ANTIGEN RETENTION AND ENZYME REACTIVITY IN THE SPLEEN OF ATLANTIC SALMON, SALMO-SALAR L, FOLLOWING ADMINISTRATION OF INJECTABLE FURUNCULOSIS VACCINES

The retention of vaccine components and phenotypes of leucocyte popula tions were examined in the spleen of Atlantic salmon, Salmo salar L., 12 weeks after intraperitoneal administration of three different furun culosis vaccines. There were marked differences between the vaccine gr oups as judged by serum antibody response and survival following chall enge with Aeromonas salmonicida. Abundant vaccine components were pres ent in the spleen following administration of the two adjuvanted vacci nes but not the non-adjuvanted vaccine. The non-adjuvanted group showe d a disrupted pattern of silver staining in the splenic ellipsoids, su ggesting possible toxic changes. Altered levels of enzyme reactivity i n the spleens of vaccinated fish suggested activation of macrophages. Computer-assisted morphometric analysis was used to demonstrate that a significant (P<0.05) increase in acid phosphatase reactivity associat ed with the melanomacrophage accumulations only occurred in the group that had shown a good response to challenge (14% mortality when contro l group = 60%), and a high level of anti-A. salmonicida antibodies. Th e findings of the present study suggest that the retention of antigen and the activation of macrophages in melanomacrophage accumulations of Atlantic salmon are of significance in vaccination against furunculos is.