OmpU elicits cross-protective bactericidal activity against Vibrio species: a surface-exposed antigen with vaccine potential.

AIMS: Vibrio parahaemolyticus is a major zoonotic pathogen. Its outer membrane proteins (OMPs) are key targets for developing vaccines. This study aimed to evaluate the potential of OmpU and VP0802 as subunit vaccine candidates against Vibrio species.

METHODS AND

RESULTS

Unlike prior studies relying on qualitative survival endpoints and narrow strain panels, we employed serum bactericidal assays and an expanded strain panel to quantify cross-protective efficacy. The recombinant proteins OmpU and VP0802 were cloned, expressed, and purified. Their native abundance, surface exposure, immunogenicity, and protective efficacy were evaluated. Both recombinant OMPs exhibited strong binding to whole-cell murine antisera in an indirect enzyme-linked immunosorbent assay (titer 1:81 000). Confocal microscopy further confirmed high surface availability, with specific anti-OmpU and anti-VP0802 sera binding to bacterial cells. Immunization results showed that OmpU induced high-titer antisera (up to 1:243 000), accompanied by broad cross-reactivity and bactericidal activity against different V. parahaemolyticus serotypes and multiple Vibrio species, with a potent bactericidal antibody titer of 1:512. In contrast, VP0802 generated lower antibody titers (up to 1:9000), reduced immunoblot band, weaker immunofluorescence signals, and significantly reduced bactericidal activity (1:32).

CONCLUSIONS

OmpU represents a promising cross-protective subunit vaccine candidate against multiple Vibrio species.