How small-molecule inhibitors of dengue-virus infection interfere with viral membrane fusion

Abstract

Dengue virus (DV) is a compact, icoshedrally symmetric, enveloped particle, covered by 90 dimers of envelope protein (E), which mediates viral attachment and membrane fusion. Fusion requires a dimer-to-trimer transition and membrane engagement of hydrophobic \"fusion loops\". We previously characterized the steps in membrane fusion for the related West Nile virus (WNV), using recombinant, WNV virus-like particles (VLPs) for single-particle experiments. Trimerization and membrane engagement are rate-limiting; fusion requires at least two adjacent trimers; availability of competent monomers within the contact zone between virus and target membrane creates a trimerization bottleneck. We have extended that work to dengue VLPs, from all four DV serotypes, finding an essentially similar mechanism. Small-molecule inhibitors of DV infection that target E block its fusion-inducing conformation change. We show that [~]15 bound molecules per particle ([~]8.5 % occupancy) completely prevent fusion, in accord with the proposed mechanism and the likely inhibitor binding site on E.\n\nImpact statementSingle-particle studies of dengue-virus membrane fusion and the effect of small-molecule inhibitors of infection clarify the viral fusion mechanism.