Construction of small molecular CTLA4 analogs with CD80-binding affinity

Area of Science:

• Immunology
• Protein Engineering
• Biotechnology

Background:

• Approved CTLA4-Fc fusion proteins and monoclonal antibodies face limitations due to their large size.
• Fibronectin type III (FN3) monobodies are explored as smaller, alternative analogs to macromolecular antibodies.

Purpose of the Study:

• To engineer novel small molecular analogs of CTLA4 using FN3 monobody scaffold.
• To investigate the binding affinity and inhibitory potential of these engineered proteins against CD80.

Main Methods:

• Grafting of CTLA4-derived peptide EL16 (from CDR3) and CDR1 onto the FN3 scaffold to create CFN13.
• Fusion of CFN13 with human IgG1 Fc to enhance its half-life, generating CFN13-Fc.
• Assessment of CD80 binding affinity and inhibition of CTLA4-CD80 interaction using various concentrations.

Main Results:

• CFN13 demonstrated 80% binding affinity compared to native CTLA4.
• CFN13-Fc exhibited dose-dependent binding to CD80 and inhibited CTLA4-Fc/CD80 interaction by up to 41.0%.
• Peptide EL16 significantly inhibited CFN13-Fc binding to CD80, indicating shared binding sites and the importance of the CDR3 motif.

Conclusions:

• Engineered FN3 monobody CFN13-Fc serves as a potent small molecular analog of CTLA4.
• The study highlights the contribution of CTLA4's CDR3 motif in CD80 binding.
• These findings offer valuable insights for developing alternative immunomodulatory protein therapeutics.