Directing T Cell Responses during Immune Reconstitution

在免疫重建过程中指导 T 细胞反应

• 批准号: 6433436
• 负责人: CRYSTAL L MACKALL
• 金额: --
• 依托单位: DIVISION OF CLINICAL SCIENCES - NCI
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/6433436
• 关键词: CD95 molecule; Ewing's tumor; T lymphocyte; antigen presenting cell; apoptosis; cellular immunity; clinical research; clinical trials; human subject; human therapy evaluation; immunoregulation; interleukin 2; neoplasm /cancer chemotherapy; neoplasm /cancer immunotherapy; polymerase chain reaction; rhabdomyosarcoma; tissue /cell culture; tumor antigens; western blottings

The objectives of this project are to study the biology of T cell regeneration and to develop therapeutic approaches which could be used in T cell depleted hosts to improve overall host immunocompetence and to direct T cell responses toward tumor-specific antigens in the setting of minimal residual neoplastic disease. Using a murine model of HY skin graft rejection, following T cell depletion, we have shown that thymectomized mice which have undergone immune reconstitution via peripheral expansion are unable to reject HY disparate skin grafts while hosts reconstituted via thymic-dependent pathways reject grafts normally. Rejection is accomplished in thymectomized mice if sufficient numbers of T cells are provided which we have shown requires approximately 10% of the normal T cell repertoire. In these experiments, we have also shown that IL-7 potently enhances thymic-independent T cell regeneration and that IL-7 therapy restores the capacity to reject HY disparate grafts in thymectomized hosts reconstituted with insufficient T cell numbers. Mechanistically, this appears to be related, at least in part, to IL-7?s ability to inhibit programmed cell death since inhibition of programmed cell death (PCD) by the use of bcl-2 transgenic T cell inocula also enhances immune competence in this model. Therefore, these results suggest that PCD may serve to limit host immune competence during peripheral expansion and raise the possibility that modulation of PCD in vivo may serve as a useful approach for enhancing immune competence in thymic-deficient TCD hosts. This model has also emphasized the critical role of IL-7 in modulating the process of peripheral expansion in vivo. Based upon these results, we have hypothesized that endogenous IL-7 production could contribute to T cell homeostasis by enhancing the process of peripheral expansion in the setting of T cell depletion. In order to test this hypothesis, we sought to evaluate serum IL-7 levels in children with T cell depletion due to HIV infection. We have observed a striking inverse correlation between serum IL-7 levels and T cell counts in children with HIV associated CD4+ depletion. Statistically, the serum IL-7 levels appear to be related to both CD4+ and CD8+ T cell counts, but not B cell counts. Current work is underway to address whether similar relationships exist in adults with T cell depletion and in T cell depletion related to cytotoxic therapy. These studies may serve to identify a new role for IL-7 in maintenance of T cell homeostasis.With regard to thymic-dependent pathways of T cell regeneration, we are currently investigating the relative importance of age- or disease-associated thymic dysfunction in limiting T cell receptor repertoire diversity following T cell depletion in humans. In order to evaluate the ability of low level thymic function to diversify the T cell receptor (TCR) repertoire over time in humans, current work is focused upon evaluation of TCR repertoire diversity in a series of pediatric patients treated with highly active antiretroviral therapy for HIV infection. We have hypothesized that even suboptimal thymopoiesis in this patient population may lead to diversification of the TCR repertoire over time. In an attempt to measure such changes in TCR diversity, we have developed a semi-quantitative approach using complementarity determining region 3 (CDR3) size analysis of serially diluted purified CD4+ T cells. Interestingly, preliminary results using this approach in normal individuals have shown significant age related changes in T cell receptor repertoire diversity. Whereas cord blood shows a diverse repertoire with as few as 10e5 input CD4 cells, young adults do not show a diverse repertoire until 5 x 10e5 input CD4 cells are utilized. Older adults (40-50 years) do not show a diverse repertoire until 1 x 10e6 input CD4+ T cells are utilized. These results suggest that measurable declines in TCR repertoire diversity occur throughout the normal human lifespan. With regard to children treated with highly active antiretroviral therapy, we have observed significantly reduced TCR repertoire diversity in children with CD4+ T cell counts <200 cells/mcl. In contrast, preliminary results in children with higher CD4+ T cell counts (e.g. >400 cells/mcl) reveal essentially normal TCR repertoire diversity. We have also used this approach to compare TCR repertoire diversity in CD45RA+ vs. CD45RO+ CD4+ T cells from patients with HIV infection. Thus far, no significant differences in repertoire diversity have been observed. Future plans involve the use of this technique to monitor changes in TCR repertoire diversity in cancer patients treated with immunorestorative therapies in the context of our ongoing clinical trials. AIDS RELATED 100%

本项目的目的是研究T细胞再生的生物学，并开发可用于T细胞耗竭宿主的治疗方法，以提高宿主的整体免疫能力，并在最小残留肿瘤疾病的背景下指导T细胞对肿瘤特异性抗原的反应。使用HY皮肤移植排斥的小鼠模型，T细胞耗竭后，我们已经表明，胸腺切除的小鼠，通过外周扩增进行免疫重建是不能拒绝HY不同的皮肤移植，而通过胸腺依赖性途径重建的主机拒绝移植正常。如果提供足够数量的T细胞，则在胸腺切除的小鼠中完成排斥，我们已经表明需要约10%的正常T细胞库。在这些实验中，我们还表明IL-7有效地增强胸腺非依赖性T细胞再生，并且IL-7治疗恢复了在T细胞数量不足的胸腺切除宿主中排斥HY不同移植物的能力。从机制上讲，这似乎是相关的，至少在一定程度上，IL-7？由于通过使用bcl-2转基因T细胞接种物抑制程序性细胞死亡（PCD）也增强了该模型中的免疫能力，因此，因此，这些结果表明，PCD可能有助于限制宿主的免疫能力在外周扩张和提高的可能性，在体内的PCD调制可能作为一个有用的方法，用于增强免疫能力在胸腺缺陷的TCD主机。该模型还强调了IL-7在体内调节外周扩张过程中的关键作用。基于这些结果，我们假设内源性IL-7的产生可以通过增强T细胞耗竭背景下外周扩增的过程来促进T细胞稳态。为了验证这一假设，我们试图评估由于HIV感染导致T细胞耗竭的儿童的血清IL-7水平。我们观察到HIV相关CD 4+耗竭儿童血清IL-7水平与T细胞计数之间存在显著的负相关性。统计学上，血清IL-7水平似乎与CD 4+和CD 8 + T细胞计数相关，但与B细胞计数无关。目前的工作正在进行中，以解决类似的关系是否存在于成人与T细胞耗竭和T细胞耗竭相关的细胞毒性治疗。这些研究可能有助于确定一个新的作用IL-7在维持T细胞homeostasis. For胸腺依赖的途径T细胞再生，我们目前正在调查的相对重要性，年龄或疾病相关的胸腺功能障碍，在限制T细胞受体库的多样性T细胞耗竭后，在人类。为了评价低水平胸腺功能使人类T细胞受体（TCR）库随时间推移而多样化的能力，目前的工作重点是评价一系列接受高效抗逆转录病毒治疗的HIV感染儿科患者的TCR库多样性。我们假设，即使是次优的胸腺生成在这个患者群体可能会导致随着时间的推移TCR库的多样化。为了测量TCR多样性的这种变化，我们开发了一种半定量方法，使用连续稀释的纯化的CD 4 + T细胞的互补决定区3（CDR 3）大小分析。有趣的是，在正常个体中使用这种方法的初步结果显示了T细胞受体库多样性的显著年龄相关变化。尽管脐带血显示出具有少至10 e5输入CD 4细胞的多样性库，但年轻成人直到利用5 × 10 e5输入CD 4细胞才显示出多样性库。老年人（40-50岁）在使用1 × 10 e6输入CD 4 + T细胞之前没有显示出多样化的库。这些结果表明，TCR库多样性的可测量的下降发生在整个正常人的寿命。对于接受高效抗逆转录病毒治疗的儿童，我们观察到CD 4 + T细胞计数<200个细胞/mcl的儿童TCR库多样性显著降低。相比之下，具有较高CD 4 + T细胞计数（例如>400个细胞/mcl）的儿童的初步结果显示基本上正常的TCR库多样性。我们还使用这种方法比较了HIV感染患者的CD 45 RA+与CD 45 RO + CD 4 + T细胞中TCR库的多样性。到目前为止，尚未观察到库多样性的显著差异。未来的计划涉及使用这种技术来监测在我们正在进行的临床试验的背景下，在癌症患者接受免疫修复治疗的TCR库多样性的变化。艾滋病相关100%