Antigenic similarity of toxins produced by Clostridium botulinum type C and D strains

Antisera against purified type C1 toxin of Clostridium botulinum and its heavy-chain component cross-neutralized type D toxin. Antisera against partially purified type D toxin cross-neutralized type C1 toxin. From the latter serum, a component which neutralized only type D toxin and a component which equally neutralized both C1 and D toxins were obtained. We concluded that the cross-neutralization was not due to the fact that type C and D strains produce both C1 and D toxins but rather to the fact that the toxins have an antigen(s) common to their molecules. The results of the agar gel-double-diffusion test also supported this conclusion.