A Salmonella Typhimurium-Typhi genomic chimera: a model to study Vi polysaccharide capsule function in vivo

PLoS Pathog. 2011 Jul;7(7):e1002131. doi: 10.1371/journal.ppat.1002131. Epub 2011 Jul 28.

Abstract

The Vi capsular polysaccharide is a virulence-associated factor expressed by Salmonella enterica serotype Typhi but absent from virtually all other Salmonella serotypes. In order to study this determinant in vivo, we characterised a Vi-positive S. Typhimurium (C5.507 Vi(+)), harbouring the Salmonella pathogenicity island (SPI)-7, which encodes the Vi locus. S. Typhimurium C5.507 Vi(+) colonised and persisted in mice at similar levels compared to the parent strain, S. Typhimurium C5. However, the innate immune response to infection with C5.507 Vi(+) and SGB1, an isogenic derivative not expressing Vi, differed markedly. Infection with C5.507 Vi(+) resulted in a significant reduction in cellular trafficking of innate immune cells, including PMN and NK cells, compared to SGB1 Vi(-) infected animals. C5.507 Vi(+) infection stimulated reduced numbers of TNF-α, MIP-2 and perforin producing cells compared to SGB1 Vi(-). The modulating effect associated with Vi was not observed in MyD88(-/-) and was reduced in TLR4(-/-) mice. The presence of the Vi capsule also correlated with induction of the anti-inflammatory cytokine IL-10 in vivo, a factor that impacted on chemotaxis and the activation of immune cells in vitro.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Capsules* / genetics
  • Bacterial Capsules* / immunology
  • Cytokines / genetics
  • Cytokines / immunology
  • Genetic Loci / immunology
  • Genomic Islands* / genetics
  • Genomic Islands* / immunology
  • Immunity, Innate*
  • Mice
  • Mice, Knockout
  • Myeloid Differentiation Factor 88 / genetics
  • Myeloid Differentiation Factor 88 / immunology
  • Polysaccharides, Bacterial* / genetics
  • Polysaccharides, Bacterial* / immunology
  • Salmonella typhi* / genetics
  • Salmonella typhi* / immunology
  • Salmonella typhi* / pathogenicity
  • Salmonella typhimurium* / genetics
  • Salmonella typhimurium* / immunology
  • Salmonella typhimurium* / pathogenicity
  • Toll-Like Receptor 4 / genetics
  • Toll-Like Receptor 4 / immunology
  • Typhoid Fever* / genetics
  • Typhoid Fever* / immunology

Substances

  • Cytokines
  • Myd88 protein, mouse
  • Myeloid Differentiation Factor 88
  • Polysaccharides, Bacterial
  • Tlr4 protein, mouse
  • Toll-Like Receptor 4