A Dual-Approach Strategy to Optimize the Safety and Efficacy of Anti-Zika Virus Monoclonal Antibody Therapeutics

Antibody-dependent enhancement of infection (ADE) is clinically relevant to Dengue virus (DENV) infection and poses a major risk to the application of monoclonal antibody (mAb)-based therapeutics against related flaviviruses such as the Zika virus (ZIKV). Here, we tested a two-tier approach for selecting non-cross-reactive mAbs combined with modulating Fc glycosylation as a strategy to doubly secure the elimination of ADE while preserving Fc effector functions. To this end, we selected a ZIKV-specific mAb (ZV54) and generated three ZV54 variants using Chinese hamster ovary cells and wild-type (WT) and glycoengineered ΔXF Nicotiana benthamiana plants as production hosts (ZV54^CHO, ZV54^WT, and ZV54^ΔXF). The three ZV54 variants shared an identical polypeptide backbone, but each exhibited a distinct Fc N-glycosylation profile. All three ZV54 variants showed similar neutralization potency against ZIKV but no ADE activity for DENV infection, validating the importance of selecting the virus/serotype-specific mAbs for avoiding ADE by related flaviviruses. For ZIKV infection, however, ZV54^CHO and ZV54^ΔXF showed significant ADE activity while ZV54^WT completely forwent ADE, suggesting that Fc glycan modulation may yield mAb glycoforms that abrogate ADE even for homologous viruses. In contrast to the current strategies for Fc mutations that abrogate all effector functions along with ADE, our approach allowed the preservation of effector functions as all ZV54 glycovariants retained antibody-dependent cellular cytotoxicity (ADCC) against the ZIKV-infected cells. Furthermore, the ADE-free ZV54^WT demonstrated in vivo efficacy in a ZIKV-infection mouse model. Collectively, our study provides further support for the hypothesis that antibody-viral surface antigen and Fc-mediated host cell interactions are both prerequisites for ADE, and that a dual-approach strategy, as shown herein, contributes to the development of highly safe and efficacious anti-ZIKV mAb therapeutics. Our findings may be impactful to other ADE-prone viruses, including SARS-CoV-2.