Structure-guided development of a high-affinity human Programmed Cell Death-1: Implications for tumor immunotherapy

Area of Science:

• Immunology
• Structural Biology
• Cancer Immunotherapy

Background:

• Programmed Cell Death-1 (PD-1) is a key immune checkpoint receptor involved in T cell exhaustion.
• Its interaction with ligands PD-L1 and PD-L2 regulates immune responses.
• Understanding the PD-1 binding interface is crucial for developing targeted immunotherapies.

Purpose of the Study:

• To determine the crystal structure of the human PD-1 ectodomain and map its ligand-binding interface.
• To engineer a high-affinity PD-1 variant with enhanced immune modulatory properties.
• To evaluate the therapeutic potential of a novel chimeric PD-1 Ig fusion protein in combination therapy.

Main Methods:

• X-ray crystallography of human PD-1 ectodomain.
• Site-directed mutagenesis to create high-affinity PD-1 mutants (HA PD-1).
• Engineering of a soluble HA PD-1 Ig fusion protein.
• In vitro assays (binding affinity, T cell proliferation, cytokine production) and in vivo tumor models (Lewis lung carcinoma).

Main Results:

• The crystal structure revealed the PD-1 binding interface.
• A high-affinity mutant PD-1 (HA PD-1) showed significantly increased binding affinity to PD-L1 and PD-L2.
• HA PD-1 Ig enhanced T cell responses in vitro and demonstrated synergistic anti-tumor effects with radiation therapy in vivo, reducing tumor burden and promoting immunological memory.

Conclusions:

• Structural insights guided the development of an effective high-affinity PD-1 Ig fusion protein.
• The engineered HA PD-1 Ig possesses potent immune-modulatory capabilities.
• Combination therapy involving enhanced PD-1 blockade shows promise for improving cancer immunotherapy outcomes.