Inhibition of the Herpesvirus Fusion Protein Using Targeted Small Molecules

Abstract

Herpesviruses are DNA viruses that cause significant disease in humans and animals. Most adults are infected with one or more herpesviruses. During herpesvirus entry into cells, fusion of the viral membrane with the host cell membrane is mediated by glycoprotein B (gB), a class III viral fusion protein that is conserved across all herpesviruses. Fusion proteins are metastable proteins that mediate fusion by inserting into a target membrane and refolding from a prefusion to a postfusion conformation to bring the viral and cellular membranes together. Crystal structures of the postfusion gB conformation have been solved, however its prefusion conformation and the details of how it refolds to execute fusion are unclear. A previous mutagenesis study demonstrated that a region in herpes simplex virus (HSV) gB, termed the coil‐arm region, contributes to fusion. This gB coil‐arm region resembles the six‐helix bundle that is predicted to provide energy to drive fusion in class I fusion proteins. We have developed a panel of small molecule compounds that are designed to target the coil‐arm region of HSV gB. The compounds were tested for the ability to inhibit entry of HSV1 and HSV2 reporter viruses and two compounds significantly decreased virus entry, exhibiting 6–11 μM IC50. Compounds were not cytotoxic and they inhibited entry when added at a step after virus binding, but before fusion. Successful identification of fusion inhibitors could lead to drug candidates that inhibit this conserved fusion protein and clarify how this fusion protein functions, potentially providing new tools to study prefusion gB.Support or Funding InformationDePaul – RFUMS Collaborative Pilot Research Grants