Directing T Cell Responses during Immune Reconstitution

我们实验室的主要重点是研究T细胞再生的生物学，并确定在免疫重建期间促进T细胞再生和引导T细胞对肿瘤抗原的反应的新方法。我们的方法包括小鼠建模，非人类灵长类动物的研究，以及T细胞耗竭患者的临床样本研究。过去一年的大部分工作都是利用T细胞耗尽的小鼠模型。通过这一点，我们研究了促进胸腺缺陷小鼠T细胞再生的机制。我们已经证明，如果只有10%的T细胞通过转移正常的成熟T细胞提供给T细胞耗尽的宿主，那么严格的免疫反应(HY皮肤移植排斥反应)就会发生。如此小的接种量意味着免疫系统中出现了大量冗余，这是一项新的发现。我们还了解到，一个人可以用T细胞活性细胞因子IL-7转移低至1%的T细胞库，并类似地恢复严格的免疫反应。这些结果令人惊讶，因为在这项工作之前，IL-7被认为是一种对早期T细胞发育很重要的细胞因子，但它对成熟T细胞的影响通常不被认为是首要的(Fry TJ，Christensen BL，Komschlie KL，Gress RE和Mackall CL)。IL-7可恢复无胸腺T细胞耗尽宿主的免疫力。血。2001；97：1525-1533)(Mackall CL，Fry TJ，Bare C，Morgan P，Gailbraith A和Gress RE.IL-7可促进骨髓移植后胸腺依赖和胸腺非依赖性T细胞的再生。血。2001年；97：1491-1497。同时，我们假设，如果治疗性剂量的IL-7能够有效地恢复T细胞耗竭宿主的免疫反应，那么在正常情况下，内源性IL-7水平可能有助于增强T细胞耗竭后的免疫活性，并有助于恢复T细胞的动态平衡。事实上，IL-7处理的小鼠有几个特征类似于T细胞耗尽的宿主。因此，我们调查了T细胞耗竭患者临床队列中的血清IL-7水平。我们观察到，在HIV感染、癌症化疗后以及一种称为特发性CD4淋巴细胞减少症的罕见疾病中，血清IL-7与CD4计数之间存在显著的负相关(Fry TJ、Connick E、Falloon J、Lederman MM、Liewehr DJ、Spritzler J、Steinberg SM、Wood LV、Yarchoan R、Zuckerman J、Landay A和Mackall CL)。IL-7在T细胞动态平衡中的潜在作用布拉德，2001；97：2983-2990)。这是首次发现IL-7可能是人类T细胞稳态的调节因子(Fry TJ和Mackall CL，《IL-7：T细胞稳态的主要调节因子？》，《免疫学趋势》，2001年出版)。由于在小鼠模型和临床样本中的这些发现，我们一直非常积极地尝试开发IL-7作为临床制剂，用于提高T细胞耗尽后的免疫力。为此，我们通过与马里兰州弗雷德里克的单抗和重组蛋白设施公司以及法国巴黎赛诺菲公司的合作，通过与NCI的MTA/CRADA合作，对非人类灵长类动物进行了IL-7给药的试验。我们希望这些研究最终将导致IL-7作为一种新的免疫保护剂进行临床试验。 此外，在过去的一年里，我们已经确定了两种新的药物，它们有可能作为免疫保护剂应用于临床。第一种是已知的促进树突状细胞发育的Flt3配体。然而，通过我们的小鼠T细胞耗竭模型，我们现在已经观察到它也促进胸腺依赖和胸腺非依赖的T细胞再生(Fry/Sinha，ASH，2001)。其次，我们已经观察到，即使在没有HIV感染的情况下，HIV蛋白酶抑制剂吲地那韦在小鼠模型中也是一种活跃的免疫保护剂。我们还参与了两个小鼠肿瘤模型，这两个模型将用于回答有关免疫恢复防止癌症复发的能力的问题。首先，我们使用的是一个已经定义了独特肿瘤抗原的膀胱肿瘤。这种抗原，称为HY，是男性相关的次要组织能力抗原，是我们在皮肤移植排斥模型中广泛研究的抗原(上文)。我们现在将确定我们是否可以同样地使用IL-7增强T细胞耗竭宿主对肿瘤复发的抵抗力。其次，我们使用的是骨肉瘤的小鼠模型。在这个模型中，肿瘤被植入肢体，在肿瘤生长后，动物随后接受截肢。然后，我们尝试调节免疫重建，并评估其对肿瘤复发的影响。这个模型与我们在患者身上观察到的骨肉瘤的临床情况非常相似。我们已经做出了令人惊讶的观察，即在缺乏任何特定肿瘤疫苗的情况下，非特异性免疫重建能够防止截肢后肿瘤的复发(Melchionda等人，提交给ASH 2001)。此外，我们没有发现在原发肿瘤生长阶段存在的淋巴细胞对肿瘤抗原具有耐受性的证据。这些研究表明，旨在恢复癌症患者全身免疫功能的治疗可能有助于防止肿瘤复发，并对临床肿瘤学具有重要意义。 与艾滋病100%相关

A primary focus of our laboratory is investigation of the biology of T cell regeneration and the identification of new approaches to enhance T cell regeneration and to direct T cell responses toward tumor antigens during the period of immune reconstitution. Our methods involve modeling in mice, studies in non-human primates and studies involving clinical samples derived from patients with T cell depletion. Much of the work in the past year has utilized mouse models of T cell depletion. Through this, we have investigated mechanisms for enhancing T cell regeneration in thymic deficient mice. We have shown that recovery of stringent immune responses (HY skin graft rejection) occurs if only 10% of the T cell repertoire is supplied to a T cell depleted host by the transfer of normal mature T cells. Such a small inocula implies that much redundancy occurs within the immune system and represents a new discovery. We also learned that one could transfer as little as 1% of the T cell repertoire with a T cell active cytokine, IL-7, and similarly restore stringent immune responses. Such results were surprising because prior to this work, IL-7 was thought of as a cytokine which was important for early T cell development, but its effects on mature T cells were not generally believed to be of primary importance (Fry TJ, Christensen BL, Komschlies KL, Gress RE and Mackall CL. IL-7 restores immunity in athymic T cell depleted hosts. Blood. 2001;97:1525-1533) (Mackall CL, Fry TJ, Bare C, Morgan P, Gailbraith A and Gress RE. IL-7 increases both thymic-dependent and thymic-independent T cell regeneration after BMT. Blood. 2001;97:1491-1497.). Simultaneously, we hypothesized that if therapeutic doses of IL-7 were able to potently restore immune responses in T cell depleted hosts, it was possible that in the normal situation, endogenous levels of IL-7 serve to enhance immune competence and contribute to the restoration of T cell homeostasis following T cell depletion. Indeed, several features of IL-7 treated mice resemble T cell depleted hosts. Thus, we investigated serum IL-7 levels in clinical cohorts of patients with T cell depletion. We observed that there was a dramatic inverse correlation between serum IL-7 and CD4 count in HIV infection, following cancer chemotherapy and in a rare disease termed idiopathic CD4 lymphopenia (Fry TJ, Connick E, Falloon J, Lederman MM, Liewehr DJ, Spritzler J, Steinberg SM, Wood LV, Yarchoan R, Zuckerman J, Landay A and Mackall CL. A potential role for IL-7 in T cell homeostasis. Blood, 2001; 97:2983-2990). These were the first insights to implicate IL-7 as a possible regulator of T cell homeostasis in humans (Fry TJ and Mackall CL, Interleukin-7: Master Regulator of T Cell Homeostasis?, Trends in Immunology, In Press, 2001). Because of these findings in both mouse models and clinical samples, we have been very actively attempting to develop IL-7 as a clinical agent which could be used to improve immunity following T cell depletion. To this end, we are engaged in trials of IL-7 administration to non-human primates through collaborations with the Monoclonal Antibody and Recombinant Protein Facility in Frederick, MD and Sanofi, Inc. in Paris, France through an MTA/CRADA with the NCI. We are hopeful that these studies will eventually lead to clinical trials of IL-7 as a new immunorestorative agent. In addition, we have identified two new agents in the past year with the potential for clinical application as immunorestorative agents. The first, flt3 ligand is known to enhance dendritic cell development. However, through our murine models of T cell depletion, we have now observed that it also enhances both thymic-dependent and thymic-independent T cell regeneration (Fry/Sinha, ASH, 2001). Secondly, we have observed that the HIV protease inhibitor, Indinavir, is active as an immunorestorative agent in mouse models, even in the absence of HIV infection. We are also engaged in two murine tumor models which will serve to answer questions regarding the ability of immune restoration to prevent recurrence of cancer. In the first, we are using a bladder tumor for which a unique tumor antigen has been defined. This antigen, termed HY, is the male associated minor histocomability antigen which is the antigen we have studied extensively in skin graft rejection models (above). We will now determine whether we can similarly enhance resistance to tumor recurrence in T cell depleted hosts using IL-7. Secondly, we are using a mouse model of osteosarcoma. In this model, the tumor is implanted into the extremity and the animal subsequently receives an amputation after tumor growth. We then attempt to modulate immune reconstitution and evaluate the effects on tumor recurrence. This model is very similar to the clinical scenario of osteosarcoma which we observe in our patients. We have made the surprising observation that non-specific immune reconstitution, in the absence of any specific tumor vaccine, is capable of preventing tumor recurrence following amputation (Melchionda et al, submitted to ASH 2001). Furthermore, we find no evidence that lymphocytes present during the phase of primary tumor growth are tolerized to the tumor antigens. These studies imply that therapies aimed at restoring general immunity in cancer patients may contribute to prevent tumor recurrence and have important implications for clinical oncology. AIDS Related 100%