Mechanisms of Selective CD28 Blockade on T Follicular Helper Cell Responses During Transplantation

摘要 肾移植是大多数终末期患者的首选治疗方式。 肾脏疾病，在患者生存和生活质量方面具有广泛接受的好处。越来越多的证据表明 供者特异性抗体(DSA)是改善肾脏术后长期预后的主要障碍 移植。共刺激阻断治疗CTLA-4Ig有望成为一种潜在的治疗方法 控制DSA的策略，显示移植后阶段DSA滴度的发生率降低 与传统的钙尿酸盐靶向免疫抑制相比。T滤泡辅助细胞(TFH)，CD4+T细胞的一个亚群 产生最佳抗体所需的细胞依赖于CD28共刺激途径。CTLA-4Ig抑制 通过结合配体CD80和CD86来激活T细胞，以防止它们与T细胞共刺激分子接触 CD28。令人不快的是，这种作用机制还不分青红皂白地阻断CD80和CD86的联合连接。 抑制CTLA-4，使T细胞失去重要的抑制信号和相互作用。我们小组已经证明了 使用选择性CD28结构域抗体(DAb)直接拮抗CD28可提高移植物存活率 与CTLA-4Ig相比，Tfh细胞介导的DSA反应受到抑制。有趣的是，供体反应性TFH 细胞分化上调CTLA4的表达，提示CTLA-4可能在介导 用抗CD28 DAb观察到明显的抑制作用。因此，在这项建议中，我们的目标是确定 CTLA-4和PD-L1协同抑制信号在改进TfH介导的抑制中的需求 选择性阻断CD28显示移植后的反应。将进行活体实验 CTLA-4和PD-L1联合CD28DAb的药理阻断作用研究 治疗观察移植物存活率和TFH细胞介导的同种免疫反应的任何变化。 使用可诱导的条件基因敲除Cre-Lox系统的进一步体内实验将被 以确定CTLA-4和/或PD-L1在增强选择性 CD28封锁。 拟议的研究项目将作为申请者综合基础设施的培训目标的框架 移植免疫学的科学研究进入学术科学家的职业生涯，其研究兴趣 将专注于开发新的免疫抑制策略，以诱导移植物特异性耐受。这些 研究将解决终末期肾脏疾病的治疗与肾移植使用一种新的 更好地抑制T细胞依赖和TFH驱动的供体特异性抗体的免疫调节策略 回应。

Abstract Kidney transplantation is the treatment modality of choice for the majority of patients suffering from end stage renal disease, with widely accepted benefits in patient survival and quality of life. Mounting evidence suggests that donor-specific antibodies (DSAs) are a major barrier to improved long-term outcomes following kidney transplantation. Costimulation blockade therapy with CTLA-4Ig has shown promise as a potential therapeutic strategy to control DSAs, showing reductions in the incidence of DSA titers in the post-transplant phase compared to traditional calcenurin targeted immunosuppression. T follicular helper (Tfh) cells, a subset of CD4+ T cells required for optimal antibody production, are reliant on the CD28 costimulatory pathway. CTLA-4Ig inhibits T cell activation by binding the ligands CD80 and CD86 to prevent their engagement with the T cell co-stimulator CD28. Undesirably, this mechanism of action also indiscriminately blocks CD80 and CD86 ligation of the co- inhibitor CTLA-4, depriving T cells of important inhibitory signals and interactions. Our group has demonstrated that use of selective CD28 domain antibody (dAb) that directly antagonizes CD28 affords improved graft survival and suppression of Tfh cell-mediated DSA responses compared to CTLA-4Ig. Interestingly, donor-reactive Tfh cells differentially upregulated CTLA4 expression, suggesting a potential role for CTLA-4 in mediating the superior inhibition observed with the anti-CD28 dAb. Therefore, within this proposal we aim to determine the requirement of coinhibitory signaling through CTLA-4 and PD-L1 in the improved suppression of Tfh-mediated responses following transplantation exhibited by selective CD28 blockade. In vivo experiments will be performed investigating the effect of pharmacological blockade of CTLA-4 and PD-L1 in conjunction with CD28 dAb treatment to observe any changes in the efficacy of graft survival and Tfh cell-mediated allo-immune responses. Further in vivo experiments utilizing the inducible conditional gene knockout Cre-Lox system will then be performed to determine the intrinsic or extrinsic role of CTLA-4 and or PD-L1 in the enhancement of selective CD28 blockade. The proposed research project will serve as a framework for the applicant’s training goals of integrating basic science research in transplantation immunology into a career as an academic scientist whose research interest will focus on developing new strategies of immunosuppression for the induction of graft-specific tolerance. These studies will address the treatment of end stage kidney disease with renal transplantation using a novel immunomodulatory strategy to better suppress T cell dependent and Tfh driven donor-specific antibody responses.