Broad cross-reactivity across sarbecoviruses exhibited by a subset of COVID-19 donor-derived neutralizing antibodies

• Main Authors: Claudia A. Jette, Alexander A. Cohen, Priyanthi N.P. Gnanapragasam, Frauke Muecksch, Yu E. Lee, Kathryn E. Huey-Tubman, Fabian Schmidt, Theodora Hatziioannou, Paul D. Bieniasz, Michel C. Nussenzweig, Anthony P. West, Jr., Jennifer R. Keeffe, Pamela J. Bjorkman, Christopher O. Barnes
• Format: Article
• Language: English
• Published: Elsevier 2021-09-01
• Series: Cell Reports
• Subjects: cryo-EM; coronavirus; neutralizing antibody; receptor-binding domain; sarbecovirus; SARS-CoV-2
• Online Access: http://www.sciencedirect.com/science/article/pii/S2211124721012146

Summary: Many anti-severe acute respiratory syndrome coronavirus 2 (anti-SARS-CoV-2) neutralizing antibodies target the angiotensin-converting enzyme 2 (ACE2) binding site on viral spike receptor-binding domains (RBDs). Potent antibodies recognize exposed variable epitopes, often rendering them ineffective against other sarbecoviruses and SARS-CoV-2 variants. Class 4 anti-RBD antibodies against a less-exposed, but more-conserved, cryptic epitope could recognize newly emergent zoonotic sarbecoviruses and variants, but they usually show only weak neutralization potencies. Here, we characterize two class 4 anti-RBD antibodies derived from coronavirus disease 2019 (COVID-19) donors that exhibit breadth and potent neutralization of zoonotic coronaviruses and SARS-CoV-2 variants. C118-RBD and C022-RBD structures reveal orientations that extend from the cryptic epitope to occlude ACE2 binding and CDRH3-RBD main-chain H-bond interactions that extend an RBD β sheet, thus reducing sensitivity to RBD side-chain changes. A C118-spike trimer structure reveals rotated RBDs that allow access to the cryptic epitope and the potential for intra-spike crosslinking to increase avidity. These studies facilitate vaccine design and illustrate potential advantages of class 4 RBD-binding antibody therapeutics.