SARS-CoV-2 spike protein S2 subunit and non-RBD epitopes (S2/non-RBD)

The SARS-CoV-2 spike protein S2 subunit and non-RBD epitopes are essential components of the viral entry mechanism, responsible for mediating membrane fusion and facilitating host cell infection (Source: NIH, 2020). While the receptor-binding domain (RBD) is the most common target for neutralizing antibodies, its high mutation rate allows the virus to escape immune pressure (Source: ResearchGate, 2022). The S2 subunit, containing the fusion peptide and heptad repeat regions, is significantly more conserved across variants and even across different betacoronaviruses, making it an attractive target for broad-spectrum or variant-proof therapeutics (Source: NIH, 2021). Non-RBD epitopes also encompass the N-terminal domain (NTD), which is involved in viral attachment to alternative receptors and the regulation of spike protein conformational changes (Source: RayBiotech, 2021). Drugs targeting these regions, such as the fusion-inhibitor peptide EK1 and various broadly neutralizing antibodies like S2P6, work by preventing the structural transitions required for viral-host membrane fusion (Source: Frontiers in Immunology, 2023). Additionally, certain small molecules like niclosamide have been identified to inhibit S2-mediated syncytia formation, which is a key driver of COVID-19 pathogenesis and tissue damage (Source: MDPI, 2021). These targets are particularly valuable for developing next-generation vaccines and antibody cocktails that remain effective against emerging variants of concern (Source: NIH, 2023). However, therapeutic development faces challenges such as the steric hindrance of buried S2 epitopes and the generally lower neutralization potency of S2-targeting antibodies compared to those targeting the RBD (Source: ResearchGate, 2022).

Other names

SARS-CoV-2 S2 subunitSARS-CoV-2 spike protein fusion machineryNon-RBD spike epitopesSARS-CoV-2 NTD and S2 domainsSpike S2 fusion protein

Inhibition of viral-host membrane fusion by blocking the formation of the six-helix bundle (6-HB) or stabilizing the prefusion conformation; blocking of S2' proteolytic cleavage; and neutralization of viral entry by targeting non-RBD attachment sites.