ISG15 REGULATION OF ANTIVIRAL IMMUNE RESPONSES

描述（由申请方提供）：最近高致病性流感病毒的爆发突出了更好地理解流感病毒致病的分子机制和宿主对这些病毒的免疫应答的需要。病毒感染触发迅速的抗病毒应答，包括从细胞如巨噬细胞和树突细胞释放促炎细胞因子。I型干扰素（IFN）通过上调大量IFN刺激基因（ISG）来协调宿主应答。一些ISG具有直接的抗病毒活性，而其他ISG通过调节免疫系统影响抗病毒应答。我们最近已经表明，这些ISG之一，ISG15，作为一个关键的IFN诱导的抗病毒分子的功能。ISG15是一种泛素同源物，其被IFN、toll受体连接和病毒感染强烈上调。ISG 15缺陷型小鼠在感染几种病毒（包括甲型流感病毒和B流感病毒）后显示出增加的致死率。然而，ISG15发挥这种抗病毒活性的机制尚不清楚。ISG15与多种细胞内蛋白质结合，靶向许多生物过程。人ISG 15也从细胞中释放出来，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。我们已经表明，病毒感染诱导ISG15缀合物形成及其释放到血清中。我们还在病毒感染后的ISG15-/-小鼠中观察到有效的促炎细胞因子应答。总之，这些数据使我们假设ISG15在病毒感染期间调节树突状细胞的功能，以调节先天免疫应答和潜在的适应性免疫应答。本提案的目的是通过以下目标来检验这一基本假设。目标1中的研究将确定ISG15缺陷树突状细胞在其对病毒感染的应答中是否具有内在缺陷。我们将评估它们产生促炎细胞因子的能力和作为抗原呈递细胞的功能。目的2中的研究将确定ISG15缺陷小鼠对病毒感染的免疫应答是否改变。最后，在目的3中，我们将检验树突细胞中ISG15的表达将使ISG15-/-小鼠免于致死的假设。从这些研究中获得的结果将为新鉴定的抗病毒分子的潜在作用机制提供重要的见解，并为未来研究ISG15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.