CD8 T Cell Response to Murine Cytomegalovirus

描述（由申请人提供）：巨细胞病毒（CMV）感染的特征是巨大的效应/记忆T细胞应答，终生维持在高水平-一种称为记忆膨胀的现象。我们已经报道，“膨胀记忆”细胞实际上是短寿命的效应细胞，不断从感染早期产生的真正的记忆细胞分化。真正的记忆细胞不容易从受感染宿主的脾脏转移到受感染的受体，我们认为它们存在于基质龛中。我们还表明，一个单周期的CMV在第一次进入人体时无法传播到它感染的细胞之外，这会驱动令人惊讶的强大记忆膨胀。这两个发现定义了我们在这个项目中试图解开的悖论：少量受感染的细胞如何呈递抗原以保持免疫系统持续激活而不被免疫根除？我们首先要问的是，关于病毒存在的信息是否通过病毒抗原的直接或交叉呈递传递给T细胞。这将通过产生表达Kb的病毒以限制抗原呈递至直接感染的细胞来实现。 接下来，我们将使用器官消化、细胞分选和生物测定的迭代过程来鉴定携带病毒基因组的细胞和将抗原呈递给T细胞的细胞。作为一种替代方法，我们将产生病毒，该病毒可用于感染cre小鼠，以将抗原表达限制在特定组织或细胞类型。最后，我们将描述潜伏感染者的特征， 细胞的免疫表型、病毒基因表达以及在与记忆性CD 8和CD 4 T细胞共过继转移后驱动记忆膨胀的充分性。了解驱动记忆膨胀的病毒程序将使我们能够智能地 工程化CMV载体作为疫苗以产生有效的免疫应答。它也将帮助我们了解CMV在某些慢性疾病中的作用，以及它与免疫衰老的假定联系。 公共卫生相关性：巨细胞病毒是一种普遍存在的人类病毒，可激发受感染宿主产生极大的免疫反应。这种巨大的免疫反应可能是有害的，有助于老年人的免疫衰老，或者当CMV用作疫苗载体时是有益的。目前尚不清楚为什么免疫反应如此之大，我们发现即使是非传染性CMV疫苗也会引起巨大的反应，这一发现进一步加深了这个谜团。该项目的目标是准确了解CMV如何激发这种前所未有的反应。使用非感染性疫苗，我们将找到驱动反应的细胞，并确定它们如何与免疫系统相互作用以驱动反应。这些知识将直接用于我们开发基于CMV的癌症疫苗的其他工作。

DESCRIPTION (provided by applicant): Cytomegalovirus (CMV) infection is characterized by enormous effector/memory T cell responses that are maintained at high levels for life- a phenomenon known as memory inflation. We have reported that "inflationary memory" cells are in fact short lived effector cells continuously differentiating from true memory cells generated early during infection. The true memory cells are not readily transferred from the spleen of an infected host to an infected recipient, and we suggest that they reside in a stromal niche. We have also shown that a single cycle CMV which is unable to spread beyond the cells it infects upon first entering the body drives surprisingly robust memory inflation. These two findings define the paradox that we seek to unravel in this project: how can a tiny number of infected cells present antigen to keep the immune system constantly activated without being subject to immune eradication? We first ask whether the information about viral presence is transmitted to T cells through direct or cross presentation of viral antigen. This will be accomplished by generating a virus expressing Kb in order to limit antigen presentation to directly infected cells. We will next use an iterative process of organ digestion, cell sorting and bioassays to identify the cells that carry the viral genome and the cells that present antigen to T cells. As an alternative approach, we will generate virus which can be used to infect cre mice to limit antigen expression to particular tissues or cell types. Finally, we will characterize the latently infected cells with respect to their immunological phenotype, their viral gene expression, and their sufficiency for driving memory inflation upon co-adoptive transfer with memory CD8 and CD4 T cells. Understanding the viral program that drives memory inflation will enable us to intelligently engineer CMV-vectors as vaccines to generate potent immune responses. It will also help us to understand CMV's role in certain chronic diseases, and its putative association with immunosenescence. PUBLIC HEALTH RELEVANCE: Cytomegalovirus is a ubiquitous human virus that excites an extremely large immune response from the infected host. This enormous immune response can be harmful, contributing to immunosenescence in the elderly, or helpful, when CMV is used as a vaccine vector. It is not known why the immune response is so large, and the mystery was heightened by our discovery that even a non-infectious CMV vaccine drives an enormous response. The goal of this project is to understand exactly how CMV excites this unprecedented response. Using the non-infectious vaccine, we will find the cells that drive the response and determine how they interact with the immune system to drive the response. This knowledge will be exploited directly in our other work to develop a CMV-based cancer vaccine.