Targeting Granzyme B to Separate GVH from GVL Responses

 描述(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疗法。供者来源的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HSCT治疗癌症患者的有效性至关重要。然而，移植物抗宿主病(GVHD)可能发生在供者T细胞破坏基因上不同的正常宿主组织时，并且仍然是异基因HSCT更成功应用的主要障碍。这项工作的目的是研究异基因造血干细胞移植后颗粒酶B(GzmB)功能的新范例。这一建议建立在我们对GzmB在GVH和GVL反应中的反直觉作用的新发现的基础上。在小鼠模型中，我们已经了解到，虽然GzmB是CD8细胞毒性T细胞(CTL)引起GVHD所必需的，但它出人意料地降低了GVL的作用。值得注意的是，这种双重有害的作用可能会揭示GzmB是一个长期渴望的靶标，允许GVH和GVL反应之间的分离。值得注意的是，造血抗原提呈细胞(APC)被证明同时启动GVH和GVL反应。然而，专业的APC(如CD8a树突状细胞)在GVL中可能比GVH反应更重要。也就是说，GVL反应可能需要APC的交叉递呈，因为肿瘤细胞经常通过有缺陷的抗原递呈来逃避免疫监视，而在缺乏专业APC的情况下，非造血组织细胞可能足以诱发GVHD。在这种背景下，我们自己的初步数据和其他人的发现表明，CTL可以利用GzmB杀死宿主专业APC，这在病毒感染模型中作为一种负反馈机制来控制CTL的扩张。综上所述，这些发现促使我们假设，GzmB介导的专业APC(或特定亚群)的损伤可能会在不影响GVH反应的情况下降低GVL反应，而GzmB也会损伤其他宿主组织，从而导致GVHD。为了验证这一假设，我们将使用过度表达或缺乏Spi6(非冗余GzmB抑制剂)的转基因小鼠来制造嵌合体，在嵌合体中，对GzmB的“抵抗”或“敏感”仅限于造血组织和非造血组织。这个独特的系统将使我们能够确定捐赠者T细胞使用GzmB破坏造血祖细胞和其他正常宿主组织从而扭曲GVL和GVH反应的机制。此外，我们将进行全面但分区的分析，以检查HSCT患者不同淋巴细胞亚群中颗粒酶A和B激活的临床相关性。综上所述，这项研究深入探讨了基本T细胞途径的新机制，并旨在构建新的干预策略，将GVHD与有益的GVL效应分开。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.