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持续存在可能是由于它在感染后不久就能对获得性免疫系统造成不可逆的损害。具有T细胞免疫抑制特性的CD4+CD25+ T调节性（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感染的猫体内具有生产性病毒感染，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+免疫应答中发挥作用，但尚不清楚这些细胞在感染后的什么时间被感染和激活，也不知道它们对早期保护性T细胞免疫应答可能有什么影响。为了确定Treg细胞在HIV感染的免疫发病机制中的作用，我们提出利用FIV模型来验证我们的假设，即CD4+CD25+ Treg细胞在FIV感染的急性阶段被感染和激活，导致CD4+ T辅助细胞（Th）抗FIV反应的免疫抑制。猫将被实验性地感染FIV的NCSU-1分离物，并在接种后每隔一周收集血液和淋巴结活检。采用Real-Time PCR和anti-FIV-gag细胞内染色测定感染时间、病毒拷贝数和CD4+CD25+和CD4+CD25-感染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表型激活标记（CD80、CD86和CTLA4）和调节功能标记(FoxP3、TGF？1)感染和未感染的CD4+CD25+和CD4+CD25- T细胞亚群在感染急性期不同时间点的差异。此外，我们将设计实验来评估CD4+CD25+ Treg细胞对靶CD4+ Th细胞免疫反应（如IL-2和IFN-y的产生和细胞增殖）的抑制功能的变化。CD4+CD25-和CD4+CD25+ T细胞群的体外感染将用于证实体内研究的结果。据估计，目前全世界有3700多万人感染艾滋病毒。FIV是一种公认的艾滋病毒/艾滋病模式。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.