Immunologic Strategies Directed Toward HIV Infection

使用有效的抗逆转录病毒疗法（ART）治疗艾滋病毒感染者，极大地改变了许多患者的临床结果，并导致艾滋病发病率和艾滋病相关死亡率大幅下降。然而，现在很清楚，ART长期抑制血浆病毒血症不太可能根除大多数感染者的HIV。此外，长期ART可能导致药物诱导的毒性，难以坚持药物治疗方案，并产生耐药病毒。因此，迫切需要开发旨在有效抑制感染个体中HIV的替代免疫策略。在过去一年，我们进行了两项研究计划，一项是临床研究，另一项是基础研究，以发展其他治疗策略。 1. HIV感染长期无进展者中CD 8 + T细胞相关抗病毒因子的鉴定 至少有两种类型的CD 8 + T细胞介导的抗病毒活性在控制HIV感染中发挥重要作用。第一种是对HIV的抑制活性，涉及以抗原特异性、HLA限制性方式裂解感染细胞，而第二种机制在不存在细胞杀伤的情况下在包括CC-趋化因子的过程中抑制病毒复制。尽管这些CC-趋化因子对HIV结合并最终进入CD 4 + T细胞和巨噬细胞发挥其抗病毒活性，但另一类目前未鉴定的抗病毒因子通过下调感染细胞中HIV的转录来抑制进入后病毒复制。我们已经构建了一个cDNA文库，从三个HIV感染的长期非进展者中分离的CD 8 + T细胞，并已开始筛选参与抑制HIV复制的基因。在鉴定出这些抗病毒候选物后，我们计划在体外表征其生物学特性，并追求旨在体内利用这些CD 8 + T细胞衍生的抗病毒因子的临床策略。 2.免疫抑制药物在HIV复制中的作用。 尽管开发了成功的治疗策略，但仍不可能根除感染个体中的HIV，主要是由于各种病毒储库的持续存在。特别是，在血浆病毒血症低于检测限的大多数感染个体中发现了具有复制能力的病毒、包括2个LTR环的HIV-1前病毒DNA以及CD 4 + T细胞中的剪接和未剪接的HIV-1 RNA。这种持久的病毒储存库已成为阻止根除艾滋病毒的主要障碍。此外，我们发现，在接受ART的病毒血症感染个体中，携带HIV-1前病毒DNA的CD 4 + T细胞频率与CD 4 +/CD 8 + T细胞比率之间存在统计学显著的负相关性（血浆病毒血症水平长期低于检测限（>2.5年））。针对最小化细胞活化的策略可能会进一步减少接受ART的患者中残留的病毒复制。为了解决这个问题，我们已经开始了一项试点临床试验，以检查轻度免疫抑制剂daclizumab的安全性和耐受性，daclizumab是一种特异性结合α亚基的人源化IgG 1单克隆抗体。在活化的淋巴细胞表面上表达的人高亲和力IL-2受体（p55 α、CD 25或Tac亚基）。考虑到免疫激活程度与HIV复制之间存在密切关系，我们的目的是确定达克珠单抗是否可以使免疫学特征正常化并减少研究受试者的血浆病毒血症。

The use of effective antiretroviral therapy (ART) to treat HIV-infected individuals has dramatically changed the clinical outcome in many patients and has led to a substantial decline in the incidence of AIDS and in AIDS-related mortality. However, it is now clear that prolonged suppression of plasma viremia by ART is not likely to eradicate HIV in most infected individuals. In addition, long-term ART may lead to drug-induced toxicities, difficulties in adhering to drug regimens, and development of drug-resistant virus. Thus, development of alternative immunologic strategies aimed at efficient suppression of HIV in infected individuals is urgently needed. Over the past year, we conducted two research projects, one clinical and one basic, to develop alternative treatment strategies. 1. Identification of CD8+ T cell-associated antiviral factors in HIV-infected long-term non-progressors At least two types of CD8+ T cell-mediated antiviral activities play an important role in controlling HIV infection. The first is a suppressive activity against HIV involving lysis of infected cells in an antigen-specific, HLA-restricted fashion, while the second mechanism inhibits viral replication in the absence of cell killing, in a process that includes CC-chemokines. Whereas these CC-chemokines exert their antiviral activity on the binding and ultimate entry of HIV into CD4+ T cells and macrophages, another class of currently unidentified antiviral factor (s) suppresses post-entry viral replication by down-regulating transcription of HIV in infected cells. We have constructed a cDNA library from CD8+ T cells isolated from three HIV-infected long-term non-progressors and have begun screening for genes involved in inhibiting of HIV replication. Upon identification of such antiviral candidates, we plan to characterize their biological properties in vitro and pursue a clinical strategy aimed at utilizing these CD8+ T cell-derived antiviral factors in vivo. 2. Role of an immunosuppressive drug in HIV replication. Despite the development of successful therapeutic strategies, it has not been possible to eradicate HIV in infected individuals, mainly due to the persistence of various viral reservoirs. In particular, replication-competent virus, HIV-1 proviral DNA including 2 LTR circles, and spliced and unspliced HIV-1 RNA in CD4+ T cells, has been found in the majority of infected individuals in whom plasma viremia is below the limit of detection. This persistent viral reservoir has emerged as the major obstacle in preventing the eradication of HIV. In addition, we find a statistically significant inverse correlation between the frequency of CD4+ T cells carrying HIV-1 proviral DNA and the CD4+/CD8+ T cell ratios in aviremic infected individuals receiving ART (with plasma viremia levels below the limit of detection for prolonged periods of time (>2.5 years). Strategies aimed at minimizing cellular activation may further diminish residual viral replication in patients receiving ART. To address this question, we have begun a pilot clinical trial to examine the safety and tolerability of a mildly immunosuppressive agent, daclizumab, a humanized IgG1 monoclonal antibody that binds specifically to the alpha subunit (p55 alpha, CD25, or Tac subunit) of the human high-affinity IL-2 receptor expressed on the surface of activated lymphocytes. Considering the existence of an intimate relationship between the degree of immune activation and HIV replication, we aim to determine whether daclizumab can normalize immunologic profiles and reduce plasma viremia in study subjects.