Defensins are important antimicrobial effector
peptides of the innate immune system, which provides protection against
bacterial infections in the intestine. Salmonella Choleraesuis and Salmonella Typhimurium are the most commonly isolated serovars in pig, but disease outcome is dependent on the Salmonella serovar. These
infections are a serious problem for the swine industry and are also posing a major threat to public health because of Salmonella-related
food-borne illnesses in human. To understand the innate immune response of pigs upon
Salmonella infections, we studied the effect of these Salmonella serovars on
defensin gene expression in the porcine ileal epithelial cell line IPEC-J2. With the use of scanning electron microscopy, we first visualized the surface characteristics of this cell line, and captured the invasion of Salmonella into the epithelial cell. Gene expression levels of porcine
beta-defensin 1 and 2 were both induced upon S. Typhimurium
infection but S. Choleraesuis had no effect. Invasion, adhesion and
defensin susceptibility of both serovars were similar, which could not explain the observed difference in host response to these Salmonellae. In addition, induction of
defensins was dependent on viability of S. Typhimurium, since Salmonella cell- or secreted components had no effect on
defensin gene expression. These results provide further insight into the porcine innate immune response towards
Salmonella infections, and could partially explain the different epidemiology of
Salmonella infections in pig.