Exploiting the VISTA Pathway to Prevent Acute GVHD and Control Steroid Refractory Disease

摘要尽管有多种药物预防，aGVHD仍影响20-70%的异基因造血细胞移植。 (Allo-HCT)患者。含V区免疫球蛋白的T细胞激活抑制因子(VistA)，阴性 检查点调节因子在静止的幼稚小鼠和人T细胞上表达。单剂激动剂Vista 在allo-HCT第0天的单抗(MAb)通过缺失和 具有并发T细胞受体(TCR)信号和90%-100%长期存活的静息幼稚T细胞的无能 生死存亡。Vista与诱导性Treg的产生、扩展、稳定性和维护有关。在急性期 移植物抗宿主病(AGVHD)，激动剂mAb增加外周Tregs；pTregs的作用程度 将探讨对操作容差的要求(目标1A)。预防aGVHD的数据有限。多克隆CD4T细胞 在MHC不同的aGVHD模型中，细胞是主要的aGVHD效应器，TCR信号转导是关键的 缺失/无能；建议使用高亲和力供体TCR转基因和多克隆CD4和/或 CD8 T细胞将评估MHC和次要抗原不同的手术耐受性和长期生存 模特们。四聚体将在激动剂mAb处理的小鼠中追踪多克隆和单克隆供体同种异体T细胞。 频繁使用的钙调神经磷酸酶抑制剂(CNI)可能会改变TCR信号，使其低于激动剂mAb所需的阈值 效果；翻译前需要进行测试(目标1C)。Vista的一个独特功能是下调T细胞的表达 激活。非同种异体反应T细胞和同种异体反应T细胞逃避激动剂mAb诱导的缺失/无能可能 允许产生白血病特异性T细胞(目标1B)。类固醇是aGVHD患者的一线治疗方法，但 只有一半的患者在第28天完全缓解；激素难治性(SR)aGVHD的1年存活率 病人是令人沮丧的。在小鼠和患者中，我们发现在肠道中髓系细胞的浸润率是T细胞的2.5倍， SR aGVHD的原始aGVHD器官。VistA在髓系细胞上的表达水平是T细胞的10倍。 激动剂mAb抑制髓系细胞的趋化并将炎性单核/巨噬细胞重新编程为抗 炎性细胞。我们假设激动型单抗重新编程肠道单核细胞/巨噬细胞可以治疗 高级aGVHD(目标2)。我们的中心假设是激动剂Vista mAb具有预防aGVHD的双重用途， 诱导T细胞操作耐受，SR aGVHD治疗，重新编程髓系细胞成为抗 煽动性的。我们的目标将检验以下假设：激动剂单抗诱导的操作耐受性 供者T细胞的同种异体特异性缺失/无能依赖于体内Treg的诱导，允许未受影响的T细胞 产生白血病特异性反应，并被移植前启动的第0天炎症或CNI颠覆 (目标1)。在目标2中，我们将检验激动剂mAb重新编程炎性单核细胞和 肠道中的巨噬细胞可以抗炎和局部释放免疫抑制细胞因子， 改善SR aGVHD，无外源性细胞因子的全身副作用。我们的研究是基础性的 翻译Noelle激动剂人Vista单抗用于aGVHD预防和SR aGVHD治疗。

Abstract Despite multi-drug prophylaxis, aGVHD affects 20-70% of allogeneic hematopoietic cell transplant (allo-HCT) patients. V-region Immunoglobulin-containing Suppressor of T cell Activation (VISTA), a negative checkpoint regulator expressed on resting naïve mouse and human T cells. A single dose of agonist VISTA monoclonal antibody (mAb) on allo-HCT day 0 causes antigen-specific operational tolerance by deletion and anergy in resting naïve T cells that have concurrent T cell receptor (TCR) signals and 90-100% long-term survival. VISTA has been linked to induced Treg generation, expansion, stability and maintenance. In acute graft-vs-host disease (aGVHD), agonist mAb increases peripheral Tregs; the extent to which pTregs contribute to operational tolerance will be explored (aim 1A). Limited data exist for aGVHD prevention. Polyclonal CD4 T cells are the dominant aGVHD effectors in MHC disparate aGVHD models and TCR signaling is critical for deletion/anergy; studies are proposed using high affinity donor TCR transgenic and polyclonal CD4 and/or CD8 T cells will assess operation tolerance and long-term survival in MHC and minor antigen disparate models. Tetramers will track polyclonal and monoclonal donor allospecific T cells in agonist mAb treated mice. Frequently used calcineurin inhibitors (CNIs) may alter TCR signals below a threshold needed for agonist mAb effects; testing is required before translation (aim 1C). A unique feature of VISTA is downregulation with T cell activation. Non-alloreactive T cells and alloreactive T cells escaping agonist mAb induced deletion/anergy may permit generation of leukemia-specific T cells (aim 1B). Steroids are first line therapy for aGVHD patients but only half the patients have day 28 complete responses; 1-year survival rate for steroid refractory (SR) aGVHD patients is dismal. In mice and patients, we show myeloid cell infiltration is 2.5-fold higher than T cells in gut, a primal aGVHD organ in SR aGVHD. VISTA is expressed on myeloid cells at >10-fold higher levels than T cells. Agonist mAb inhibits myeloid cell chemotaxis and reprograms inflammatory monocytes/macrophages into anti- inflammatory cells. We hypothesize that agonist mAb reprograming of gut monocytes/macrophages can treat SR aGVHD (aim 2). Our central hypothesis is agonist VISTA mAb has dual uses for aGVHD prevention, inducing T cell operational tolerance, and SR aGVHD therapy, reprogramming myeloid cells to be anti- inflammatory. Our aims will test the hypotheses that: Operational tolerance induced by agonist mAb allospecific deletion/anergy of donor T cells depends on in vivo Treg induction, permits unaffected T cells to generate leukemia-specific responses, and is subverted by day 0 inflammation or CNIs initiated pre-transplant (aim 1). In aim 2, we will test the hypothesis that agonist mAb reprograms inflammatory monocytes and macrophages in the gut to be anti-inflammatory and locally release of immune suppressive cytokines, ameliorating SR aGVHD without systemic side-effects of exogenous cytokines. Our studies are foundational for translation of Noelle’s agonist human VISTA mAb for aGVHD prevention and SR aGVHD therapy.