Replacing the complementarity-determining regions in a human antibody with those from a mouse

Area of Science:

• Immunology
• Molecular Biology
• Biochemistry

Background:

• Antibody variable domains contain hypervariable regions, known as complementarity-determining regions (CDRs), which form the antigen-binding site.
• Transplanting antigen-binding sites between antibody frameworks is a key challenge in antibody engineering.

Purpose of the Study:

• To investigate the feasibility of transplanting an antigen-binding site by grafting CDRs from a mouse antibody to a human antibody framework.
• To determine if this 'CDR replacement' strategy can confer the original antibody's antigen-binding properties to the new construct.

Main Methods:

• The complementarity-determining regions (CDRs) from the heavy-chain variable region of mouse antibody B1-8 were grafted onto the corresponding CDR positions of a human myeloma protein.
• The engineered human-mouse chimeric antibody was tested for its ability to bind the hapten NP-cap, and its affinity was compared to the original mouse antibody.

Main Results:

• The engineered antibody, when combined with the B1-8 mouse light chain, successfully acquired the hapten-binding affinity of the original mouse antibody B1-8.
• The affinity constant (KNP-cap) for the engineered antibody was measured at 1.9 microM, closely matching the B1-8 antibody's affinity of 1.2 microM.

Conclusions:

• CDR grafting is a viable strategy for transferring antigen-binding specificity between antibody frameworks.
• This 'CDR replacement' technique offers a promising approach for developing human monoclonal antibodies by leveraging the specificity of existing mouse monoclonal antibodies.