Immunological cross-reactivity and cross-protection of outer membrane protein OmpU among Vibrio species

Abstract:

[Objective] To study the immunological cross-reactivity and cross-protection characteristics of OmpU in Vibrio species. [Methods] The ompU genes from 10 Vibrio strains were cloned, sequenced, followed by bioinformatics analysis. Western blot and whole-cell ELISA assay were used respectively to determine immunological cross-reaction feature and subcellular location of OmpU with rabbit serum against recombinant OmpU from V. parahaemolyticus ATCC17802, V. alginolyticus ATCC33787, V. vulnificus ATCC27562, V. mimicus ATCC33653 and V. cholera Vb0. Finally, the cross-protective property of recombinant OmpU (V. cholera-derived) was evaluated through vaccination and subsequent challenge with heterogeneous virulent Vibrio strains in mice. [Results] The similarities of OmpU proteins of Vibrio ranged from 73.0 to 100% intra-species, and from 58.6 to 89.0% inter-species. Furthermore, homologous epitopes were found in OmpU and shared by different species of Vibrios. Western blot of rabbit serum against recombinant OmpU showed cross-recognition intra- and inter-species. Bands were observed ranging from 35 to 40 kDa. Whole-cell ELISA assay further confirmed that the antiserum of recombinant OmpU from V. parahaemolyticus ATCC17802, V. vulnifgicus ATCC27562 and V. mimicus ATCC33653 recognized the tested Vibrio species, implying that epitopes of OmpU were located on the cell surface. Recorded relative percent survival of the vaccinated group varied from 43.0 to 100%, showing that mice were protected from Vibrio infection after immunization with OmpU protein. [Conclusion] OmpU was a conserved antigen among tested Vibrio species and might be a universal vaccine candidate for the prevention of Vibriosis.