Anti-idiotypic single-chain variable fragment antibody partially mimic the functionally spatial structure of Cry2Aa toxin

Abstract

The anti-idiotypic antibody is widely used in the field of immunology to simulate structural features or even induce the biological activity of antigens. In this study, we obtained seven anti-idiotypic single-chain variable fragments (scFv) antibodies of Cry2Aa toxin from a phage-displayed mutant library constructed using error-prone PCR technique. A mutant designated 2–12B showed the best binding ability amongst all anti-idiotypic scFv isolates to Plutella xylostella brush border membrane vesicles (BBMVs). 2–12B and Cry2Aa toxin shared a potential receptor of polycalin in P. xylostella BBMVs. Homology modeling and molecular docking demonstrated that 2–12B and Cry2Aa toxin have seven common binding amino acid residues in polycalin. Insect bioassay results suggested that 2–12 had insecticidal efficacy against P. xylostella larvae. These results indicated that the Cry2Aa anti-idiotypic scFv antibody 2–12B partially mimicked the structure and function of Cry2Aa toxin. The anti-idiotypic scFv antibody provides the basic material for the future study of surrogate molecules or new insecticidal materials.