Mechanisms of immune suppression during arthritogenic alphavirus infections

描述（由申请人提供）：关节炎源性甲病毒，包括罗斯河病毒（RRV）和基孔肯雅病毒（CHIKV），是重新出现的蚊子传播的甲病毒，可引起使人衰弱的肌肉骨骼炎症性疾病的地方性和爆炸性流行。在南太平洋、非洲和亚洲发生了涉及数百万人的重大疫情。欧洲本地获得性CHIKV疾病暴发以及RRV和CHIKV感染旅行者返回非流行地区，包括美国，突出了这些病毒将继续传播到新地区的担忧。目前还没有治疗甲病毒引起的风湿病的特异性疗法，也没有获得许可的疫苗。RRV和CHIKV感染的一个显著特征是在高达64%的感染者中发展为慢性、丧失能力的肌肉骨骼疾病，这在人类和动物模型中都与受影响组织的持续感染有关。因此，了解控制关节炎源性甲病毒感染的免疫机制对于开发新的治疗策略至关重要。利用概括人类疾病重要方面的小鼠模型，我们在RRV和chikv感染小鼠的肌肉骨骼组织中检测到丰富的硝基酪氨酸，这是一种过氧亚硝酸盐活性的标志物。过氧亚硝酸盐是一种有效的诱导剂，可引起组织损伤和抑制T细胞反应。精氨酸酶1 （Arg1）和诱导型一氧化氮合酶（iNOS; Nos2）是协同产生过氧亚硝酸盐的酶，在RRV和chikv感染小鼠的炎症病变和组织浸润性巨噬细胞中上调，并且在RRV感染后晚期，髓细胞中缺乏Arg1或Nos2表达的小鼠减少了病毒载量和组织损伤，表明Arg1和iNOS阻碍了宿主对RRV感染的控制。另外的初步数据表明，骨髓细胞Arg1作用于感染部位的T细胞，以限制病毒的控制。基于这些数据，我们假设关节炎源性甲病毒感染在肌肉骨骼组织中诱导局部免疫抑制环境，促进持续感染和慢性疾病。我们拟确定iNOS和arg1介导的过氧亚硝酸盐产生抑制T细胞反应的机制，并确定促进巨噬细胞免疫抑制活性的细胞因子信号通路，以预防控制肌肉骨骼组织中的RRV感染并促进慢性疾病。这些研究将确定Arg1和iNOS的作用，以及调节其表达的信号通路，在宿主控制急性和慢性关节炎源性甲病毒感染和组织损伤中的作用，并将有助于开发新的宿主靶向治疗策略来治疗甲病毒诱导的风湿病。

DESCRIPTION (provided by applicant): Arthritogenic alphaviruses, including Ross River virus (RRV) and chikungunya virus (CHIKV), are re-emerging, mosquito-transmitted alphaviruses that cause both endemic and explosive epidemics of debilitating musculoskeletal inflammatory disease. Major outbreaks have occurred in the South Pacific, Africa, and Asia involving millions of persons. Locally-acquired CHIKV disease outbreaks in Europe and the return of RRV and CHIKV-infected travelers to nonendemic regions, including the United States, has highlighted concern that these viruses will continue to spread to new areas. There are no specific therapies for the treatment of alphavirus-induced rheumatological disease and no licensed vaccines. A striking feature of RRV and CHIKV infections is the development of chronic, incapacitating musculoskeletal disease in up to 64% of infected individuals, which has been linked in both humans and animal models to persistent infection in the affected tissues. Thus, understanding the immunological mechanisms that control arthritogenic alphavirus infection is essential for the development of new therapeutic strategies. Utilizing mouse models that recapitulate important aspects of human disease, we detected abundant nitrotyrosine, a marker of peroxynitrite activity, in the musculoskeletal tissues of RRV- and CHIKV-infected mice. Peroxynitrite is a potent inducer of nitrative stress that causes tissue damage and suppresses T cell responses. Arginase 1 (Arg1) and inducible nitric oxide synthase (iNOS; Nos2), enzymes that synergize to produce peroxynitrite, were upregulated in inflammatory lesions and tissue-infiltrating macrophages of RRV- and CHIKV-infected mice, and mice lacking Arg1 in myeloid cells or Nos2 expression had reduced viral loads and tissue damage at late times post-RRV infection, indicating that Arg1 and iNOS thwart host control of RRV infection. Additional preliminary data suggests that myeloid cell Arg1 acts on T cells at the sites of infection to limit virus control. Based on these data, we hypothesize that arthritogenic alphavirus infection induces a localized immunosuppressive environment in musculoskeletal tissues that promotes persistent infection and chronic disease. We propose to define mechanisms by which iNOS and Arg1-mediated production of peroxynitrite suppresses T cell responses, and to define the cytokine signaling pathways that promote the immunosuppressive activity of macrophages, to prevent control of RRV infection in musculoskeletal tissues and promote chronic disease. These studies will define the role of Arg1 and iNOS, and signaling pathways that regulate their expression, in host control of acute and chronic arthritogenic alphavirus infection and tissue injury and will aid the development of new host-targeted therapeutic strategies to treat alphavirus-induced rheumatological disease.