Novel Lineages of SARS-CoV-2 Receptor Binding Domain Monoclonal Antibodies Demonstrate Broad and Potent Neutralization Across SARS-CoV-2 and Other Sarbecoviruses 9206

Abstract Description SARS-CoV-2 neutralizing monoclonal antibodies (mAbs) serve as therapeutic agents to prevent or treat SARS-CoV-2 infection and have potential use against related coronaviruses (sarbecoviruses). However, evolving SARS-CoV-2 variants have rendered many mAbs ineffective. Therefore, we sought to identify potent mAbs with greater cross-reactivity; focusing on a donor with cross-reactive serum neutralization that has longitudinal samples spanning vaccine doses and a breakthrough infection. Using single-cell sorting with S-2P and RBD probes; Rapid Assembly, Transfection and Production of Immunoglobulins (RATP-Ig); and 10X Genomics sequencing, we identified multiple B cell lineages with shared genetic origins, neutralization patterns, and epitope target. The mAbs were isolated from multiple timepoints, including several isolated after three vaccine doses with the ancestral sequence. Notably, these mAbs exhibited broad neutralization despite a lack of exposure to newer variants via vaccination or infection. The mAbs neutralized all SARS-CoV-2 variants including the latest, XEC, as well as multiple SARS-CoV and SARS-CoV-related animal viruses. Based on binding competition assays, they mapped to a class I/IV epitope. Cryo-EM studies defined a compact, conserved epitope that avoids variable amino acid positions, consistent with broad cross-reactivity. Continued investigation of these mAbs may prove useful for the development of clinical therapeutics and optimization of vaccine strategies. Topic Categories Vaccines and Immunotherapy (VAC)