Identification of a minimal peptide derived from heptad repeat (HR) 2 of spike protein of SARS-CoV and combination of HR1-derived peptides as fusion inhibitors

The heptad repeats (HR1 and HR2) of the spike protein of SARS-CoV are highly conserved regions forming a critical 6-helix bundle during the fusion step of virus entry and are attractive targets of entry inhibitors. In this study, we report that a minimal HR2 peptide, P6 of 23-mer, can block the fusion of SARS-CoV with an IC(50) of 1.04 ± 0.22 μM. This finding supports the structural prediction of the deep groove of HR1 trimer as a target for fusion inhibitors, and suggests P6 as a potential lead peptide for future drug development. Moreover, combination of an HR-1 peptide, N46, and its mutated version, N46eg, shows synergistic inhibition with an IC(50) of 1.39 ± 0.05 μM and combination index of 0.75 ± 0.15, suggesting a common strategy to achieve promising inhibition by HR1 peptide for other class I envelope viruses.