Intestinal epithelial barrier dysfunction protects against pathogen translocation during initial infection (1111.2)

Abstract

Myosin light chain kinase (MLCK) is essential for pathophysiological epithelial tight junction regulation. Transgenic mice with intestinal epithelial‐specific expression of constitutively‐active MLCK (CA‐MLCK) demonstrate increased permeability and susceptibility to immune‐mediated colitis. However, the effect of barrier dysfunction on enteric infection remains unknown. Within 30 min after mucosal application of DsRed‐labeled Salmonella typhimurium (SL3201 108 CFU), CA‐MLCK mice exhibited a 5‐fold reduction in bacterial translocation compared to wildtype (WT). This protection also occurred 1 h after oral infection with Toxoplasma gondii, in which tachyzoite invasion was reduced in CA‐MLCK mice relative to WT, 1.5±0.6 vs 4.0±1.0 tachyzoite/mm2 villus, respectively. Intraepithelial lymphocytes expressing the γδ T‐cell receptor (γδ IEL) protect against pathogen invasion. Time‐lapse confocal microscopy revealed enhanced γδ IEL surveillance of the villous epithelium in CA‐MLCK mice compared to WT with more rapid migration (4.2±0.1 vs 3.8±0.1μm/min) and reduced localization to the lateral intercellular space (26±1.7 vs 32±3.3%). However, loss of γδ T cells in CA‐MLCK mice did not alter Salmonella transmigration compared to WT. These data indicate that increased γδ IEL epithelial surveillance is not sufficient for the reduced pathogen invasion observed during early infection in CA‐MLCK mice.Grant Funding Source: Supported by NIH DK61931 and DK68271, UChicago DDRCC, Gastro‐intestinal Research Foundation