Tolerance Induction in a GalT-KO Pig-to-Baboon Model Through Mixed Chimerism

由于混合嵌合体已经在小鼠和人源化的小鼠模型中显示出来(项目3) 不仅能够诱导中枢T细胞耐受，而且还能防止新的抗体反应和关闭 现有的抗体反应，异种混合嵌合体的建立仍然是一个有吸引力的手段 以达到异种移植的耐受性。在Galt-KO微型猪问世之前，尝试 跨越猪到灵长类动物屏障的混合嵌合体的实现归因于灵长类动物天然的高水平 半乳糖抗原的抗体。然而，尽管GALT-KO细胞表面没有半乳糖抗原 造血细胞(HSC)，我们发现这些细胞可以迅速从血液循环中清除。 巴布亚在输液后不久，躲避了混合嵌合体的建立。我们的数据显示，其中两个 在这种清除中起作用的最重要的因素是：1)非半乳糖决定簇的天然抗体， 它们不同地存在于不同的狒狒中；以及2)缺乏物种特有的细胞膜 CD47是一种蛋白质，它是抑制先天免疫系统快速清除细胞的必需蛋白质 发行量。这项提案的目标是克服这两个障碍，以便建立混合 恒河猴体内GALT-KO-HSC的异种嵌合。具体来说，我们将：1)优化异种骨 避免自然和诱导的抗-Nal抗体的骨髓植入；2)人 CD47基因转导的GALT-KO猪骨髓植入狒狒体内的实验研究 人CD47表达载体；3)检测GALT-KO猪HSC在狒狒体内的植入效果， 单独或与带血管猪胸腺移植联合应用 Galt-KO异种肾移植的耐受性目标3将应用目标1和目标2的调查结果以及战略 在本计划项目1中开发的用于诱导移植的混合嵌合体方法 在这种临床前的、不协调的物种组合中，对器官移植的耐受性。此外，这些实验 计划将提供关于异种干细胞移植和免疫学的基本信息 灵长类动物异种排斥和耐受诱导的途径。因此，这些研究 对异种移植的最终应用具有理论和实践意义。 一种临床模式。

Since mixed chimerism has been shown in mouse and humanized mouse models (Project 3) to have the ability not only to induce central T cell tolerance, but also to prevent new antibody responses and turn off existing antibody responses, the establishment of xenogeneic mixed chimerism remains an attractive means for achieving xenograft tolerance. Before GalT-KO miniature swine were available, the failure of attempts to achieve mixed chimerism across the pig-to-primate barrier was attributed to high levels of primate natural antibodies to the Gal antigen. However, despite the absence of the Gal antigen on the cell surface of GalT-KO hematopoeitic cells (HSC), we have found that these cells are rapidly cleared from the circulation of baboons shortly after infusion, eluding the establishment of mixed chimerism. Our data indicate that two of the most important factors playing a role in this clearance are: 1) natural antibodies to non-Gal determinants, which are variably present in different baboons; and 2) absence of the species-specific cell-membrane protein, CD47, which is required to inhibit the innate immune system from rapidly clearing cells from the circulation. The goal of this proposal is to overcome these two barriers in order to establish mixed xenogeneic chimerism of GalT-KO HSC in baboons. Specifically, we will: 1) Optimize xenogeneic bone marrow engraftment by avoiding natural and induced anti-non-Gal antibodies; 2) Test effect of human CD47 on engraftment of porcine marrow in baboons using GalT-KO pig bone marrow transduced with a human CD47 expression vector; and 3) Test the effect of GalT-KO pig HSC engraftment in baboons, either alone or in combination with vascularized porcine thymus transplantation, on the induction of tolerance of GalT-KO renal xenografts. Aim 3 will apply the findings of Aims 1 and 2, as well as strategies developed in Project 1 of this Program Project, to the mixed chimerism approach for inducing transplantation tolerance to organ xenografts in this preclinical, discordant species combination. In addition, the experiments planned will provide basic information on xenogeneic stem cell engrafment and on the immunologic pathways responsible for xenogeneic rejection and tolerance induction in primates. As such, these studies should have both theoretical and practical implications for the eventual application of xenotransplantation as a clinical modality.