformation
  • Complement C3 / metabolism*
  • Gene Expression Regulation, Bacterial
  • Immunoglobulin G / metabolism
  • Lipopolysaccharides / chemistry
  • Liver / microbiology
  • Macrophages
  • Mice
  • Mice, Inbred C57BL
  • O Antigens / chemistry
  • Polysaccharides, Bacterial / genetics
  • Polysaccharides, Bacterial / metabolism*
  • Protein Binding
  • Receptors, Complement / metabolism*
  • Salmonella Infections, Animal / immunology*
  • Salmonella typhi / genetics
  • Salmonella typhi / metabolism
  • Salmonella typhi / physiology*
  • Spleen / microbiology

Substances

  • Complement C3
  • Immunoglobulin G
  • Lipopolysaccharides
  • O Antigens
  • Polysaccharides, Bacterial
  • Receptors, Complement
  • capsular polysaccharide, Salmonella