MOLECULAR VARIATION BETWEEN THE ALPHA-TOXINS FROM THE TYPE STRAIN (NCTC-8237) AND CLINICAL ISOLATES OF CLOSTRIDIUM-PERFRINGENS ASSOCIATED WITH DISEASE IN MAN AND ANIMALS

The alpha-toxin produced by the type strain of Clostridium perfringens (NCTC 8237) was shown to differ from the a-toxins produced by most st rains of C. perfringens isolated from man and from calves with respect to reactivity with a neutralizing monoclonal antibody (DY2F5D11). The difference in antibody binding correlated with three differences in t he deduced amino acid sequence (Ala(174) to Asp(174); Thr(177) to Ala( 177); Ser(335) to Pro(335)) of the alpha-toxins, Using octapeptides sy nthesized on the basis of the amino acid sequences from these regions of variability, it was shown that the Ala(174) to Asp(174) change had the greatest effect on reducing the binding of monoclonal antibody DY2 F5D11 to the alpha-toxin, These differences did not affect the enzymic or toxic properties of the protein, However, the phospholipase C acti vity of the alpha-toxin produced by strain NCTC 8237 was more suscepti ble to inactivation by chymotrypsin, The changes in amino acid sequenc e did not affect the ability of a C-terminal domain vaccine, derived f rom the alpha-toxin of strain NCTC 8237, to induce protection against the alpha-toxin from a bovine enteric strain of C. perfringens.