Observation of membrane frusion on the interaction of Trichomonas vaginalis with human vaginal epithelial cells

The in vitro cytopathic effect of Trichomonas vaginalis on epithelial cells was analyzed through the interaction of two parasite strains with freshly collected human vaginal epithelial cells (HVECs) from normal women. Videomicroscopy, light and electron microscopy (scanning and transmission), freeze-fracture, the tracer lanthanum nitrate, and the periodic acid-thiosemicarbazide-silver proteinate techniques were used to analyze regions of close contact between the HVECs and T. vaginalis. After 2 h of interaction, all HVECs were dead, whereas all the trichomonads were alive. Microscopic observations demonstrated that in addition to previously described regions of adhesion and interdigitations, areas of continuity between the cytoplasm of the two interacting cells were found. They were not easy to find since they correspond to focal spots placed in different depths of the section. When these regions were depicted, the plasma membranes of the T. vaginalis and the vaginal epithelial cells seemed to be fused.