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Tetanus toxin detoxification by formaldehyde induces polymerization to a variable extent. It was previously reported that a monomeric 7S-toxoid could be isolated from the composite toxoid. This 7S-toxoid exhibited a specific flocculating activity similar to that of the parent toxin. It was also found that after adsorption onto calcium phosphate it was more immunogenic in mice than the composite toxoid. In the present paper it was demonstrated that the 7S-toxoid is immunogenic in humans as a fluid vaccine administered by intradermal route. It is somewhat less efficient than adsorbed vaccines in primo-vaccination, but is quite comparable to them in booster injections. These results were shown to be statistically significant. Untoward reactions were rare and mild. The use of such a fluid vaccine is to be recommended in allergic patients, whose state might possibly be affected unfavourably by the combined injection of an adjuvant.

An antigenic, atoxic polypeptide fragment isolated from tetanus toxin, designated as B-IIb fragment, was shown to bind in vitro both to immobilized gangliosides and isolated crude synaptic membranes. The binding affinity of the B-IIb fragment for gangliosides and crude synaptic membranes was found to be greater than that of the toxin. This fragment also was capable of competing more efficiently for the toxin receptor sites of synaptic membranes than the toxin.