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

描述(申请人提供)：天然的胸腺来源的CD4+CD25+T调节细胞对自身反应性的CD4+和CD8+T细胞的免疫抑制对于维持外周自身耐受至关重要。最近的数据表明，除了抗自身的自然Treg细胞外，在周围淋巴组织中被病原体激活的Treg细胞群可能在控制对感染的过度炎症反应方面发挥主要作用。自然和病原体诱导的Treg细胞在表型和功能上是相似的，因为它们表达CD25、GITR和转录调节蛋白Foxp3，并且对抗原激活的T细胞具有免疫抑制作用，这表明自然和外周激活的Treg细胞可能属于同一谱系。然而，我们最近在FIV AIDS慢病毒感染中证明了病原体诱导的Treg细胞与自然Treg细胞的不同之处在于它们在表面表达转化生长因子-2(mTGF-2+)，并且mTGF-2介导Treg抑制功能，也可能控制外周Treg的动态平衡。本文提出的实验将进一步探索这些观察结果，以检验以下假设：外周免疫组织中的Treg细胞是对感染性物质的免疫调节过程的正常组成部分，而艾滋病慢病毒在Treg的激活和功能上凌驾于正常对照之上，导致慢性免疫抑制活性和异常的Treg稳态。在急性感染FIV的NCSU1分离株的猫身上，将对CD4+CD25+Treg细胞进行表型(mTGF-2+，Foxp3+)和功能(抑制ConA诱导的增殖和CD4+Th细胞对IL2的抑制，CD8+T细胞对干扰素-3的抑制)的评估。将进行FIV、Gag、EL ISA和RT-PCR检测，以确定Treg的激活是否与病毒感染有关。MTGF-2在Treg抑制功能中的作用将通过使用转化生长因子-2和转化生长因子-2RII中和抗体来确定。为了研究mTGF-2在维持FIV+猫外周Treg动态平衡中的作用，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细胞诱导的Th细胞向Treg细胞的转化，我们将利用转化生长因子-2和转化生长因子-2RII中和抗体来阻断这一转化过程。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细胞的抑制和表型转换，以维持其动态平衡；2)艾滋病慢病毒感染如何超过正常对照组，影响Treg细胞的激活和功能，导致慢性Treg诱导的免疫抑制和异常的Treg动态平衡。公共卫生相关性：T调节(Treg)细胞在维持保护性免疫反应和与原发感染相关的免疫病理学之间的平衡方面发挥着关键作用。我们认为，艾滋病慢病毒感染，如HIV，超过了正常对照的Treg细胞的激活和功能，导致慢性Treg细胞的激活和全球免疫抑制和艾滋病。了解艾滋病毒如何利用这种正常的免疫调节机制，这将在本提案中得到解决，这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.