Induction of neutralizing antibodies against Tityus serrulatus scorpion toxins by immunization with a mixture of defined synthetic epitopes.

We have used the Spot method of multiple peptide synthesis to prepare sets of immobilized overlapping peptides of uniform size (15 mer), covering the complete amino acid sequences of TsNTxP a non-toxic and immunogenic protein and TsIV, an alpha-type toxin that is the major lethal component of the venom of scorpion Tityus serrulatus. Anti-TsNTxP antibodies binding to peptides, revealed three antigenic regions, one in the N-terminal, the second in the central part and the other in the C-terminal part of TsNTxP. One peptide epitope in the C-terminal part of TsIV was identified with anti-TsIV neutralizing rabbit antibodies. Anti-peptide antibodies were raised against these four peptides all together covalently coupled to keyhole limpet hemocyanin (KLH) and found to neutralize in vitro the toxic effects of the T. serrulatus venom. Quantities of venom equivalent to 13.5 LD(50) were effectively neutralized by 1ml of the anti-peptide serum. The antigenic specificities of the anti-peptides were compared by an indirect enzyme-linked immunosorbent assay (ELISA) using synthetic peptides and crude venoms from T. serrulatus, T. bahiensis, T. cambridgei, T. stigmurus, Androctonus autralis Hector and Centruroides sculpturatus to coat the microtitration plates. The anti-peptide antibodies had a comparable high reactivity with the crude venom of T. serrulatus, moderate binding to T. bahiensis, T. cambridgei, T. stigmurus and Centruroides sculpturatus venoms but were unable to recognize the venom of Androctonus autralis Hector. These results show that by using peptides derived from the sequence of scorpion toxins, the generation of anti-peptide antibodies able to neutralize the cognate venom appears to be an alternative strategy for the easy preparation of antivenoms.