The role of epitope-specific antibodies and Fc effector functions in determining disease severity during secondary dengue virus infection

Abstract

Dengue remains the most prevalent vector-borne disease globally and poses a significant global public health challenge. Despite this, no universally adopted vaccine or targeted antiviral therapy currently exists. While most infections cause mild or no symptoms, some individuals develop severe disease, particularly when re-infected with a different dengue virus (DENV) serotype. Pre-existing immune responses, including antibodies generated during an initial infection shape the subsequent disease outcome. However, the precise immune mechanisms responsible for this increased risk remain poorly defined. In this thesis, we investigated how antibody responses to the major surface protein of DENV, the envelope (E) protein, influence clinical outcome in a cohort of Cambodian children undergoing a post-primary DENV2 infection. The systematic review identified a knowledge gap where limited evidence is available connecting antibody specificity and function with clinical outcome in naturally acquired human DENV infection. To address this gap, we developed a multiplex serological assay to quantify antibodies targeting distinct E-protein epitopes and successfully isolated epitope-specific antibody subsets from human plasma. Our findings demonstrate that antibodies targeting the fusion loop epitope contributed to pathology via antibody-dependent enhancement of infection, whereas antibodies binding to quaternary epitopes on the E-dimer protein offered protection from severe dengue and showed stronger and broader neutralizing activity. Complementarily, droplet-based microfluidic imaging showed that antibody-secreting cells targeting quaternary epitopes were exclusively detected in subclinical dengue cases, suggesting a protective role of these antibodies against symptomatic infection. Furthermore, we identified that antibody Fc-mediated effector functions were associated with disease severity, with antibody-dependent complement deposition (ADCD) and antibody-dependent enhancement of infection (ADE) both correlating with more severe clinical presentations. Taken together, these findings show that both the epitope specificity of anti-E antibodies and their Fc-mediated effector functions contribute to clinical outcome following post-primary DENV2 infection. These data provide insights relevant to dengue vaccine design, biomarker discovery, and therapeutic antibody development.