ISG15 REGULATION OF ANTIVIRAL IMMUNE RESPONSES

描述(申请人提供)：最近爆发的高致病性流感病毒突显了更好地了解流感病毒发病的分子机制和宿主对这些病毒的免疫反应的必要性。病毒感染会引发迅速的抗病毒反应，包括从巨噬细胞和树突状细胞等细胞释放促炎细胞因子。I型干扰素(IFN)通过上调大量干扰素刺激基因(ISGs)来协调宿主的反应。一些ISGs具有直接的抗病毒活性，而其他ISGs则通过调节免疫系统来影响抗病毒反应。我们最近发现其中一个ISG，ISG15，作为干扰素诱导的抗病毒的关键分子发挥作用。ISG15是一种泛素同系物，受IFN、Toll受体结扎和病毒感染的强烈上调。ISG15缺陷小鼠在感染几种病毒后显示出更高的致死率，包括甲型和乙型流感病毒。然而，ISG15发挥这种抗病毒活性的机制尚不清楚。ISG15可与多种细胞内蛋白结合，靶向多种生物过程。人ISG15也从细胞中释放出来，发挥细胞因子的作用，激活包括树突状细胞在内的免疫细胞。我们已经证明，病毒感染诱导ISG15结合物的形成和其释放到血清中。我们还在病毒感染后的ISG15-/-小鼠中看到了强有力的促炎细胞因子反应。综上所述，这些数据使我们得出这样的假设，即ISG15在病毒感染期间调节树突状细胞的功能，以调节先天免疫反应，并可能调节获得性免疫反应。这项提议的目标是通过以下目标来检验这一潜在的假设。目标1中的研究将确定ISG15缺陷的树突状细胞在对病毒感染的反应中是否存在内在缺陷。我们将评估它们产生促炎细胞因子和作为抗原提呈细胞的能力。AIM 2上的研究将确定ISG15缺陷小鼠对病毒感染的免疫反应是否发生改变。最后，在目标3中，我们将测试在树突状细胞中表达ISG15将把ISG15-/-小鼠从死亡中拯救出来的假设。这些研究的结果将为新发现的抗病毒分子的潜在作用机制提供重要的见解，并为未来对ISG15活性的研究提供必要的基础。

DESCRIPTION (provided by applicant): Recent outbreaks of highly pathogenic influenza virus have highlighted the need for a better understanding of the molecular mechanisms of influenza virus pathogenesis and the host immune response to these viruses. Viral infection triggers a prompt anti-viral response, including the release of proinflammatory cytokines from cells such as macrophages and dendritic cells. Type I interferons (IFNs) coordinate the host response by upregulating a large number of IFN stimulated genes (ISGs). Several ISGs have direct antiviral activity, while others impact upon the antiviral response by modulating the immune system. We have recently shown that one of these ISGs, ISG15, functions as a critical IFN induced anti-viral molecule. ISG15 is an ubiquitin homolog that is strongly upregulated by IFNs, toll receptor ligation, and viral infection. ISG15 deficient mice display increased lethality following infection with several viruses, including both influenza A and B viruses. Yet the mechanism by which ISG15 exerts this antiviral activity is unknown. ISG15 conjugates to a wide array of intracellular proteins, targeting numerous biological processes. Human ISG15 is also released from cells and functions as a cytokine, activating immune cells including dendritic cells. We have shown that viral infection induces both ISG15 conjugate formation and its release into the serum. We also see a potent proinflammatory cytokine response in ISG15-/- mice following viral infection. Together, these data lead us to the hypothesis that ISG15 regulates the function of dendritic cells during viral infection to modulate the innate, and potentially the adaptive immune response. The goal of this proposal is to test this underlying hypothesis via the follow Aims. The studies in Aim 1 will determine if ISG15 deficient dendritic cells have an intrinsic defect in their response to viral infection. We will evaluate their ability to produce proinflammatory cytokines and function as antigen presenting cells. The studies in Aim 2 will determine if the immune response to viral infection in altered in ISG15 deficient mice. Finally, in Aim 3 we will test the hypothesis that expression of ISG15 in dendritic cells will rescue ISG15-/- mice from lethality. The results obtained from these studies will provide important insight into a potential mechanism of action for a newly identified antiviral molecule, and provide the necessary groundwork for future investigations into ISG15 activity.