Enhancing Treg Therapeutic Efficacy in GVHD

描述（由申请人提供）：胸腺源性CD4+25+FoxP3+调节性T细胞（Tregs）需要抑制自身免疫和限制外来抗原反应。我们的首次人体I期剂量递增试验证明，体外扩增的人Tregs在显著降低急性移植物抗宿主病（GVHD）发生率方面是有效的。确定了统一疗效的两个主要限制：问题1（实现最佳抑制）：抑制百分比是可变的。问题2（维持足够的Treg: teeffector比率）：达到1:5.5的比率远低于小鼠预防GVHD所需的e1:1的比率；移植后2周未检测到Tregs。目标1将关注问题1。PKC-q协调免疫功能，导致其运动到免疫突触（T细胞和抗原呈递细胞之间的直接接触点），而不是treg。PKC-q缺陷的小鼠效应物不能引起GVHD，但可以保留抗肿瘤和抗病原体反应。用小分子PKC-q抑制剂处理的Tregs具有增强的抑制功能，并且在抑制小鼠结肠炎方面更有效。在目标1中，重点是问题1，我们将在体外或体内使用小分子PKC-q抑制剂来验证小鼠和人类Treg抑制GVHD的效力受到PKC-q进入免疫突触的限制。在目标2中，重点关注问题2，我们将验证持续的IL-2R信号通路将为Treg扩增和GVHD抑制提供PKC- q独立途径的假设。我们将使用3种策略来改善Treg介导的GVHD抑制：(a)给予IL-2/抗IL-2抗体复合物或低剂量IL-2优先扩增小鼠和人Treg对teffators；(b)在小鼠和人类Treg中组成性表达STAT5b，基于我们的发现，组成性STAT5b促进小鼠Treg的产生、增殖和功能，包括抑制GVHD，绕过对体内有限量的IL-2的需要；(c)使用GSK-3b抑制剂增加b-catenin信号传导

DESCRIPTION (provided by applicant): Thymic-derived CD4+25+FoxP3+ regulatory T cells (Tregs) are required to suppress autoimmunity and limit foreign antigen responses. Our first-in-human phase I dose escalation trial of ex vivo expanded human Tregs proved efficacious in significantly reducing the incidence of acute graft-vs-host disease (GVHD). Two major limitations to uniform efficacy were identified: Problem 1 (achieving optimal suppression): The %suppression was variable. Problem 2 (maintaining adequate Treg:Teffector ratios): Ratios of 1:5.5 achieved were well below the desired ratios of e1:1 need for GVHD prevention in mice; no Tregs were detected by 2 weeks post-transfer. Aim 1 will focus on Problem 1. PKC-q coordinates immune function, which results in its movement to the immunological synapse (direct contact point between T cell and antigen-presenting cell) in Teffectors but not Tregs. PKC-q deficient murine Teffectors are unable to cause GVHD but can retain anti-tumor and anti- pathogen responses. Tregs treated with a small molecule PKC-q inhibitor had augmented suppressor function and were more effective in suppressing murine colitis. In aim 1, focused on Problem 1, we will use small molecule PKC-q inhibitors in vitro or in vivo to test the hypotheses that murine and human Treg potency for GVHD suppression is limited by movement of PKC-q into the immunological synapse. In aim 2, focused on Problem 2, we will test the hypothesis that sustained IL-2R signaling pathways will provide a PKC- q independent route to Treg expansion and GVHD suppression. We will use 3 strategies to improve Treg mediated GVHD suppression: (a) administer IL-2/anti-IL2 antibody complexes or low dose IL-2 to preferentially expand murine and human Tregs vs Teffectors; (b) Constitutively express STAT5b in murine and human Tregs based upon our findings that constitutive STAT5b promotes murine Treg generation, proliferation and function including GVHD suppression, bypassing the need for IL-2, present in limiting amounts in vivo; and (c) increase b-catenin signaling using a GSK-3b inhibitor in vitro or expressing a stabilized b-catenin in human Tregs since stabilized b-catenin reduces Treg dependency upon IL-2 and provides a marked enhancement of murine Treg survival and efficacy in preventing colitis. In aim 3, we will select the best 1-2 approaches, derived from studies in aims 1 and 2, for testing in preclinical GVHD models for the preservation of beneficial immune responses later post-transplant. Long-term chimeras that do not succumb to GVHD lethality, as a result of preferred approaches developed aims 1 and 2, will be challenged with leukemia cells or bacterial or viral pathogens to quantify the extent to which the immune system can respond to life-threatening complications post-transplant.