Antibody response to the 89-kDa outer membrane protein of Brucella in bovine brucellosis.

The antibody response of cattle to the minor 89-kDa outer-membrane protein (OMP) of brucella was measured by indirect ELISA with the purified protein and compared with the antibody response to smooth lipopolysaccharide (S-LPS). Pre-incubating sera with sonicated cell extracts of Escherichia coli prevented the binding of antibodies from uninfected animals to the 89-kDa OMP, suggesting the presence of one or more cross-reactive epitopes on this protein. In cattle infected experimentally with Brucella abortus, the antibody response to the 89-kDa OMP was later and less intense than that to S-LPS. In naturally infected cattle, 68% of animals showing an antibody response to S-LPS also showed an antibody response to the 89-kDa OMP. Results indicate that specific epitopes of the 89-kDa OMP in combination with those of other OMPs could be useful for diagnosis of brucellosis in cattle.