Antibodies against Vibrio salmonicida lipopolysaccharide (LPS) and whole bacteria in sera from Atlantic salmon (Salmo salar L.) vaccinated during thesmolting and early post-smolt period

The antibody response to Vibrio salmonicida LPS was studied by ELISA and im munoblot after vaccination of salmon with an aqueous vaccine containing the bacterium. The vaccination of the groups took place from February to July. Antibodies to LPS were present in all sera. Sera from unvaccinated fish an d samples collected a short time after vaccination contained low antibody l evels. The antibody levels in vaccinated groups increased with time after v accination except for fish vaccinated during the smelting period. For these fish groups decreasing levels were found in the autumn. Vaccination provid ed high levels of antibodies to LPS at least 6 months later, even with low water temperatures at primary and secondary vaccination. Fish vaccinated du ring smelting at higher water temperatures reached high antibody levels a s hort time after vaccination, but for these groups a decrease took place res ulting in the lowest antibody levels of the vaccinated groups in September. Immunoblots showed that antibody reacted with low molecular weight compone nts corresponding to the O-side chain. Immunoblots using whole bacteria as antigen showed a few immunoreactive bands and individual reaction patterns with respect to location of the bands and immunodominance. (C) 2001 Academi c Press.