In vivo antibody diversification targeting a conserved coronavirus epitope.

Area of Science:

• Immunology
• Virology
• Structural Biology

Background:

• The CR3022 monoclonal antibody (mAb) targets a conserved epitope on the receptor-binding domain (RBD) of SARS-CoV.
• Diversifying antibody responses is crucial for combating evolving viral threats like SARS-CoV-2.

Purpose of the Study:

• To investigate the utility of human B cell receptor (BCR) knock-in mice for broadening antibody responses.
• To engineer enhanced antibodies against SARS-CoV-2 and related coronaviruses using BCR knock-in mice.

Main Methods:

• Immunization of high- and low-affinity CR3022 BCR knock-in mice with SARS-CoV-2 Wuhan RBD trimers.
• Characterization of antibody affinity, neutralization breadth, and structural analysis of key mutations.

Main Results:

• Generated antibodies retained SARS-CoV neutralization and showed enhanced affinity and neutralization against SARS-CoV-2 strains and variants (Delta, Omicron KP.3).
• Broadened reactivity was observed against bat coronaviruses WIV1 and BtKY72.
• Structural analysis identified mutations critical for enhanced binding and neutralization.

Conclusions:

• Human BCR-expressing mouse models are effective for generating antibodies with broad neutralizing activity against viral epitopes.
• This strategy holds promise for developing next-generation antibody therapeutics against diverse coronaviruses.