Respiratory syncytial virus prefusion F protein, antigenic site II (RSV F Site II)

The Respiratory syncytial virus (RSV) prefusion F protein, antigenic site II, is a critical neutralizing epitope located on the RSV fusion (F) glycoprotein [1, 2]. The F protein is a class I viral fusion protein that mediates the fusion of the viral envelope with the host cell membrane, a process essential for viral entry and infection [5, 12]. Antigenic site II is a highly conserved, conformational epitope found on both the metastable prefusion and the stable postfusion forms of the F protein [1, 6]. It is the primary target of the monoclonal antibody palivizumab (Synagis), which is used for the prophylaxis of severe RSV disease in high-risk infants [1, 11]. In the context of disease, RSV is a leading cause of lower respiratory tract infections, such as bronchiolitis and pneumonia, particularly in infants and the elderly [2, 5]. Targeting site II with neutralizing antibodies prevents the structural rearrangement of the F protein, thereby inhibiting membrane fusion and viral entry [1, 13]. While newer antibodies targeting site Ø (such as nirsevimab) offer higher potency, site II remains a foundational target in RSV immunology and vaccine design [6, 15]. Therapeutic challenges include the emergence of viral escape mutants with mutations in the site II region and the need for high antibody concentrations to achieve effective protection [1, 9].

Other names

Antigenic site IISite II of RSV F proteinAntigenic site APalivizumab binding siteRSV fusion glycoprotein site II

Neutralization of the virus by binding to the F protein and blocking the fusion of viral and cellular membranes, thereby preventing viral entry into host cells.