SURVIVAL AND HUMORAL ANTIBODY-RESPONSE OF ATLANTIC SALMON, SALMO-SALAR L., VACCINATED AGAINST AEROMONAS-SALMONICIDA SSP. ACHROMOGENES

Atlantic salmon were vaccinated against Aeromonas salmonicida ssp. ach romogenes(Asa) by injection with three vaccines developed in our labor atory and an autogenous bacterin (IcelandBiojec.OO, IBOO) produced by a commercial vaccine producer. The humoral antibody responses to bacte rial antigens were monitored by ELISA and Western blotting. The fish w ere challenged by infection with Asa 6 and 12 weeks post-vaccination, Protection was induced in all groups of vaccinated fish. The protectio n achieved was time-dependent. The autogenous bacterin, IBOO, induced a protective immune response later than our experimental vaccines. All the vaccines tested induced specific antibody response that increased between 6 and 12 weeks after vaccination. The antibody response was m ainly directed against the A-layer protein, but antibodies to other ba cterial components were also detected. Significant correlation was obt ained between the antibody titre to extracellular Asa antigens, induce d by the different vaccine preparations, and survival of vaccinated fi sh challenged by a virulent Asa strain. Furthermore, the detection of antibodies directed against an extracellular toxic metallo-caseinase, AsaP1, in fish sera correlated with protection.