Characterization of Tritrichomonas foetus antigens by use of monoclonal antibodies.

The specificity for and function of monoclonal antibodies against Tritrichomonas foetus were characterized. Four monoclonal antibodies generated by immunization of mice with live T. foetus were selected on the basis of enzyme-linked immunosorbent assay reactions. The approximate molecular masses of the predominant proteins were determined by Western blotting (immunoblotting). Monoclonal antibody TF3.8 recognized a predominant band at approximately 155 kilodaltons, whereas TF3.2 reacted with several bands. Monoclonal antibodies TF1.17 and TF1.15 recognized broad bands between 45 and 75 kilodaltons. The first two antibodies (TF3.8 and TF3.2) did not react with the surface of T. foetus, as determined by live-cell immunofluorescence, agglutination, and immobilization, whereas two other monoclonal antibodies (TF1.17 and TF1.15) did react with surface epitopes, as determined by these criteria. The latter two monoclonal antibodies also mediated complement-dependent killing of T. foetus and prevented of adherence of organisms to bovine vaginal epithelial cells. One antibody, TF1.15, also killed in the absence of complement. Since these functions are in vitro correlates of protection, the antigens recognized by these monoclonal antibodies may induce protective immunity.