Induced Regulatory T Cells Promote Tolerance When Stabilized by Rapamycin and IL-2 In Vivo

Abstract

Natural regulatory T cells (nTregs) play an important role in tolerance; however, the small numbers of cells obtainable potentially limit the feasibility of clinical adoptive transfer. Therefore, we studied the feasibility and efficacy of using murine-induced regulatory T cells (iTregs) for the induction of tolerance after bone marrow transplantation. iTregs could be induced in large numbers from conventional donor CD4 and CD8 T cells within 1 wk and were highly suppressive. During graft-versus-host disease (GVHD), CD4 and CD8 iTregs suppressed the proliferation of effector T cells and the production of proinflammatory cytokines. However, unlike nTregs, both iTreg populations lost Foxp3 expression within 3 wk in vivo, reverted to effector T cells, and exacerbated GVHD. The loss of Foxp3 in iTregs followed homeostatic and/or alloantigen-driven proliferation and was unrelated to GVHD. However, the concurrent administration of rapamycin, with or without IL-2/anti–IL-2 Ab complexes, to the transplant recipients significantly improved Foxp3 stability in CD4 iTregs (and, to a lesser extent, CD8 iTregs), such that they remained detectable 12 wk after transfer. Strikingly, CD4, but not CD8, iTregs could then suppress Teff proliferation and proinflammatory cytokine production and prevent GVHD in an equivalent fashion to nTregs. However, at high numbers and when used as GVHD prophylaxis, Tregs potently suppress graft-versus-leukemia effects and so may be most appropriate as a therapeutic modality to treat GVHD. These data demonstrate that CD4 iTregs can be produced rapidly in large, clinically relevant numbers and, when transferred in the presence of systemic rapamycin and IL-2, induce tolerance in transplant recipients.

Chronic graft-versus-host disease: biological insights from preclinical and clinical studies

“…122 Treg number or function perturbations lead to the development of autoimmune diseases and are thought to contribute to aGVHD and cGVHD pathology. 8,10,123 Both preclinical and clinical studies demonstrate that donor graft Treg number inversely correlates with aGVHD, [124][125][126][127][128] and cGVHD is associated with decreased numbers of circulating Tregs. 21,[129][130][131] Factors contributing to diminished Treg numbers in cGVHD recipients remain to be fully elucidated although there are multiple candidates including diminished thymic production, reduced proliferative capacity of naive Tregs, 132 and a failure in memory Treg survival due to their increased susceptibility to apoptosis.…”

Therapeutic regulatory T-cell adoptive transfer ameliorates established murine chronic GVHD in a CXCR5-dependent manner

“…9 These complexes preferentially bind to CD25 hi cells, which results in Treg expansion in a variety of disease models. [9][10][11] As a result, IL-2/mAb complexes may be superior to IL-2 for Treg expansion in cGVHD. Treg infusions also increase Treg numbers, and, unlike IL-2-based therapies, only a single dose may be required.…”

Combination Therapy Using IL-2/IL-2 Monoclonal Antibody Complexes, Rapamycin, and Islet Autoantigen Peptides Increases Regulatory T Cell Frequency and Protects against Spontaneous and Induced Type 1 Diabetes in Nonobese Diabetic Mice

“…The administration of IL-2/anti-IL-2 mAb (clone JES6-1) complexes in vivo has been shown to increase polyclonal Treg numbers in lymphoid organs (29). It has also been reported that the mammalian target of rapamycin inhibitor rapamycin can selectively inhibit proliferation of CD4 + effector T cells, enhance the expansion of Tregs (30,31), and maintain the stability of expanded Tregs (32,33). Therefore, we hypothesized that a combined treatment comprising an islet Ag (BDC2.5 cognate mimetope), IL-2/IL-2 mAb complexes, and rapamycin could act in synergy to expand Ag-specific Tregs in lymphoid organs.…”