CLOSTRIDIUM BOTULINUM TYPE A TOXOIDS

Highly toxic filtrates of cultures of C. botulinum, Type A, when treated with 0.5% formalin and incubated at 37 °C. for several weeks became non-toxic. These toxoids induced resistance in mice and guinea-pigs to several thousand times the amount of Type A botulinus toxin required to kill a normal animal of the same species.In general, three 1.0 ml. doses of the fluid toxoid protected over 60% of inoculated mice against 100,000 lethal doses of Type A botulinus toxin. Six weeks after receiving a 5.0 ml. dose of fluid toxoid, some 88% of guinea-pigs survived the injection of 160,000 lethal doses of Type A toxins. The antitoxic titres of their sera ranged from < 0.001 to 10 units per ml. Alum precipitation increased the effectiveness of the toxoid as an immunizing agent in mice; two 1.0 ml. doses protected about 80% of mice against 100,000 lethal doses of Type A toxin. In guinea-pigs, the immunity induced by 5.0 ml. of alum-precipitated toxoid was similar to that observed following the injection of 5.0 ml. of the fluid material. No correlation was apparent between the flocculative titre of the culture filtrates before and after formalinization and their antigenicity.