IAI Accepts, published online ahead of print on 9 November 2009

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Infect. Immun. doi:10.1128/IAI.00972-09
Copyright (c) 2009, American Society for Microbiology and/or the Listed Authors/Institutions. All Rights Reserved.

The Salmonella enterica serotype Typhi Vi capsular antigen is expressed after entering the ileal mucosa

Quynh T. Tran, Gabriel Gomez, Sangeeta Khare, Sara D. Lawhon, Manuela Raffatellu, Andreas J. Bäumler, Dharani Ajithdoss, Soma Dhavala, and L. Garry Adams^*

Department of Veterinary Pathobiology, College of Veterinary Medicine, Texas A&M University, College Station, TX 77843-4467, USA; Department of Medical Microbiology and Immunology, School of Medicine, University of California at Davis, One Shields Avenue, Davis, CA 95616-8645, USA; Department of Statistics, College of Science, Texas A&M University, College Station, TX 77843-4467, USA

^* To whom correspondence should be addressed. Email: gadams{at}cvm.tamu.edu.

Salmonella enterica serotype Typhi, the etiological agent of typhoid fever, produces the Vi-capsular antigen, a virulence factor absent in Salmonella enterica serotype Typhimurium. Previous studies suggest that the capsule-encoding viaB locus reduces inflammatory responses in intestinal tissue, however, there are currently no data regarding the in vivo expression of this locus. Here we implemented direct and indirect methods to localize and detect Vi antigen expression within polarized intestinal epithelial cells and in the bovine ileal mucosa. We report that tviB, a gene necessary for Vi production in S. Typhi, was significantly up regulated during invasion of intestinal epithelial cells in vitro. During infection of bovine ligated loops, tviB was expressed at levels significantly higher in calf tissue than in the the inoculum. The presence of the Vi capsular antigen was detected in calf ileal tissue via fluorescence microscopy. Together, these results support the concept that expression of the Vi capsular antigen is induced when S. Typhi transits from the intestinal lumen into the ileal mucosa.