Designing and Expression of Recombinant Chimeric Protein Containing CtxB and OmpW from Vibrio Cholerae and Evaluation of Its Immunogenicity

Background: Cholera disease caused by Vibrio cholerae remains a major cause of morbidity and mortality throughout the world. Various strategies with different proteins as immunogens have been tried for vaccine development, none of which have been sufficiently effective to preclude cholera. Chimeric proteins, with their ability to present multiple antigens at the same time, can play important roles in immunization. Objective: To evaluate the immunogenicity of a chimeric construct, comprised of OmpW and CtxB as immunogenic proteins of Vibrio cholera, in BALB/c mice. Methods: The construct was designed after bioinformatics assessments and then expressed in E.coli. Chimeric protein, OmpW, and CtxB were purified with Ni-NTA chromatography and confirmed by Western blotting. Mice were immunized with purified recombinant proteins. The antibody titers and specificity of the immune sera were then analyzed by ELISA and challenged on the pups of immunized mice with 1, 5 and 10 LD50. Mice ileal loop assay was also performed. Results: Significant differences were observed in antibody titers in immunized mice compared to the control groups. Infant mouse challenge was performed so as to compare the protective efficacies of the selected immunogen regimens. Of the Pups from dams immunized with chimeric protein which received 1 LD50, 75% survived. Pups belonging to PBS-immunized dams, experienced 100% mortality. The serum raised toward immunogenic construct, inhibited cholera toxin activity in ileal loop test up to 68%. Conclusion: Chimeric construct is able to induce the immune system and provide up to 75% inhibition of toxin activity against 1 LD50 of Vibrio cholerae.