Vibrio antigens of polyvalent vaccines enhance the humoral immune response to Aeromonas salmonicida antigens in Atlantic salmon (Salmo salar L)

Seven experimental oil-adjuvanted vaccines containing Aeromonas salmonicida and one or more of the following components: Vibrio salmonicida, Vibrio anguillarum serovar O1 and V. anguillarum serovar O2, were compared to a monovalent A. salmonicida vaccine regarding their ability to induce antibody production against A. salmonicida in Atlantic salmon. Enzyme-linked immunosorbent assay (ELISA) tests were used to measure the humoral immune response against various antigen preparations from A. salmonicida; bacterial cell-sonicate, A-layer protein and lipopolysaccharide. The effects of the different Vibrio spp, on the generation of specific antibodies were estimated through a factorial statistical design. The results showed that stronger humoral immune responses to A. salmonicida antigens were induced in fish vaccinated with the various polyvalent vaccines, compared to fish vaccinated with the monovalent furunculosis vaccine. V. salmonicida tended to be the most important component for this enhancement, although V. anguillarum also contributed. Immunological cross-reactions between A. salmonicida and V. salmonicida is a possible mechanism. (C) 1997 Academic Press Limited.