Adhesion of Tritrichomonas foetus to bovine vaginal epithelial cells

An in vitro culture system of bovine vaginal epithelial cells (BVECs) was d eveloped to study the cytopathogenic effects of Tritrichomonas foetus and t he role of lipophosphoglycan (LPG)-like cell surface glycoconjugates in adh esion of parasites to host cells. Exposure of BVEC monolayers to T. foetus resulted in extensive damage of monolayers. Host cell disruption was measur ed quantitatively by a trypan blue exclusion assay and by release of H-3 fr om [H-3]thymidine-labeled host cells. Results indicated contact-dependent c ytotoxicity of host cells by T. foetus. The cytopathogenic effect was a fun ction of T. foetus density. Metronidazole- or periodate-treated T. foetus s howed no damage to BVEC monolayers. A related human trichomonad, Trichomona s vaginalis, showed no cytotoxic effects, indicating species-specific host- parasite interactions. A direct binding assay was developed and used to inv estigate the role of a major cell surface LPG-like molecule in host-parasit e adhesion. The results of competition experiments showed that the binding to BVECs was displaceable, was saturable, and yielded a typical binding cur ve, suggesting that specific receptor-ligand interactions mediate the attac hment of T. foetus to BVECs. Progesterone-treated BVECs showed enhanced par asite binding. T. foetus LPG inhibited the binding of T. foetus to BVECs; t he LPG from T. vaginalis and a variety of other glycoconjugates did not. Th ese data imply specificity of LPG on host-parasite adhesion. Periodate-trea ted parasites showed no adherence to host cells, indicating the involvement of carbohydrate containing molecules in the adhesion process.