Campylobacter jejuni infection suppressed Cl⁻ secretion induced by CFTR activation in T-84 cells.

Campylobacter jejuni causes foodborne disease associated with abdominal pain, gastroenteritis, and diarrhea. These symptoms are induced by bacterial adherence and invasion of host epithelial cells. C. jejuni infection can occur with a low infective dose, suggesting that C. jejuni may have evolved strategies to cope with the bacterial clearance system in the gastrointestinal tract. The mucosa layer is the first line of defense against bacteria. Mucus conditions are maintained by water and anion (especially Cl(-)) movement. Cystic fibrosis transmembrane conductance regulator (CFTR) is the main Cl(-) channel transporting Cl(-) to the lumen. Mutations in CFTR result in dehydrated secreted mucus and bacterial accumulation in the lungs, and recent studies suggest that closely related pathogenic bacteria also may survive in the intestine. However, the relationship between C. jejuni infection and CFTR has been little studied. Here, we used an (125)I(-) efflux assay and measurement of short-circuit current to measure Cl(-) secretion in C. jejuni-infected T-84 human intestinal epithelial cells. The basic state of Cl(-) secretion was unchanged by C. jejuni infection, but CFTR activator was observed to induce Cl(-) secretion suppressed in C. jejuni-infected T-84 cells. The suppression of activated Cl(-) secretion was bacterial dose-dependent and duration-dependent. A similar result was observed during infection with other C. jejuni strains. The mechanism of suppression may occur by affecting water movement or mucus condition in the intestinal tract. A failure of mucus barrier function may promote bacterial adhesion or invasion of host intestinal epithelial cells, thereby causing bacterial preservation in the host intestinal tract.

VopB1 and VopD1 are essential for translocation of type III secretion system 1 effectors of Vibrio parahaemolyticus.

Vibrio parahaemolyticus is a pathogenic Vibrio species that causes food-borne acute gastroenteritis, often related to the consumption of raw or undercooked seafood. Vibrio parahaemolyticus has 2 type III secretion systems (T3SS1 and T3SS2). Here, we demonstrate that VP1657 (VopB1) and VP1656 (VopD1), which share sequence similarity with Pseudomonas genes popB (38%) and popD (36%), respectively, are essential for translocation of T3SS1 effectors into host cells. A VP1680CyaA fusion reporter system was constructed to observe effector translocation. Using this reporter assay we showed that the VopB1 and VopD1 deletion strains were unable to translocate VP1680 to host cell but that the secretion of VP1680 into the culture medium was not affected. VopB1 or VopD1 deletion strains did not enhance cytotoxicity and failed to activate mitogen-activated protein kinases and secretion of interleukin-8, which depend on VP1680. Thus, we conclude that VopB1 and VopD1 are essential components of the translocon. To target VopB1 and VopD1 may have therapeutic potential for the treatment or prevention in V. parahaemolyticus infection.