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

The Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) Omicron XBB.1.5 spike protein is the primary surface glycoprotein of the XBB.1.5 subvariant, a recombinant of the BA.2.10.1 and BA.2.75 lineages (WHO, 2023). It mediates viral entry into host cells by binding to the Angiotensin-Converting Enzyme 2 (ACE2) receptor via its Receptor Binding Domain (RBD) (Nature, 2023). XBB.1.5 is characterized by the F486P mutation, which significantly enhances its binding affinity to ACE2 compared to its predecessor XBB.1, contributing to its high transmissibility (The Lancet Infectious Diseases, 2023). This target is notorious for its extensive immune evasion, rendering most previously authorized monoclonal antibodies, such as cilgavimab and tixagevimab, ineffective (NEJM, 2023). Consequently, the host immune system requires updated stimulation, leading to the development of XBB.1.5-specific monovalent mRNA and protein-based vaccines (FDA, 2023). These vaccines aim to elicit neutralizing antibodies and T-cell responses that can specifically recognize the mutated epitopes of the XBB.1.5 spike protein to prevent infection and severe disease (CDC, 2023).

Other names

XBB.1.5 spike proteinKraken variant spike proteinSARS-CoV-2 Omicron XBB.1.5 S-proteinSpike glycoprotein (XBB.1.5)

Induction of neutralizing antibodies and T-cell responses targeting the spike protein to block ACE2 binding and viral entry.