Bovine veneral vibriosis: antigenic variation of the bacterium during infection.

Host parasite relationships in the female genital tract were studied in bovine venereal vibriosis by investigating agglutinin production and alterations in superficial antigens of the bacterium during the course of infection in two heifers. Cervicovaginal mucus (CVM) steamed cell agglutinins were shown to appear earlier and remain at consistently higher levels than whole-cell agglutinins. Whole-cell agglutinin titers fluctuated much more than steamed cell titers, suggesting possible changes in whole-cell antigens. Marked antigenic variation was demonstrated in successive monthly CVM isolates from the two heifers by agglutination tests with rabbit antisera of various specificities. Some changes in CVM antibody specificity during the infection were noted also. Antigenic variation in the bacterium was proposed as a mechanism for maintenance of the asymptomatic cervicovaginal carrier state in the presence of antibody.