Direct Regulation of CD8 T Cells by Interferon gamma

描述（由申请方提供）：竞技场病毒是人类病毒性出血热（VHF）的多种病原体之一。由于与这些感染相关的死亡率和发病率很高，并且有可能被用作生物恐怖主义制剂，因此沙粒病毒被归类为A类病原体。目前，还没有疫苗提供对人类竞技场病毒感染的保护。旧大陆竞技场病毒包括拉沙病毒和淋巴细胞性脉络丛脑膜炎病毒（LCMV）。有证据表明，由CD 8 T细胞介导的细胞免疫在防御LCMV和最有可能的拉沙病毒中是重要的。因此，针对这些病毒的疫苗需要产生有效的CD 8 T细胞记忆。然而，诱导CD 8 T细胞记忆的机制尚未得到很好的理解，目前，这是一个深入研究的领域。通常，CD 8 T细胞应答可以分为三个不同的阶段：（1）扩增阶段，此时初始T细胞经历抗原驱动的增殖和分化成效应细胞，（2）收缩阶段，此时90-95%的扩增的T细胞被消除，和（3）记忆阶段，此时剩余的5%的扩增的CD 8 T细胞作为记忆T细胞存活延长的时间段。产生的记忆性CD 8 T细胞的数量取决于扩增的程度和收缩的幅度。由于保护性免疫依赖于阈值数量的记忆性CD 8 T细胞的诱导，因此对调节T细胞应答的扩张和收缩阶段的机制进行透彻的理解至关重要。在小鼠中使用充分表征的LCMV模型，我们已经获得了强有力的初步数据，即IFN γ受体（IFN γ R）信号传导在限制在T细胞应答的收缩期存活的抗原特异性记忆CD 8 T细胞的数量中起重要作用。基于这一点，可以提出一个强有力的理由来调节IFN γ R信号传导以增加疫苗接种期间记忆性CD 8 T细胞的数量。理解IFN γ R调节LCMV特异性CD 8 T细胞应答的潜在机制是本提案的重点。具体目标是：（1）通过利用TCR转基因小鼠、骨髓嵌合小鼠和IFN γ，确定在T细胞上相对于非T细胞表达的IFN γ R在体内调节CD 8 T细胞应答中的重要性。（无反应的转基因T细胞，（2）探讨IFN γ R信号在LCMV收缩期调控中的时空调控作用。特异性CD 8 T细胞应答，通过抗体阻断实验和通过开发转基因小鼠模型，其中T细胞谱系中的IFN γ R表达可以随意开启和关闭，以及（3）确定IFN γ R缺乏对LCMV特异性记忆性CD 8 T细胞的定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和其他病毒的疫苗。

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.