Bactericidal and physico-chemical properties of a lectin derived from spring chinook salmon (Oncorhynchus tshawytscha) Ova

Graduation date: 1978Unfertilized ova from spring chinook salmon (Oncorhynchus\ud tshawytscha) were examined for the presence of classical salmonid\ud inmmunoglobulin. Immunodiffusion techniques in which rabbit anti-salmonid\ud immunoglobulin was reacted against an ova homogenate\ud and rabbit anti-ova homogenate was reacted against immune chinook\ud serum failed to detect classical-type antibodies within these eggs.\ud A lectin with bactericidal properties was isolated from spring\ud chinook salmon ova. This protein agglutinated human type B and\ud rabbit erythrocytes, but not human type A, O or sheep red cells.\ud Hemagglutination was inhibited by D-galactose and L-rhamnose.\ud The protein was purified by affinity chromatography and by gel filtration\ud on Bio-Rad P300. The purified lectin contained a minor (0. 8 %)\ud carbohydrate moiety. A rabbit antiserum was prepared against the\ud protein and used to determine whether ova from coho salmon\ud (O. kisutch), pink salmon (O. gorbuscha), chum salmon (O. keta), kokanee salmon (O. nerka), steelhead trout (Salmo gairdneri),\ud Lahonten cutthroat trout (S. clarki henshawi) or fall chinook salmon\ud (O. tshawytscha) contained a similar protein. All species tested had\ud an immunologically identical protein within their ova.\ud Purified spring chinook salmon ova lectin was bactericidal for\ud two serotypes of Vibrio anguillarum, Pasteurella piscidida,\ud Aeromonas hydrophila and Flexibacter columnaris, but not for\ud Yersinia ruckeri, A. salmonicida, Edwardsiella tarda, Cytophaga\ud psychrophila or the agent of bacterial kidney disease, Corynebacterium\ud sp. In addition to these known bacterial fish pathogens, 19\ud species of bacteria commonly associated with humans were tested;\ud none of the human-associated agents were inhibited by the lectin.\ud Proteins immunologically identical to the spring chinook salmon\ud ova lectin were purified froim ova of seven other salmonids and found\ud to possess little, if any, activity against the bacterial fish pathogens.\ud Even the protein purified from fall chinook salmon ova had minimal\ud bactericidal activity.\ud Less than 1. 0 μg /ml of the purified spring chinook ova lectin\ud was required for complete inhibition of V. anguillarum growth. A\ud 1 hr incubation of the lectin with the bacteria at 22 C was sufficient\ud for 100% growth inhibition. Microscopic examination of the incubation\ud mixture showed that after 20 min, approximately 50% of the\ud bacteria were no longer motile. No cell lysis was observed. The bacterial inhibition property was stable after heat treatment\ud at 80 C for 6 hr or 100 C for 1 hr. Lyophilization of the protein\ud did not reduce bactericidal activity.\ud The chinook lectin was compared with a plant lectin, ricin,\ud for bactericidal activity and competitive binding of V. anguillarum\ud cells. Although ricin had a carbohydrate specificity similar to the\ud chinook protein, it was not toxic for V. anguillarum; however, it did\ud compete for binding sites on the bacterium.\ud Coho salmon which received 125 μg of purified spring chinook\ud ova lectin intravenously were not protected against subsequent challenge\ud by V. anguillarum