Severe acute respiratory syndrome coronavirus 2 spike glycoprotein (Omicron XBB.1.5 variant) (SARS-CoV-2 S protein (XBB.1.5))

The SARS-CoV-2 spike protein of the Omicron XBB.1.5 variant is a class I fusion glycoprotein that serves as the primary mediator of viral attachment and entry into host cells (UniProt P0DTC2). It consists of two subunits, S1 and S2, where S1 contains the receptor-binding domain (RBD) that targets the human Angiotensin-Converting Enzyme 2 (ACE2) receptor (PubMed: 36754319). The XBB.1.5 variant, a descendant of the XBB recombinant lineage, features a key F486P mutation that enhances its binding affinity to ACE2 while maintaining significant immune evasion capabilities (Nature: 10.1038/s41586-023-05901-9). This protein is the central antigen for the 2023-2024 monovalent COVID-19 vaccines, including those from Pfizer-BioNTech, Moderna, and Novavax, which were specifically updated to match this variant's profile (FDA, 2023). Therapeutic strategies targeting this protein focus on neutralizing the virus by blocking the RBD-ACE2 interaction or preventing the conformational changes required for membrane fusion. However, the rapid evolution of the spike protein poses a continuous challenge for the long-term efficacy of monoclonal antibodies and vaccine-induced immunity (Cell: 10.1016/j.cell.2022.12.018).

Other names

Spike glycoproteinS proteinKraken variant spikeXBB.1.5 S proteinSARS-CoV-2 S protein

Induction of neutralizing antibodies that bind to the receptor-binding domain (RBD) of the spike protein, preventing its interaction with the host ACE2 receptor and inhibiting viral entry into cells (PubMed: 37015473).