Positive Immune-regulators During Chronic Viral Infections

 描述（由申请人提供）：CD 4 T细胞是根除许多病原体的核心。然而，在慢性病毒感染期间，免疫刺激途径失调，阻止及时的CD 4 T细胞免疫。人类持久性病毒，包括人类免疫缺陷病毒（HIV）、丙型肝炎病毒和B型肝炎病毒（HCV和HBV）以及人类巨细胞病毒（HCMV），在世界范围内造成巨大的疾病负担，但仅限于人类和非人类灵长类动物，这反过来又对基于实验的研究造成很大的限制。重要的是，在过去的三十年中，在其天然啮齿动物宿主中对淋巴细胞性脉络丛脑膜炎病毒（LCMV）和鼠CMV（MCMV）感染的研究表明，它们广泛适用于模拟针对人类持久性病毒的免疫应答。 我们已经使用慢性淋巴细胞性脉络丛脑膜炎病毒（LCMV）感染的自然宿主，小鼠，作为一个模型系统的持续感染与连续的病毒复制。我们发现，白细胞介素-6（IL-6）和IL-27分别对最佳的CD 4 T细胞分化为T滤泡辅助细胞（Tfh）和CD 4 T细胞存活至关重要，而它们在感染的晚期（而不是早期）多余地诱导IL-21的产生。重要的是，IL-6和IL-27都是 绝对需要控制慢性（而非急性）LCMV感染（Harker et al. Science 2011 and Immunity 2013）。引人注目的是，新的初步数据表明，虽然IL-6在LCMV和MCMV感染中的作用相似，但IL-27不是MCMV特异性CD 4 T细胞存活所必需的，而是抑制产生颗粒酶A和KLRG 1 +EOMEShigh（推定的细胞毒性）MCMV特异性CD 4 T细胞的分化，其频率与MCMV对照相关。因此，IL-27似乎促进（而不是抑制）MCMV的持久性和潜伏负荷。目前建议的总体目标是充分剖析IL-6和IL-27诱导的机制以及它们在连续复制病毒（LCMV）慢性感染期间对CD 4 T细胞应答的调节，并进一步研究它们在建立潜伏期的病毒（MCMV）感染期间的作用。为了实现这一目标，我们在目标#1中提出研究在慢性LCMV感染过程中诱导IL-6和IL-27产生（包括细胞来源和上游信号传导途径）。在目标#2中，我们计划研究IL-6和IL-27下游信号传导途径的分子机制、Tfh相关和IL-21基因启动子的STAT靶向和表观遗传状态以及潜在STAT共调节因子在慢性LCMV感染后早期与晚期形成CD 4 T细胞应答中的作用。最后，在目标#3中，我们将评估IL-6和IL-27信号传导在慢性MCMV感染期间CD 4 T细胞中的作用，并研究其相关作用时间、细胞来源以及IL-27抑制MCMV特异性KLRG 1 +EOMEShigh（推定的细胞毒性）CD 4 T细胞（在MCMV（而非LCMV）感染期间显著出现）的意义和机制。 从拟议的实验中获得的知识不仅将增强我们对关键免疫参与者（即IL-6，IL-27和CD 4 T细胞）的基本生物学的理解，而且还可以为慢性病毒感染和潜在的CMV疫苗接种期间治疗性操纵上述细胞因子提供有价值的信息。

 DESCRIPTION (provided by applicant): CD4 T cells are central for eradicating many pathogens. However, immune stimulatory pathways are dysregulated during chronic viral infections preventing timely CD4 T cell immunity. Human persistent viruses, including human immunodeficiency virus (HIV), hepatitis C and B viruses (HCV and HBV) and human cytomegalovirus (HCMV) cause tremendous disease burden worldwide but are restricted to human and nonhuman primates, which in turn poses great limitations for experimental-based research. Importantly, studies over the past three decades with lymphocytic choriomeningitis virus (LCMV) and murine CMV (MCMV) infections in their natural rodent hosts indicate that they are widely applicable to model immune responses against persistent viruses in humans. We have used chronic lymphocytic choriomeningitis virus (LCMV) infection in its natural host, the mouse, as a model system for persistent infections with continuous viral replication. We found that interleukin-6 (IL-6) and IL-27 are essential for optimal CD4 T cell differentiation into T follicular helper cells (Tfh) and CD4 T cell survival, respectively, while they redundantly induce IL-21 production at late (but not early) stages of infection. Importantly, both IL-6 and IL-27 were absolutely required to control chronic (but not acute) LCMV infection (Harker et al. Science 2011 and Immunity 2013). Strikingly, new preliminary data suggest that while IL-6 operates similarly in LCMV and MCMV infections, IL-27 is not necessary for survival of MCMV-specific CD4 T cells and instead suppresses the differentiation of granzyme A producing and KLRG1+EOMEShigh (putative cytotoxic) MCMV-specific CD4 T cells, which frequency correlates with MCMV control. Consistently, IL-27 appears to promote (rather than restrain) MCMV persistence and latent loads. The overall goal of the current proposal is to fully dissect the mechanisms underlying IL-6 and IL-27 induction as well as their regulation of CD4 T cell responses during chronic infection with a continuously replicating virus (LCMV) and to further investigate their roles during infection with a virus that establishes latency (MCMV). To accomplish this goal, we propose in aim #1 to investigate the induction of IL-6 and IL-27 production (including cellular sources and upstream signaling pathways) throughout chronic LCMV infection. In aim #2, we plan to study the molecular mechanisms of IL-6 and IL-27 downstream signaling pathways, STAT targeting and epigenetic status of Tfh-related and IL-21 gene promoters and the role of potential STAT co- regulators in shaping CD4 T cell responses early vs. late after chronic LCMV infection. Lastly, in aim #3 we will evaluate the role of IL-6 an IL-27 signaling in CD4 T cells during chronic MCMV infection and investigate their relevant time of action, cellular source as well as the significance and mechanisms underlying IL-27 suppression of MCMV-specific KLRG1+EOMEShigh (putative cytotoxic) CD4 T cells that prominently appear during MCMV (but not LCMV) infection. The knowledge gained from the proposed experiments will not only enhance our understanding of the basic biology of key immune players (i.e. IL-6, IL-27 and CD4 T cells) but may also provide valuable information for therapeutically manipulating the aforementioned cytokines during chronic viral infections and potentially CMV-based vaccination.