High-affinity PD-1 molecules deliver improved interaction with PD-L1 and PD-L2

Area of Science:

• Immunology
• Molecular Biology
• Biotechnology

Background:

• Programmed death (PD)-1 is a key inhibitory checkpoint molecule crucial for immune homeostasis.
• Soluble PD-1 (sPD-1) can block PD-1/PD-L1 interactions, boosting T cell antitumor functions.
• Natural sPD-1 exhibits low affinity for PD-L1, limiting its therapeutic use.

Purpose of the Study:

• To engineer a high-affinity PD-1 variant for enhanced binding to PD-L1 and PD-L2.
• To evaluate the therapeutic potential of this engineered PD-1 variant in cancer immunotherapy.

Main Methods:

• Directed molecular evolution and phage display technology were employed to generate PD-1 variants.
• Structural analysis identified key amino acid mutations responsible for affinity enhancement.
• Functional assays assessed the mutant's ability to block PD-1/ligand interactions and enhance lymphocyte responses.

Main Results:

• A PD-1 variant with significantly increased affinity for PD-L1 (approx. 3000-fold) and PD-L2 (approx. 70-fold) was successfully generated.
• Mutations at amino acid positions 124 and 132 were identified as critical for the enhanced binding.
• The high-affinity PD-1 mutant effectively competed with PD-L1/PD-L2 antibodies and promoted T cell proliferation and IFN-γ release.

Conclusions:

• The engineered high-affinity PD-1 variant demonstrates superior binding to PD-L1 and PD-L2 compared to natural sPD-1.
• This variant has the potential to serve as a novel therapeutic agent for immune-checkpoint blockade in cancer therapy.