Evidence showing a different repertoire of antibodies against unfolded cobrotoxin in anticobrotoxin and anti-reduced and S-carboxymethylated cobrotoxin antisera.

Antibodies which specifically reacted with reduced and S-carboxy-methylated(RCM) cobrotoxin were purified from anticobrotoxin antisera and anti-RCM-cobrotoxin antisera, respectively. Results using a competitive immunoassay revealed that the antibodies from anti-RCM-cobrotoxin antisera had a greater affinity for RCM-cobrotoxin than for cobrotoxin. Whereas the reactivity of the antibodies from the anticobrotoxin antisera toward cobrotoxin and RCM-cobrotoxin had a reversed order of binding. In contrast to observations made with S. aureus V8 protease-digest hydrolysates, the antigenic structures of RCM-cobrotoxin recognized by antibodies from anti-RCM-cobrotoxin antisera were notably affected following hydrolysis of RCM-cobrotoxin with chymotrypsin. Moreover, the chymotryptic hydrolysates showed a comparable reactivity as RCM-cobrotoxin toward the antibodies purified from anticobrotoxin antibodies, but a decrease in antigenicity with the V8 protease hydrolysates. These results reveal that the repertoire of antibodies against the unfolded cobrotoxin are not the same in anticobrotoxin and anti-RCM-cobrotoxin antisera. Moreover, it suggests that the repertoire of antibodies from the different sources against the same antigen can be differentiated by measurement of their reactivities with the proteolytic hydrolysates of the antigen.