Studies on mechanisms of protective immunity of fish and dissemination of pathogenic microorganisms in aquatic environment.

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1. Phagocytosis of peritoneal macrophages of rainbow trout against Vibrio anguillarum was enhanced by the presence of antibody and complement. The trout injected with killed V. anguillarum showed not only protective immunity prior to the detection of antibody but also activation of macrophages. C reactive proteinof trout serum activated complement.2. Isolation of causative agent of epitheliocystis disease of red sea bream was failed but its cultivation in vitro was succesful by co-cultivation. The disease was artificially reproduced in young red sea bream. Size of the causative agent was estimated as 0.51 m in average.3. Number of Vibrio haemolvticus. which was carried by two brackish gastropodmolluscs, Clithon retropictus and Corbicula japonica, considerably varied individually. About 30 % of Vibrio isolates from these molluscs were positive for Kanagawa haemolysin, Upon experimental inoculation, the Vibrio settled in these molluscs but not in Nerita albicilla.4. Carp (Cyprinus carpio … More ) immunized with crude lipopolysaccharid of Aeromonas hydrophila demonstrated strong protective immunity prior to the detection of antibody, This immunity was not transferred with antibody but transferred with non-adhesive kidney cells. Phagocytosis of macrophage was increased. Culture fluid of kidney cells of immunized carp enhanced phagocytosis of non-immunized carp.5. JOV-1 virus was recovered from cultured oyster obtained from Ishikawa, Iwate and Hiroshima Prefectures. Virus recovery was ngative from Japanese littleneck, mussel, scallop and abalone. Mortality of rainbow trout and salmon after inoculation with the virus markably depended on water temperature. Lower temperature than 10 C induced high mortality in younger fish.6. ELISA antibody was produced by inoculation of rainbow trout with virulent or killed Aeromonas salmonicida and was in parallel with agglutinin and dilution of serum. Using ELISA, almost no cross-reaction was observed between A. salmonicida and antigenically related bacteria. There was no relationship between protective immunity in fish and ELISA or agglutinin. Less