Development of in-House Recombinant OMP31 (rOMP31) Protein Based Latex Bed Test for the Diagnosis of Ovine and Caprine Brucellosis

Brucella melitensis is a major cause of brucellosis in human and small ruminants. For prevention and control of brucellosis accurate, inexpensive, simple, rapid and specific diagnosis is prerequisite in livestock as well as in humans. Many tests are available including gold standard isolation methods. However, there is a paucity of early, effective, sensitive door step diagnosis tests for detection of brucellosis in both livestock and humans. For the purpose, outer membrane proteins of B. melitensis are considered as important Non-lipo-polysacchride immunodominant candidate antigen. The present study describes the development and evaluation of a B. melitensis specific recombinant Omp31 based latex agglutination test (LAT) for the detection of antibodies to B. melitensis in goats. The rOmp31 gene was cloned in pET-32 and protein was expressed in E. coli BL21 cells and purified by Ni-NTA chromatography. Carboxylated modified polystyrene latex particles were coated with purified rOmp31 and evaluated for detection of antibodies against B. melitensis in goat sera. The validation of developed recombinant Omp31 antigen with other serological tests and sera containing B. abortus antibodies revealed that it was more sensitive and accurate as compared to the Rose Bengal Plate test (RBPT) with specificity for B. melitensis. Moreover, the test is rapid, simple, inexpensive, and suitable for detection of specific antibodies in B. melitensis infection under field conditions. LAT test more sensitive and specific for diagnosis as compare to RBPT.