Evaluation of the Combined Use of Major Outer Membrane Proteins in the Serodiagnosis of Brucellosis

Background: Brucellosis is a zoonotic disease that causes substantial public health problems and endangers the development of animal husbandry in endemic areas. Early diagnosis of infected animals and humans is a crucial step in reducing the incidence of brucellosis. In this study, we designed different combinations of Brucella major outer membrane proteins (omps) including omp10, Omp16, omp19, omp25, omp31 and BP26 as antigens and evaluated their efficiency in serodiagnosis for brucellosis. The efficiency assay was conducted using the method of indirect enzyme-linked immunosorbent assay (iELISA) together with a collection of brucellosis-positive sera and healthy sera from multiple species (161 from human, 120 from goat and 144 from cattle). The diagnostic effectiveness of each omp combination was analyzed by receiver operating characteristic (ROC) curve with the software GraphPad Prism version 6.05. Results: Hie omp25/omp31/BP26 combination showed the best efficiency in diagnosis for human brucellosis. The area under the ROC curve (AUC) was 0.995 and, compared with the serum tube agglutination test (SAT) and the Rose Bengal plate agglutination test (RBPT), the positive and negative diagnostic accuracies of iELISA were 94.59% (105/111) and 100.0% (50/50), respectively. Evaluation of the 120 goat and 144 cattle serum samples showed that the best combination for diagnosing both omp31/BP26, the AUC was 0.9262 in goat and 0.9344 in cattle, and compared with those of SAT and RBPT, the positive and negative diagnostic accuracies in goat were 72.73% (48/66) and 100.0% (54/54), respectively. The positive and negative diagnostic accuracies in cattle were 79.79% (75/94) and 100.0% (50/50), respectively. Cross-reaction assays showed that omp25/omp31/BP26 and omp31/BP26 do not cross with other common pathogens. Conclusion: The results indicated that combinations of omps, as protein antigens, can be used to diagnose brucellosis with high accuracy in human, goat and cattle. Keywords: brucellosis, diagnosis, outer membrane proteins, iELISA