Depletion, Repopulation and Tolerance in Sensitized Recipients

虽然在美国的大多数肾移植中使用多克隆抗体或alemtuzumab来耗尽免疫细胞，但我们的实验室已经在人类和非人类灵长类动物(NHP)中表明，耗竭后的动态平衡再繁殖与B细胞激活、BAFF水平升高和新的供体特异性同种抗体(DSA)有关。我们还表明，在NHP耗竭后，贝拉塔塞特能够抑制这种DSA。最近，我们在一个预敏的NHP模型中显示，阻断CD28和CD154结合蛋白酶体抑制可显著降低移植前的同种异体抗体水平，扰乱生发中心并减少浆细胞数量。然而，仅通过蛋白酶体抑制来耗尽浆细胞也与生发中心和TFH细胞的激活有关。因此，免疫细胞的耗尽在耐受性方面既会带来有益的后果，也会带来有害的后果。该项目旨在确定在致敏宿主中促进耐受性的免疫细胞耗尽的因素。我们认为，淋巴细胞和浆细胞的耗尽和随后的动态平衡重新繁殖既提供了形成同种异体反应免疫系统以有利于耐受的机会，也提供了破坏调节、引发病毒感染和诱导同种异体反应克隆激活的风险。我们假设，致敏宿主中免疫细胞耗尽的后果会产生免疫系统的代偿反应，这种反应是可预测的，需要通过治疗控制来促进耐受性。为了探索这一假说，我们提出了三个具体目标：1)开发更安全和更有效的方法，以降低预防同种异体移植的同种异体抗体、浆细胞和记忆B细胞的数量和数量，在肾移植前使用蛋白酶体抑制和补充辅助治疗；2)重塑免疫谱系，使用耗竭、供体特异性输血和雷帕霉素来促进致敏受者的调节、AICD和前耐受性动态平衡重新形成；以及3)评估在移植后免疫抑制方案中加入和不使用雷帕霉素作为促进移植肾长期存活的安全性和有效性，如SA1和2中所述。

While perioperative immune cell depletion with either polyclonal antibody or alemtuzumab is used in the majority of renal transplants in the U.S., our lab has shown in both humans and non-human primates (NHP) that homeostatic repopulation following depletion is associated with B cell activation, elevated BAFF levels, and de novo donor-specific alloantibody (DSA). We have also shown that Belatacept is capable of suppressing such DSA in NHP following depletion. Recently, we have shown in a presensitized NHP model that blockade of CD28 and CD154 in combination with proteasome inhibition substantially lowers alloantibody levels pre-transplant, disrupting germinal centers and lowering plasma cell numbers. However, depletion of plasma cells by proteasome inhibition alone is also associated with germinal center and Tfh cell activation. Thus, depletion of immune cells leads to both beneficial and deleterious consequences with respect to tolerance. This project seeks to define the elements of immune cell depletion in sensitized hosts that foster tolerance. We believe that lymphocyte and plasma cell depletion and subsequent homeostatic repopulation present both an opportunity to shape the alloreactive immune repertoire to favor tolerance, and a risk to disrupt regulation, ignite viral infection and induce activation of alloreactive clones. We hypothesize that the consequences of immune cell depletion in sensitized hosts create compensatory responses by the immune system that are predictable and need to be therapeutically controlled to promote tolerance. To explore this hypothesis, we propose 3 specific aims: 1) To develop safer and more effective means to lower the amount and number of allospecific antibodies, plasma cells, and memory B cells that prevent allotransplantation using proteasome inhibition together with complementary adjuvant therapies prior to renal transplantation; 2) To reshape the immune repertoire using depletion, donor-specific transfusion, and rapamycin to promote regulation, AICD, and pro-tolerant homeostatic repopulation in the sensitized recipient; and 3) To evaluate the safety and efficacy of Belatacept with and without Rapamycin as components of post-transplant immunosuppressive regimens promoting long-term survival of renal allografts following desensitization therapy as described in SA1 and 2 above.