Department of Pediatrics, Division of Blood and Marrow Transplantation, University of Minnesota Cancer Center, Minneapolis, Minnesota, USA.
Ben Towne Center for Childhood Cancer Research, Seattle Children's Research Institute, Seattle, Washington, USA; Department of Pediatrics, University of Washington, Seattle, Washington, USA.
Cytotherapy. 2021 Aug;23(8):704-714. doi: 10.1016/j.jcyt.2021.02.118. Epub 2021 Apr 20.
Adoptive transfer of suppressive CD4+CD25+ thymic regulatory T cells (tTregs) can control auto- and alloimmune responses but typically requires in vitro expansion to reach the target cell number for efficacy. Although the adoptive transfer of expanded tTregs purified from umbilical cord blood ameliorates graft-versus-host disease in patients receiving hematopoietic stem cell transplantation for lymphohematopoietic malignancy, individual Treg products of 100 × 10 cells/kg are manufactured over an extended 19-day time period using a process that yields variable products and is both laborious and costly. These limitations could be overcome with the availability of 'off the shelf' Treg.
Previously, the authors reported a repetitive restimulation expansion protocol that maintains Treg phenotype (CD4+25++127-Foxp3+), potentially providing hundreds to thousands of patient infusions. However, repetitive stimulation of effector T cells induces a well-defined program of exhaustion that leads to reduced T-cell survival and function. Unexpectedly, the authors found that multiply stimulated human tTregs do not develop an exhaustion signature and instead maintain their Treg gene expression pattern. The authors also found that tTregs expanded with one or two rounds of stimulation and tTregs expanded with three or five rounds of stimulation preferentially express distinct subsets of a group of five transcription factors that lock in Treg Foxp3expression, Treg stability and suppressor function. Multiply restimulated Tregs also had increased transcripts characteristic of T follicular regulatory cells, a Treg subset.
These data demonstrate that repetitively expanded human tTregs have a Treg-locking transcription factor with stable FoxP3 and without the classical T-cell exhaustion gene expression profile-desirable properties that support the possibility of off-the-shelf Treg therapeutics.
过继转移抑制性 CD4+CD25+胸腺调节性 T 细胞（tTregs）可以控制自身免疫和同种免疫反应，但通常需要体外扩增以达到疗效所需的靶细胞数量。虽然从脐带血中纯化的扩增 tTregs 的过继转移可以改善接受造血干细胞移植治疗淋巴血液恶性肿瘤的患者的移植物抗宿主病，但个体 Treg 产品的 100×10 个细胞/kg 需要使用延长至 19 天的过程来制造，该过程产生可变的产品，既费力又昂贵。如果有“现成的”Treg，这些限制可以得到克服。
作者先前报道了一种重复再刺激扩增方案，该方案维持 Treg 表型（CD4+25++127-Foxp3+），有可能提供数百至数千次患者输注。然而，效应 T 细胞的重复刺激会诱导出一种明确的衰竭程序，导致 T 细胞存活和功能降低。出乎意料的是，作者发现，多次刺激的人 tTregs 不会产生衰竭特征，而是维持其 Treg 基因表达模式。作者还发现，用一轮或两轮刺激扩增的 tTregs 和用三轮或五轮刺激扩增的 tTregs 优先表达一组五个转录因子中的不同亚群，这些转录因子锁定 Treg Foxp3 表达、Treg 稳定性和抑制功能。多次再刺激的 Tregs 也具有 T 滤泡调节细胞（Treg 亚群的特征转录本）的增加转录本。
这些数据表明，反复扩增的人 tTregs 具有 Treg 锁定转录因子，其 Foxp3 稳定且没有经典 T 细胞衰竭基因表达谱——这是支持现成 Treg 治疗的理想特性。
