Immunogencity of HSA-L7/L12 (Brucella abortus Ribosomal Protein) in an Animal Model

Background: The immunogenic Brucella abortus ribosomal protein L7/L12 is a promising candidate antigen for the development of subunit vaccines against brucellosis. Objective: This study was aimed to evaluate the protection of recombinant Human Serum Albumin (HAS)-L7/L12 fusion protein in Balb/c mice. Methods: The amplified L7/L12 gene was cloned in pYHSA5 vector, pYHSA5-L7/L12 construct was transformed in Saccharomyces cerevisiae and the expressed protein from supernatant was purified by affinity chromatography. Balb/c mice were immunized in five groups by tHSA-L7/L12 fusion protein (group 1), Brucella abortus S19 (group 2), HSA (group 3), recombinant L7/L12 (group 4), PBS (group 5). ELISA to detect antibody production, LTT test to assess antigen specific lymphocyte response were conducted prior to virulent B. abortus strain 544 challenge two weeks after the last injection. Bacterial counts from spleens of immunized mice were done four weeks after challenge. Results: In ELISA tests, the specific antibodies exhibited a dominance of immunoglobulin IgG1 over IgG2a. In addition, the tHSA-L7/L12 fusion protein and L7/L12 elicited a strong T-cell proliferative response upon restimulation in vitro with recombinant tHSA-L7/L12 and L7/L12, suggesting the induction of a cellular immunity response in vivo. However, there was no significant difference in proliferative response of L7/L12 and tHSA-L7/L12 fusion protein (p>0.05). The L7/L12 and tHSA-L7/L12 fusion protein vaccines could also induce significant protection against challenge with the virulent strain B. abortus 544 in Balb/c mice (p≤0.05). Conclusion: The tHSA-L7/L12 fusion protein, similar to L7/L12 has the ability to induce antigen specific lymphocyte proliferation, stimulate humoral immunity and engender protection.