Induction of CXC chemokine messenger-RNA expression in chicken oviduct epithelial cells by Salmonella enterica serovar enteritidis via the type three secretion system-1.

The messenger-RNA (mRNA) expression of selected cytokines and chemokines in primary chicken oviduct epithelial cells (COEC) was determined following in vitro infections with wild-type or type three secretion system (T3SS)-mutant Salmonella enterica serovar Enteritidis (SE) strains. All SE strains examined in this study elicited the expression of proinflammatory immune mediators including inducible nitric oxide synthase (iNOS), CXCLi1 (K60), CXCLi2 (IL-8), CCLi3 (K203), and CCLi4 (MIP-1beta). SE also triggered the expression of an anti-inflammatory cytokine, IL-10, but repressed TGF-beta3 transcription. Both T3SS-1 (sipA and sipB) and T3SS-2 (pipB and ssaV) mutants showed reduced capacity, compared to the wild-type SE, to stimulate iNOS mRNA expression in COEC. T3SS-1 (sipA and sipB) mutants were significantly impaired in their ability to induce the expression of CXCLi1 and CXCLi2. T3SS-2 mutants displayed a wild-type phenotype in terms of modulating the expression of chemokines and cytokines in COEC. The expression of iNOS, but not CXC chemokines, correlated with the number of intracellular bacteria in COEC. Genetic complementation of the sipA mutation restored a wild-type phenotype. Thus, SE induction of CXCLi1 and CXCLi2 was sipA-dependent. These results provide enhanced insights into the complex interplay between local host innate immune system and bacterial virulence factors.