INDUCTION OF PHAGOCYTIC BEHAVIOR IN HUMAN EPITHELIAL-CELLS BY ESCHERICHIA-COLI CYTOTOXIC NECROTIZING FACTOR TYPE-1

Cytotoxic necrotizing factor type 1 (CNF1) from strains of pathogenic Escherichia coli induces in human epithelial HEp-2 cells, a profound r eorganization of the actin cytoskeleton into prominent stress fibres a nd membrane ruffles. We report here that this process is associated wi th induction of phagocytic-like activity. CNF1-treated cells acquired the ability to ingest latex beads as well as non-invasive bacteria suc h as Listeria innocua, which were taken as a model system. Uptake of b acteria was similar to pathogen-induced phagocytosis, since L. innocua transformed with DNA coding for the pore-forming toxin listeriolysin O behaved, with respect to intracellular growth, like the invasive, pa thogenic species L. monocytogenes. Our results raise the possibility t hat, in vivo, pathogenic CNF1-producing E. coli may invade epithelia b y this novel induced phagocytic-like mechanism.