Immunological, biochemical, and functional properties of two antigens isolated from the salmonid fish pathogen Vibrio anguillarum serotype O2

The majority of studies examining the outer membrane (OM) components of V. anguillarum O2 have focused on lipopolysaccharides (LPSs) as the major agents of antigenic specificity and as the major protective antigens of whole cell vaccine preparations. However, evidence suggests that surface-exposed antigens other than LPS may contribute to the antigenicity and virulence of this bacterium. Monoclonal antibody 15C4 recognized a surface-exposed epitope on a 23 kDa antigen. The epitope was specific to V. anguillarum serotypes O1 through O8, V. ordalii and V. salmonicida, the three major agents of vibriosis in salmonid fish. The antigen was purified to homogeneity, however its identity and functional properties remain to be determined. The 40 kDa major OM protein of V. anguillarum 02 was purified and identified as belonging to the superfamily of bacterial porin proteins. Cross-reactive porin epitopes were conserved amongst V. anguillarum strains of serotypes O1 through O8 and amongst all species of Vibrio tested. Thus, both antigens examined have strong potential as immunodiagnostic agents, as immunogenic components of the OM and as possible contributors to virulence of the salmonid fish pathogen V. anguillarum O2.