Studies in pig-to-primate cardiac xenotransplantation

猪到灵长类动物心脏异种移植的研究

• 批准号: 6987516
• 负责人: CHRISTOPHER G.A. MCGREGOR
• 金额: $ 88.15万
• 依托单位: MAYO CLINIC ROCHESTER
• 依托单位国家: 美国
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-07-01 至 2010-06-30
• 项目状态: 已结题
• 来源: https://reporter.nih.gov/project-details/6987516
• 关键词: antigen antibody reaction; baboons; biopsy; blood chemistry; genetic manipulation; genetically modified animals; graft versus host disease; heart function; heart transplantation; immune response; immunocytochemistry; immunologic assay /test; immunopathology; immunosuppressive; nonhuman therapy evaluation; swine; transplant rejection; transplantation immunology; xenotransplantation

DESCRIPTION: The broad long-term objective of this application is to achieve sustained life-supporting cardiac xenograft survival in the pig-to-primate model using a protocol consisting of a genetically-engineered donor heart, a combination of currently available immunosuppressive drugs and techniques, and modalities to detect and treat rejection episodes that will allow clinical application of cardiac xenotransplantation. Pig-to-primate xenotransplantation (XTx) has been limited by antibody mediated rejection (AMR) initially to the Galactose a -1,3 Galactose (a-Gal) antigen. Anti-Gal AMR has been prevented in our laboratory using a-Gal polymers and specific immunosuppressive (IS) regimens. After 7 years of XTx research a median survival of 96 days in heterotopic transgenic pig heart to baboon transplants has been achieved. In the orthotopic, life-supporting position, survival of over 5 and 8 weeks has been reached, the best outcomes to date. As an alternative to a-Gal polymers, we have bred homozygous pigs deficient in the synthesis of the a-Gal antigen (GGTA1-KO). Recent heterotopic transplants with GGTA1-KO donors exhibit similar prolonged survival. Despite eliminating anti-Gal antibody, the xenograft (Xg) is rejected by a non-Gal anti-pig antibody response. The overall hypotheses of this proposal are 1) that the optimal pig donor to resist AMR is a GGTA1-KO;hCRP transgenic; 2) the use of clinically applied immunosuppression can result in prolonged cardiac Xg function in the absence of a-Gal antigen; and 3) that Xg rejection can be diagnosed and treated by current methods for antibody control in patients with preformed antibodies. The proposal has three specific aims. Specific Aim 1, to determine the preferred transgenic donor for pig-to-primate cardiac XTx by comparing survival, histology, immunohistology and immune responses using GGTA1-KO and GGTA1-KO;hCRP donor organs. The outcome addresses a central issue in pig-to-primate XTx, namely the role of the a-Gal antigen and the impact of hCRP's, on both graft outcomes and mechanisms of rejection. Furthermore, this work will define the base genetics that should be used for future genetic modifications. Specific Aim 2 is to identify the minimal level of immunosuppression compatible with prolonged organ survival. Using donor organs defined in SA 1 these experiments will determine whether an immunosuppressive regimen based on current clinical IS for presensitized allograft recipients can control Xg rejection resulting in prolonged Xg survival. These experiments will define the relative contribution of basal IS and therapies that seek to block indirect antigen presentation and T-cell help. Specific Aim 3 is to use orthotopic cardiac XTx to define the physiological function of the Xg and identify parameters (functional, biochemical, hematological and biophysical) that allow the detection of rejection and test methodologies to reverse these events. While Xg failure is associated with the presence of anti-pig antibody there is as yet no definitive proof that rejection is antibody mediated. These life-supporting transplants will allow the development of methods to accurately detect rejection based on cardiac function. In addition, by attempting to reverse rejection episodes with plasmapheresis we will identify the initiating mechanism of graft rejection. This proposal, if successful, lays the groundwork for the clinical application of cardiac XTx.

描述：这项应用的长期目标是在猪到灵长类动物模型中实现持续的维持生命的异种心脏移植存活，使用的方案包括基因工程供体心脏，目前可用的免疫抑制药物和技术的组合，以及检测和治疗排斥事件的模式，这将允许异种心脏移植的临床应用。猪到灵长类动物的异种移植（XTx）受到抗体介导的排斥反应（AMR）的限制，最初是针对半乳糖a- 1,3半乳糖（a- gal）抗原。在我们的实验室中，使用a-Gal聚合物和特异性免疫抑制（IS）方案可以预防抗gal AMR。经过7年的XTx研究，异位转基因猪心脏移植到狒狒的中位生存期为96天。在正位，生命支持体位，生存超过5和8周，迄今为止最好的结果。作为a-Gal聚合物的替代品，我们培育了缺乏a-Gal抗原（GGTA1-KO）合成的纯合子猪。最近GGTA1-KO供体的异位移植也表现出类似的延长生存期。尽管消除了抗gal抗体，异种移植物（Xg）被非gal抗猪抗体反应排斥。本提案的总体假设是：1)抗AMR的最佳猪供体是GGTA1-KO；hCRP转基因;2)临床应用免疫抑制可导致a-Gal抗原缺失时心脏Xg功能延长；3)现有抗体控制方法可以诊断和治疗预形成抗体患者的Xg排斥反应。该提案有三个具体目标。特异性目的1，通过比较GGTA1-KO和GGTA1-KO的存活、组织学、免疫组织学和免疫应答，确定猪转灵长类动物心脏XTx的首选转基因供体；hCRP供体器官该结果解决了猪到灵长类动物XTx的一个核心问题，即a- gal抗原的作用和hCRP的影响，对移植结果和排斥机制的影响。此外，这项工作将确定基础遗传学应该用于未来的遗传修饰。特异性目的2是确定与延长器官存活相容的最小免疫抑制水平。使用SA 1中定义的供体器官，这些实验将确定基于当前临床IS的免疫抑制方案是否可以控制Xg排斥反应，从而延长Xg存活时间。这些实验将确定基础IS和寻求阻断间接抗原呈递和t细胞帮助的治疗的相对贡献。具体目标3是使用原位心脏XTx来定义Xg的生理功能，并确定允许检测排斥反应的参数（功能，生化，血液学和生物物理）和测试方法来逆转这些事件。虽然Xg失败与抗猪抗体的存在有关，但目前还没有明确的证据表明排斥反应是抗体介导的。这些维持生命的移植将有助于开发基于心脏功能准确检测排斥反应的方法。此外，通过尝试用血浆置换逆转排斥事件，我们将确定移植物排斥的启动机制。如果该建议成功，将为心脏XTx的临床应用奠定基础。