Shaping Functional Avidity of CAR T Cells: Affinity, Avidity, and Antigen Density That Regulate Response

Area of Science:

• Immunotherapy
• Molecular immunology
• Cancer biology

Background:

• Chimeric antigen receptors (CARs) redirect T cells to target cancer cells.
• CAR T-cell therapy has succeeded in blood cancers but faces challenges in solid tumors.
• Optimizing CAR design is critical for effective solid tumor immunotherapy.

Purpose of the Study:

• To investigate the functional impact of CAR biophysical binding properties (affinity, avidity, antigen density) on T-cell activity.
• To establish a controllable experimental system for evaluating CAR T-cell responses.
• To inform the rational design of CARs for solid cancer treatment.

Main Methods:

• Generated a series of CARs targeting melanoma antigen Tyr/HLA-A2 with varying binding affinities (K_D 4–400 nmol/L).
• Transduced CARs into T cells and sorted by receptor expression levels.
• Assessed CAR T-cell activity against target cells with different antigen densities in vitro and in vivo.

Main Results:

• Observed nonmonotonic relationships between CAR affinity, antigen density, and T-cell function.
• Identified an interrelation between CAR avidity and target antigen density.
• In vitro and in vivo antitumor activity measurements confirmed these findings.

Conclusions:

• CAR T-cell function is significantly influenced by the interplay of binding affinity, avidity, and target antigen density.
• Understanding these biophysical properties is key to improving CAR T-cell therapy for solid tumors.
• This research provides a foundation for the rational design of next-generation CAR T cells.