Protection of BALB/c mice against pathogenic Brucella abortus and Brucella melitensis by vaccination with recombinant Omp16

Objective(s): Prevention of the globally spread zoonotic infection, brucellosis which affects an extensive range of hosts is still challenging researchers. There are no approved vaccines for the prevention of human disease and those used for animal brucellosis have adverse properties, which limit their application. We investigated the immunological and protective effects of recombinant 16 kDa outer membrane protein of Brucella abortus (Omp16) which introduced a new candidate for brucellosis subunit vaccine. Materials and Methods: Brucella Omp16 gene was cloned in pET-23a and expressed in Escherichia coli BL21 (DE3). Recombinant Omp16 (rOmp16) was purified using nickel resin and confirmed by Western blot analysis. BALB/c mice were immunized with rOmp16, afterward, specific serum antibodies and cytokine responses were evaluated. Protection of immunized mice against pathogenic B. abortus 544 and B. melitensis 16M was evaluated by the intraperitoneal bacterial challenge. Results: Sequencing results of the recombinant plasmid vector along with Western blotting confirmed the cloning procedure. Recognition of rOmp16 by specific IgG from serum samples of infected cases suggests the stimulation of immune response to this protein. Significant total serum IgG along with remarkable IgG1 and IgG2a response to the protein was recorded. A significant increase in IFN-γ, and IL-4 levels were observed from splenocyte cultures of immunized mice which were stimulated with rOmp16 suggesting the development of T-lymphocyte mediated immunity against the recombinant antigen. Conclusion: The intraperitoneal challenge with B. abortus 544 and B. melitensis 16M confirmed that rOmp16 is able to elicit efficient protective immune responses in the animal host.