CD4+ T Cells in Acute Versus Chronic HCV Infection

描述（由申请方提供）：CD4 T细胞应答对于控制动物和人类的病毒感染至关重要。然而，令人惊讶的是，人们对什么构成了保护性CD4应答以及导致CD4 T细胞衰竭的机制知之甚少。最近在鉴定和分离病毒特异性CD4 T细胞以及分析少量细胞的功能和转录状态方面的技术进展现在允许回答关于CD4 T细胞在慢性与急性感染中的作用和命运的基本问题，期望结果将使合理的疫苗设计以及靶向免疫干预的发展成为可能。为了更好地定义直接在人体中的CD4 T细胞应答的关键方面，我们将使用丙型肝炎病毒（HCV）感染的模型。HCV感染了全世界近2亿人，尽管抗病毒治疗最近取得了进展，但在可预见的未来，HCV仍将是世界上一个紧迫的临床问题。因此，替代治疗方式以及预防性疫苗仍然是高度优先事项。最重要的是，HCV允许研究急性和慢性病毒感染，从而保护和无效的免疫，因为估计30%的感染受试者自发清除病毒，而其余的发展为慢性感染和肝炎。作为我们研究的关键资源，我们已经建立了一个标本库，其中包括来自1000多名HCV+受试者队列的30，000多个PBMC和15，000多个血浆样本，其中包括感染后6个月内的近300名个体。基于我们最近的发现，即几乎所有受试者在HCV感染后都引发了可测量的和典型的多特异性CD4应答，我们假设HCV特异性CD4 T细胞之间的功能差异决定了HCV感染的结果，持续性感染通过激活T细胞抑制途径导致CD4耗竭，病毒能够通过向不易识别的方向突变来绕过CD4应答，变体。因此，在目标1中，我们将测试急性HCV感染中的CD4应答是否在分泌细胞因子的能力方面不同，这些细胞因子有助于协调免疫系统的不同分支，以及在启动与T细胞存活相关的细胞内程序方面不同。目的2将通过询问HCV特异性CD4 T细胞的不同功能和不同命运是否由不同T细胞抑制途径的激活驱动来扩展这些研究，特别考虑肝内CD4 T细胞。在目标3中，我们将定义病毒逃逸突变对HCV持续存在的作用。在拟议的研究结束时，我们希望已经建立了CD4 T细胞如何帮助控制病毒感染的详细了解，以及保护性CD4免疫与失败的CD4应答的区别。这些结果可能对慢性病毒感染的预防和治疗产生重大影响，而不仅仅是HCV感染。

DESCRIPTION (provided by applicant): CD4 T cell responses are of critical importance for the control of viral infections in animals and humans. Yet surprisingly little is known about what constitutes a protective CD4 response as well as the mechanisms that lead to CD4 T cell failure. Recent technological advances in identifying and isolating virus-specific CD4 T cells and in analyzing the functional and transcriptional state of small numbers of cells now allow to answer basic questions about the role and fate of CD4 T cells in chronic versus acute infection, with the expectation that the results will enable rationale vaccine design as well as the development of targeted immunotherapeutic interventions. In order to better define critical aspects of the CD4 T cell response directly in humans, we will use the model of hepatitis C virus (HCV) infection. HCV infects almost 200 millions people worldwide and despite recent progress in antiviral therapies will remain a pressing clinical problem in the world for the foreseeable future. Thus alternative therapeutic modalities as well as prophylactic vaccines remain a high priority. Most importantly for this proposal, HCV allows to study both acute and chronic viral infection and thus protective and ineffective immunity, since an estimated 30% of infected subjects clear the virus spontaneously while the rest develop chronic infection and hepatitis. As a critical resource for our studies we have established a specimen bank with more than 30,000 PBMC and over 15,000 plasma samples from cohorts with more than 1000 HCV+ subjects, including almost 300 individuals within 6 months post infection. Based on our recent findings that virtually all subjects prime a measurable and typically multi-specific CD4 response upon HCV infection we hypothesize that functional differences between HCV-specific CD4 T cells define the outcome of HCV infection, that persistent infection gives rise to CD4 exhaustion through the activation of T cell inhibitory pathways and that the virus is able to circumvent the CD4 response by mutating towards less recognizable variants. Thus in aim 1 we will test whether CD4 responses in acute HCV infection differ in their capacity to secrete cytokines that help coordinate the different arms of the immune system and in the initiation of intracellular programs associated with T cell survival. Aim 2 will extend these studies by asking whether different functions and a different fate of the HCV-specific CD4 T cells is driven by the activatio of distinct T cell inhibitory pathways, with special consideration of intrahepatic CD4 T cells. In aim 3 we will define the role of viral escape mutations for persistence of HCV. At the end of the proposed studies we expect to have established a detailed understanding of how CD4 T cells can help to control viral infections and what differentiates protective CD4 immunity from a failed CD4 response. These results could have major implications for the prophylaxis and treatment of chronic viral infections, beyond HCV infection alone.