Immunogenic efficacy of DNA and protein-based vaccine from a chimeric gene consisting OmpW, TcpA and CtxB, of Vibrio cholerae.

Vibrio cholerae is one of the major causes of morbidity and mortality in developing countries. CtxB, responsible for toxin binding to eukaryotic cells, TcpA, involved in bacterial colonization, and OmpW, the highly conserved extracellular protein, are the three of the significant essential virulence factors in V. cholerae with enhanced immunogenic properties. Increasing emergence of antimicrobial-resistant strains (AMR) highlights the urgent need for new therapeutic agents. Uncomplicated high yield production, simple design, inducing either or both humoral and cellular immunity, and long-term immune responsiveness are some of the advantages of IgG antibodies over other immunotherapy agents. Chimeric proteins have the potential of presenting multiple antigens to immune system, simultaneously. Thus, the current study was aimed to evaluate the stability and protective efficacy of DNA and protein-based vaccine candidates of a chimeric gene harboring OTC (OmpW, TcpA and CtxB) against V. cholerae. The immunogenicity and specificity of induced IgGs were confirmed through indirect ELISA and western blot analysis, respectively. The DNA and protein immunized mice sera were able to neutralize the cytotoxicity effects of the cholera toxin (CT) at 5% and 10% dilutions in Y1 cell line, and inhibited 60% and 68% of the bacterial adhesion to HT-29 cells, respectively. The DNA and protein immunized sera provided 99% and 95% viability percent in spleen cell viability assays, and inhibited the bacteria-induced fluid accumulation in ileal loop assay at 1/80 and 1/160 dilutions, respectively. Different groups of passively immunized infant mice and actively immunized adult mice were challenged with V. cholerae. The OTC construct provided high survival rates against lethal infection, and significantly reduced the bacterial loads. Our results highlight the potential therapeutic effect of the recombinant OTC chimeric construct, either as a DNA or protein vaccine, due to its remarkable immunogenicity and protectivity against V. cholerae.