Determining Regulatory Pathways That Maintain FOXP3 in Human T regulatory Cells

自身免疫性疾病，如类风湿关节炎（RA）和I型糖尿病是由过度激活的免疫细胞驱动的。一种称为调节性T细胞（Tregs）的免疫细胞可以有效地阻止不受控制的免疫系统激活并预防自身免疫性疾病。将Tregs用于治疗结肠炎、1型糖尿病和其他免疫相关疾病的初步临床试验已经显示出令人鼓舞的结果。此外，Treg细胞功能的证据在Treg特异性基因FoxP3突变的患者中是明显的。Foxp3突变导致人类严重的自身免疫性疾病，称为IPEX（免疫失调多内分泌病肠病x连锁）综合征。因此，所有这些对人类的观察清楚地表明，treg对于控制免疫系统的过度激活是必不可少的。然而，Foxp3在treg中的表达在人体内是如何被控制的，目前还不完全清楚。因此，这项拨款提案的目标是了解人类Foxp3是如何被调节的。我们发现了一种新的调控分子（天冬酰胺内肽酶；AEP），它可以控制小鼠Treg细胞的功能。AEP直接切割和降解Tregs中的FoxP3蛋白，并消除其抑制功能。除此之外，我们还发现Tregs上的一种称为程序性细胞死亡受体-1 （PD-1）的受体可以显著下调AEP在Tregs中的表达。通过扩展小鼠对人类的研究，我们发现了AEP在人类Treg细胞中的表达，但其在人类Treg细胞中的功能和重要性尚不清楚。在这项拨款申请中，我们的目标是了解AEP在人类treg和其他T辅助细胞亚群中的功能和重要性。我们将研究是否：1；AEP控制Treg细胞中的FoxP3，以及阻断AEP是否会增加Treg细胞功能2。如果PD-1和其他类似的辅助受体可以阻断AEP在Tregs3中的表达。确定AEP是否在人类其他T辅助细胞亚群中表达，并测试其在这些亚群中的功能。我们提出，如果AEP在人类Treg中具有类似的功能，那么就有可能以AEP为靶点，以产生能够有效控制各种自身免疫性疾病的工程化Treg细胞疗法。这种靶向治疗将使那些患有慢性自身免疫性疾病的患者的生活质量得到改善。目前对这些患者的治疗标准包括皮质类固醇等免疫抑制药物；长期使用会产生意想不到的副作用。工程细胞疗法不仅可以控制自身免疫，而且可以在达到免疫细胞控制后从体内删除。这些疗法的成功在癌症领域已经很明显，因此为产生治疗自身免疫的类似细胞疗法提供了原理证明

Autoimmune diseases such as rheumatoid arthritis (RA) and Type I diabetes are driven by over-activated immune cells. A type of immune cell called regulatory T cell (Tregs) can efficiently stop uncontrolled immune system activation and prevent autoimmune diseases. Pilot clinical trials using Tregs as a therapy for diseases such as colitis, type 1 diabetes and other immune related diseases have shown promising results. Furthermore, evidence of Treg cell function is apparent in patients with mutation in Treg specific gene called FoxP3. Foxp3 mutation results in severe autoimmune disease in humans which is known as IPEX (immunodysregulation polyendocrinopathy enteropathy X-linked) syndrome. Therefor all these observations in humans clearly demonstrate that Tregs are indispensable for controlling over-activation of the immune system.However, how Foxp3 expression in Tregs are controlled within the human body is still not fully understood. Therefore, the goal of this grant proposal is to understand how human Foxp3 is regulated.We have discovered a new regulatory molecule (asparaginyl endopeptidase; AEP) that can control Treg cell function in mice. AEP directly cleaved and degraded FoxP3 protein in Tregs and abolished their suppressive function. In addition to this observation, we also found that AEP expression in Tregs can be significantly down-regulated by a receptor on Tregs called programmed cell death receptor-1 (PD-1). By extending our mouse studies in humans, we have discovered the expression of AEP in human Tregs but its function and importance in human Treg cells is unknown. In this grant proposal, we aim to understand the function and importance of AEP in human Tregs and other T helper cell subsets. We will study whether:1. AEP controls FoxP3 in human Treg cells and whether blocking AEP increases Treg cell function2. If PD-1 and other similar coreceptors can block AEP expression in Tregs3. Determine if AEP is expressed in other T helper cell subsets in humans and test its function within these subsets.We propose that if AEP has a similar function in human Tregs, then it would be possible to target AEP in order to generate engineered Treg cell therapies that can efficiently control a variety of autoimmune disease. Such targeted therapies will enable a better quality of life for those patients who suffer from chronic autoimmune diseases. The current standard of care for these patients include global immune suppressive drugs such as corticosteroids; the long-term use of which can result in unwanted side effects. Engineered cell therapies can not only control autoimmunity but can be deleted from the body on reaching immune cell control. Success of these therapies is already apparent in the cancer field therefore providing a proof of principle for generating similar cell therapies for treating autoimmuntiy