Salmonella enterica serovar Choleraesuis is an enteric pathogen of swine, producing septicemia, enterocolitis, pneumonia, and hepatitis. The initial molecular events at the site of Salmonella infection are hypothesized to be critical in the initiation of innate and adaptive immune responses; however, the acute immune response elicited by porcine intestinal tissues is not well understood. To address this need, we employed explants of jejunal Peyer's patch (JPP) mucosa from pigs to examine Salmonella-induced immune responses under controlled conditions as well as to overcome limitations of whole animal approaches. JPP explants mounted in Ussing chambers maintained normal histological structure for 2 h and stable short-circuit current and electrical conductance for 2.5 h. After ex vivo luminal exposure to Salmonella serovar Choleraesuis, JPP responded with an increase in mRNA expression of IL-1β and IL-8, but not TNFα. Increased IL-1β and IL-8 expression were dependent on efficient Salmonella adhesion and internalization, whereas mutant Salmonella did not induce inflammatory cytokine expression. Commensal enteric bacteria, present in some experiments, also did not induce inflammatory cytokine expression. These findings indicate that Salmonella uptake by Peyer's patch is important in the induction of an innate response involving expression of IL-1β and IL-8, and that ex vivo intestinal immune tissue explants provide an intact tissue model that will facilitate investigation of mucosal immunity in swine.
Bibliographical noteFunding Information:
This work was partially supported by the National Research Initiative of the USDA Cooperative State Research, Education and Extension Service (Grant Numbers 2002-35204-11705 and 2003-35205-2840) and by National Institutes of Health (Grant R01 DA-10200). KAH was supported by the NIH/NIDA training (Grant T32-DA-07239). We thank Dr. Roy Curtiss III (Department of Biology, Washington University, St. Louis, MO), who generously provided the Salmonella enterica serovar Choleraesuis strains χ3246 and χ4522, and Dr. Benedict T. Green (U.S.D.A., Meat Animal Research Center, Clay Center, NE) for technical assistance and methods development. We would also like to thank LaRae Peterson and Colleen Finnegan for technical assistance.
- Animal models
- Mucosal immunology