Chimeric antigen receptor costimulation domains modulate human regulatory T cell function.

Area of Science:

• Immunology
• Cell Therapy
• Transplantation Immunology

Background:

• Regulatory T cells (Tregs) are crucial for immune tolerance and preventing autoimmune diseases.
• Adoptive Treg immunotherapy shows promise but can be improved by antigen-specific, long-lived Treg cells.
• Chimeric antigen receptors (CARs) can be engineered onto Tregs to confer antigen specificity.

Purpose of the Study:

• To investigate the impact of different costimulatory domains within CARs on Treg function and phenotype.
• To evaluate the efficacy of antigen-specific CAR Tregs in suppressing immune responses in vitro and in vivo.
• To determine the optimal CAR design for therapeutic applications in immune suppression.

Main Methods:

• Primary human Tregs were genetically modified with CARs containing various costimulatory domains (CD28, 4-1BB).
• In vitro analyses assessed Treg phenotype (Foxp3 expression, surface markers) and function (cytokine production, suppressive capacity).
• In vivo studies evaluated CAR Treg accumulation, antigen-specific T cell suppression, and inhibition of graft rejection in a relevant model.

Main Results:

• CAR and costimulatory domain presence did not affect Foxp3 expression but influenced Treg surface phenotype and cytokine production.
• CD28 costimulation maintained Treg suppressive function, while 4-1BB costimulation did not.
• In vivo, CAR Tregs localized to antigen-expressing sites and suppressed effector T cells; only CD28-based CAR Tregs potently inhibited graft rejection.

Conclusions:

• CD28 signaling is critical for maintaining CAR Treg suppressive function and in vivo efficacy.
• Antigen-specific CAR Tregs, particularly those with CD28 costimulation, demonstrate potent tissue-specific immune suppression.
• CD28-based CAR Tregs represent a promising strategy for clinical applications in transplantation and autoimmune diseases.