HTGTS-Rep-Seq for Humanized Antibodies that Broadly Neutralize Omicron Sub-variants
During V(D)J recombination antibody diversity is enhanced by non-templated junctional modifications that generate immensely diverse heavy chain (HC) and light chain (LC) complementarity-determining 3 antigen-contact regions (CDR3s). We previously developed a mouse model that generates diverse antibody repertoires by rearranging a single human VH1-2 and Vk1-33, associated with highly diverse CDR3s generated by V(D)J recombination with mouse Ds and/or Js. Immunization of this model with SARS-CoV-2 D614G spike elicited an antibody that potently neutralized SARS-CoV-2 variants through Omicron BA.2.754. Here, we report a next generation mouse model in which a single VH1-2 rearranges to human D3-3 and JH6, generating diverse HC-CDR3s much longer on average than those of our prior model. Omicron BA.4/.5 spike ferritin nanoparticle-immunization of the new model elicited four highly-related humanized antibodies that potently neutralize downstream Omicron sub-variants. All four antibodies had 12 AA HC-CDR3s with two aromatic amino acids that engage an epitope comprising a hydrophobic patch opened-up by early omicron lineage mutations and conserved in subsequent variants. Immunization of our prior, shorter CDR3-based model, elicited slightly less potent neutralizing antibodies that bound the same Omicron epitope, and were similar in all other aspects to those from the long, fully-human CDR3 model. One tested antibody from each set reduced lung viral titers in a mouse-adapted BQ1.1 challenge. The antibodies we describe are highly related to, but more potent than, recently described antibodies from omicron-infected humans.  These studies validate the utility of single human VH- and Vk-rearranging mice for discovering humanized antibodies that neutralize emerging pathogens.