EFB Dengue Literature Review

Antibody-Dependent Enhancement

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Antibody-Dependent Enhancement

Overview

Antibody-dependent enhancement (ADE) is a mechanism by which pre-existing cross-reactive antibodies, at sub-neutralising concentrations, bind to virus particles and facilitate their uptake into Fcγ receptor (FcγR)-bearing cells (monocytes, macrophages), thereby enhancing viral replication rather than preventing it. In dengue, ADE is one of the leading hypotheses to explain why secondary heterotypic infections are associated with increased disease severity (DHF/DSS). The model posits that cross-reactive antibodies generated during a primary infection bind the secondary serotype with insufficient avidity to neutralise it but sufficient affinity to promote FcγR-mediated entry into myeloid cells.

Key Points from Literature

  • Near-universal ADE activity of dengue plasmablast-derived mAbs: 45/53 mAbs generated from sorted acute-phase plasmablasts in secondary DENV2 infection enhanced DENV infection of U937 cells (FcγR⁺ monocytic cell line) at 1 µg/ml. Enhancement ranged from 5-fold to 161-fold across DENV1–4. ADE was independent of neutralisation potency — even potently neutralising mAbs caused enhancement. Cross-reactive neutralising mAbs caused greater average fold-enhancement than mono-neutralising mAbs. Only 2/53 DENV-reactive mAbs (32.2F04 and 39.3G03) did not enhance infection (see Priyamvada2016 - Cross-Reactive Memory Plasmablasts in Secondary Dengue, n=4 secondary DHF, FcγR-bearing U937 ADE assay).
  • ADE and neutralisation are not mutually exclusive: The most potently neutralising mAb that was also DENV2-specific (31.3F03) exhibited the highest cross-serotypic ADE in the entire panel — demonstrating that ADE is a property of the antibody at sub-neutralising concentrations or against heterotypic serotypes, not a marker of poor neutralisation capacity per se (see Priyamvada2016 - Cross-Reactive Memory Plasmablasts in Secondary Dengue, n=4 secondary DHF, 53 mAbs).
  • ADE is more relevant for future exposures than current infection: The authors note that viremia in dengue patients subsides before the peak plasmablast response (days 6–7), making it unlikely that acutely produced ADE-competent antibodies enhance the current infection. Rather, these antibodies enter the serum pool and may enhance subsequent heterotypic infections — connecting the acute plasmablast wave to long-term susceptibility to severe dengue (see Priyamvada2016 - Cross-Reactive Memory Plasmablasts in Secondary Dengue, n=4 secondary DHF, 53 mAbs).
  • Massive plasmablast expansion without corresponding neutralising antibody: In secondary dengue with complications (DFC), plasmablasts averaged 46% of B cells (peak 87%) and >70% were DENV-specific by ELISpot, yet PRNT₅₀ neutralising titres to all four DENV serotypes did not correlate with plasmablast frequency. This disconnect between antibody quantity and neutralising quality is consistent with a substantial fraction of plasmablast-derived antibodies being non-neutralising — and therefore potentially ADE-competent at physiological concentrations (see GarciaBates2013 - Plasmablast Response and Dengue Severity, n=84 dengue cohort, ELISpot + PRNT₅₀).
  • Neutralising antibody paradox replicated in dengue: Anti-NS1 and anti-prM/M/E IgG (binding, non-neutralising antibodies) were elevated in severe dengue (p=0.04 and p=0.03 respectively), while FRNT₅₀ neutralising titres did not differ between mild and severe groups. This replicates the direction of the neutralising antibody paradox first described in COVID-19 — suggesting that the Extrafollicular Response may produce antibodies that bind virus but fail to neutralise, a profile consistent with ADE-mediating potential. However, the dengue FRNT₅₀ was tested against DENV-2 only (n=10 severe subgroup), limiting interpretability (see Ansari2025 - Peripheral T Helper Subset Drives B Cell Response in Dengue, n=60 dengue cohort — underpowered for FRNT, single-serotype limitation; council caveats: day-of-sampling confounder for severity associations).
  • Cross-disease neutralising antibody paradox in COVID-19: In critically ill COVID-19 patients with EF B cell activation, anti-RBD antibodies (IgM, IgG, IgA) and confirmed neutralising activity were highest in the worst-outcome patients (ICU, death) — the same patients with the most SLE-like EF activation profile. This paradox — functional neutralising antibodies produced via an EF pathway yet correlating with poor prognosis — establishes a cross-disease pattern relevant to ADE interpretation: high total antibody output from the EF pathway may include a non-neutralising fraction that enhances rather than protects, even when the same individual also produces neutralising antibodies (see Woodruff2020 - EF B Cell Responses in COVID-19, n=17 COVID-19, 24-marker spectral FCM + scVDJ — n=1 for repertoire claims).
  • PB-derived mAbs are an incomplete window into ADE risk: Plasmablast-derived antibodies are predominantly E-specific and more potently neutralising than memory B cell-derived antibodies, yet the PB repertoire does not represent the full memory B cell pool. Bone marrow-resident long-lived plasma cells — an unmeasured compartment — may also contribute ADE-competent antibodies. Measuring plasmablast ADE activity alone may underestimate or mischaracterise the in vivo ADE risk (see Bhattacharya2016 - Memory B Cell Subset Selection in Secondary Dengue, commentary — no original data, cites Appanna2016 and Seifert2015).

Contradictions & Debates

  • The in vitro ADE assay (U937 cells, single mAb concentration) does not capture the concentration-dependent balance between neutralisation and enhancement that exists in vivo. At sufficiently high concentrations, most antibodies neutralise; at sub-neutralising dilutions, they enhance. Whether the plasmablast-derived antibody concentrations achieved in patient serum fall within the enhancing or neutralising range is unknown.
  • The Extrafollicular Response produces non-neutralising IgG that correlates with disease severity but not with neutralising titres — the “neutralizing Ab paradox” now documented in both dengue (Ansari2025: FRNT₅₀ flat by severity while binding IgG elevated) and COVID-19 (Woodruff2020: highest neutralising titres in worst outcomes). Whether this non-neutralising fraction is specifically the ADE-mediating subset has not been tested — it is a plausible but undemonstrated connection. The gap is significant: if EF-derived non-neutralising IgG is ADE-competent, it would mechanistically link the EF pathway to dengue severity, but no study has directly assayed ADE activity of EF-phenotype B cell-derived antibodies.

Original Antigenic Sin, Plasmablast, IgG, Memory B Cell, Extrafollicular Response, Germinal Center, Somatic Hypermutation, Peripheral Helper T Cell

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