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Infect Immun. 1989 December; 57(12): 3914-3921

Effect of Clostridium difficile enterotoxin A on ultrastructure of Chinese hamster ovary cells.

Department of Microbiology, Medical College of Wisconsin, Milwaukee 53226.

ABSTRACT

Electron microscopical immunocytochemistry and light microscopy were used to study the effect of Clostridium difficile enterotoxin A (EA) on cultured Chinese hamster ovary (CHO) cells. At 4 degrees C, immunocytochemically detected EA was randomly distributed along the plasma membrane; when cells were subsequently transferred to 37 degrees C, the EA moved into coated pits and coated vesicles within 2 min. Within 2 h of incubation at 37 degrees C with EA, the perinuclear cytoplasm of the CHO cells became highly refractile, and in 4 h, most of the cells were round; however, the majority of rounded cells excluded erythrosin B while remaining firmly attached to the culture dish plastic. When EA was removed from the cultured cells within 2 h, the cells returned to a normal morphology and formed a confluent monolayer. The nuclei of rounded cells were irregularly shaped; cytoplasmic intermediate filaments were collapsed toward the nucleus. Long bundles of parallel, 11-nm-diameter filaments appeared in the nuclei after 3 h of incubation with EA and disappeared by the fourth hour of incubation. Intoxicated cells did not undergo mitosis. Thus, EA was internalized, at least in part, by receptor-mediated endocytosis and subsequently affected the nuclei of CHO cells.