Morphological studies of the cytotoxicity of Trichomonas vaginalis to normal human vaginal epithelial cells in vitro.

In vitro cultured monolayers of normal human vaginal epithelial cells were incubated with axenic cultures of Trichomonas vaginalis. Two strains freshly isolated from patients with trichomoniasis and one strain that had been maintained in axenic culture for several years were studied. Freshly isolated trichomonads showed amoeboid movements, adherence to epithelial cell surfaces, and were cytotoxic to epithelial cells in vitro. In contrast, the laboratory strain maintained for years in axenic culture did not adhere to the epithelial cell monolayer and was only cytotoxic at a concentration 100 times that of freshly isolated trichomonads. Electron microscopy of monolayers exposed to T vaginalis for 24 hours showed that all epithelial cells in intimate contact with trichomonads had more or less disintegrated, whereas in monolayers exposed for six hours some of the epithelial cells in contact with T vaginalis were normal. T vaginalis organisms with amoeboid morphology contained a dense network of microfilaments in the part of the trichomonad that was in contact with an epithelial cell. Occasionally a pseudopodium was projected into the cytoplasm of disintegrated epithelial cells.