T cell function in murine gammaherpesvirus infection

描述(申请人提供)：人类伽马疱疹病毒，爱泼斯坦-巴尔病毒和人类疱疹病毒-8，对免疫抑制的个人，如艾滋病患者，造成严重的健康问题。抗病毒T细胞的免疫监测通常包含受感染的细胞，然而，当这种免疫监测失败时，病毒转化的细胞可能会长大并导致疾病。CD8T细胞对伽马疱疹病毒的反应特征相对较好，但越来越多的人认识到CD4T细胞反应在免疫监测中也可能发挥重要作用。然而，在人类系统中，对伽马疱疹病毒特异性CD4T细胞的功能和体内活性的详细剖析是不可能的。因此，我们转向了一种高度易处理的小鼠模型--小鼠伽马疱疹病毒-68，以解决有关CD4T细胞反应的重要问题。阻碍对CD4T细胞反应进行详细研究的一个重要问题是，它们的出现频率非常低。在这里，我们通过使用感染前CD4T细胞频率增加的系统来避免这个问题，使用T细胞受体转基因的CD4T细胞和含有适当抗原的重组MHV-68。随着感染的进展，这个系统可以用来跟踪病毒特异性的CD4T细胞反应。在具体目标1中，我们将使用该系统来确定MHV-68感染中CD4T细胞反应的功能和表型特征。此外，我们将确定维持CD4T细胞反应以使其能够长期存在所必需的因素。在具体目标2中，我们将重点介绍CD4T细胞应答的另一个重要作用--树突状细胞的许可。这一依赖于CD40的过程是将CD4T细胞“帮助”传递给CD8T细胞反应所必需的。在这个目标中，我们将确定树突状细胞的生物学如何在有或没有CD40的情况下发生变化，以在分子水平上理解MHV-68感染期间的许可。我们的第三个具体目标集中在缺乏T细胞帮助的小鼠中MHV-68感染失去控制的机制。我们的初步数据详细说明了一种在CD40缺陷小鼠中重新建立对MHV-68感染的控制的方法，在这种情况下，病毒在肺部自发地重新激活。因此，本节建议了解这种效应背后的确切机制，这可能对患有反复感染伽马疱疹病毒引起的疾病的艾滋病患者有重要的治疗益处。

DESCRIPTION (provided by applicant): The human gammaherpesviruses, Epstein-Barr virus and Human Herpesvirus-8, pose significant health problems in immunosuppressed individuals such as AIDS patients. Immune surveillance by antiviral T cells normally contains infected cells, however when this immune surveillance fails virus-transformed cells can outgrow and cause disease. The CD8 T cell response to gammaherpesviruses is relatively well characterized, but there is a growing appreciation that the CD4 T cell response may also play an important role in immune surveillance. However, a detailed dissection of the function and in vivo activity of gammaherpesvirus-specific CD4 T cells is not possible in human systems. Therefore we turned to a highly tractable mouse model, murine gammaherpesvirus-68, to address important questions regarding the CD4 T cell response. One significant problem which hinders the detailed study of CD4 T cell responses is that they are present at a very low frequency. Here we avoid this problem by using a system where the frequency of CD4 T cells is enlarged prior to infection, using T cell receptor transgenic CD4 T cells and recombinant MHV-68 containing the appropriate antigen. This system can then be used to track the virus-specific CD4 T cell response as the infection progresses. In Specific Aim 1 we will use this system to determine the functional and phenotypic characteristics of the CD4 T cell response in MHV-68 infection. In addition we will determine the factors necessary for sustaining the CD4 T cell response so that it can endure long-term. In Specific Aim 2 we will focus on another important role of the CD4 T cell response - licensing of dendritic cells. This CD40-dependent process is necessary for the transmission of CD4 T cell 'help' to the CD8 T cell response. In this aim we will determine how the biology of dendritic cells changes in the presence or absence of CD40, to understand licensing during MHV-68 infection on a molecular level. Our third Specific Aim focuses on the mechanism behind the loss of control of MHV-68 infection in mice deficient in T cell help. Our preliminary data detail a method of re-establishing control of MHV-68 infection in CD40-deficient mice, where the virus spontaneously reactivates in the lungs. Therefore this section proposes to understand the precise mechanism behind this effect, which may have important therapeutic benefit in AIDS patients suffering from disease caused by recurrent gammaherpesvirus infection.