An electron microscope study of the interaction between Trichomonas vaginalis and epithelial cells of the human amnion membrane.

The mechanism of cytopathogenicity of Trichomonas vaginalis is not well established. Adhesion of T. vaginalis to human epithelial cells is considered a prerequisite for parasitic infection and its pathogenic effect. To investigate cytopathological changes in the host caused by T. vaginalis infection, human amnion membrane was used as an in vitro model. T. vaginalis strain WAA38 from axenic culture was allowed to interact with the epithelial layer of the human amnion membrane for 6 and 9 h. Structural changes resulting from the interaction between parasite and host cells were studied with transmission (TEM) and scanning (SEM) electron microscopy. Analysis of the electron microscope data showed that T. vaginalis established contact with the host cells as early as after 6 h of incubation; however, a close attachment of parasites to the epithelial cells occurred only after 9 h. Amoeboid T. vaginalis formed numerous cytoplasmic extensions and adhered to the epithelial cells mostly through the portions of their body opposite the undulating membrane. A dense network of microfilaments was seen at the site of contact between T. vaginalis and epithelial cells. Damaged and desquamated epithelial cells were seen with TEM and SEM only in the areas where parasites were in direct contact with target cells.