SARS-CoV-2 spike protein receptor-binding domain (RBD) conserved non-receptor-binding motif (non-RBM) epitope (SARS-CoV-2 RBD non-RBM epitope)

The SARS-CoV-2 spike protein receptor-binding domain (RBD) conserved non-receptor-binding motif (non-RBM) epitope is a highly stable antigenic region on the viral spike protein that is distinct from the ACE2-interacting surface [1]. While the receptor-binding motif (RBM) is subject to intense selective pressure and frequent mutation, these non-RBM epitopes are often conserved across the Sarbecovirus subgenus due to structural or functional constraints [2][3]. These sites are typically targeted by Class 3 and Class 4 neutralizing antibodies, which bind to the side or inner faces of the RBD, respectively [2]. Therapeutic monoclonal antibodies, such as Sotrovimab, target these conserved regions to maintain neutralizing activity against variants of concern that have evolved to escape RBM-targeting antibodies [4]. The primary mechanism of action involves sterically hindering the conformational changes required for viral-host membrane fusion or facilitating the clearance of infected cells through Fc-mediated effector functions [4]. As such, these epitopes are primary targets for the development of broadly neutralizing therapeutics and next-generation vaccines aimed at providing variant-proof immunity [5]. Clinical monitoring of mutations within these epitopes is essential to ensure the continued efficacy of monoclonal antibody therapies.

Other names

Class 3 RBD epitopeClass 4 RBD epitopeS309-siteCR3022-siteConserved sarbecovirus epitope

Neutralization of viral entry by sterically hindering conformational changes of the spike protein or blocking membrane fusion, often maintaining activity across variants due to epitope conservation [1][4].