MIXED HEMATOPOIETIC CELL CHIMERISM IN A MODEL

虽然骨髓移植（BMT）可以治愈许多患有血红蛋白病的患者，但目前的骨髓移植预备方案毒性太大，以至于很少有患者在出现严重且往往不可逆转的疾病并发症之前可以选择这种方案。此外，许多患者没有合适的hla匹配供体，因此没有这种治疗选择。在这个实验室里，我们之前已经在小鼠身上证明了混合嵌合的诱导提供了一种造血重建模式，这种模式涉及毒性更小的制备方案，并且可能适用于跨越MHC屏障。本研究计划的总体目标是将混合淋巴造血嵌合的研究扩展到小型猪，以便为研究这种模式在治疗血红蛋白病中的应用提供一个大型动物临床前模型。具体来说，我们打算：1)将我们的非清髓方案推广到小型猪身上，利用亚致死全身照射诱导混合嵌合；2)确定非常高剂量（“大剂量”）PBSC在不辐照的情况下实现混合嵌合和耐受性的潜力；3)确定混合嵌合诱导后淋巴、髓、红系前体相对重构的研究参数；4)确定混合嵌合诱导后宿主和供体T细胞群体相互耐受诱导的机制。我们的初步数据表明所有这些目标都是可行的，并且表明微型猪模型可能允许我们设计一种临床适用的方案，用于混合嵌合治疗血红蛋白病。

Although bone marrow transplantation (BMT) would offer a cure to many patients with hemoglobinopathies, current preparative regimens for BMT are so toxic that few patients are offered this option until they have developed severe, and often irreversible complications of their disease. In addition, many patients do not have a suitable HLA-matched donor, and therefore do not have this therapeutic option. In this laboratory, we have previously demonstrated in mice that the induction of mixed chimerism provides a mode of hematopoietic reconstitution which involves much less toxic preparative regimens and may be applicable across MHC barriers. The overall objective of this research proposal is to extend our studies of mixed lymphohematopoietic chimerism to miniature swine in order to provide a large animal preclinical model to study the application of this modality to the cure of hemoglobinopathies. Specifically, we intend to: 1) Extend our non-myeloablative regimen for the induction of mixed chimerism, utilizing sublethal whole body irradiation, to miniature swine; 2) Determine the potential of very high doses ("megadoses") of PBSC to achieve mixed chimerism and tolerance without irradiation; 3) Study parameters involved in determining the relative reconstitution of lymphoid, myeloid and erythroid precursors following the induction of mixed chimerism; and 4) Determine the mechanism(s) of mutual tolerance induction in host and donor T cell populations following the induction of mixed chimerism. Our preliminary data indicate feasibility of all of these aims, and suggest that the miniature swine model may permit us to design a clinically applicable protocol for the use of mixed chimerism in the treatment of hemoglobinopathies.