A fluorescence polarization assay using an engineered human respiratory syncytial virus F protein as a direct screening platform.

Human respiratory syncytial virus (hRSV) typically affects newborns and young children. Even though it can cause severe and, in some cases, lifelong respiratory infections, there are currently no Food and Drug Administration (FDA)-approved therapeutics that control this virus. The hRSV F protein facilitates viral fusion, a critical extracellular event that can be targeted for therapeutic intervention by disrupting the assembly of a postfusion 6-helix bundle (6HB) within the hRSV F protein. Here we report the development of a fluorescence polarization (FP) assay using an engineered hRSV F protein 5-helix bundle (5HB). We generated the 5HB and validated its ability to form a 6HB in an FP assay. To test the potential of 5HB as a screening tool, we then investigated a series of truncated peptides derived from the "missing" sixth helix. Using this FP-based 5HB system, we have successfully demonstrated that short peptides can prevent 6HB formation and serve as potential hRSV fusion inhibitors. We anticipate that this new 5HB system will provide an effective tool to identify and study potential antivirals to control hRSV infection.