A vulnerable, membrane-proximal site in human respiratory syncytial virus F revealed by a prefusion-specific single-domain antibody.
Rossey, I., Hsieh, C.L., Sedeyn, K., Ballegeer, M., Schepens, B., Mclellan, J.S., Saelens, X.(2021) J Virol 95
- PubMed: 33692208 
- DOI: https://doi.org/10.1128/JVI.02279-20
- Primary Citation of Related Structures:  
7LVU, 7LVW - PubMed Abstract: 
Human respiratory syncytial virus (RSV) is a major cause of lower respiratory tract disease, especially in young children and the elderly. The fusion protein (F) exists in a pre- and postfusion conformation and is the main target of RSV-neutralizing antibodies. Highly potent RSV-neutralizing antibodies typically bind sites that are unique to the prefusion conformation of F. In this study we screened a single-domain antibody (VHH) library derived from a llama immunized with prefusion-stabilized F and identified a prefusion F-specific VHH that can neutralize RSV A at subnanomolar concentrations. Structural analysis revealed that this VHH primarily binds to antigenic site I while also making contacts with residues in antigenic site III and IV. This new VHH reveals a previously underappreciated membrane-proximal region sensitive for neutralization. Importance RSV is an important respiratory pathogen. This study describes a prefusion F-specific VHH that primarily binds to antigenic site I of RSV F. This is the first time that a prefusion F-specific antibody that binds this site is reported. In general, antibodies that bind to site I are poorly neutralizing, whereas the VHH described here neutralizes RSV A at subnanomolar concentrations. Our findings contribute to insights into the RSV F antigenic map.
Organizational Affiliation: 
VIB-UGent Center for Medical Biotechnology, Technologiepark-Zwijnaarde 75, 9052 Ghent, Belgium.