Potent and broadly neutralizing antibodies against sarbecoviruses elicited by single ancestral SARS-CoV-2 infection

Abstract

Monoclonal antibody (mAb) therapeutics hold promise for both preventing and treating infectious diseases, especially among vulnerable populations. However, the emergence of various variants of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) presents challenges for current mAb treatments, emphasizing the need for more potent and broadly neutralizing antibodies. In this study, we employed an unbiased screening approach to discover broadly neutralizing antibodies and successfully isolated two mAbs from individuals with only exposure to ancestral SARS-CoV-2. One of these antibodies, CYFN1006-1, exhibited robust cross-neutralization against a spectrum of SARS-CoV-2 variants, including the latest JN.1 and KP.2 variants, with consistent IC50 values ranging from [~]1 to 5 ng/mL. Notably, it also displayed broad neutralization activity against SARS-CoV and related sarbecoviruses, such as WIV1, SHC014, RaTG13, and GD-Pangolin. Structural analysis revealed that these mAbs target shared hotspot but mutation-resistant epitopes, with their Fabs locking the RBD in the "down" conformation through interactions with adjacent Fabs and RBDs, and cross-linking Spike trimers into di-trimers to block viral infection. In vivo studies conducted in a JN.1-infected hamster model validated the protective efficacy of CYFN1006-1, emphasizing its therapeutic potential. These findings suggest that, through meticulous approaches, rare antibodies with cross-neutralization activities against SARS-CoV-2 and related sarbecoviruses can be identified from individuals with exclusively ancestral virus exposure.