DEVELOPMENT AND COMPARATIVE PERFORMANCE EVALUATION OF INDIRECT ELISA TESTS USING DIFFERENT Brucella abortus ANTIGENS FOR BOVINE BRUCELLOSIS DIAGNOSIS

This study aimed to develop and compare the diagnostic performance of five different Brucella abortus antigens in an iELISA platform for the diagnosis of the disease, considering the interference of vaccine antigens and cross-reactions with antibodies induced by other bacterial species. The antigens evaluated were acetone inactivated whole cell, soluble antigen (BASA), smooth lipopolysaccharide (sLPS) and O-polysaccharide (OPS) from B. abortus 544 and gamma-irradiated (γ-irradiated) B. abortus 2308. All were produced, quantified and assessed for their composition and potential in the diagnostic platform. After analysis, sLPS and OPS-iELISAs revealed the highest values of DSe and DSp (diagnostic specificity), both above 99% (99% CI: 97.77–99.99% and 97.74–99.94%, respectively, for sLPS; 96.19–99.99% and 96.05–99.90%, respectively, for OPS), followed by gamma irradiated and BASA-iELISAs, which obtained less precise but still good performance (∼96% for DSe and DSp - 99% CI, with 99% CIs ranging from 81.63% to 99.71%) under the same conditions. In contrast, the iELISA using acetone inactivated antigen demonstrated values below 80% (99% CI: 13.02–99.98% for DSe and 12.79–99.75% for DSp), being the lowest-performing platform among those developed. These results show that sLPS and OPS-iELISAs are high-performance diagnostic tests, demonstrating the most promising diagnostic performance among the evaluated assays. Gamma irradiated and BASA-iELISAs demonstrated good performance, suggesting potential for further evaluation as screening tests. Finally, acetone inactivated antigen-iELISA showed inferior performance, indicating that this antigen may be unsuitable for use in diagnostic platforms.