Directed evolution of a stem-helix-targeting antibody enables MERS-CoV cross-neutralization through enhanced binding...

Area of Science:

• Virology
• Immunology
• Structural Biology

Background:

• Broadly neutralizing antibodies (bnAbs) targeting conserved regions of betacoronavirus spike proteins are crucial for pandemic preparedness.
• The S2 subunit's conserved regions offer potential targets for pan-betacoronavirus immunity.

Purpose of the Study:

• To isolate and characterize human monoclonal antibodies targeting conserved betacoronavirus spike regions.
• To engineer an antibody for enhanced binding and neutralization of divergent betacoronaviruses, specifically MERS-CoV.
• To elucidate the structural basis for antibody-epitope interactions and engineering strategies.

Main Methods:

• Isolation of monoclonal antibody CC65.1 from SARS-CoV-2 convalescent donor.
• Binding and neutralization assays against various betacoronaviruses (SARS-CoV-2, MERS-CoV, sarbecoviruses).
• Directed evolution to enhance antibody affinity for MERS-CoV spike S2 region.
• High-resolution structural analysis of antibody-epitope complexes.

Main Results:

• CC65.1 targets the conserved S2 stem helix region and neutralizes sarbecoviruses, including SARS-CoV-2.
• Engineered variants of CC65.1 acquired potent MERS-CoV-neutralizing activity through enhanced binding affinity.
• Structural analysis identified key mutations responsible for improved binding and epitope engagement.

Conclusions:

• Rational antibody engineering can expand the breadth of bnAbs against divergent betacoronaviruses.
• Engineered bnAbs targeting the S2 region represent promising candidates for broad betacoronavirus countermeasures.
• This strategy provides a framework for developing cross-lineage immunity against future pandemic threats.