Toxicity of Papain-digested Tetanus Toxin

Fragment B of tetanus toxin (Helting, T. B., and Zwisler, 0. (197’7) J. Biol. Chem. 252, 187-193), obtained after digestion with papain, gel chromatography, immunoabsorption, and repeated gel chromatography, was atoxic in experimenta’l animals at concentration levels sufficient to induce protective antibody synthesis. However, mice injected with 200 pg of highly purified Fragment B appear normal for approximately 48 h. Between 48 and 72 h after inoculation, the animals develop a characteristic syndrome involving respiratory difficulty, loss of weight, failure to take food, retraction of their abdominal muscles, and finally, death. Convulsions or spastic paralysis of the injected limb, typical features associated with classical tetanus, never developed after administration of Fragment B. In contrast, the muscular activity decreased somewhat in agreement with a more flaccid appearance of the hind legs. The effect of Fragment B could be abolished by homologous antisera administered together with the antigen. Antisera given at later stages progressively lost their capacity to interfere with the action of Fragment B. Whereas this time dependence of the efficacy of the antibody was similar to that observed for parent tetanus toxin, the action of the latter substance was also inhibited by antisera directed against Fragment C, the second split product of tetanus toxin released upon papain digestion of the molecule. AntiFragment C serum did not react with Fragment B and could not interfere with its action. It is suggested that Fragment B has lost the capacity of the parent toxin molecule to induce the syndrome of spastic paralysis but has retained some characteristic functions of tetanus toxin which may play an important role in interfering with the autonomous nervous system.