Generation of Human Domain Antibody Fragments as Potential Insecticidal Agents against Helicoverpa armigera by Cadherin-Based Screening.

New insecticidal genes and approaches for pest control are a hot research area. In the present study, we explored a novel strategy for the generation of insecticidal proteins. The midgut cadherin of () was used as a target to screen materials that have insecticidal activity. After three rounds of panning, the phage-displayed human domain antibody B1F6, which not only binds to the cadherin CR9-CR11 but also significantly inhibits Cry1Ac toxins from binding to CR9-CR11, was obtained from a phage-displayed human domain antibody (DAb) library. To better analyze the relevant activity of B1F6, soluble B1F6 protein was expressed by BL21 (DE3). The cytotoxicity assays demonstrated that soluble B1F6 induced Sf9 cell death when expressing cadherin on the cell membrane. The insect bioassay results showed that soluble B1F6 protein (90 μg/cm) caused 49.5 ± 3.3% larvae mortality. The midgut histological results showed that soluble B1F6 caused damage to the midgut epithelium of larvae. The present study explored a new strategy and provided a basic material for the generation of new insecticidal materials.