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

描述(由申请人提供)：证据表明，艾滋病毒的持久性可能是由于其在感染确立后不久就不可逆转地损害获得性免疫系统的能力造成的。具有T细胞免疫抑制特性的CD4CD25T调节(Treg)细胞可能是早期T细胞免疫功能障碍的中介细胞。在HIV感染者和FIV感染的猫中，CD4CD25 Treg细胞具有生产性病毒感染，并在体内被激活以发挥强大的免疫抑制功能。虽然在体外，CD4CD25 Treg细胞已被证明在调节针对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，或者它们对早期保护性T细胞免疫反应有什么影响。为了确定Treg细胞在HIV感染的免疫发病机制中的作用，我们建议利用FIV模型来检验我们的假设，即在FIV感染的急性阶段，CD4 CD25 Treg细胞被感染并激活，导致CD4T辅助(Th)细胞抗FIV反应的免疫抑制。猫将被实验感染FIV的NCSU-1分离株，接种后每隔一周将收集血液和淋巴活检。实时定量聚合酶链式反应和抗FIV-Gag细胞内染色将用于确定感染时间、病毒拷贝数以及感染的CD4CD25和CD4CD25 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技术将检测感染和未感染的CD4CD25和CD4CD25-T细胞亚群在感染急性期不同时间点的表型活化标志物(CD80、CD86和CTLA4)和调节功能标志物(FoxP3、转化生长因子β1)的表达。此外，还将设计实验来评估CD4 CD25 Treg细胞对靶向CD4Th细胞免疫反应的抑制功能的变化，如IL-2和干扰素-γ的产生和细胞增殖。在体外感染的CD4CD25-和CD4CD25T细胞群体将被用来证实从体内研究获得的结果。据估计，目前全球有超过3700万人感染艾滋病毒。FIV是一种公认的艾滋病毒/艾滋病模型。这些实验的结果将对未来对抗艾滋病毒和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.