T cell circuits that sense antigen density with an ultrasensitive threshold

Area of Science:

• Immunology
• Synthetic Biology
• Cancer Therapy

Background:

• Overexpressed tumor antigens like EGFR and HER2 are targets for chimeric antigen receptor (CAR)-T cell therapy.
• CAR-T cells can cause toxic off-tumor effects due to low-level antigen expression on normal tissues.
• Existing CAR-T cell therapies lack precise antigen-density discrimination.

Purpose of the Study:

• To engineer a T cell circuit for precise discrimination of target antigen density.
• To improve the safety and efficacy of CAR-T cell therapy by minimizing off-tumor toxicity.
• To create a sigmoidal response threshold for T cell activation based on antigen levels.

Main Methods:

• Designed a two-step positive-feedback circuit using a low-affinity synthetic Notch receptor and a high-affinity CAR.
• The synthetic Notch receptor controls the expression of the HER2-specific CAR.
• Tested T cells with the engineered circuit in vitro and in vivo for target cell discrimination.

Main Results:

• The engineered circuit enables T cells to discriminate targets based on a sigmoidal antigen-density threshold.
• Increasing HER2 density cooperatively enhances both CAR expression and T cell activation.
• T cells demonstrated sharp discrimination between normal and cancer cells with 100-fold HER2 density difference.

Conclusions:

• The novel feedback circuit allows therapeutic T cells to accurately distinguish cancer cells from normal tissues.
• This approach significantly improves the safety profile of CAR-T cell therapy by preventing off-tumor reactions.
• The engineered T cells exhibit enhanced specificity and potential for more effective cancer treatment.