The Optimization of Bioorthogonal Epitope Ligation within MHC-I Complexes

Area of Science:

• Immunology
• Biochemistry
• Chemical Biology

Background:

• Cytotoxic T-lymphocyte (CTL) activation via antigen recognition is crucial for adaptive immunity against viruses and cancers.
• Studying the vast diversity of peptides binding to Major Histocompatibility Complex type-I (MHC-I) on cells is challenging due to limited available methods.
• Existing approaches struggle to quantify the full spectrum of peptide-MHC-I complexes (pMHC-I) present on cellular surfaces.

Purpose of the Study:

• To introduce and validate a novel bioorthogonal chemistry-based approach for quantifying specific pMHC-I complexes on cells.
• To demonstrate the feasibility of modifying epitope peptides with bioorthogonal groups for detection.
• To establish a new tool for analyzing the peptide repertoire presented by MHC-I.

Main Methods:

• Utilizing bioorthogonal chemistry to modify epitope peptides with specific functional groups.
• Ensuring modified peptides maintain wild-type-like binding to MHC-I.
• Employing Cu(I)-catalyzed Huisgen cycloaddition for bioorthogonal ligation with fluorogenic probes.
• Quantifying specific pMHC-I complexes on cell surfaces.

Main Results:

• Successfully modified epitope peptides with bioorthogonal groups that retained MHC-I binding.
• Demonstrated efficient bioorthogonal ligation using fluorogenic probes and click chemistry.
• Enabled the quantification of specific pMHC-I complexes on cells.
• Developed a method for detecting antigenic peptides lacking prior detection tools.

Conclusions:

• The developed bioorthogonal chemistry approach provides a powerful new tool for quantifying pMHC-I complexes.
• This method overcomes limitations in studying the peptide-MHC-I repertoire diversity.
• It facilitates the quantification of previously undetectable antigenic peptides, enhancing the antigen presentation toolkit.