[Toxoids of botulinum toxin type G]

Clostridium botulinum type G toxin was obtained by the dialysis sac culture method. Crude toxin was submitted to precipitation either by 4.5 M (NH4)2SO4 (Table 2) or ethanol 96% up to 25% final concentration (Table 3). Aliquots of crude toxin and fractions from the precipitation methods were activated by trypsin, detoxificated by formalin and adsorbed with aluminum phosphate. Twelve preparations of toxoids (Table 1) were obtained and assayed in laboratory animals. The immune response was studied through the toxin-antitoxin neutralization test, set up at a level of 4,000 mouse LD50 per ml. Guinea pigs had the highest titer of antitoxin (64,000 anti-mouse-LD50/ml) after its immunization with toxoid prepared with toxin precipitated by 4.5 M ammonium sulphate activated by trypsin and adsorbed with aluminum phosphate. Rabbits responded with a lower titer of antitoxin but had a similar response than guinea pigs to the same toxoids (Table 5). Chickens did not show any antitoxin response above 4,000 anti-mouse-LD50 per ml.