IMMUNOBLOT ANALYSIS OF HUMORAL IMMUNE-RESPONSES TO MYCOBACTERIUM-BOVIS IN EXPERIMENTALLY INFECTED CATTLE - EARLY RECOGNITION OF A 26-KILODALTON ANTIGEN

Development of a serodiagnostic test for bovine tuberculosis necessita tes an understanding of the humoral immune responses of animals follow ing infection with Mycobacterium bovis. The antibody responses in grou ps of calves challenged intranasally with different doses of M. bovis (approximately 10(2), 10(4), and 10(6) CFU) or placed in contact with the infected animals were analyzed by immunoelectrophoretic blotting i n which a whole-cell sonicate of M. bovis was utilized as an antigen. Antibody responses were evident early in infections in which calves we re exposed to high doses of M. bovis, while in groups exposed to lower doses, the time until antibody was detected increased as the challeng e dose decreased. In cattle exposed to M. bovis, immunoblot analysis s howed antibody responses to three main antigens of 26, 22, and 16 kDa. It was further demonstrated that antibody responses to the 26-kDa ant igen appeared earliest in the course of infection. Preliminary investi gations in this study have identified a 26-kDa antigen for potential u se in improved serodiagnosis by enzyme-linked immunosorbent assays.