Immunogenicity and immunoprotective potential of recombinant OmpC and TrxA-OmpC from Vibrio parahaemolyticus

Studies exploring the potential of outer membrane protein C (OmpC) as a vaccine candidate and diagnostic antigen for Vibrio parahaemolyticus remain limited. In this study, native OmpC and a thioredoxin-fused form (TrxA-OmpC) were successfully expressed in a prokaryotic system and evaluated for their surface exposure and immunogenicity. Surface accessibility of OmpC in the presence of bacterial surface polysaccharides was investigated using antisera raised against polysaccharide-deficient mutant strains. Immune responses induced by both recombinant proteins were assessed through immunoassays, Western blotting, and serum bactericidal assays. The results demonstrated that although surface polysaccharides partially masked OmpC epitopes, OmpC remained accessible on the bacterial surface. Both OmpC and TrxA-OmpC induced strong antibody responses with high titers (27K-729K) and showed cross-reactivity with V. parahaemolyticus and two other Vibrio species. Moreover, antisera against TrxA-OmpC exhibited stronger antibody-dependent bactericidal activity at a serum dilution of 1:8, compared with 1:2 for OmpC antisera. These findings suggest that OmpC is an immunogenic surface antigen with promising in vitro bactericidal activity, although its in vivo protective efficacy requires further investigation.