SARS-CoV-2 non-receptor binding domain epitopes (Non-RBD epitopes)

SARS-CoV-2 non-receptor binding domain (non-RBD) epitopes encompass antigenic regions on the viral spike protein—specifically the N-terminal domain (NTD) and the S2 subunit—as well as other structural proteins such as the nucleocapsid (N), membrane (M), and envelope (E) proteins [3, 6, 10]. While the receptor-binding domain (RBD) is the primary target for most neutralizing antibodies, non-RBD epitopes are often more conserved across different variants and lineages, offering a strategic advantage for developing broad-spectrum or pan-coronavirus therapeutics [14, 20, 23]. The NTD contains an antigenic supersite targeted by potent neutralizing antibodies that interfere with viral attachment or conformational changes [22, 24]. The S2 subunit is critical for membrane fusion, and antibodies targeting its conserved stem helix or fusion peptide can block viral entry across diverse sarbecoviruses [12, 14, 23]. Beyond the spike, the N protein is essential for viral RNA packaging and assembly, making it a target for small-molecule inhibitors like K31 [1, 4]. Therapeutic strategies targeting these non-RBD sites aim to overcome the high mutation rates seen in the RBD, though they often exhibit lower individual neutralization potency compared to RBD-specific agents [5, 23]. These targets are also vital for diagnostic purposes, as anti-N antibodies are frequently used as biomarkers for past infection [2, 18].

Other names

Non-RBD spike regionsN-terminal domain (NTD) epitopesS2 subunit epitopesSARS-CoV-2 nucleocapsid (N) proteinSARS-CoV-2 membrane (M) proteinSARS-CoV-2 envelope (E) protein

Inhibition of viral membrane fusion, neutralization of viral entry, inhibition of viral RNA binding and assembly, and induction of antibody-dependent cellular cytotoxicity (ADCC)