Post-transplant vaccines to enhance graft-versus-leukemia responses

描述（由申请人提供）：同种异体造血干细胞移植（HSCT）后的根治性移植物抗白血病（GvL）反应来自：(1)恢复正常免疫，从而克服白血病或治疗引起的免疫缺陷；(2)识别宿主白血病相关抗原，消除白血病细胞。同种异体造血干细胞移植的一个优先目标是学习如何在最小毒性的情况下产生一致和有效的GvL反应。在本提案的母临床试验中，我们对患有晚期慢性淋巴细胞白血病（CLL）的同种异体造血干细胞移植后患者进行免疫接种，疫苗由辐照的自体白血病细胞和辐照的表达GM-CSF的旁观者细胞组成。供体淋巴细胞输注（DLI）是一种有效的血液恶性肿瘤免疫疗法，我们之前的研究表明，当DLI诱导持续缓解时，这与T细胞新生的快速恢复以及针对白血病相关抗原的多价B和T细胞免疫有关。我们假设，强效的细胞疫苗也可能通过恢复免疫能力和诱导cll反应性T细胞来增强egvl。为了验证这一假设，我们将评估CLL疫苗对恢复正常免疫能力和诱导针对肿瘤特异性抗原而不是自身或同种抗原的T细胞免疫的影响。在Aim 1中，我们将研究疫苗如何影响重构免疫细胞的分布，重点关注T细胞激活状态、扩增和库的变化。在Aim 2中，我们将确定相对于广泛表达的自身抗原，T细胞对cll特异性的反应性的平衡，因为全细胞疫苗既包含cll特异性抗原，也包含广泛表达的自身抗原。为了开发有效和安全的GvL应答，我们最终将需要靶向在CLL细胞上独家表达的抗原。在Aim 3中，为了在接种CLL疫苗的患者中找到CD8+ T细胞的抗原靶点，我们将使用两种方法：首先，使用表达文库来识别T细胞靶点；其次，利用肿瘤DNA与种系DNA的大规模平行测序来鉴定新抗原的新方法。为了确定所确定的免疫效应是否可以归因于疫苗接种，而不是单纯的HSCT，我们将平行分析一组接受同种异体HSCT但未接种疫苗的CLL患者。由于我们正在研究移植后免疫反应随时间的发展，我们提出的研究需要专门的新鲜样本收集和处理。通过研究免疫重建和确定接种疫苗患者的目标白血病抗原，我们将为开发下一代疫苗奠定基础，以刺激高度特异性的白血病限制性免疫，同时降低对正常组织的毒性。公共卫生相关性：我们建议研究一种新型白血病细胞疫苗（在造血干细胞移植后使用）对慢性淋巴细胞白血病（CLL）患者增强抗CLL免疫的影响，通过检查：(1)免疫细胞群的恢复，以及(2)新供体T细胞对CLL细胞的特异性反应程度。我们的研究依赖于在特定时间点收集和处理参与该临床试验的患者（以及未接种疫苗的对照患者）的新鲜血液和骨髓样本，以描述和敏感地检测移植和接种疫苗后免疫反应的产生。从这些拟议的研究中获得的信息将帮助我们开发下一代含有更具有CLL特异性的蛋白质的疫苗，从而实现我们开发可治愈的、无毒的CLL免疫治疗的长期目标。（摘要结束）

DESCRIPTION (provided by applicant): A curative graft-versus-leukemia (GvL) response following allogeneic hematopoietic stem cell transplantation (HSCT) results from the: (1) restoration of normal immunity, thus overcoming leukemia- or treatment-induced immune deficiencies; and (2) recognition of host leukemia-associated antigens and elimination of leukemic cells. A high priority goal in allo-HSCT is to learn how to generate consistent and potent GvL responses with minimal toxicity. In the parent clinical trial to this proposal, we immunize post-allo-HSCT patients who have advanced chronic lymphocytic leukemia (CLL) with a vaccine consisting of irradiated autologous leukemia cells together with irradiated bystander cells expressing GM-CSF. Our prior studies on donor lymphocyte infusion (DLI), an effective immunotherapy for hematologic malignancies, established that when DLI induces lasting remission, this was associated with rapid recovery of T cell neogenesis, and polyvalent B and T cell immunity targeting leukemia-associated antigens. We hypothesize that potent cell-based vaccines may also enhanceGvL by restoring immune competence and inducing CLL-reactive T cells. To test this hypothesis, we will assess the effects of a CLL vaccine on restoration of normal immune competence and induction of T cell immunity targeting tumor-specific antigens more than self- or allo-antigens. In Aim 1, we will examine how the vaccines affect the distribution of reconstituting immune cells, focusing on changes in the activation state, expansion and repertoire of T cells. In Aim 2, we will determine the balance of T cell reactivity against CLL-specific relative to broadly-expressed self-antigens, since whole cell vaccines contain both CLLspecific antigens and broadly expressed self antigens. To develop effective and safe GvL responses, we will ultimately require targeting of antigens with exclusive expression on CLL cells. In Aim 3, to find such antigenic targets of CD8+ T cells in vaccinated CLL patients, we will use two approaches: first, expression libraries to identify T cell targets; second, a novel approach to identify neoantigens using massively parallel sequencing of tumor DNA vs. germline DNA. To determine whether the identified immunologic effects can be attributed to vaccination, and not HSCT alone, we will analyze in parallel a control group of CLL patients undergoing allo-HSCT but without vaccination. Since we are examining the development of immune responses over time following transplant, our proposed studies require dedicated fresh sample collection and processing. By studying immune reconsitution and identifying target leukemia antigens in vaccinated patients, we will have a foundation for developing the next generation of vaccines to stimulate highly specific leukemia-restricted immunity while reducing toxicity against normal tissues. Public Health Relevance: We propose to investigate the impact of a novel leukemia cell vaccine (administered following hematopoietic stem cell transplantation) on patients with chronic lymphocytic leukemia (CLL) to boost anti-CLL immunity, by examining: (1) the recovery of immune cell populations, and (2) the extent to which the new donor T cells are specifically reactive against CLL cells. Our studies rely on the collection and processing of fresh blood and bone marrow samples from patients participating in this clinical trial (and nonvaccinated control patients) at specific time points in order to delineate and sensitively detect the generation of immune responses after transplant and vaccination. Information gained from these proposed studies will help us develop the next generation of vaccines containing proteins that are more CLL-specific, and thereby achieve our long-term goal of developing curative, non-toxic immune-based treatment for CLL. (End of Abstract)