Structural and functional characterization of an anti-West Nile virus monoclonal antibody and its single-chain variant produced in glycoengineered plants

Previously, our group engineered a plant-derived monoclonal antibody (MAb pE16) that efficiently treated West Nile virus (WNV) infection in mice. In this study, we developed a pE16 variant consisting of a single-chain variable fragment (scFv) fused to the heavy chain constant domains (C_H) of human IgG (pE16scFv-C_H). pE16 and pE16scFv-C_H were expressed and assembled efficiently in Nicotiana benthamiana {increment}XF plants, a glycosylation mutant lacking plant-specific N-glycan residues. Glycan analysis revealed that {increment}XF plant-derived pE16scFv-C_H ({increment}XFpE16scFv-C_H) and pE16 ({increment}XFpE16) both displayed a mammalian glycosylation profile. {increment}XFpE16 and {increment}XFpE16scFv-C_H demonstrated equivalent antigen-binding affinity and kinetics, and slightly enhanced neutralization of WNV in vitro compared with the parent mammalian cell-produced E16 (mE16). A single dose of {increment}XFpE16 or {increment}XFpE16scFv-C_H protected mice against WNV-induced mortality even 4 days after infection at equivalent rates as mE16. This study provides a detailed tandem comparison of the expression, structure and function of a therapeutic MAb and its single-chain variant produced in glycoengineered plants. Moreover, it demonstrates the development of anti-WNV MAb therapeutic variants that are equivalent in efficacy to pE16, simpler to produce, and likely safer to use as therapeutics due to their mammalian N-glycosylation. This platform may lead to a more robust and cost-effective production of antibody-based therapeutics against WNV infection and other infectious, inflammatory or neoplastic diseases.