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

尽管有多种药物预防，但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细胞活化抑制因子（VISTA），阴性 在静息的幼稚小鼠和人T细胞上表达的检查点调节因子。单剂量激动剂VISTA 在allo-HCT第0天的单克隆抗体（mAb）通过缺失引起抗原特异性操作耐受， 静息幼稚T细胞无反应性，具有并行T细胞受体（TCR）信号和90-100%的长期 生存VISTA与诱导的Treg产生、扩增、稳定性和维持有关。急性 在移植物抗宿主病（aGVHD）中，激动剂mAb增加外周T淋巴细胞; 将探索操作耐受性（目标1A）。aGVHD预防的数据有限。多克隆CD 4 T 细胞是MHC不同aGVHD模型中主要的aGVHD效应器，TCR信号传导对于aGVHD至关重要 缺失/无反应性;建议使用高亲和力供体TCR转基因和多克隆CD 4和/或 CD 8 T细胞将评估MHC和次要抗原不同的患者的手术耐受性和长期生存 模型四聚体将追踪激动剂mAb处理的小鼠中的多克隆和单克隆供体同种异体特异性T细胞。 经常使用的钙调磷酸酶抑制剂（CNI）可能会改变TCR信号低于激动剂mAb所需的阈值， 效果;翻译前需要进行测试（目标1C）。VISTA的一个独特特征是下调T细胞 activation.非同种异体反应性T细胞和逃避激动剂mAb诱导的缺失/无反应性的同种异体反应性T细胞可能 允许产生白血病特异性T细胞（目的1B）。类固醇是aGVHD患者的一线治疗， 只有一半的患者在第28天完全缓解;类固醇难治性（SR）aGVHD的1年生存率 病人很沮丧。在小鼠和患者中，我们发现骨髓细胞浸润比肠道中的T细胞高2.5倍， SR aGVHD中的原始aGVHD器官。VISTA在骨髓细胞上以比T细胞高>10倍的水平表达。 激动剂mAb抑制髓样细胞趋化性并将炎性单核细胞/巨噬细胞重编程为抗- 炎症细胞我们假设，肠道单核细胞/巨噬细胞的激动剂mAb重编程可以治疗 SR aGVHD（目标2）。我们的中心假设是激动剂VISTA mAb对于aGVHD预防具有双重用途， 诱导T细胞操作耐受和SR aGVHD治疗，将骨髓细胞重编程为抗- 煽动性我们的目的是验证以下假设：激动剂mAb诱导的操作耐受 供体T细胞的同种特异性缺失/无反应性依赖于体内Treg诱导，允许未受影响的T细胞 产生白血病特异性反应，并被第0天炎症或移植前启动的CNI破坏 (aim 1）。在目标2中，我们将检验激动剂mAb重编程炎性单核细胞的假设， 肠道中的巨噬细胞抗炎并局部释放免疫抑制细胞因子， 改善SR aGVHD而没有外源性细胞因子的全身副作用。我们的研究是基础的 用于翻译Noelle激动剂人VISTA mAb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.