Generation of antigen-specific and functionally stable Treg cells from effector/memory T cells for cell therapy of immunological diseases

One strategy for antigen-specific immunosuppression is to convert antigen-specific conventional T cells (Tconvs) into Foxp3 ⁺ regulatory T cells (Tregs) that are as stably suppressive as naturally occurring Tregs (nTregs). To achieve the conversion in vitro for mice and humans, we induced high Foxp3 expression in antigen- and IL-2-stimulated Tconvs by CDK8/19 inhibition, and established Treg-specific epigenetic changes by depriving CD28 co-stimulation during in vitro Treg induction to specifically promote the expression of Treg signature genes, especially Foxp3 . Repeating this process, with intermittent resting cultures containing IL-2 only, enabled in a short duration efficient conversion of naïve as well as effector/memory CD4 ⁺ Tconvs, including Th1, Th2 and Th17 cells, into Foxp3 ⁺ Tregs, which were similar to nTregs in transcription and epigenetic modification. Induced Tregs (iTregs) thus generated were indeed functionally and phenotypically stable in vivo and effectively suppressed inflammatory bowel disease and graft-versus-host disease in mouse models. Adoptive cell therapy with such effector/memory Tconv-derived, functionally stable, iTregs would be able to achieve antigen- and disease-specific treatment of immunological diseases.