Respiratory syncytial virus fusion glycoprotein F (antigenic site II) (RSV F (site II))

The Respiratory syncytial virus (RSV) fusion glycoprotein F is a Class I viral fusion protein that is essential for the viral life cycle, mediating both the fusion of the viral envelope with the host cell membrane and the subsequent formation of syncytia between infected and healthy cells (McLellan et al., 2013, Science). Antigenic site II is a highly conserved, conformational epitope located on the F protein, characterized by a helix-turn-helix motif involving residues 262–275 (Arbiza et al., 1992, J Gen Virol). This specific site is present on both the metastable pre-fusion (preF) and the stable post-fusion (postF) conformations of the protein, making it a reliable target for immune recognition. Site II is the primary target of Palivizumab, a humanized monoclonal antibody used clinically for the prevention of severe lower respiratory tract disease in high-risk infants (The IMpact-RSV Study Group, 1998, Pediatrics). By binding to site II, antibodies prevent the critical conformational changes necessary for the F protein to execute membrane fusion, effectively neutralizing the virus's ability to infect host cells (Magro et al., 2012, PNAS). While newer targets such as site Ø (specific to the pre-fusion form) have shown higher neutralizing potency, site II remains a cornerstone of RSV immunology due to its high degree of conservation across both RSV A and B subtypes and its established success in passive immunization strategies (Graham, 2017, Immunol Rev).

Other names

RSV F proteinRespiratory syncytial virus fusion proteinAntigenic site IISite ARSV F site II epitope

Neutralization of viral entry by binding to a highly conserved helix-turn-helix motif, which sterically inhibits the structural rearrangements of the F protein required to transition from the pre-fusion to the post-fusion state, thereby preventing the fusion of viral and host cell membranes (Magro et al., 2012, PNAS; McLellan et al., 2013, Science).