Direct Regulation of CD8 T Cells by Interferon gamma

描述（由申请人提供）：竞技场病毒是人类病毒性出血热（VHF）的众多病原之一。由于与这些感染相关的高死亡率和发病率，以及被用作生物恐怖主义制剂的潜力，沙粒病毒被列为A类病原体。目前，还没有疫苗可以保护人类免受竞技场病毒感染。旧大陆竞技场病毒包括拉沙病毒和淋巴细胞脉络丛脑膜炎病毒（LCMV）。有证据表明，由CD8 T细胞介导的细胞免疫在防御LCMV和最有可能的拉沙病毒方面是重要的。因此，针对这些病毒的疫苗需要产生有效的CD8 T细胞记忆。然而，诱导CD8 T细胞记忆的机制尚不清楚，目前这是一个深入研究的领域。通常，CD8 T细胞的反应可以分为三个不同的阶段：(1)扩增阶段，即初始T细胞经历抗原驱动的增殖并分化为效应细胞；(2)收缩阶段，即90-95%的扩增T细胞被消除；(3)记忆阶段，即剩余5%的扩增CD8 T细胞作为记忆T细胞存活较长时间。记忆性CD8 T细胞的数量取决于扩张的程度和收缩的程度。由于保护性免疫依赖于记忆性CD8 T细胞阈值数量的诱导，因此彻底了解T细胞反应扩张和收缩阶段的调节机制至关重要。利用表征良好的小鼠LCMV模型，我们已经获得了强有力的初步数据，表明IFNgamma受体（IFNgamma）信号传导在限制抗原特异性记忆CD8 T细胞在T细胞反应收缩期存活的数量方面起着重要作用。在此基础上，一个强有力的案例可以用来调节IFNgammaR信号，以增加接种期间记忆性CD8 T细胞的数量。了解IFNgammaR调控lcmv特异性CD8 T细胞反应的机制是本提案的重点。具体目标是：(1)利用TCR转基因小鼠、骨髓嵌合小鼠和IFN（无应答）转基因T细胞，确定IFNgammaR在T细胞与非T细胞上表达在体内调节CD8 T细胞应答中的重要性。(2)通过抗体阻断实验和建立T细胞谱系中IFNgammaR表达可随意开启和关闭的转基因小鼠模型，研究IFNgammaR信号时空调控在调节lcmv特异性CD8 T细胞收缩期中的重要性；(3)确定IFNgammaR缺乏对lcmv特异性记忆CD8 T细胞的质性和功能属性的影响。这些研究应有助于开发针对竞技场病毒的疫苗，特别是针对其他病毒的疫苗。

DESCRIPTION (provided by applicant): Arena viruses are one of the many etiologic agents of viral hemorrhagic fever (VHF) in humans. Because of the high rates of mortality and morbidity associated with these infections, and the potential of being used as agents of bioterrorism, are arenaviruses are classified under category A pathogens. At the present time, there are no vaccines to provide protection against arena viral infections in human beings. The Old World arena viruses include the Lassa virus and lymphocytic choriomeningitis virus (LCMV). Evidence indicate that cellular immunity mediated by CD8 T cells is important in defense against LCMV, and most likely Lassa virus. Therefore, vaccines against these viruses need to engender potent CD8 T cell memory. However, the mechanism(s) of induction of CD8 T cell memory are not well understood and currently, this is an area of intense investigation. Typically, CD8 T cell responses can be divided into three distinct phases: (1) the expansion phase when naive T cells undergo antigen-driven proliferation and differentiation into effector cells, (2) the contraction phase when 90-95% of the expanded T cells are eliminated, and (3) the memory phase when the remaining 5% of the expanded CD8 T cells survive for extended periods as memory T cells. The number of memory CD8 T cells generated is dependent upon the extent of expansion and the magnitude of contraction. Since protective immunity is dependent upon the induction of a threshold number of memory CD8 T cells, it is critical to gain a thorough understanding of the mechanisms that regulate the expansion and contraction phases of the T cell response. Using the well-characterized LCMV model in mice, we have obtained strong preliminary data that IFNgamma receptor (IFNgammaR) signaling plays an important role in limiting the number of antigen-specific memory CD8 T cells that survive the contraction phase of the T cell response. Based on this a strong case can be made to modulate IFNgammaR signaling to augment the number of memory CD8 T cells during vaccination. Understanding the mechanisms underlying the regulation of LCMV-specific CD8 T cell response by IFNgammaR is the focus of this proposal. The specific aims are: (1) To determine the importance of IFNgammaR expressed on T cells vs. non-T cells in regulating CD8 T cell responses in vivo by utilizing TCR transgenic mice, bone marrow chimeric mice, and IFN( unresponsive transgenic T cells, (2) To investigate the importance of temporal and spatial control of IFNgammaR signaling in the regulation of the contraction phase of LCMV-specific CD8 T cell response by antibody blocking experiments and by developing a transgenic mouse model in which IFNgammaR expression in T-cell lineage can be turned on and off at will, and (3) To determine the effect of IFNgammaR deficiency on the qualitative and functional attributes of LCMV-specific memory CD8 T cells. These studies should aid in the development of vaccines against arena viruses in particular and other viruses in general.