Blocking common gamma chain cytokine signaling ameliorates T-cell-mediated pathogenesis in disease models

The common γ chain (γc; IL2RG) is a subunit of the interleukin (IL) receptors for the γc cytokines IL2, IL4, IL7, IL9, IL15, and IL21. Because of the lack of appropriate neutralizing antibodies recognizing IL2RG, it has been difficult to thoroughly interrogate the role of γc cytokines in inflammatory and autoimmune disease settings. To determine whether γc cytokines might be targeted for T-cell-mediated disease prevention and treatment, we generated a new γc cytokine receptor antibody, REGN7257. Biochemical, structural and in vitro analysis showed that REGN7257 binds with high affinity to IL2RG and potently blocks signaling of all γc cytokines. In nonhuman primates, REGN7257 efficiently suppressed T-cells without impacting granulocytes, platelets or red blood cells. Using REGN7257, we showed that γc cytokines drive T-cell-mediated disease in mouse models of graft-versus-host disease (GVHD) and multiple sclerosis, by impacting multiple aspects of the pathogenic response. Importantly, we discovered that our xenogeneic GVHD mouse model recapitulates hallmarks of both acute and chronic GVHD, with T-cell expansion/infiltration into tissues and liver fibrosis, as well as hallmarks of immune aplastic anemia, with bone marrow aplasia and peripheral cytopenia. And we showed that γc cytokines contribute to disease pathology by driving all of these features. Overall, by demonstrating that broad inhibition of γc cytokine signaling with REGN7257 protects from immune-mediated disorders, our data provide evidence of γc cytokines as key drivers of pathogenic T-cell responses, offering a potentially novel strategy for the management of T-cell-mediated diseases. Freshly isolated human PBMCs were activated with beads coated with anti-CD3 and anti-CD28. PBMCs with and without activation are incubated with REGN7257 (anti-IL2RG) or isotype for 3 days. PBMCs from 5 unique donors were isolated. Each condition was tested in duplicate. Experimental autoimmune encephalomyelitis (EAE) is the mouse model of human MS and is useful to investigate immune cell infiltration into the central nervous system. EAE was induced in all test animals. Three treatment groups: PBS treatment (n=8), IgG4 isotype control treatment (n=9), and REGN7257 treatment (n=10).

共同γ链（common γ chain，缩写γc；IL2RG）是γc家族细胞因子白细胞介素（interleukin, IL）-2、IL-4、IL-7、IL-9、IL-15及IL-21对应的白细胞介素受体的亚基。由于缺乏可特异性识别IL2RG的中和抗体，此前难以全面探究γc家族细胞因子在炎症性及自身免疫性疾病中的功能与作用。为明确γc家族细胞因子是否可作为T细胞介导性疾病的防治靶点，本研究开发了一种新型γc细胞因子受体抗体REGN7257。生物化学、结构生物学及体外实验分析结果显示，REGN7257可与IL2RG高亲和力结合，并能强效阻断所有γc家族细胞因子的信号转导通路。在非人灵长类动物体内，REGN7257可有效抑制T细胞活化，且不会对粒细胞、血小板及红细胞的数量与功能产生影响。利用REGN7257，本研究证实，在移植物抗宿主病（graft-versus-host disease, GVHD）及多发性硬化（multiple sclerosis, MS）的小鼠模型中，γc家族细胞因子通过调控致病性免疫应答的多个环节，介导T细胞依赖性疾病的发生。值得注意的是，本研究发现异种移植物抗宿主病小鼠模型可重现急性与慢性GVHD的典型病理特征，包括T细胞增殖、组织浸润及肝纤维化，同时还具备免疫性再生障碍性贫血的标志性表现，即骨髓造血衰竭与外周血细胞减少。研究同时证实，γc家族细胞因子通过驱动上述所有病理特征，参与疾病进程。总体而言，本研究通过证明采用REGN7257广泛抑制γc细胞因子信号通路可保护机体免受免疫介导性疾病的损伤，证实γc家族细胞因子是致病性T细胞应答的关键驱动因子，为T细胞介导性疾病的临床管理提供了一种潜在的全新策略。

将新鲜分离的人外周血单个核细胞（peripheral blood mononuclear cell, PBMC）用包被有抗CD3与抗CD28抗体的免疫磁珠进行活化。将活化与未活化的PBMC分别与REGN7257（抗IL2RG抗体）或同型对照（isotype）共孵育3天。本研究共分离得到5名不同健康供者的PBMC，每个实验条件均设置复孔进行检测。

实验性自身免疫性脑脊髓炎（experimental autoimmune encephalomyelitis, EAE）是模拟人类多发性硬化的经典小鼠模型，可用于研究免疫细胞向中枢神经系统的浸润过程。本研究对所有受试动物均成功诱导了EAE模型。实验分为3个治疗组：PBS治疗组（n=8）、IgG4同型对照治疗组（n=9）及REGN7257治疗组（n=10）。