Complementarity-determining region clustering may cause CAR-T cell dysfunction.

Area of Science:

• Immunology
• Cancer Biology
• Biotechnology

Background:

• Chimeric antigen receptor (CAR)-T cell therapy shows promise for cancer treatment.
• Designing optimal CARs is complex, with single-chain variable fragments (scFvs) defining specificity via complementarity-determining regions (CDRs).

Purpose of the Study:

• To investigate the impact of CDR loops on CAR clustering and T cell function.
• To identify mechanisms of antigen-independent CAR-T cell activation and dysfunction.

Main Methods:

• Engineered CARs with identical frameworks but varying CDR sequences.
• Assessed CAR clustering on T cell surfaces.
• Measured antigen-independent T cell activation markers (cell size, IFN-γ secretion).
• Evaluated CAR-T cell exhaustion, cell death, and tumor cell responsiveness.

Main Results:

• CDR loops were found to mediate CAR clustering on the T cell surface.
• CAR clustering induced antigen-independent T cell activation, evidenced by increased cell size and IFN-γ secretion.
• This tonic signaling resulted in CAR-T cell exhaustion, activation-induced cell death, and reduced anti-tumor activity.

Conclusions:

• Antigen-independent tonic signaling can be triggered by CDR-mediated CAR clustering.
• This phenomenon, not predictable from scFv sequences alone, impacts CAR-T cell efficacy.
• Evaluating unstimulated CAR-T cell activity is crucial for predicting therapeutic outcomes.