CD28 Costimulatory Domain-Targeted Mutations Enhance Chimeric Antigen Receptor T-cell Function

Area of Science:

• Immunology
• Cancer Biology
• Cell Therapy

Background:

• Chimeric antigen receptor (CAR) T-cell therapy shows promise but faces challenges due to limited understanding of CAR T-cell biology and antitumor mechanisms.
• CARs with CD28 costimulatory domains can lead to T-cell exhaustion and reduced persistence, hindering therapeutic efficacy.

Purpose of the Study:

• To investigate the impact of specific CD28 subdomain mutations (YMNM, PRRP, PYAP) on CAR T-cell costimulation, function, and persistence.
• To enhance CAR T-cell antitumor activity and survival through optimized costimulation.

Main Methods:

• Generation of CAR T cells with null mutations in CD28 subdomains.
• In vivo studies in mice to assess survival advantage and CAR T-cell function.
• Ex vivo analysis of CAR T-cell sensitivity to antigen and PD-L1 stimulation, including cytokine production and exhaustion-related gene expression.

Main Results:

• CAR T cells with a PYAP CD28 endodomain mutation demonstrated a significant survival advantage in mice (100% survival vs. 50% for unmutated).
• Mutant CAR T cells exhibited increased sensitivity to antigen and PD-L1 stimulation, indicated by enhanced cytokine production.
• Reduction in exhaustion-related transcription factors and genes (Nfatc1, Nr42a, Pdcd1) was observed in mutant CAR T cells.

Conclusions:

• Mutations in the CD28 endodomain can optimize CAR T-cell costimulation, leading to improved survival and function.
• This strategy offers a pathway for developing more potent and persistent CAR T-cell therapies.
• Optimizing CAR T-cell costimulation is crucial for advancing the development of enhanced CAR T-cell therapies.