SEROLOGICAL RESPONSE TO IN-VITRO SHED ANTIGEN(S) OF TRITRICHOMONAS-FETUS IN CATTLE

We developed a serological assay for detection of (i) an erythrocyte-a dhering molecule(s) shed by the bovine venereal pathogen Tritrichomona s foetus and (ii) serum antibodies to this antigen(s) in exposed cattl e. Sera from exposed and unexposed cattle were tested for their abilit y to induce complement-mediated lysis of bovine erythrocytes that had been previously incubated overnight at room temperature in pH-adjusted supernatants of T, foetus culture media. Eight of 180 serum specimens from six groups of presumably unexposed cows or heifers showed a posi tive (greater than or equal to 1:2) hemolytic titer (specificity = 95. 6%). Thirteen of 14 females in two experimentally infected groups show ed a positive hemolytic titer following infection (sensitivity = 94%). In experimentally infected heifers, there was little correlation (r(2 ) = 0.33) between serum hemolytic titers with respect to shed antigen and titers obtained in serum enzyme-linked immunosorbent assays in whi ch whole T. foetus served as the antigen. Serum hemolytic titers rose 3 to 4 weeks sooner than did previously described vaginal mucus immuno globulin G1 or immunoglobulin A titers with respect to whole cell anti gen or TF1.17 subunit antigen, respectively. Among 14 chronically infe cted bulls, only 6 (43%) showed a positive hemolytic titer. This study is the first, to our knowledge, to show a specific serological respon se in the host to an in vitro-shed antigen(s) of T, foetus and suggest s a useful diagnostic test for potentially exposed herds.