Antibody-Dependent Enhancement in Flavivirus Infections: From Fc Receptor Signaling to Vaccine and Therapeutic Design

Infections caused by flaviviruses, including dengue virus (DENV), Zika virus (ZIKV), and West Nile virus (WNV), can lead to severe hemorrhagic or neurological disease. Antibody-dependent enhancement (ADE) remains a major obstacle to the development of safe flavivirus vaccines and antibody-based therapeutics. ADE includes ADE of infection, in which antibodies increase in viral entry, replication, or infection load, and ADE of disease, in which antibody-dependent inflammatory and immunopathological responses exacerbate disease severity. Previous reviews have largely addressed the general virological and immunological mechanisms of ADE, but few have integrated antibody isotypes and subclasses, Fc-region modifications, Fc receptor diversity, host FcγR polymorphisms, and complement activation within a translational framework. Consequently, how these factors jointly shape ADE of infection, progression to ADE of disease, and individual risk remains incompletely understood. Here, we synthesize evidence linking antibody properties, Fc receptor expression and signaling, FcγR genetic variation, and complement regulation to both forms of ADE. We then discuss how these findings can inform antigen selection, Fc engineering, complement-informed intervention, and systems serology-based risk stratification. By connecting mechanistic evidence with vaccine and therapeutic development, this review offers a framework for designing safer flavivirus interventions and advancing individualized assessment of ADE risk.