Vaccination of cattle with Mycoplasma bovoculi antigens: evidence for field immunity.

Cattle previously exposed to Mycoplasma bovoculi developed a high serum IgG and cellular responses detected by ELISA and lymphocyte blastogenesis respectively, when immunized with three M. bovoculi antigen preparations (two non-ionic detergent extracts and a killed whole organism). Similar responses to the detergent immunogen were observed in colostrum-deprived calves free of M. bovoculi. Following ocular challenge with live M. bovoculi all animals including the control group cleared the organism. However the organism colonized the eyes of the colostrum-deprived calves. These observations indicate that previous exposure to M. bovoculi confers immunity to reinfection and that none of the vaccines provided a protective activity against the organism.