IN-VITRO DEGRADATION OF AEROMONAS-SALMONICIDA AND LIMULUS-POLYPHEMUS HEMOCYANIN BY ATLANTIC SALMON, SALMO-SALAR L MACROPHAGES

Cultivated Atlantic salmon head kidney macrophages endocytosed and dig ested iodinated formaldehyde-fixed Aeromonas salmonicida antigens effe ctively. The degradation was time-dependent as demonstrated by increas ed acid soluble radioactivity obtained in macrophage media with time a fter the addition of antigens. Gel chromatography of the degraded mate rial revealed a peak of radioactivity corresponding to molecular weigh ts between 1000 and 6500 Da. In vitro degradation of Limulus polyphemu s hemocyanin (LPH) adsorbed to mineral particles was less efficient co mpared to the degradation of whole bacterial cells, whereas degradatio n of soluble LPH was negligible. There were no significant differences in the rate of processing at 4 (6), 12 and 18 degrees C. Inhibition s tudies using ammonium chloride, a substance that raises the pH of endo somes and lysosomes, showed decreased intracellular degradation of A. salmonicida in a dose-dependent manner. Monensin, a substance reported to block receptor-mediated phagocytosis, very effectively reduced the extent of processing whereas leupeptin and pepstatin, specific inhibi tors of the major classes of cysteine and aspartic proteinases respect ively, only slightly affected the processing. (C) 1995 Academic Press Limited