T84 CELLS IN CULTURE AS A MODEL FOR ENTEROAGGREGATIVE ESCHERICHIA-COLI PATHOGENESIS

Enteroaggregative Escherichia call (EAEC) is an important cause of per sistent diarrhea in many developing parts of the world, yet the pathog enetic mechanisms of EAEC diarrhea are unknown, Experiments with anima l models suggest that EAEC strains damage the intestinal mucosa, and a putative cytotoxin has been described. To characterize the mucosal ef fects of EAEC, we studied strain 042, which we have shown to cause dia rrhea in adult volunteers. Strain 042 was incubated in an in vitro org an culture model with biopsy-derived normal intestinal mucosa from ped iatric patients. Strain 042 adhered strongly to samples of jejunal, il eal, and colonic mucosa, In addition, scanning electron microscopic ex amination of in vitro-infected intestinal biopsies revealed cytotoxic effects marked by exfoliation of mucosal epithelial cells. To develop an in vitro model to study these effects, we incubated 042 with polari zed monolayers of the human intestinal epithelial cell Lines Caco-2 an d T84. Strain 042 adhered strongly to T84 cells but not to Caco-2 cell s. T84 cells infected with 042 displayed marked toxic effects, most pr ominently in areas where bacteria were adhering, The apical membrane o f damaged cells exhibited vesiculation and shedding of microvilli. The cytoplasm of affected cells displayed subnuclear vacuolization, and i n some cases, nuclei of affected cells became separated from the surro unding cytoplasm, Severely affected cells ruptured, releasing their nu clei. Vacuolated remnant cells were seen throughout the monolayer, Str ain 042 was not internalized by T84 cells. We concluded that EAEC stra in 042 alters intestinal cell morphology, ultimately leading to cell d eath, Although the factor(s) required for this effect remains to be el ucidated, T84 cells may serve as a valuable model in EAEC pathogenesis studies.