Targeting Granzyme B to Separate GVH from GVL Responses

 描述（由申请人提供）：异基因造血干细胞移植（HSCT）是一种治疗恶性血液病和其他疾病的潜在治疗方法。供体来源的T细胞能够识别和攻击宿主肿瘤细胞，产生有益的移植物抗白血病/淋巴瘤（GVL）效应，这对于癌症患者的HSCT的有效性至关重要。然而，移植物抗宿主病（GVHD）可能会发展时，供体T细胞损伤的遗传不同的正常宿主组织，并仍然是一个主要的障碍，更成功的应用同种异体HSCT。这项工作的目标是研究一个新的范例，关于颗粒酶B（Gzm B）功能后同种异体造血干细胞移植。该提议是基于我们对GzmB在GVH和GVL反应中的反直觉作用的新发现。使用鼠模型，我们已经了解到，虽然GzmB是CD 8+细胞毒性T细胞（CTL）引起GVHD所必需的，但它出乎意料地减少了GVL效应。值得注意的是，这种双重有害作用可能揭示GzmB作为长期期望的靶标，允许GVH和GVL应答之间的分离。值得注意的是，造血抗原呈递细胞（APC）显示启动GVH和GVL应答。然而，专业的APC（例如，CD 8a+树突状细胞）对于GVL应答可能比GVH应答更重要。也就是说，GVL应答可能需要APC的交叉呈递，因为肿瘤细胞通常通过缺陷的抗原呈递逃避免疫监视，而非造血组织细胞可能足以在不存在专职APC的情况下诱导GVHD。在这种情况下，我们自己的初步数据和其他人的发现表明，CTL可以使用GzmB杀死宿主的专职APC，这在病毒感染模型中作为控制CTL扩增的负反馈机制。总之，这些发现促使我们假设GzmB介导的专职APC（或特定亚群）的损伤可能会减少GVL应答而不影响GVH应答，而GzmB也会损伤其他宿主组织，从而引起GVHD。为了检验这一假设，我们将使用Spi 6（非冗余GzmB抑制剂）过表达或缺陷的转基因小鼠来制造嵌合体，其中对GzmB的“抗性”或“敏感性”仅限于造血组织与非造血组织。这种独特的系统将使我们能够确定供体T细胞使用GzmB破坏造血APC和其他正常宿主组织从而使GVL和GVH应答偏斜的机制。此外，我们将进行全面但分区的分析，以检查颗粒酶A和B活化在HSCT患者的各种淋巴细胞亚群中的临床相关性。总之，这项研究深入研究了一个基本的T细胞通路的新机制，旨在构建新的干预策略，可以从有益的GVL效应中分离GVHD。这些新的概念和干预策略可能有可能导致更好的生存和改善HSCT患者的生活质量。

 DESCRIPTION (provided by applicant): Allogeneic hematopoietic stem cell transplantation (HSCT) is a potentially curative treatment for hematologic malignancies and other diseases. Donor-derived T cells are capable of identifying and attacking host tumor cells, producing the beneficial graft-versus-leukemia/lymphoma (GVL) effect that is crucial for the effectiveness of HSCT for cancer patients. However, graft-versus-host disease (GVHD) may develop when donor T cells damage the genetically distinct normal host tissues, and remains a major obstacle for more successful applications of allogeneic HSCT. The goal of this work is to examine a new paradigm regarding Granzyme B (GzmB) function after allogeneic HSCT. This proposal is built on our novel discovery of the counter-intuitive role of GzmB in GVH and GVL responses. Using murine models, we have learned that while GzmB is required for CD8+ cytotoxic T cells (CTLs) to cause GVHD, it unexpectedly diminishes the GVL effect. Remarkably, this dual detrimental role may reveal GzmB as a long-desired target, allowing separation between GVH and GVL responses. Notably, hematopoietic antigen-presenting cells (APCs) were shown to initiate both GVH and GVL responses. However, professional APCs (e.g., CD8a+ dendritic cells) may be more important for GVL than GVH responses. That is, GVL response may require cross-presentation by APCs because tumor cells often escape immunosurveillance via defective antigen presentation, while non-hematopoietic tissue cells may be sufficient to induce GVHD in the absence of professional APCs. In this context, our own preliminary data and the findings of others show that CTLs can use GzmB to kill host professional APCs, which serves as a negative feedback mechanism for the control of CTL expansion in viral infection models. Together, these findings prompt us to hypothesize that GzmB-mediated damage of professional APCs (or specific subsets) may diminish GVL response without affecting GVH response, while GzmB also damages other host tissues thereby causing GVHD. To test this hypothesis, we will use transgenic mice that overexpress or are deficient for Spi6 (the non-redundant GzmB inhibitor) to make chimeras in which either "resistance" or "sensitivity" to GzmB is confined to hematopoietic vs. non-hematopoietic tissues. This unique system will allow us to determine the mechanisms by which donor T cells use GzmB to damage hematopoietic APCs and other normal host tissues thereby skewing GVL and GVH responses. In addition, we will perform comprehensive but compartmentalized analyses to examine the clinical relevance of Granzymes A and B activation in various lymphocyte subsets in HSCT patients. In summary, this study delves into novel mechanisms of a fundamental T cell pathway, and aims to construct new intervention strategies that can separate GVHD from the beneficial GVL effect. These new concepts and intervention strategies may have the potential to lead to better survival and improved quality of life for HSCT patients.