Two stages of enteropathogenic Escherichia coli intestinal pathogenicity are up and down-regulated by the epithelial cell differentiation

Abstract

Pathogens and eucaryotic cells are active partners during the process of pathogenicity. To gain access to enterocytes and to cross the epithelial membrane, many enterovirulent microorganisms interact with the brush border membrane-associated components as receptors. Recent reports provide evidence that intestinal cell differentiation plays a role in microbial pathogenesis. Human enteropathogenic Escherichia coli (EPEC) develop their pathogenicity upon infecting enterocytes. To determine if intestinal epithelial cell differentiation influences EPEC pathogenicity, we examined the infection of human intestinal epithelial cells by JPN 15 (pMAR7) [EAF⁺ eae⁺] EPEC strain as a function of the cell differentiation. The human embryonic intestinal INT407 cells, the human colonic T₈₄ cells, the human undifferentiated HT-29 cells (HT-29 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 quantitative determination using metabolically radiolabeled bacteria, as well as by light, scanning and tranmission electron microscopy. [EAF⁺ eae⁺] EPEC bacteria efficiently colonized the cultured human intestinal 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^−/+ cells and on colonic crypt T₈₄ 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 differentiation. In contrast, efficient cell-entry of [EAF⁺ eae⁺] EPEC bacteria occured in recently differentiated Caco-2 cells and decreased when the cells were fully differentiated. Our results provide evidence that the intestinal cell differentiation could play a dual role in EPEC pathogenesis: it up-regulates intestinal cell colonization and down-regulates intestinal cell invasion.