In vivo evolution of antibody CR3022 expands cross-neutralization of SARS-CoV-2 variants and informs pan-sarbecovirus immunity

The epitope that monoclonal CR3022 binds to represents a promising target for broad protection against a wide range of human and zoonotic coronaviruses. We develop a powerful model to evaluate antibody affinity maturation in vivo using immunoglobulin (Ig)-humanized mice that express the predicted germline heavy chain of antibody CR3022. Severe acute respiratory syndrome coronavirus (SARS-CoV)/SARS-CoV-2 sequential immunization leads to the convergent evolution of the germline CR3022 through somatic hypermutation (SHM), resembling the affinity-matured CR3022 from a human but now also adapting to key variants and divergent sarbecoviruses. While simple prime-boost strategies drive CR3022-epitope targeting, an intensive vaccination protocol elicits dominant responses to other epitopes. X-ray crystal structures reveal that SARS-CoV-2-neutralizing CR3022-like antibodies exhibit enhanced affinity by increasing polar and electrostatic interactions. Overall, these findings show that CR3022-like clones can be readily adapted through SHM to increase breadth and potency to sarbecoviruses by relatively minor shifts in affinity with appropriate vaccination strategies.