High affinity antibody to cobrotoxin prepared from the derivatives of glutaraldehyde-detoxified cobrotoxin.

High affinity antibodies to cobrotoxin were obtained by immunization with derivatives of glutaraldehyde (GA)-modified cobrotoxin. The derivatives completely lost lethality and binding activity to nicotinic acetylcholine receptors (nAChR), but retained the same antigenicity as cobrotoxin toward anti-cobrotoxin antibody. Owing to hyperimmunization with these low toxicity derivatives, a high affinity antibody to cobrotoxin was induced in a short period. We also showed that the derivatives of cobrotoxin may have altered local conformation, and residues which contribute to the intensity of binding between antigen and antibody may consequently be exposed. Hence, the modified derivatives have increased binding affinity to anti-cobrotoxin antibody. In addition, since high affinity antibodies prepared using the derivatives exhibit more potent binding affinity to cobrotoxin than conventional anti-cobrotoxin antibody, the specific neutralizing capacity of the high affinity antibodies is greatly increased. These results lead to the conclusion that the derivatives of GA-modified cobrotoxin have the same antigenicity as the native toxin, and can be used as immunogens for the production of high affinity antibodies to cobrotoxin.