ISG15 REGULATION OF ANTIVIRAL IMMUNE RESPONSES

描述（由申请人提供）：最近爆发的高致病性流感病毒突出表明需要更好地了解流感病毒发病机制的分子机制和宿主对这些病毒的免疫反应。病毒感染引发迅速的抗病毒反应，包括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（IFNs）通过上调大量IFN刺激基因（ISGs）来协调宿主反应。一些isg具有直接抗病毒活性，而其他isg通过调节免疫系统影响抗病毒反应。我们最近发现其中一个isg， ISG15，作为IFN诱导的关键抗病毒分子发挥作用。ISG15是一种泛素同源物，受干扰素、toll受体连接和病毒感染的强烈上调。ISG15缺陷小鼠在感染多种病毒（包括甲型和乙型流感病毒）后显示出更高的致死率。然而，ISG15发挥这种抗病毒活性的机制尚不清楚。ISG15结合广泛的细胞内蛋白，靶向许多生物过程。人类ISG15也从细胞中释放出来，并作为细胞因子发挥作用，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结合物的形成和释放到血清中。我们还看到ISG15-/-小鼠在病毒感染后出现了强有力的促炎细胞因子反应。综上所述，这些数据使我们提出了ISG15在病毒感染期间调节树突状细胞的功能以调节先天和潜在的适应性免疫反应的假设。本提案的目标是通过以下目标来检验这个潜在的假设。Aim 1的研究将确定ISG15缺陷树突状细胞对病毒感染的反应是否存在内在缺陷。我们将评估它们产生促炎细胞因子的能力和作为抗原提呈细胞的功能。Aim 2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Aim 3中，我们将验证树突状细胞中ISG15的表达将拯救ISG15-/-小鼠免于死亡的假设。这些研究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，并为进一步研究ISG15的活性提供必要的基础。

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.