Preventing Xenograft Rejection by Molecular Chimerism

描述(由申请人提供)： 人类器官移植的严重短缺促使人们探索使用非人类供体器官进行异种移植的可能性。猪现在被认为是最有可能作为临床异种移植供体的物种。为了使异种移植成功，需要克服的第一个主要免疫障碍是针对猪组织上碳水化合物表位Gal(Alpha1-3)Gal(Beta1-4)GIcNAc-R(AlphaGal)的人类天然抗体(NAB)的排斥反应。与人类一样，葡萄糖转移酶UDP半乳糖：β-D-半乳糖基-1，4-N-乙酰-D-D-氨基葡萄糖α(1-3)半乳糖基转移酶(E.C.2.4.1.151，以下简称为αGT)基因缺失的基因敲除小鼠(GTO)在所有组织上都缺乏αGal表位，并在它们的血清中形成对αGal反应的NAB。我们之前在GTO小鼠身上已经证明，利用逆转录病毒转导建立分子嵌合体的骨髓基因工程可以用于诱导对α-Gal的长期稳定耐受，并防止抗体介导的心脏移植的超急性排斥反应。这些结果表明，在BM来源的细胞中表达逆转录病毒转导的AlphaGT基因的动物的免疫谱系中，产生AlphaGal反应性抗体的B细胞在功能上被消除。这项提议的目的是验证这样一个假设，即分子嵌合体的建立可以类似地用于在非人类灵长类动物中诱导对AlphaGal表位的耐受。其具体目的是：1)确定分子嵌合体对灵长类动物产生α-Gal反应性NAB的影响；以及2)确定分子嵌合体的诱导是否导致灵长类动物对α-Gal的耐受，并确定其机制。这些研究将为异种移植领域和基因治疗诱导B细胞耐受的应用提供重要的实用机制信息，并可能促进我们对形成B细胞谱系的自我非我歧视的理解。此外，这些研究可能普遍适用于在自身免疫个体中重建B细胞耐受性。

DESCRIPTION (provided by applicant): The acute shortage of human organs for transplantation has stimulated exploration into the possibility of using non-human donor organs for xenotransplantation. Pigs are now regarded as the most likely species to serve as donors for clinical xenotransplantation. The first major immunological barrier to overcome to allow successful xenotransplantation is rejection by natural antibodies (NAB) present in humans that are directed toward the carbohydrate epitope Gal(alpha1-3)Gal(beta1-4)GIcNAc-R (alphaGal) on porcine tissues. Like humans, knockout mice (GTo) carrying a null mutation in the gene encoding the glucosyltransferase UDP galactose:beta-D- galactosyl-1,4-N-acetyI-D-glucosaminide alpha(1-3)galactosyltransferase (E.C. 2.4.1.151, hereafter referred to as alphaGT) lack alphaGal epitopes on all tissues and develop in their serum NAB reactive against alphaGal. We have shown previously in GTo mice that genetic engineering of bone marrow (BM) using retroviral transduction to establish molecular chimerism can be used to induce long-term stable tolerance to alphaGal and prevent antibody mediated hyperacute rejection of cardiac transplants. These results demonstrate that B cells producing alphaGal reactive antibodies are functionally eliminated from the immunological repertoire of animals that express the retrovirally transduced alphaGT gene in BM derived cells. The goal of this proposal is to test the hypothesis that establishment of molecular chimerism can be similarly used to induce tolerance to the alphaGal epitope in non-human primates. The specific aims are to: 1) Determine the effect of molecular chimerism on production of alphaGal reactive NAB in primates; and 2) Determine whether the induction of molecular chimerism leads to tolerance to alphaGal in primates and determine the mechanism. These studies should provide practical mechanistic information important for the field of xenotransplantation and to the application of gene therapy to induce B cell tolerance, and may also advance our understanding of self-nonself discrimination in shaping the B cell repertoire. Furthermore, these studies may be generally applicable for re-establishing B cell tolerance in individuals with autoimmunity.