Effect of Treg Cells on CD4+Th Immune Responses During Acute FIV Infection

描述（由申请人提供）：有证据表明，HIV 的持续存在可能是由于其在感染后不久就能够不可逆转地损害获得性免疫系统的能力。具有 T 细胞免疫抑制特性的 CD4 CD25 T 调节 (Treg) 细胞可能是这种早期 T 细胞免疫功能障碍的介质。 CD4 CD25 Treg 细胞在 HIV 感染者和 FIV 感染猫中具有高效的病毒感染，并在体内被激活以发挥有效的免疫抑制功能。虽然 CD4 CD25 Treg 细胞已被证明在体外调节针对 HIV 和 FIV 抗原的 CD4 和 CD8 免疫反应中发挥作用，但尚不清楚这些细胞在感染后的什么时间被感染和激活，或者它们可能对早期保护性 T 细胞免疫反应产生什么影响。为了确定 Treg 细胞在 HIV 感染免疫发病机制中的作用，我们建议利用 FIV 模型来检验我们的假设，即 CD4 CD25 Treg 细胞在 FIV 感染的急性期被感染并激活，导致 CD4 T 辅助细胞 (Th) 细胞抗 FIV 反应的免疫抑制。猫将通过实验感染 FIV 的 NCSU-1 分离株，并在接种后每隔 1 周收集一次血液和淋巴结活检。实时PCR和抗FIV-gag细胞内染色将用于确定感染时间、病毒拷贝数以及CD4 CD25和CD4 CD25感染的T细胞的绝对数量。这些数据将与 RT-PCR 检测到的血浆病毒血症水平相关。流式细胞术和细胞分选将评估感染急性期不同时间点感染和未感染的 CD4 CD25 和 CD4 CD25-T 细胞亚群中表型激活标记物（CD80、CD86 和 CTLA4）和调节功能标记物（FoxP3、TGF?1）的表达。此外，还将设计实验来评估CD4 CD25 Treg细胞对靶CD4 Th细胞免疫反应的抑制功能的变化，例如IL-2和IFN-γ的产生和细胞增殖。 CD4 CD25-和CD4 CD25 T细胞群的体外感染将用于证实体内研究获得的结果。目前估计艾滋病毒感染全世界超过 3700 万人。 FIV 是一个完善的 HIV/AIDS 模型。这些实验的结果将对未来针对 HIV 和 FIV 的治疗策略产生影响，并有助于我们目前对 Treg 细胞功能的理解。

DESCRIPTION (provided by applicant): Evidence suggests that HIV persistence may result from its ability to irreversibly damage the acquired immune system shortly after infection is established. CD4+CD25+ T regulatory (Treg) cells with T cell immunosuppressive properties are possible mediators of this early T cell immune dysfunction. CD4+CD25+ Treg cells harbor a productive virus infection in HIV infected people and FIV infected cats, and are activated for potent immunosuppressor function in vivo. While CD4+CD25+ Treg cells have been shown to play a role in regulating CD4+ and CD8+ immune responses against HIV and FIV antigens in vitro, it is not known at what time following infection these cells become infected and activated or what effect they might have on the early protective T cell immune response. To determine the role of Treg cells in the immunopathogenesis of HIV infection we propose to utilize the FIV model to test our hypothesis that CD4+CD25+ Treg cells become infected and activated during the acute stage of FIV infection leading to the immunosuppression of CD4+ T helper (Th) cell anti-FIV responses. Cats will be experimentally infected with the NCSU-1 isolate of FIV and blood and lymph node biopsies will be collected at 1 week intervals following inoculation. Real-Time PCR and anti-FIV-gag intracellular staining will be used to determine the time of infection, number of copies of the virus and absolute numbers of CD4+CD25+ and CD4+CD25- infected T cells. These data will be correlated with plasma viremia levels as detected by RT-PCR. Flow cytometry and cell sorting will assess the expression of phenotypic activation markers (CD80, CD86 and CTLA4) and markers for regulatory function (FoxP3, TGF?1) in infected and non-infected CD4+CD25+ and CD4+CD25- T cell subsets at different time points during the acute phase of infection. In addition, experiments will be designed to assess changes in the suppressive function of CD4+CD25+ Treg cells on target CD4+ Th cell immune responses, such as IL-2 and IFN-y production and cell proliferation. In vitro infection of CD4+CD25- and CD4+CD25+ T cell populations will be used to corroborate the results obtained from in vivo studies. HIV is currently estimated to infect more than 37 million people worldwide. FIV is a well established model of HIV/AIDS. The results of these experiments will have implications in future therapeutic strategies against HIV and FIV, and contribute to our current understanding of Treg cell function.