Allogeneic chimerism in murine sickle cell disease

描述(申请人提供)：镰状细胞病是一种衰弱的遗传性血红蛋白疾病，是世界上最常见的单基因疾病。造血干细胞移植是SCD的唯一根治方法；然而，毒性的清髓调节方案和异基因移植的障碍限制了其在有主要并发症的儿童和HLA相合的供者中的应用。新的骨髓抑制/免疫抑制移植策略正在涌现，以降低发病率和死亡率，并通过故意诱导混合造血嵌合体使更多的患者获得细胞移植。然而，这些方案提出了重要的问题，可以在临床前模型中最好地解决。使用仅表达人类镰状血红蛋白的镰状细胞病小鼠模型，我们定义了一种非清髓性移植方案，在纠正该疾病的血液学和病理学表现的同时，诱导混合造血嵌合体和对不同MHC捐赠者的耐受。在目标1中，我们将扩展这些研究，以确定为镰状细胞疾病提供血液学和/或生理学治疗的供者嵌合体的水平。我们将确定极低水平的干细胞嵌合体是否可以诱导和维持同种异体耐受，以及转基因细胞群体是否可以扩大以提供永久纠正的混合嵌合状态。镰状细胞病现在被认为是多种细胞类型之间复杂的炎性相互作用，导致病理结果。这些相互作用也可能是干细胞移植治疗镰状细胞病的排斥率增加的原因。在目标2中，我们将研究参与这一排斥过程的炎症和免疫学机制。我们将研究共刺激阻断抵抗排斥、免疫效应群体、黏附分子和细胞因子在同种异体排斥反应中的参与和贡献。这些目的是为研究混合嵌合体和镰刀细胞病的病理生理学之间的关系以及镰刀细胞病移植中发现的增强的排斥率提供一种全面的系统方法。这两个目标都解决了移植耐受和排斥的基本机制，并提供了设计未来非清髓性移植方案所需的关键临床前数据。

DESCRIPTION (provided by applicant): Sickle cell disease is a debilitating inherited hemoglobin disorder that is the most common single-gene disease in the world. Hematopoietic stem cell transplantation is the only curative therapy for SCD; however toxic myeloablative conditioning regimens and barriers to allotransplantation have limited its use to children with major complications and HLA matched donors. New myelosuppressive/immunosuppressive transplant strategies are emerging to reduce morbidity and mortality and to make cell transplantation available to a larger number of patients by intentionally inducing mixed hematopoietic chimerism. However, these protocols raise significant issues that can be best addressed in a preclinical model. Using a murine model of sickle cell disease that expresses exclusively human sickle hemoglobin we have defined a non-myeloablative transplant protocol that induces mixed hematopoietic chimerism and tolerance to MHC disparate donors while correcting hematologic and pathologic manifestations of the disease. In Aim 1, we will extend these studies to determine the levels of donor chimerism that provide hematologic and/or physiologic cure of sickle cell disease. We will determine if very low levels of stem cell chimerism can induce and maintain allogeneic tolerance, and whether genetically modified cell populations can be expanded to provide a permanently corrective mixed chimeric state. Sickle cell disease is now recognized as having complex inflammatory interactions between multiple cell types that lead to pathological outcomes. These interactions may also be responsible for the increased rate of rejection found in stem cell transplantation for sickle cell disease. In Aim 2 we will investigate inflammatory and immunological mechanisms involved in this rejection process. We will investigate co-stimulation blockade resistant rejection, immune effector populations, adhesion molecules and cytokines for their involvement and contribution to allogeneic rejection. These aims provide a comprehensive systematic approach to studying the relationship between mixed chimerism and sickle pathophysiology and the enhanced rejection rate found in transplantation for sickle cell disease. Both Aims address basic mechanisms of transplantation tolerance and rejection as well as providing the critical preclinical data that are required for the design of future non-myeloablative transplants protocols.