Antigenicity of Clostridium botulinum type-E formol toxoid.

Tryptic activation of prototoxin of Clostridium botulinum type E increased the lethal toxicity by 250-fold, but no compatible increase in the antitoxin-combining power resulted. The formol toxoid derived from prototoxin and that from trypsin-activated 12S toxin were the same in the antigenic specificity, but prototoxin toxoid stimulated formation of a larger amount of antitoxin in guinea pigs and rabbits. The prototoxin toxoid stimulated formation of the antitoxin to satisfactorily high levels in human volunteers without causing unfavorable reactions.