The coronavirus disease 2019 (COVID-19) pandemic has focused attention on the need to develop effective therapies against the causative agent, SARS-CoV-2, and also against other pathogenic coronaviruses (CoV) that have emerged in the past or might appear in future. Researchers are therefore focusing on steps in the CoV replication cycle that may be vulnerable to inhibition by broad-spectrum or specific antiviral agents. The conserved nature of the fusion domain and mechanism across the CoV family make it a valuable target to elucidate and develop pan-CoV therapeutics. In this article, we review the role of the CoV spike protein in mediating fusion of the viral and host cell membranes, summarizing the results of research on SARS-CoV, MERS-CoV, and recent peer-reviewed studies of SARS-CoV-2, and suggest that the fusion mechanism be investigated as a potential antiviral target. We also provide a supplemental file containing background information on the biology, epidemiology, and clinical features of all human-infecting coronaviruses, along with a phylogenetic tree of these coronaviruses.
SARS-CoV, MERS-CoV, and SARS-CoV-2 entry (receptor binding and membrane fusion) is governed by the viral spike (S) protein.
A predicted furin cleavage in SARS-CoV-2 differentiates it from SARS-CoV, and may affect its entry and transmissibility.
The proposed SARS-CoV-2 FP using a pairwise sequence alignment with SARS-CoV shows 93% sequence homology.
S protein can be activated for early plasma membrane or late endosomal membrane entry depending on protease availability.
The fusion peptide is well conserved across the CoV family, making it a good target for pan coronavirus antivirals.