Functional Analyses of Antiviral CD4+ T Cell Responses

说明(申请人提供)：保护性免疫，无论是由感染或接种疫苗诱导的，都依赖于足够数量和足够质量的记忆B&T细胞的产生。这一过程的成功在很大程度上依赖于CD4+T细胞提供的“帮助”。CD4+T细胞在协调适应性免疫反应中发挥着核心作用，但它们的丰度受到调节的机制、反复抗原接触的重要性以及它们为CD8+T细胞提供帮助的方式都仍不确定。这项应用的总体目标是(I)继续我们的研究，即在体内，干扰素如何调节CD4+T细胞的数量和质量，以及体内与持久性病毒抗原的接触如何影响它们(AIMS 1和2)；以及(Ii)研究CD4+T细胞如何提供良好的抗病毒CD8+T细胞记忆所需的帮助(AIMS 3和4)。目的1.确定干扰素是如何直接作用的？信号对原代和记忆中的CD4+T细胞的丰度有着深远的影响。我们已经证明，CD4+T细胞可以直接对干扰素？是内存池中容量的100倍。我们会在什么时候确定干扰素的效果？基因表达发生了什么变化；哪些细胞产生了这种重要的细胞因子。目的2.探讨延长MHC-II类抗原提呈时间对CD4+T细胞数量和质量的影响。众所周知，在慢性感染期间，持续抗原可以显著改变T细胞的反应。然而，在急性病毒感染的模型中，抗原持久性问题的定义要少得多。我们发现，在急性病毒感染后的数周内，MHC-II类细胞呈现病毒抗原。我们将测量持久性抗原对CD4+T细胞功能的影响。抗原驱动的干扰素吗？生产塑造了CD4+T细胞的反应？目的3.探讨病毒特异性和非特异性CD4+T细胞的免疫功能。我的实验室是首批表明在急性病毒感染后建立CD8+T细胞记忆的关键细胞之一，这一观察结果已得到多个实验室的证实和推广。令人惊讶的是，CD4+T细胞似乎能够以一种非特异性(“非同源”)的方式为CD8+T细胞提供帮助。我们将比较针对病毒表位特异的CD4+T细胞和不能识别病毒的CD4+T细胞的帮助。目的4.确定干扰素？是CD4+T细胞帮助的关键介质。最终的目标包括两条线索：(I)CD4+T细胞的帮助是发育良好的CD8+T细胞记忆所必需的事实；(Ii)我们最近的发现是干扰素？对CD8+T细胞记忆的发育至关重要。可能会产生干扰素？是不是CD4+T细胞帮助CD8+T细胞记忆发育的“纽带”？干扰素的作用是什么？对于特定的和非特定的CD4+辅助T细胞也是如此？公共卫生相关性：CD4+T细胞在调节对感染和疫苗接种的免疫反应中发挥核心作用。令人惊讶的是，我们不知道他们到底做了什么，以及他们是如何做到的。事实上，最近的一些数据表明，即使疫苗不能刺激CD4+T细胞的反应，它们也可能起到很好的作用。这项拨款申请调查了围绕着重要但鲜为人知的细胞的几个问题。

DESCRIPTION (provided by applicant): Protective immunity, whether induced by infection or by vaccination, relies on the generation of memory B & T cells in sufficient quantity, and of sufficient quality. The success of this process is heavily dependent on "help" that is provided by CD4+ T cells. CD4+ T cells play a central role in orchestrating the adaptive immune response but the mechanism by which their abundance is regulated, the importance of recurrent antigen contact, and the means by which they provide help to CD8+ T cells all remain uncertain. The overall goals of this application are (i) to continue our studies of how CD4+ T cell quantity and quality are regulated in vivo by IFN?, and how they are affected by in vivo contact with persistent virus antigen (Aims 1 & 2); and (ii) to investigate how CD4+ T cells provide the help that is required for the development of good antiviral CD8+ T cell memory (Aims 3 & 4). Aim 1. To determine how direct IFN? signaling exerts its profound effects on the abundance of primary and memory CD4+ T cells. We have shown that CD4+ T cells that can respond directly to IFN? are 100- fold more abundant in the memory pool. We will determine when the effect of IFN? is exerted; what changes in gene expression occur as a result; and which cells produce this important cytokine. Aim 2. To evaluate the effects of prolonged MHC class II antigen presentation on CD4+ T cell quantity and quality. It is well-established that, during chronic infection, persistent antigen can dramatically alter the T cell response. However, the issue of antigen persistence is much less well-defined in models of acute viral infection. We have found that MHC class II presents virus antigen for weeks after acute virus infection. We shall measure the effects of persistent antigen on CD4+ T cell functions. Does antigen- driven IFN? production sculpt the CD4+ T cell response? Aim 3. To investigate the help that is provided by virus-specific and non-specific CD4+ T cells. My lab was among the first to show that CD4+ T cells played a key role in establishing CD8+ T cell memory following acute virus infection, an observation that has been confirmed and extended by a number of labs. Surprisingly, CD4+ T cells seem to be able to provide help to CD8+ T cells in a non-specific ("noncognate") fashion. We shall compare the helpfulness of CD4+ T cells that are specific for a viral epitope, with the helpfulness of CD4+ T cells that cannot recognize the virus. Aim 4. To determine if IFN? is a key mediator of CD4+ T cell help. The final Aim draws together two threads: (i) the fact that CD4+ T cell help is required for the development of good CD8+ T cell memory and (ii) our recent finding that IFN? is vitally important for the development of CD8+ T cell memory. Might IFN? be the "link" by which CD4+ T cells help the development of CD8+ T cell memory? Is the role of IFN? the same for specific & non-specific CD4+ helper T cells? PUBLIC HEALTH RELEVANCE: CD4+ T cells play a central role in regulating the immune response to infection and vaccination. Surprisingly, we do not know exactly what they do, and how they do it. Indeed, some recent data suggest that vaccines might work quite well even if they do not stimulate CD4+ T cell responses. This grant application investigates several of the questions surrounding the important, but poorly-understood, cells.