Antigen specificity, suppressive mechanism & regulation of CD4+ regulatory T cell

描述(由申请人提供)：最近的研究表明，CD4调节性T(Treg)细胞可以抑制最佳抗肿瘤免疫所需的CD4和CD8效应细胞反应。这些观察结果可能至少部分解释了为什么用癌症疫苗(包括MHC I类限制性肿瘤抗原或多肽)诱导强烈而持久的抗肿瘤反应的尝试在很大程度上是不成功的。该项目的目标是开发新的策略，将平衡从CD4 Treg细胞介导的抑制性免疫反应转变为有效的T辅助免疫反应，从而产生持久的抗肿瘤免疫，从而最终摧毁肿瘤。其基本原理是，肿瘤细胞不仅通过分泌白介素10和转化生长因子-β来提供抑制环境，而且通过呈递肿瘤相关或特异性配体，在局部肿瘤部位主动招募和激活CD4 Treg细胞。这些肿瘤抗原特异性的CD4 Treg细胞反过来对有效的抗癌T细胞反应产生强大的抑制作用。申请人实验室的研究已经从癌症患者的临床样本中建立了几个抗原特异性的CD4 Treg细胞系和克隆。这些独特的细胞，再加上几项新开发的技术，应该能够识别肿瘤特异性CD4 Treg细胞的重要配体，进而允许对一个新概念进行更严格的测试--将动态平衡从抑制性的CD4Treg细胞转移到有利于T辅助细胞介导的抗肿瘤反应的环境，可能会提高癌症免疫治疗的有效性。为了验证我们的新概念和假设，我们提出了三个具体的研究目标：(1)利用已建立的CD4 Treg细胞系/克隆来鉴定这些细胞的配体编码基因，然后表征蛋白质产物的自然性质；(2)剖析CD4 Treg细胞的免疫抑制机制和调节，以获得动物模型中假设检验所需的关键信息；(3)使用TCR转基因小鼠和B16肿瘤模型来调节或逆转体内CD4 Treg细胞的抑制功能。这项为期5年的计划中提出的策略将应用于不同的肿瘤抗原，并在不同的动物模型中进行测试，以验证CD4 Treg/效应细胞平衡的变化确实有助于更有效的癌症免疫治疗。这些研究的积极结果将为治疗癌症患者开辟新的机会，也许还会为治疗传染病和自身免疫性疾病开辟新的机会。

DESCRIPTION (provided by applicant): Recent studies suggest that CD4+ regulatory T (Treg) cells can suppress the CD4+ and CD8+ effector cell responses needed for optimal antitumor immunity. These observations may explain, at least in part, why attempts to elicit strong and durable antitumor responses with cancer vaccines (comprising MHC class I- restricted tumor antigens or peptides) have been largely unsuccessful. The goals of this project are to develop new strategies to shift the balance from CD4+ Treg cell-mediated suppressive immune response toward effective T helper immune response, thus generating long-lasting antitumor immunity for the ultimate tumor destruction. The underlying rationale is that tumor cells not only provide a suppressive environment by secreting interleukin (IL)-10 and TGF-beta, but also actively recruit and activate CD4+ Treg cells at local tumor sites by presenting tumor-associated or -specific ligands. These tumor antigen-specific CD4+ Treg cells, in turn, exert potent suppressive effects on effective T cell responses against cancer. Research in the applicant's laboratory has established several antigen-specific CD4+ Treg cell lines and clones from clinical samples taken from cancer patients. These unique cells, together with several newly developed technologies, should enable identification of important ligands for tumor-specific CD4+ Treg cells, permitting in turn more rigorous testing of a novel concept--that shifting the dynamic balance from suppressive CD4+ Treg cells to a milieu favoring T-helper-mediated antitumor responses may boost the effectiveness of cancer immunotherapy. To test our novel concept and hypothesis, we proposes three specific research aims: (1) use established CD4+ Treg cell lines/clones to identify genes encoding the ligands of these cells and then characterize the natural properties of the protein products; (2) dissect the immunosuppressive mechanisms and regulation of the CD4+ Treg cells to gain critical information needed for hypothesis testing in animal models; (3) use TCR transgenic mice and the B16 tumor model to modulate or reverse the suppressive function of CD4+ Treg cells in vivo. The strategies emerging from this 5-year proposal will be applied to different tumor antigens, tested in different animal models, to verify that a shift in the CD4+ Treg/effector cell balance is indeed conducive to more effective cancer immunotherapy. A positive outcome of these studies would open new opportunities for treating cancer patients and perhaps infectious and autoimmune diseases as well.