An amphipathic, α-helical (AH) peptide derived from the N-terminal region of the hepatitis C virus (HCV) NS5A protein represents a breakthrough, broad-spectrum antiviral drug candidate. It ruptures the lipid envelope of virus particles in a size-dependent manner. The size range of virus particles susceptible to treatment with AH peptide encompasses a wide range of deadly viral pathogens including dengue, HCV and HIV. Uniquely compared to other antiviral medicines in development or in the clinic, the virocidal activity of the AH peptide was originally discovered by surface science techniques probing model biological interfaces—namely lipid vesicles serving as surrogates for lipid-enveloped virus particles. Quartz crystal microbalance with dissipation (QCM-D) monitoring identified that addition of the AH peptide ruptures a layer of intact lipid vesicles to promote structural transformation to a planar lipid bilayer on gold and titanium oxide. Based on this in situ structural transformation, we have used simultaneous QCM-D monitoring and optical reflectometry to determine the antiviral mode of action of AH peptide, including a vesicle swelling process which occurs during the binding interaction. Using a newly developed total internal reflection fluorescence microscopy (TIRF)-based single vesicle assay, we have also investigated how AH peptide interacts with lipid membranes to induce membrane curvature-dependent pore formation and membrane destabilization. Importantly, the preference of AH peptide to selectively rupture virus particles of small size appears to be related to membrane strain-dependent pore formation. Compared to other known proteins and peptides, AH peptide is unique due to its combination of high potency and specificity for curved membranes. Collectively, these results lay the groundwork for the engineering of AH peptide therapeutics with optimized properties as well as for the broader application of surface science techniques to antiviral drug discovery and development.

Biography