miRNA-mediated premature T cell aging in vaccine failure during viral infection

描述(申请人提供)：这项建议的总体目标是阐明慢性感染通过调节microRNAs和导致迟钝的疫苗反应来调节T细胞过早老化的机制，目的是开发有效的方法来提高病毒感染者的疫苗效力。为此，我们将在慢性丙型肝炎病毒(丙型肝炎病毒)感染的背景下，使用乙肝疫苗失败的模型。该建议是基于这样一个事实，即由于共同的风险因素，乙肝病毒与丙型肝炎病毒和/或艾滋病毒合并感染是常见的，因此需要接种乙肝疫苗以防止重叠感染及其相关的发病率和死亡率的增加；然而，病毒感染者的疫苗反应通常是迟钝的。在老年人中也观察到这种现象，他们经常对疫苗接种无效，提高受感染人口和老年人口的接种率的努力也没有成功。这在一定程度上是因为我们对在这些环境中抑制疫苗反应的机制缺乏了解。在研究病毒感染对T细胞功能的影响中，我们和其他人最近发现，慢性丙型肝炎病毒感染导致T细胞功能障碍，其机制是通过上调衰老标志物，包括杀伤细胞凝集素样受体亚家族G成员1(KLRG1)和双特异性磷酸酶6(DUSP6)，伴随着CD4T细胞中microRNA-181a(MiR181)水平的下降。值得注意的是，这些变化与丙型肝炎病毒感染者的CD4T细胞功能受损有关，与年龄匹配的乙肝疫苗应答者(HBVR)相比，这些变化在乙肝疫苗无应答者(HBVNR)中更为突出。随着年龄的增长，KLRG1上调并导致T细胞受体(TCR)信号的抑制，而DUSP6增加并导致TCR激活阈值的重新校准；miR181下降以允许一组与T细胞抑制相关的基因的翻译。然而，在丙型肝炎病毒感染过程中miR181/KLRG1/DUSP6表达以及调节T细胞过早老化和疫苗反应的机制仍不清楚。在这项提议中，我们假设丙型肝炎病毒诱导的miR181的缺失通过上调KLRG1和/或DUSP6的表达来调节T细胞的过早老化，从而靶向这些抑制通路可能拯救受损的CD4T细胞功能，并随后增强病毒感染个体的钝化疫苗应答。为了验证这一假设，我们将实现以下三个具体目标：目标1将定义 目的2将确定在丙型肝炎病毒感染期间，miR181在调节T细胞中KLRG1和/或DUSP6表达方面的作用；目的3将研究在病毒感染个体中，miR181丢失和KLRG1/DUSP6表达对T细胞功能和疫苗反应的影响。这项转化性研究具有重要意义，因为它提供了一个工作模型，以探索可能是疫苗反应减弱的基本机制，特别是在艾滋病毒、血液透析、移植和癌症造成的免疫损害的背景下。

DESCRIPTION (provided by applicant): The overall goal of this proposal is to elucidate the mechanisms by which chronic infection mediates premature T cell aging through regulation of microRNAs and leading to blunted vaccine responses, with an aim to develop effective approaches to improve vaccine efficacy in virus-infected individuals. To this end, we will use a model of hepatitis B virus (HBV) vaccine failure in the setting of chronic hepatitis C virus (HCV) infection. The proposal is based on the fact that co-infection of HBV with HCV and/or HIV is common due to shared risk factors, and as such HBV vaccine is required to prevent super-infection and its associated increase in morbidity and mortality; however, vaccine responses in virus-infected individuals are often blunted. This phenomenon is also observed in the elderly, who frequently fail to respond to vaccinations and attempts to improve the rate of immunizations in both infected and aged populations have been unsuccessful. This is in part due to our poor understanding of the mechanisms that inhibit vaccine responses in these settings. In studying the effect of viral infection on T cell functions, we and others have recently found that chronic HCV infection leads to T cell dysfunction mediated through up-regulation of aging markers, including killer cell lectin- like receptor subfamily G member 1 (KLRG1) and dual specific phosphatase 6 (DUSP6), concomitant with a decline of microRNA-181a (miR181) levels in CD4 T cells. Remarkably, these alterations are associated with impaired CD4 T cell functions in HCV-infected individuals and are more prominent in HBV vaccine non- responders (HBV-NR) compared to age-matched HBV vaccine responders (HBV-R). With increasing age, KLRG1 is up-regulated and leads to inhibition of T cell receptor (TCR) signaling, whereas DUSP6 is increased and leads to recalibration of the TCR activation threshold; miR181 declines to permit translation of a set of genes related to T cell inhibition. However, the mechanisms underlying miR181/KLRG1/DUSP6 expression and regulation of premature T cell aging and vaccine responses during HCV infection remain unknown. In this proposal, we hypothesize that HCV-induced loss of miR181 mediates premature T cell aging by up-regulating KLRG1 and/or DUSP6 expressions, such that targeting these inhibitory pathways may rescue impaired CD4 T cell functions and subsequently boost blunted vaccine responses in virus-infected individuals. To test this hypothesis, we will carry out the following three specific aims: Aim 1 will define the epigenetic, transcriptional and translational mechanisms that control miR181 expression in T cells during HCV infection; Aim 2 will determine the role of miR181 in regulating KLRG1 and/or DUSP6 expression in T cells during HCV infection; Aim 3 will examine the consequences of miR181 loss and KLRG1/DUSP6 expression in T cell function and vaccine response in virus-infected individuals. This translational study is significant in that it provides a working model t explore mechanisms that may be fundamental to diminished vaccine responses in general, particularly in the setting of immunocompromise by HIV, hemodialysis, transplantation, and cancer.