Affinity maturation endows potent activity onto class 6 SARS-CoV-2 broadly neutralizing antibodies
Abstract
The emergence of SARS-CoV-2 variants of concern (VOCs) has greatly diminished the neutralizing activity of previously FDA-approved monoclonal antibodies (mAbs), including that of antibody cocktails and of first-generation broadly neutralizing antibodies such as S309 (Sotrovimab). In contrast, antibodies targeting cryptic conformational epitopes of the receptor binding domain (RBD) have demonstrated broad activity against emerging variants, but exert only moderate neutralizing activity, which has so far hindered clinical development. Here, we utilize in vitro display technology to identify and affinity-mature antibodies targeting the cryptic class 6 epitope, accessible only in the “up” conformation of the SARS-CoV-2 spike trimer. Increasing antibody affinity into the low picomolar range endowed potent neutralization of VOCs and protection of hACE2 mice from viral challenge. Cryoelectron microscopy and crystal structures of two affinity-matured antibodies (4C12-B12 and 4G1-C2) in complex with RBD highlighted binding modes and epitopes distal from mutational hotspots commonly overserved in VOCs, providing direct structural insights into the observed mutational resistance. Moreover, we further demonstrate that antibodies targeting the class 6 epitope, rather than being an artifact of in vitro selection, are common in the IgG1 + memory B cell repertoire of convalescent patients and can be induced in human antibody V-gene transgenic mice through immunization. Our results highlight the importance of very high (picomolar) affinity in the development of neutralizing antibodies and vaccines and suggest an affinity threshold in the provision of broad and long-lasting immunity against SARS-CoV-2.
Article Details
Journal Info
Proceedings of the National Academy of Sciences
National Academy of Sciences
Authors (27)
Ohan Mazigi
Garvan Institute of Medical Research
David B. Langley
Garvan Institute of Medical Research
Jake Y. Henry
Garvan Institute of Medical Research
Deborah L. Burnett
Garvan Institute of Medical Research
Meghna Sobti
University of New South Wales Sydney, St. Vincent’s Clinical School, Faculty of Medicine
Gregory J. Walker
University of New South Wales Sydney, School of Biomedical Sciences, Faculty of Medicine
Romain Rouet
Garvan Institute of Medical Research
Harikrishnan Balachandran
University of New South Wales Sydney, School of Biomedical Sciences, Faculty of Medicine
Helen Lenthall
Garvan Institute of Medical Research
Jennifer Jackson
Garvan Institute of Medical Research
Stephanie Ubiparipovic
Garvan Institute of Medical Research
Peter Schofield
Simon H. J. Brown
School of Chemistry and Molecular Bioscience, Molecular Horizons, and Australian Research Council Centre for Cryo-electron Microscopy of Membrane Proteins, University of Wollongong
Sebastian R. Schulz
Division of Molecular Immunology, Friedrich-Alexander University Erlangen-Nürnberg
Markus Hoffmann
Infection Biology Unit, German Primate Center–Leibniz Institute for Primate Research
Stefan Pöhlmann
Infection Biology Unit, German Primate Center–Leibniz Institute for Primate Research
Jeffrey Post
Prince of Wales Hospital
Marianne Martinello
Kirby Institute, University of New South Wales Sydney
Golo Ahlenstiel
Blacktown Mt. Druitt Hospital
Anthony Kelleher
Kirby Institute, University of New South Wales Sydney
William D. Rawlinson
University of New South Wales Sydney, School of Biomedical Sciences, Faculty of Medicine
Stuart G. Turville
University of New South Wales Sydney, School of Biomedical Sciences, Faculty of Medicine
Rowena A. Bull
University of New South Wales Sydney, School of Biomedical Sciences, Faculty of Medicine
Alastair G. Stewart
University of New South Wales Sydney, St. Vincent’s Clinical School, Faculty of Medicine
Hans-Martin Jäck
Division of Molecular Immunology, Friedrich-Alexander University Erlangen-Nürnberg
Christopher C. Goodnow
Garvan Institute of Medical Research
Daniel Christ