Sequence homology between tetanus and botulinum toxins detected by an antipeptide antibody

The extent of immunological similarity between tetanus toxin and botulinum toxins A, B, C1, and E was studied by using 10 antibodies produced against synthetic peptides representing different sequences of tetanus toxin, mouse antitetanus serum, and human Tetanus Immune Globulin. Antibodies produced against the synthetic peptides recognized tetanus toxin in an enzyme-linked immunosorbent assay and on Western blots (immunoblots) but did not appear to recognize the native protein. One of the antitetanus peptide antibodies, which was produced against a peptide from the amino terminal, cross-reacted with three of the four botulinum toxins on immunoblots. This antibody, 1, reacted strongly with botulinum toxins B and C1 and weakly with E but did not recognize type A toxin. None of the other peptide antibodies cross-reacted with the botulinum toxins. Mouse antitetanus serum and human Tetanus Immune Globulin did not recognize any of the botulinum toxins on immunoblots. The amino-terminal region of the light chain of tetanus toxin and botulinum toxin types A, B, C1, and E are known to have sequence homology. Our data demonstrate that for tetanus toxin and botulinum toxin types B, C1, and E this region also has immunological homology. Type A, which has the least amount of homology with tetanus toxin in this region, does not share this immunological homology. These data also suggest that although the native structures of tetanus and botulinum toxins have relatively few common immunological determinants, the two toxins may contain short stretches of identical or very similar amino acid sequences.