Antigenic site II on fusion glycoprotein of respiratory syncytial virus (None commonly used; occasionally referred to as "site II" in the literature[1][4])

Antigenic site II is a well-defined epitope located on the fusion (F) glycoprotein of the respiratory syncytial virus (RSV). The F protein is essential for viral entry, mediating the fusion of the viral envelope with host cell membranes. Site II is highly conserved and accessible in both prefusion and postfusion conformations of the F protein. It is the target of clinically used monoclonal antibodies such as palivizumab, which prevent RSV infection by binding to site II and blocking the conformational changes necessary for membrane fusion. The structural and antigenic features of site II have made it a key target for both prophylactic antibody therapy and rational vaccine design against RSV[1][2][4].

Other names

Site IIAntigenic site IIRSV F antigenic site IIPalivizumab epitope (because it is the binding site for the monoclonal antibody palivizumab)[4]

Neutralization: Antibodies binding to antigenic site II block the conformational change of the F protein required for viral membrane fusion, thus preventing RSV entry into host cells[4]. Steric inhibition: Antibodies at this site directly block essential protein rearrangement during infection.