Preventing Xenograft Rejection by Molecular Chimerism

描述（由申请人提供）： 人体器官移植的严重短缺刺激了对使用非人类供体器官进行异种移植的可能性的探索。猪目前被认为是最有可能作为临床异种移植供体的物种。要克服以允许成功异种移植的第一个主要免疫学障碍是被存在于人类中的天然抗体（NAB）排斥，所述天然抗体针对猪组织上的碳水化合物表位Gal（α 1 -3）Gal（β 1 -4）GlcNAc-R（α Gal）。与人类一样，在编码葡糖基转移酶UDP半乳糖：β-D-半乳糖基-1，4-N-乙酰基-D-氨基葡糖苷α（1-3）半乳糖基转移酶（E.C. 2.4.1.151，下文称为alphaGT）在所有组织上都缺乏alphaGal表位，并在其血清中产生针对alphaGal的反应性NAB。我们先前已经在GTo小鼠中表明，使用逆转录病毒转导以建立分子嵌合体的骨髓（BM）的基因工程可用于诱导对α Gal的长期稳定耐受性并防止抗体介导的心脏移植的超急性排斥。这些结果表明，产生α Gal反应性抗体的B细胞从在BM衍生细胞中表达逆转录病毒转导的α GT基因的动物的免疫组库中功能性消除。该提议的目的是检验分子嵌合体的建立可以类似地用于在非人灵长类动物中诱导对α Gal表位的耐受性的假设。具体目标是：1）确定分子嵌合对灵长类动物中α Gal反应性NAB产生的影响;和2）确定分子嵌合的诱导是否导致灵长类动物对α Gal的耐受性并确定机制。这些研究将为异种移植领域和诱导B细胞耐受的基因治疗的应用提供重要的实用机制信息，也可能促进我们对形成B细胞库的自我-非自我歧视的理解。此外，这些研究可普遍适用于重建自身免疫个体的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.