Modulatory effect of Vibrio cholerae toxin co-regulated pilus on mucins, toll-like receptors and NOD genes expression in co-culture model of Caco-2 and peripheral blood mononuclear cells (PBMC).

Vibrio cholerae, the causative agent of cholera, tend to colonize the small intestine as a Gram-negative pathogen. The intestinal mucus layer forms mucin physical barrier, consisted of high molecular weight proteins. Regarding the role of toxin-coregulated pilus (TCP) as one of the most important colonization factors of V. cholerae, this experimental study was designed to determine the role of TcpA in induction of mucin production and its regulatory effect on innate immunity molecules including toll like receptors (TLRs) and Nucleotide-binding oligomerization domain-containing proteins (NODs) using Caco2- PBMC co-cultures as an interactive model. The rTcpA protein of V. cholerae was expressed in BL21 Escherichia coli, purified using Ni-column chromatography and confirmed by western blotting. Nontoxic doses of rTcpA was determined on Caco-2 cell lines and different concentrations of rTcpA (1, 5, 10 and 50 μg/mL) showed a statistically significant effect on the expression of muc genes (MUC3 and MUC4) in a dose-dependent manner. This finding is supposed to facilitate physical adhesion and colonization of V. cholerae in intestinal lumen. The rTcpA moderately stimulated the expression of tlr4 and overexpressed tlr1, both of which are supposed to induce a mucosal protective response against bacterial infection. NOD2 was significantly increased which suggests that it may contribute in pro-inflammatory responses observed in cholera disease. No change in NOD1 expression was seen which might be attributed to the non-invasive nature of V. cholerae as an intestinal pathogen. In conclusion, the rTcpA protein of V. cholerae showed a statistically significant modulatory effect on the human gut epithelium gene expression which would help promising protection in prophylaxis applications.