Glioma immunotherapy targeting IDH mutation-derived epitope and immunosuppression

摘要 异柠檬酸脱氢酶(IDH)酶IDH1和IDH2的突变是早期和频繁的遗传 WHO II或III级较低级别弥漫性胶质瘤(LGG)以及继发性胶质母细胞瘤的改变， 从LGG发展而来的。尽管IDH突变体(IDH-mut)lgG与更长的生存期有关 与IDH野生型(IDH-WT)LGG相比，大多数IDH-MUT LGG患者最终死于这种疾病。 IDH-MUT患者确诊时的中位年龄比IDH-WT患者年轻，提示更多 IDH-MUT患者的治疗机会，如免疫治疗。所有IDH1和IDH2突变都赋予了 α-酮戊二酸(αKG)转化为2-羟基戊二酸(R-)-对映体的新功能增强活性 2HG)，并协调全基因组的表观遗传学变化。大约90%的IDH突变是单一的 IDH1第132位碱基突变用组氨酸(H；R132H)取代精氨酸(R)。作为一种针对 IDH1(R132H)衍生的表位通过免疫治疗，我们最近克隆了T细胞受体(TCR)的cDNA， 对IDH1(R132H)衍生的多肽表位(IDH1-TCR)具有特异性反应。如果没有免疫治疗， 众所周知，LGG被相对较少的T细胞渗透，这意味着LGG可能表现出一种独特的 免疫抑制机制。为了支持这一点，我们最近证明了IDH突变和R- 2HG导致效应T细胞趋化因子减少，如CXCL10，从而抑制渗透 胶质瘤中效应性T细胞的数量。我们的数据还显示，突变的IDH1特异性抑制物恢复了CXCL10和 增强以T细胞为基础的免疫治疗对临床前IDH-mut胶质瘤小鼠模型的疗效。 最后，我们的数据表明，R-2HG还抑制髓系细胞产生CXCL10。在当前 提案，我们将基于这些数据来评估我们的中心假设，即IDH-MUT胶质瘤可能是 通过适当调节免疫球蛋白微环境和靶向 IDH1(R132H)衍生的新抗原表位。我们将测试以下具体目标： 目的1.确定IDH突变对胶质瘤浸润性髓系细胞的影响。因为髓系细胞可以 作为抗原提呈细胞(APC)的功能，我们将描述IDH突变对胶质瘤浸润性的影响 并确定抑制突变型IDH是否能促进其APC功能。 目的2.确定IDH(1R132H)表位是如何被IDH1-TCR提呈和识别的。我们会 确定与IDH1(R132H)表位反应的TCRs的抗原特异性和亲和力。我们还将评估 IDH1-TCR是如何识别各种人类白细胞抗原II类分子所呈现的表位的。 目的3.在临床前模型中确定IDH1-TCR-Th1细胞ACT的疗效和机制。 利用人类白细胞抗原A2.DR1转基因小鼠，我们将评估两个相互非排斥的机制假说：1) Th1细胞作为细胞毒性T淋巴细胞(CTL)直接杀伤HLAII类+IDH1(R132H)+胶质瘤细胞， 2)Th1细胞促进CD8+CTL的交叉激发，进而杀死胶质瘤细胞。

ABSTRACT Mutations of the isocitrate dehydrogenase (IDH) enzymes IDH1 and IDH2 are early and frequent genetic alterations in WHO grade II or III lower grade diffuse gliomas (LGG), as well as in secondary glioblastomas, which progress from LGG. Although IDH mutant (IDH-MUT) LGGs are associated with longer survival compared to IDH wild type (IDH-WT) LGGs, most IDH-MUT LGG patients eventually succumb to the disease. The median age at diagnosis is younger in IDH-MUT patients than IDH-WT patients, suggesting more therapeutic opportunities for IDH-MUT patients, such as immunotherapy. All IDH1 and IDH2 mutations confer a novel gain-of-function activity by converting α-ketoglutarate (αKG) to (R)-enantiomer of 2-hydroxyglutarate (R- 2HG), and coordinate genome-wide epigenetic changes. Approximately 90% of all IDH mutations are a single base mutation at position 132 of IDH1 replacing arginine (R) with histidine (H; R132H). As a way to target the IDH1 (R132H)-derived epitope by immunotherapy, we recently cloned cDNAs for T-cell receptors (TCR) that are specifically reactive to the IDH1(R132H)-derived peptide epitope (IDH1-TCR). Without immunotherapy, LGGs are known to be infiltrated by relatively few T-cells, implying that LGG may exhibit a unique immunosuppression mechanism. To support this, we have recently demonstrated that IDH mutations and R- 2HG lead to decreased effector T-cell-attracting chemokines, such as CXCL10, thereby suppressing infiltration of effector T-cells in gliomas. Our data also show that a mutant IDH1-specific inhibitor recovered CXCL10 and enhanced the efficacy of T-cell-based immunotherapy in preclinical mouse models of IDH-MUT gliomas. Finally, our data indicate that R-2HG also suppresses CXCL10 production by myeloid cells. In the current proposal, we will build on these data to evaluate our central hypothesis that IDH-MUT gliomas could be susceptible to immunotherapy by proper modulation of the LGG microenvironment and targeting of the IDH1(R132H)-derived neoantigen epitope. We will test the following Specific Aims: Aim 1. Determine the effects of IDH mutations on glioma-infiltrating myeloid cells. As myeloid cells could function as antigen-presenting cells (APCs), we will delineate the effects of IDH mutations on glioma-infiltrating myeloid cells and determine whether inhibition of mutant IDH can promote their APC functions. Aim 2. Determine how the IDH(1R132H) epitope is presented and recognized by the IDH1-TCRs. We will determine antigen-specificity and avidity of TCRs reactive to the IDH1(R132H) epitope. We will also evaluate how IDH1-TCRs recognize the epitope presented by a variety of HLA-class II molecules. Aim 3. Determine the efficacy and mechanisms of ACT with IDH1-TCR-Th1 cells in preclinical models. Using HLA-A2.DR1 transgenic mice, we will evaluate two mutually non-exclusive mechanistic hypotheses: 1) Th1-cells function as cytotoxic T lymphocytes (CTLs) and directly kill HLA-class II+ IDH1(R132H)+ glioma cells, and 2) Th1-cells promote cross-priming of CD8+ CTLs, which in turn kill glioma cells.