# Recurrent SARS-CoV-2 Omicron broadly neutralizing humanized antibodies in different single human VH1-2-rearranging mouse models

## TL;DR

Researchers developed a new mouse model that produces human-like antibodies to neutralize SARS-CoV-2 Omicron variants more effectively than previous models.

## Contribution

A new humanized mouse model with longer CDR3s was developed, producing more potent antibodies against SARS-CoV-2 Omicron subvariants.

## Key findings

- Antibodies from the new model neutralized Omicron variants more potently than those from the prior model.
- Both models produced antibodies that reduced viral titers in mouse models of Omicron BQ1.1.
- The new antibodies target a conserved epitope on the Omicron spike protein.

## Abstract

Mouse models that generate antibody repertoires from human gene segments that predominantly encode single antibody lineages are useful for evaluating preclinical HIV-1 vaccine strategies. One such model was used for discovery of a humanized antibody that potently neutralized SARS-CoV-2 variants through the first several Omicron variants. Here, we describe a new, related humanized mouse model that generates a different antibody repertoire. Immunization with a SARS-CoV-2 Omicron spike protein immunogen elicited related humanized antibodies from both models that potently neutralized Omicron variants, with antibodies from the new model being more potent. Both sets of new antibodies reduced Omicron BQ1.1 viral titers in mouse models. These studies validate use of such mouse models for discovery of humanized antibodies against newly evolving pathogens.

During V(D)J recombination, antibody diversity is enhanced by nontemplated 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 Vκ1-33, 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 related 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 subvariants. 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 related in their epitope recognition to recently described antibodies from Omicron-infected humans. These studies validate the utility of single human VH- and Vκ-rearranging mice for discovering humanized antibodies that neutralize emerging pathogens.