Disease resistance and immune parameters in Atlantic salmon (Salmo salar L.) with genetically different trypsin isozymes

Genetic variation in responses to vaccination of both specific and non-specific immune parameters were observed in individual Atlantic salmon, possessing different trypsin isozyme patterns in the pyloric caeca and exhibiting different growth rates. Total serum protein concentration and total complement haemolytic activity (CH50) were similar after vaccination, while total IgM, lysozyme activity and spontaneous complement haemolytic activity (SH50) in the sera were significantly different between salmon with different trypsin phenotypes (P<0·05). The values highly correlated with protein concentration in the sera, such as IgM, CH50 activity and SH50 activity (R2>0·4,P <0·0001), should be expressed relative to the concentration of serum protein as specific production in response to vaccination. A tendency of differences in the production of specific antibodies against Aeromonas salmonicida after 5 months vaccination was observed between the Atlantic salmon with and without the trypsin variant TRP-2*92, although the values were not statistically different (P=0·12). Whilst it is not known whether vaccinated salmon of different trypsin phenotypes exhibit differences in disease resistance, unvaccinated fish showed similar disease resistance to natural infection with furunculosis or by experimental cohabitant challenge with A. salmonicida ssp. salmonicida.