Humanized Mouse Models of Severe Combined Immunodeficiency

描述（由申请方提供）：严重联合免疫缺陷（SCID）是一组异质性致死性先天性疾病，其特征为缺乏T淋巴细胞。T细胞从骨髓来源的T祖细胞发育，其迁移到胸腺并在输出到血液之前分化。最常见的形式，X连锁SCID，是由于缺乏共同的γ链（？c）表达。由于缺乏X连锁SCID的小鼠模型，我们仍然对为什么缺乏的原因知之甚少。c损害T细胞发育。该项目的目标是确定在没有？c在T祖细胞生成、胸腺接种和/或胸腺内发育水平上是异常的。我们推测T细胞的发育在T细胞祖细胞阶段受到影响，在胸腺内发育的早期阶段受到更严重的影响。我们进一步假设，分化失败，而不是在增殖/生存的缺陷，导致发展中的绝对块，这种失败可以通过重建的特定组件获救？c信号通路。在目标1，我们将研究正常的表达？c在人T细胞祖细胞中的表达，并研究T祖细胞是否存在于X连锁SCID患者的骨髓中。在目标2和目标3中，我们将创建人源化小鼠，c缺陷免疫系统，使用一种新的NOD-scid免疫缺陷小鼠品系，可以支持体内人T细胞分化（NOD/scid II 2 rgnull）。目的2：我们将用正常人骨髓重建NOD/scid I12 rgnull小鼠，其中？c已被短发夹RNA的慢病毒表达敲除。使用这些“？c基因敲除小鼠，“我们将分析骨髓和胸腺，并表征T细胞分化阻滞的精确性质。在目的3中，我们将用来自X-连锁SCID患者的骨髓重建NOD/scid I12 rgnull小鼠。然后，我们将使用这种“人源化X-SCID”小鼠模型来测试STAT 5通路或Akt通路的激活是否可以在缺乏？C.人源化小鼠将使我们能够在易于处理的动物系统中繁殖正常和异常的人类免疫系统，并弥合目前存在于小鼠模型和人类疾病之间的差距。我们相信这个模型也将最终导致发现对人类免疫发育至关重要的新基因和SCID的新疗法。公共卫生相关性：T细胞是免疫系统的重要组成部分。先天性缺乏T细胞（严重联合免疫缺陷或SCID）或获得性免疫缺陷（如艾滋病，骨髓移植后或癌症治疗后）都会导致显著的发病率和死亡率。通过研究为什么T细胞不能以最常见的SCID形式发育，我们希望开发出增强T细胞发育的疗法，从而反过来增强T细胞依赖性免疫反应。

DESCRIPTION (provided by applicant): Severe combined immunodeficiency (SCID) is a heterogeneous group of fatal congenital disorders characterized by the absence of T lymphocytes. T cells develop from bone marrow derived T progenitors that migrate to the thymus and differentiate before export to the blood. The most common form, X-linked SCID, is caused by lack of common gamma chain (?c) expression. Because mouse models for X-linked SCID are lacking, we still know surprisingly little about why lack of ?c impairs T cell development. The goal of this project is to determine the stage(s) at which T cell development in the absence of ?c is aberrant, at the level of T progenitor generation, thymus seeding and/or intrathymic development. We hypothesize that T development will be affected at the T progenitor stage and more severely affected at an early stage of intrathymic development. We further hypothesize that failure of differentiation, rather than defects in proliferation/survival, causes an absolute block in development and that this failure can be rescued by reconstituting the specific components of the ?c signaling pathway. In Aim 1, we will examine the normal expression of ?c in human T cell progenitors and investigate whether T progenitors are present in the bone marrow of patients with X-linked SCID. In Aim 2 and Aim 3, we will create humanized mice bearing ?c deficient immune systems, using a new strain of NOD-scid immunodeficient mice that can support human T cell differentiation in vivo (NOD/scid Il2rgnull). In Aim 2 we will reconstitute NOD/scid Il2rgnull mice with normal human bone marrow in which ?c has been knocked down by lentiviral expression of short hairpin RNA. Using these "?c knockdown mice," we will analyze bone marrow and thymus, and characterize the precise nature of the T cell differentiation block. In Aim 3 we will reconstitute NOD/scid Il2rgnull mice with bone marrow from patients with X-linked SCID. We will then use this "humanized X-SCID" mouse model to test whether activation of the STAT5 pathway or Akt pathway can restore T cell development in the absence of ?c. Humanized mice will give us the ability to propagate normal and aberrant human immune systems in a tractable animal system and bridge the gap that currently exists between mouse models and human disease. We believe this model will also ultimately lead to discovery of novel genes critical for human immune development and novel therapies for SCID. PUBLIC HEALTH RELEVANCE: T cells are an essential component of the immune system. Congenital absence of T cells (severe combined immunodeficiency or SCID) or acquired immunodeficiency (such as in AIDS, following bone marrow transplantation or after cancer treatment) all cause significant morbidity and mortality. By studying why T cells fail to develop in the most common form of SCID, we hope to develop therapies that enhance T cell development and thus in turn enhance T cell dependent immune responses.