Protective Immunity of a Novel Multi-Epitope Vaccine Encoding OMP31, TF, BLS, SOD, BP26, and L9 Against Brucella spp. Infection

Background: Brucella is a type of bacteria that causes a disease known as brucellosis in both humans and animals. Many different vaccine formulations are available for this disease; however, vaccines based on epitopes have shown to be effective, especially in combating this pathogen. In the present study, we designed a multi-epitope vaccine against brucellosis using a chimeric protein that combines segments from various Brucella proteins known to contain both B- and T-cell epitopes. Methods: In this study, a vaccine candidate was developed using multiple epitopes derived from various proteins, including OMP31, TF, BLS, SOD, BP26, and L9. These epitopes were selected based on their high density of both B-cell and T-cell epitopes. The construct of the vaccine candidate was inserted into a pEGFP-N1 vector and introduced into HEK-293T cells. Subsequently, the vaccine was tested on different groups of mice; some received the expressed protein in E. coli, while others received the DNA vaccine candidate. An ELISA assay was employed to evaluate the humoral immune response. Results: Both the MEB protein (Pro/Pro) and pCI-MEB plasmid/MEB protein (DNA/Pro) groups showed a specific humoral response. The anti-DNA vaccine antibody titer did not rise as high as that of the protein groups; however, the observed protection indicated the efficiency of the DNA vaccine in activating the immune system. Conclusion: While the chimeric DNA vaccine candidate induced a weaker humoral response, it remained effective in protecting against virulent strains of B. abortus and B. melitensis in the challenge route.