Trichomonas adhere and phagocytose sperm cells: adhesion seems to be a prominent stage during interaction

Tritrichomonas foetus and Trichomonas vaginalis are extracellular parasites of the urogenital tract of cattle and humans, respectively. They cause infertility and abortion, but there is no documented information on the susceptibility of bovine sperm cells to this cattle parasite. The aim of this present work was to study the effects provoked by T. foetus and T. vaginalis when in interaction with bovine and human sperm cells. The bovine and human spermatozoa were obtained from uninfected bulls and men, respectively, and were exposed to living trichomonads over different periods of time. Light microscopy, video microscopy, scanning, and transmission electron microscopy first revealed a tropism, then a close proximity followed by a tight adhesion between these two different cells. A decrease in the spermatozoa motility was observed as well intense semen agglutination. The adhesion between trichomonads to the sperm cell occurred either by the flagella or sperm head. Motile parasites were observed during the next 12 h, whereas sperm cells in contact with the parasites rapidly became immotile. The parasites were able to maintain the sperm cells attached to their cell surface, followed by phagocytosis. This process began with a tight membrane-membrane adhesion and the incorporation of the sperm cell within an intracellular vacuole. Afterwards, the sperm cell was gradually digested in lysosomes. Many trichomonads were injured and/or died on making contact with the spermatozoa possibly due to necrosis. Results from this study demonstrated that both T. foetus and T. vaginalis interact with sperm cells provoking damage and death of these reproductive cells. Differences in the behavior of both trichomonads were evident, showing that T. vaginalis was much more virulent than T. foetus. The possible role of trichomonads in reproductive failure is discussed.