Immunological cross reactions between Aeromonas salmonicida and Vibrio salmonicida in Atlantic salmon (Salmo salar L.) and rabbit

Immunological cross reactions between Aeromonas salmonicida and three species of Vibrio were evaluated. Each of five groups of Atlantic salmon were injected with one of the following oil-adjuvanted bacterins: Aeromonas salmonicida ss. salmonicida, Vibrio salmonicida, Vibrio anguillarum serovar O1 and Vibrio anguillarum serovar O2 or with placebo. In addition, rabbits were immunised with the same oil-adjuvanted bacterins of A. salmonicida or V. salmonicida. The levels of specific antibodies against A. salmonicida antigens 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 against V. salmonicida produced antibodies that crossreacted with antigen preparations of A. salmonicida in ELISA, Western blotting and CIE (rabbit only). CIE and Western blotting showed that rabbit anti-V. salmonicida reacted with antigens on A. salmonicida other than the homologous antisera. Fish immunised against V. salmonicida were significantly protected in a cohabitant A. salmonicida challenge. These cross reactions may explain the superior protection against furunculosis achieved with polyvalent vaccines against furunculosis, vibriosis and cold water vibriosis compared to a monovalent A. salmonicida vaccine. (C) 1998 Academic Press Limited.