| Research Abstract |
The 50 % lethal doses (LD_<50>) of purified salmolysin for white-spotted char on intramuscular and intraperitoneal injection were 196 and 556 mu/kg. The LD_<50> for rainbow trout on intramuscular injection was 58 mu/kg. Salmolysin was detoxificated by heat-treatment at 60 ^0C for 30 min, or by formalin-treatment for 1 week. Salmolysin toxoid was injected to white-spotted char intramuscularly. As the result, agglutinating antibody titer was reached to maximum after 3 weeks. White-spotted char were immunized with salmolysin toxoid by intramuscular injection or immersion method, after, that, the fish were cahllenged with Aeromonas salmonicida. AS the result, survival ratio of immunized fish was higher than that of non-immunized fish. These results indicate that salmolysin toxoid is an effective immunogen against furunculosis. Salmolysin antitoxin was purified from the serum of white-spotted char by ammonium sulfate precipitation, anion-exchange chromatography on DEAE-cellulose, and gel filtration on Sephatose 6B. Furthermore, salmolysin produced in the culture supernatant of A. salmonicida and in the focus tissue of infected fish was detected by enzyme linked immuno-sorbent assay. On the other hand, the red blood cells of salmonids were peculiarly lysed by salmolysin, however, the red blood cells of fowls and mammalia were not lysed by the toxin. Since the sensitivity of salmonid red blood cells to the toxin was different, it was suggested that the surface structure of salmonid erythrocytes varies with the genus level. Salmolysin did not show phospholipase C activity and was not reactivated by thiolcompound. The hemolytic catibity of salmoysin was not affected by phospholipids, however, the activity was stimulated by asialoglycophorin.
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