HTLV Pathogenesis in SCID-IL2R-gamma-null Mice

描述（由申请人提供）：HTLV-1与成人T细胞白血病（ATL）和称为HAM/TSP的神经系统疾病的发展有关。由于缺乏概括其发病机制的动物模型，对HTLV白血病发生的基本机制的理解受到了限制。HTLV-1感染人造血祖细胞和造血干细胞（CD34+）（分别为HPCs和hsc），用感染的CD34+细胞接种NOD/SCID小鼠可导致人造血，并将病毒感染传播到成熟的人T细胞和单核细胞。HTLV-1感染和Tax1在CD34+造血干细胞中的表达可能在体内分化过程中维持病毒潜伏期、隔离病毒和HTLV感染的传播中发挥作用。我们假设HTLV-1感染的BM中的CD34+细胞在体内充当病毒感染的储存库，并且这些细胞中的Tax1表达引发了在ATL发展中表现出来的诱变事件。新开发的NOD- scid IL2R-null小鼠将用于表征HTLV在体内复制的动力学，并确定感染是否导致白血病发生。慢病毒载体（LV）介导的Tax1转导进入人CD34+细胞将评估这种病毒癌蛋白在NOD-scid il - 2r缺失小鼠T淋巴生成中的作用。我们建议评估htlv感染细胞亚群中通常与ATL发展相关的肿瘤抑制基因突变。我们独特的专业知识组合将使我们能够开发一种新的范式来检查HTLV感染和Tax表达诱导的造血干细胞中的分子事件，这些事件有助于病毒介导的白血病发生。目的1：在HTLV-1感染CD34+ HPCs的NOD-scid il - 2r缺失小鼠中，表征HTLV感染、复制倾向性和人造血重建后的白血病发生。确定HTLV-1感染是否扰乱体内造血功能并诱导白血病发生。确定受htlv感染的造血干细胞和祖细胞引起的淋巴细胞增生中肿瘤抑制基因的突变是否与ATL患者相似。目的2：在NOD- scid il - 2r -null -hu小鼠模型中，利用慢病毒载体（LV）介导的CD34+ HPCs转导和造血重建，研究Tax1和Tax2在T淋巴生成中的作用。目的3：利用含有外源Tax基因的HTLV-1和HTLV-2的感染性重组原病毒克隆研究NOD-scid il - 2r -null -hu小鼠的感染情况。确定HTLV HBZ在体内的复制动力学和发病机制。人T细胞白血病病毒（HTLV）引起成人T细胞白血病（ATL）和一种称为HAM/TSP的神经系统疾病。我们推测HTLV感染人类干细胞并使细胞易致白血病，导致感染的“癌症干细胞”。在支持人类淋巴细胞发育的免疫缺陷小鼠中建立HTLV感染模型，将使我们能够确定HTLV感染导致人类干细胞白血病的分子事件。

DESCRIPTION (provided by applicant): HTLV-1 has been linked to the development of adult T cell leukemia (ATL) and a neurological disorder termed HAM/TSP. Limitations in the understanding of fundamental mechanisms of leukemogenesis by HTLV have predominantly been hampered by the lack of an animal model which recapitulates pathogenesis. HTLV-1 infects human hematopoietic progenitor and stem (CD34+) cells (HPCs and HSCs, respectively) and inoculation of NOD/SCID mice with infected CD34+ cells results in human hematolymphopoiesis and dissemination of viral infection to mature human T cells and monocytes. HTLV-1 infection and Tax1 expression in CD34+ HSCs may play a role in maintenance of viral latency, sequestration of virus and in dissemination of HTLV infection during differentiation in vivo. We postulate that HTLV-1 infected CD34+ cells in the BM serve as a reservoir for viral infection in vivo and that Tax1 expression in these cells initiates mutagenic events which manifest in development of ATL. The newly-developed NOD- scid IL2R-null mouse will be used to characterize the kinetics of HTLV replication in vivo and determine if infection results in leukemogenesis. Lentiviral vector (LV) mediated transduction of Tax1 into human CD34+ cells will evaluate the role of this viral oncoprotein on T lymphopoiesis in NOD-scid IL2R-null hu mice. We propose to evaluate HTLV-infected cell subpopulations for mutations in tumor suppressor genes commonly associated with ATL development. Our unique combination of expertise will allow us to develop a novel paradigm to examine the molecular events in hematopoietic stem cells induced by HTLV infection and Tax expression which contributes to virally-mediated leukemogenesis. Specific Aims are: Aim 1: Characterize HTLV infection, replication tropism and leukemogenesis following reconstitution of human hematopoiesis in NOD-scid IL2R-null mice with HTLV-1 infected CD34+ HPCs. Establish if HTLV-1 infection perturbs hematopoiesis in vivo and induces leukemogenesis. Determine whether mutations in tumor suppressor genes occur in lymphoproliferations arising from infected HTLV-infected hematopoietic stem and progenitor cells are similar to those in ATL patients. Aim 2: Examine the role of Tax1 and Tax2 on T lymphopoiesis using lentivirus vector (LV) -mediated transduction of CD34+ HPCs and reconstitution of hematopoiesis in the NOD- scid IL2R-null -hu mouse model. Aim 3: Investigate infection of the NOD-scid IL2R-null -hu mouse using infectious recombinant proviral clones of HTLV-1 and HTLV-2 containing the heterologous Tax genes. Determine the replication kinetics and pathogenesis of HTLV HBZ in vivo. Human T cell leukemia virus (HTLV) causes Adult T cell leukemia (ATL) and a neurological disorder termed HAM/TSP. We speculate that HTLV infects human stem cells and predisposes cells to become leukemogenic, resulting in an infected "cancer stem cell". Modeling HTLV infection in an immune deficient mouse which supports the development of human lymphocytes will allow us to define molecular events induced by HTLV infection in human stem cells which result in leukemia.