Screening for Peptides to Bind and Functionally Inhibit SARS-CoV-2 Fusion Peptide Using Mirrored Combinatorial Phage Display and Human Proteomic Phage Display

Antiviral peptides derived from the heptad region of RNA viral entry proteins inhibit both retroviral and coronaviral fusion in vivo. Another key region for SARS-CoV-2 fusion is the evolutionarily conserved fusion peptide (FP), motivating us to identify peptides that bind FP and might inhibit viral entry across coronaviruses. We screened the NEB PhD-7mer random combinatorial phage display library against FP, synthesised as a D-peptide. This strategy was used to identify peptides from the L-library that could then be synthesised as proteolytically resistant D peptides. We selected the top seven peptides that were not seen in another published screen with this library, as these were more likely to be specific. All seven D-peptides had no impact on the infection of Vero-E6/TMPRSS2 cells by SARS-CoV-2. We also screened a proteomic derived phage display library from the disordered regions of human proteins. Two overlapping peptides were identified from a region of OTUD1, which is known to influence various viral infections. However, a synthetic peptide based on their sequences failed to markedly inhibit viral entry. Thus, while two alternative phage display screening strategies identified potential binding peptides, none of these peptides in their current forms represented strong candidates for direct viral inhibition.