An adapted in vitro assay to assess Campylobacter jejuni interaction with intestinal epithelial cells: Taking into stimulation with TNFα.

Campylobacter jejuni is the most prevalent foodborne bacterial infection agent. This pathogen seems also involved in inflammatory bowel diseases in which pro-inflammatory cytokines, such as tumor necrosis factor α (TNFα), play a major role. C. jejuni pathogenicity has been extensively studied using in vitro cell culture methods, and more precisely "healthy" cells. In fact, no information is available regarding the behavior of C. jejuni in contact with TNFα-stimulated cells. Therefore, this research was designed to investigate the effect of TNFα on C. jejuni interaction with human intestinal epithelial cells (HT29 and HT29-MTX). To ensure IL-8 production induced by TNFα, human rtTNFα was added to HT29 and HT29-MTX before adhesion and invasion assays. About 108 CFU bacteria of C. jejuni strains cells were added to measure their adherence and invasion abilities using TNFα-stimulated cells versus non stimulated cells. Exposure to TNFα results in IL-8 overproduction by intestinal epithelial cells. In addition, the effect of TNFα pre-treatment on C. jejuni adhesion and internalization into eukaryotic cells is strain-dependent. Indeed, the adhesion/invasion process is affected in <50% of the strains tested when TNFα is added to the intestinal cells. Interestingly, TNFα affects more strains in their ability to adhere to and invade the mucus-secreting HT29-MTX cells. Among the 10 strains tested, the aero-tolerant C. jejuni Bf strain is one of the most virulent. These results suggest that the TNFα signalling pathway could participate in the internalization of C. jejuni in human intestinal cells and can help in understanding the pathogenicity of this microorganism in contact with TNFα-stimulated cells.