2 STAGES OF ENTEROPATHOGENIC ESCHERICHIA-COLI INTESTINAL PATHOGENICITY ARE UP AND DOWN-REGULATED BY THE EPITHELIAL-CELL DIFFERENTIATION

Pathogens and eucaryotic cells are active partners during the process of pathogenicity. To gain access to enterocytes and to cross the epith elial membrane, many enterovirulent microorganisms interact with the b rush border membrane-associated components as receptors. Recent report s provide evidence that intestinal cell differentiation plays a role i n microbial pathogenesis. Human enteropathogenic Escherichia coli (EPE C) develop their pathogenicity upon infecting enterocytes. To determin e if intestinal epithelial cell differentiation influences EPEC pathog enicity, we examined the infection of human intestinal epithelial cell s by JPN 15 (pMAR7) [EAF(+) eae(+)] EPEC strain as a function of the c ell differentiation. The human embryonic intestinal INT407 cells, the human colonic T-84 cells, the human undifferentiated HT-29 cells (HT-2 9 Std) and two enterocytic cell lines, HT-29 glc(-/+) and Caco-2 cells , were used as cellular models. Cells were infected apically with the EPEC strain and the cell-association and cell-entry were examined by q uantitative determination using metabolically radiolabeled bacteria, a s well as by light, scanning and tranmission electron microscopy. [EAF (+) eae(+)] EPEC bacteria efficiently colonized the cultured human int estinal cells. Diffuse bacterial adhesion occurred to undifferentiated HT-29 Std and INT407 cells, whereas characteristic EPEC cell clusters were observed on fully differentiated enterocytic HT-29 glc(-/+) cell s and on colonic crypt T-84 cells. As shown using the Caco-2 cell line , which spontaneously differentiates in culture, the formation of EPEC clusters increased as a function of the epithelial cell differentiati on. In contrast, efficient cell-entry of [EAF(+) eae(+)] EPEC bacteria occured in recently differentiated Caco-2 cells and decreased when th e cells were fully differentiated. Our results provide evidence that t he intestinal cell differentiation could play a dual role in EPEC path ogenesis: it up-regulates intestinal cell colonization and down-regula tes intestinal cell invasion.