Immunological cross reactions betweenAeromonas salmonicidaandVibrio salmonicidain Atlantic salmon (Salmo salarL.) and rabbit

Immunological cross reactions betweenAeromonas salmonicidaand three species ofVibriowere evaluated. Each of five groups of Atlantic salmon were injected with one of the following oil-adjuvanted bacterins:Aeromonas salmonicidass.salmonicida,Vibrio salmonicida,Vibrio anguillarumserovar O1 andVibrio anguillarumserovar O2 or with placebo. In addition, rabbits were immunised with the same oil-adjuvanted bacterins ofA. salmonicidaorV. salmonicida. The levels of specific antibodies againstA. salmonicidaantigens were measured in an ELISA, and the responses were characterised in Western blotting and crossed immunoelectrophoresis (CIE). Protective immunity against furunculosis in the various groups of Atlantic salmon was measured in a virulent cohabitant challenge. Atlantic salmon and rabbit vaccinated againstV. salmonicidaproduced antibodies that cross-reacted with antigen preparations ofA. salmonicidain ELISA, Western blotting and CIE (rabbit only). CIE and Western blotting showed that rabbit anti-V. salmonicidareacted with antigens onA. salmonicidaother than the homologous antisera. Fish immunised againstV. salmonicidawere significantly protected in a cohabitantA. salmonicidachallenge. These cross reactions may explain the superior protection against furunculosis achieved with polyvalent vaccines against furunculosis, vibriosis and cold water vibriosis compared to a monovalentA. salmonicidavaccine.