Potent neutralization and therapeutic efficacy of bovine rotavirus-specific VHH antibodies in infected calves.

Bovine rotavirus is one of the main pathogens causing acute diarrhea in calves under 1 month of age, posing a serious threat to intensive cattle farming, and there are no effective therapeutic agents owing to the mixed infection of bovine rotavirus (BRV) with other pathogens. In this study, we successfully constructed a phage display antibody library by immunizing Bactrian camels, with a capacity of 6.5 × 108 and a recombinant positive rate of 81.25%. Three high-activity variable heavy-chain domains (VHH) were obtained by using BRV as the antigen, and the gene fragments were ligated with the prokaryotic expression vector pET-22b(+). The recombinant VHH was successfully expressed under induction by isopropyl β-D-1-thiogalactopyranoside (IPTG). In addition, the recombinant VHH could specifically bind to BRV in an enzyme-linked immunosorbent assay (ELISA) and cellular immunofluorescence assays. The neutralizing activity of VHH was further confirmed by a virus neutralization test. Furthermore, our data showed that recombinant VHH could alleviate symptoms such as diarrhea and high fever, and reduce the amount of virus release in a BRV-challenged calf model. These results suggest that the single-domain antibodies against BRV screened in this study offer an effective treatment in BRV infection, facilitating the development of novel therapeutics for BRV.