Comparative evaluation of the immunodominant proteins of Brucella abortus for the diagnosis of cattle brucellosis

The present serodiagnosis of brucellosis in livestock is based on the whole cell or smooth lipopolysaccharide of the organism in which specificity is hampered by the cross-reactivity, especially with the antibodies against O:9 organism. The problem can be addressed by screening for better immunodominant antigens. Hence, the present study was undertaken to screen protein antigens of for their diagnostic potential in cattle brucellosis. Protein antigens of (n=10) non-reactive to antibodies against O:9 were selected, expressed in , assessed the reactivity of expressed recombinant proteins by Western blot, standardized indirect-enzyme-linked immunosorbent assay (ELISA) for detecting antibodies in cattle serum, and comparative evaluation was done. All the selected protein antigens were expressed and in the Western blot with antibodies positive cattle serum, six recombinant ( protein 26 [BP26], Cu-Zn Superoxide dismutase [SodC], I-1885, Serine protease, Bacterioferritin, and Lumazine Synthase [BLS]) proteins showed reaction whereas none of the proteins showed reactivity with negative cattle serum. ELISA has been done using known positive and negative cattle sera samples (n=113 each) in which the performance of recombinant proteins in diagnosing brucellosis was in the order of BP26 > BLS > SodC followed by rest of the proteins. BP26 based ELISA was found to be better with area under the curve as 0.953, and diagnostic sensitivity, diagnostic specificity, and Youden's index of 90.27%, 95.58%, and 0.8584, respectively, with the excellent agreement (k=0.85). BP26 could be a potential diagnostic antigen among the immunodominant proteins of in ruling out O:9 infection while diagnosing brucellosis in cattle herds.