A vulnerable, membrane-proximal site in human respiratory syncytial virus F revealed by a prefusion-specific single-domain antibody

Iebe Rossey; Ching-Lin Hsieh; Koen Sedeyn; Marlies Ballegeer; Bert Schepens; Jason S Mclellan; Xavier Saelens

doi:10.1128/JVI.02279-20

A vulnerable, membrane-proximal site in human respiratory syncytial virus F revealed by a prefusion-specific single-domain antibody

J Virol. 2021 May 10;95(11):e02279-20. doi: 10.1128/JVI.02279-20. Epub 2021 Mar 10.

Authors

Iebe Rossey^{1

2

3}, Ching-Lin Hsieh⁴, Koen Sedeyn^{1

2

3}, Marlies Ballegeer^{1

2

3}, Bert Schepens^{1

2

3}, Jason S Mclellan⁴, Xavier Saelens^{5

2

3}

Affiliations

¹ VIB-UGent Center for Medical Biotechnology, Technologiepark-Zwijnaarde 75, 9052 Ghent, Belgium.
² Department of Biomedical Molecular Biology, Ghent University, Technologiepark-Zwijnaarde 71, 9052 Ghent, Belgium.
³ Department of Biochemistry and Microbiology, Ghent University, Technologiepark-Zwijnaarde 75, 9052 Ghent, Belgium.
⁴ Department of Molecular Biosciences, The University of Texas at Austin, Austin, Texas, USA 78712.
⁵ VIB-UGent Center for Medical Biotechnology, Technologiepark-Zwijnaarde 75, 9052 Ghent, Belgium xavier.saelens@vib-ugent.be.

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.ImportanceRSV 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.