AIDS Lentivirus-induced TGF-beta+ Treg cells Mediate T cell Immune Dysfunction

描述（由申请人提供）：天然胸腺源性CD4+CD25+ T调节细胞对自身反应性CD4+和CD8+ T细胞的免疫抑制对于维持外周自身耐受性至关重要。最近的数据表明，除了抗自身天然Treg细胞外，外周淋巴组织中被病原体激活的Treg细胞群可能在控制感染过度“炎症”反应中发挥重要作用。天然Treg细胞和病原体诱导的Treg细胞在表型和功能上相似，因为它们表达CD25、GITR和转录调节蛋白Foxp3，并且对抗原活化的T细胞具有免疫抑制作用，这表明天然Treg细胞和外周活化的Treg细胞可能属于同一谱系。然而，我们最近在FIV艾滋病慢病毒感染中证明，病原体诱导的Treg细胞与天然Treg细胞的不同之处在于，它们在表面表达TGF-2 (mTGF-2+)， mTGF-2介导Treg抑制功能，也可能控制外周Treg稳态。本文提出的实验将进一步探索这些观察结果，以验证外周免疫组织中的Treg细胞是对感染因子的免疫调节过程的正常组成部分，并且艾滋病慢病毒超越了对Treg激活和功能的正常控制，导致慢性免疫抑制活性和异常Treg稳态。将评估急性感染FIV NCSU1分离株的猫的CD4+CD25+ Treg细胞的表型（mTGF-2+, Foxp3+）和功能（CD4+ Th细胞抑制cona诱导的增殖和il -2， CD8+ T细胞抑制IFN-3）。FIV gag ELISA和RT-PCR检测将用于确定Treg激活是否与病毒感染相关。mTGF-2在Treg抑制功能中的作用将通过使用TGF-2和TGF-2RII中和抗体来确定。为了研究mTGF-2通过从CD4+ Th细胞池中募集来维持FIV+猫外周Treg稳态的作用，我们将mTGF-2+ Treg细胞与CD4+ Th细胞孵育，并分析靶细胞CD25、Foxp3、mTGF-2的表达和抑制功能。为了证实mTGF-2+ Treg细胞诱导Th细胞转化为Treg细胞，我们将利用TGF-2和TGF-2RII中和抗体阻断转化过程。这些研究将解决两个重要的免疫学问题：1)CD4+CD25+ Treg细胞如何介导CD4+和/或CD8+ Th群体的抑制和表型转化以维持其稳态；2)艾滋病慢病毒感染如何超越对Treg细胞激活和功能的正常控制，导致慢性Treg诱导的免疫抑制以及Treg稳态异常。公共卫生相关性：T调节性（Treg）细胞在维持保护性免疫反应和与原发性感染相关的免疫病理之间的平衡中发挥关键作用。我们认为艾滋病慢病毒感染如HIV超越了正常控制Treg细胞激活和功能，导致慢性Treg细胞激活和整体免疫抑制和艾滋病。了解艾滋病毒是如何利用这种正常的免疫调节机制的，这将在本提案中得到解决，将有助于开发更好的治疗方式。

DESCRIPTION (provided by applicant): Immune suppression of self-reactive CD4+ and CD8+ T cells by natural, thymic-derived CD4+CD25+ T regulatory cells is crucial for the maintenance of peripheral self-tolerance. Recent data suggest that in addition to anti-self natural Treg cells, a population of Treg cells, activated in the peripheral lymphoid tissues by pathogens may play a major role in controlling excessive "inflammatory" responses to infection. Natural and pathogen-induced Treg cells are phenotypically and functionally similar in that they express CD25, GITR, and the transcriptional regulatory protein Foxp3, and are immunosuppressive for antigen-activated T cells, suggesting that natural and peripheral activated Treg cells may be of the same lineage. However, we have recently demonstrated in the FIV AIDS lentiviruses infection that pathogen-induced Treg cells differ from natural Treg cells in that they express TGF-2 on their surface (mTGF-2+) and that mTGF-2 mediates Treg suppressor function and may also control peripheral Treg homeostasis. The experiments proposed herein will further explore these observations to test the hypothesis that Treg cells in the peripheral immune tissues are a normal component of the immune regulatory process to infectious agents and that AIDS lentiviruses over-ride the normal controls on Treg activation and function, resulting in chronic immunosuppressive activity and abnormal Treg homeostasis. CD4+CD25+ Treg cells will be assessed phenotypically (mTGF-2+, Foxp3+) and functionally (inhibition of ConA-induced proliferation and IL2 by CD4+ Th cells and IFN-3 by CD8+ T cells) in cats acutely infected with the NCSU1 isolate of FIV. FIV gag ELISA and RT-PCR assays will be performed to determine if Treg activation is associated with virus infection. The role of mTGF-2 in Treg suppressor function will be determined by the use of TGF-2 and TGF-2RII neutralizing antibodies. To investigate the role of mTGF-2 in maintaining peripheral Treg homeostasis in FIV+ cats by recruitment from the CD4+ Th pool, we will incubate mTGF-2+ Treg cells with CD4+ Th cells and analyze the target cells for expression of CD25, Foxp3, mTGF-2 and for suppressor function. To confirm the mTGF-2+ Treg cells induced conversion of Th cells to Treg cells, we will utilize TGF-2 and TGF-2RII neutralizing antibodies to block the conversion process. These studies will address two important immunological issues: 1) how do CD4+CD25+ Treg cells mediate suppression and phenotypic conversion of CD4+ and/or CD8+ Th populations to maintain their homeostasis; and 2) how do AIDS lentivirus infections over-ride the normal controls over Treg cell activation and function, resulting in chronic Treg-induced immunosuppression, as well as abnormal Treg homeostasis. PUBLIC HEALTH RELEVANCE: T regulatory (Treg) cells play a pivotal role in maintaining the balance between protective immune responses and immunopathology associated with primary infections. We believe that AIDS lentivirus infections such as HIV over-ride the normal controls over Treg cell activation and function, resulting in chronic Treg cell activation and global immunosuppression and AIDS. Understanding how HIV co-opts this normal immune regulatory mechanism, which will be addressed in this proposal, will aid in the development of better therapeutic modalities.