Identification and localization of an adhesin on the surface of Tritrichomonas foetus

Tritrichomonas foetus is a mucosal parasite of the urogenital-vaginal tract of cattle that strongly adheres to erythrocytes, which suggests that it presents an adhesin that recognizes red blood cells from different animal species and blood groups. In the present report we describe a cell-fractionation method for obtainment of a membrane fraction of T. foetus, which adhered to red blood cells. The T. foetus adhesin was obtained after parasite lysis and fractionation followed by ultracentrifugation, whereby a 100,000-g pellet fraction showed a strong hemagglutinating activity. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of this fraction, of erythrocyte ghosts, and of ghosts allowed to interact with the parasite membrane fraction revealed the presence of a 100-kDa protein as the putative adhesin. Polyclonal antibodies obtained in rabbits immunized with this protein recognized proteins of 100 and 90 kDa as determined by immunoblotting. Confocal laser scanning microscopy and transmission electron microscopy of cells incubated first in the presence of the antibody and subsequently in the presence of fluorescein- or gold-labeled goat anti-rabbit IgG showed labeling of the protozoan surface as well as of some cytoplasmic vesicles.