Oxidative stress and AICD in memory T cell persistence

描述（由申请人提供）：CD8+ T细胞通过激活、分裂和分化过程对抗原刺激作出反应，产生大量活化的效应细胞溶解T淋巴细胞（CTL）。许多癌症患者携带的前体CTL可以被激活，对许多“自我”肿瘤相关的表位做出反应。在某些情况下，用其中一些抗原表位接种疫苗可诱导抗肿瘤反应。然而，肿瘤发展成功逃避宿主免疫系统的各种分子和细胞机制已经被确定。这些机制中的一些靶向抗肿瘤效应CTL，不能通过仅针对激活抗肿瘤免疫反应的免疫治疗来纠正。我们的初步数据表明，携带效应记忆表型的T细胞在外源性氧化应激条件下优先功能失调，但在抗原遭遇时也会增加激活诱导细胞死亡（AICD）。在发生AICD的CTL中可以观察到超氧化物产生的增加，这可以通过超氧化物歧化酶模拟MnTBAP预处理来挽救。根据我们的初步数据，我们假设记忆T细胞亚群之间氧化还原状态的差异调节了对AICD或凋亡的敏感性。利用携带HLA-A2限制性酪氨酸特异性功能TCR的新型转基因h3T小鼠的mat -127-35表位特异性人CTL和T细胞，我们拟在CD4+和CD8+ T细胞上进行以下研究：1)确定T细胞亚群（TCM vs TEM）的氧化还原状态差异是否通过影响内在信号分子调节氧化应激诱导的凋亡和AICD的敏感性；2)确定氧化应激介导的记忆T细胞亚群凋亡和AICD的外源性差异调节因素（中医与TEM）；3)建立体内模型，评价抗氧化处理的T细胞或抗氧化酶转导的T细胞在肿瘤消退、持续和记忆中的作用。我们相信，这项工作的成功完成将有助于确定可用于改善接受过继T细胞治疗的癌症患者的效应CTL存活和长期记忆发展的靶标。

DESCRIPTION (provided by applicant): CD8+ T cells respond to antigen stimulation through a process of activation, division, and differentiation to generate a large pool of activated effector cytolytic T lymphocytes (CTL). Many cancer patients harbor precursor CTL that can be activated to respond to many "self" tumor-associated epitopes. Vaccination with some of these epitopes can induce anti-tumor responses in some cases. However, various molecular and cellular mechanisms that tumors develop to successfully evade the host immune system have been identified. Some of these mechanisms target anti-tumor effector CTL that cannot be corrected by immunotherapy aimed only at activation of anti-tumor immune responses. Our preliminary data shows that effector memory phenotype bearing T cell becomes preferentially dysfunctional under conditions of exogenous oxidative stress but also undergo increased activation induced cell death (AICD) on antigenic encounter. Increased superoxide production can be seen in CTL undergoing AICD that can be rescued by pretreatment with superoxide dismutase mimetic MnTBAP. Based on our preliminary data we hypothesize that differential redox status between memory T cell subsets regulates the sensitivity towards AICD or apoptosis. Using MART-127-35 epitope specific human CTL and T cells from our novel transgenic h3T mouse that carries HLA-A2 restricted tyrosine specific functional TCR on both CD4+ and CD8+ T cells we propose to carry out the following: 1) To determine if differential redox state of the T cell subsets (TCM vs. TEM) regulates sensitivity to oxidative stress induced apoptosis and AICD by effecting intrinsic signaling molecules.; 2) To determine extrinsic factors that differentially regulate oxidative stress mediated apoptosis and AICD of memory T cell subsets (TCM vs. TEM); and 3) To establish an in vivo model for evaluation of antioxidant treated T cells or antioxidant enzyme transduced T cells in tumor regression, persistence and memory. We believe that successful completion of the proposed work would help identify targets that could be used to improve survival of effector CTL and long-term memory development in patients receiving adoptive T cell therapy for cancer. PUBLIC HEALTH RELEVANCE: Despite T lymphocytes activated by cancer vaccination are virtually competent to attack and destroy neoplastic cells, the reason for their inefficacy in controlling tumor regression has been puzzling. Our data shows that it is both oxidative stress and antigen mediated preferential death of antigen-experienced/memory phenotype bearing CTL that might result in inadequate function. Since persistence of CTL is an important factor that affects the outcome of any immunotherapy protocol we believe that protecting effector lymphocytes by identifying and targeting the pathways to rescue CTL from premature death, their anti-tumor effect could be substantially improved.