Use of recombinant Brucella outer membrane proteins 19, 25, and 31 for serodiagnosis of bovine brucellosis

BACKGROUND AND AIM: Brucellosis remains one of the most common zoonoses. The current anti-brucellosis measures are largely deemed ineffective due to a lack of specificity of conventional serological tests. This study evaluated the use of Brucella outer membrane protein (Omp)19 for serodiagnostic testing. MATERIALS AND METHODS: The antigenicity of recombinant Brucella Omp19, Omp25, and Omp31 was examined in serum samples from mice and rabbits immunized with Omp19 or Brucella abortus 19 whole cell (WC) and 12 and 152 cows experimentally or naturally infected with brucellosis, respectively. Serum samples were collected from 151 cows that were vaccinated with B. abortus 19 and 12 unvaccinated heifers that were maintained on a brucellosis-free farm. RESULTS: Immunization with Omp19 resulted in antibody production in mice after a single injection without the use of adjuvant. Serum antibodies obtained from rabbits immunized with inactivated B. abortus strain 19 WC targeted Omps by enzyme-linked immunosorbent assay (ELISA) and Western blot. Antibodies targeting Omp19 were identified in all B. abortus strain 544 experimentally infected cows at day 14 post-inoculation (p.i.); Omp25 was detected by ELISA at day 28 p.i., while an ELISA targeting Omp31 was negative for 25% of cows at this time point. Omp19 and Omp25 were readily detected by sera from cows from a new epizootic focus. Antibodies recognizing Omps were also detected in >50% of the animals maintained in a brucellosis-free herd at 10 months after vaccination. CONCLUSION: Brucella Omp19 in combination with Omp25 and Omp31 may be utilized as target antigens in an ELISA designed for serological testing of unvaccinated cattle.