Experimental studies on immunization against sea-snake venom

Abstract

Erabu-umihebi snake (laticauda semifasciata) is a sea-snake whose venom has a strong toxicity, and 6.25γ (dry weight) of the venom will kill a mouse within an hour.The action of the venom seems to be neurotoxic: death may result from motorparalysis and respiratory failure. There is no evidence of local symptom.As no medicine could completely neutralize the toxicity of sea-snake venom, it has been considered quite difficult to produce antitoxic serum in experimental animals. The success of our experiment-immunization against toxic action of sea-snake venom in rabbits-is due to the use of the venom-gland fixed with 10% formalin.The venom-gland was taken out from living laticauda semifasciata and fixed in 10% formalin, and preserved for several months. Washing formalin off with water, the material was emulsified, and used as an immunogen.One gramme weight of the fixed antigen, together with Freund's incomplete adjuvant, was subcutaneously injected into rabbits. Four weeks after the first injection, 0.1g emulsion of toxic gland was injected as a booster. Neutralizing value of the serum from the rabbits, obtained one week after the last immunization, showed: in vitro test, 0.1ml of the blood serum can neutralize 37.5γ-50γ of the venom. And in vivo test, intravenous injection of the same amount of the serum is able to cure the symptom of paralysis in mice caused by 25γ venom.0.1ml of the antivenin of laticauda semifasciata, thus obtained, is found to be also efficacious in neutralizing in vitro the venom of hydrophis cyanocinctus (the lethal dose for a mouse, 25γ). The fact suggests the use of laticauda semifasciata serum against the venoms of hydrophiinae sea-snakes, numerous bite cases of which have been reported in the South Seas area.