Brucellosis is a zoonotic disease transmitted to humans either from animals or from their products. Although brucellosis can be found worldwide, the Mediterranean Basin, South and Central America, Eastern Europe, Asia, Africa, the Caribbean, and the Middle East have currently been listed as high-risk regions. The genus Brucella is classified in at least nine species. Brucella melitensis is the global pathogenic species of Brucella. The outer membrane protein 31, (Omp31) from B. melitensis is considered as a protective immunogen and an important candidate vaccine. Contamination of purified Omp31 protein by biochemical methods has made some restrictions in practical experiments. In this study, the Omp31coding gene of B. melitensis Rev 1 strain was inserted in pET32b(+) plasmid with extra His-tag sequence. The integrity of the constructed plasmid was confirmed using restriction enzyme mapping and sequencing. Omp31 was expressed after induction with IPTG in Escherichia coli BL21. Recombinant Omp31 (rOmp31) was purified by chromatography through Ni-agarose. The electrophoresis showed successful purification and immunoblotting confirmed immunereactivity of rOmp31. Obtained rOmp31 could be used as a research experimental tool in protection assays to find its potential as a vaccine candidate.

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