The Capsule Encoding theviaBLocus Reduces Interleukin-17 Expression and Mucosal Innate Responses in the Bovine Intestinal Mucosa during Infection withSalmonella entericaSerotype Typhi

Abstract

TheviaBlocus contains genes for the biosynthesis and export of the Vi capsular antigen ofSalmonella entericaserotype Typhi. Wild-type serotype Typhi induces less CXC chemokine production in tissue culture models than does an isogenicviaBmutant. Here we investigated the in vivo relevance of these observations by determining whether the presence of theviaBregion prevents inflammation in two animal models of gastroenteritis. UnlikeS. entericaserotype Typhimurium, serotype Typhi or a serotype TyphiviaBmutant did not elicit marked inflammatory changes in the streptomycin-pretreated mouse model. In contrast, infection of bovine ligated ileal loops with a serotype TyphiviaBmutant resulted in more fluid accumulation and higher expression of the chemokine growth-related oncogene alpha (GROα) and interleukin-17 (IL-17) than did infection with the serotype Typhi wild type. There was a marked upregulation of IL-17 expression in both the bovine ligated ileal loop model and the streptomycin-pretreated mouse model, suggesting that this cytokine is an important component of the inflammatory response to infection withSalmonellaserotypes. Introduction of the clonedviaBregion into serotype Typhimurium resulted in a significant reduction of GROα and IL-17 expression and in reduced fluid secretion. Our data support the idea that theviaBregion plays a role in reducing intestinal inflammation in vivo.