Immunomodulatory Function of Human T Cell Leukemia Virus Type 2 (HTLV-2)

描述（由申请人提供） 人类T白血病病毒1型（HTLV-1）及其遗传对应物HTLV-2是最早描述的人类逆转录病毒。与人类免疫缺陷病毒（HIV-1）不同，HTLV-1和HTLV-2感染通常在个体的整个一生中是沉默和无症状的。HIV-1与HTLV-1和HTLV-2之间观察到的差异病理学最可能归因于调节病毒复制、潜伏期和宿主细胞内转运的病毒辅助基因的差异。在HTLV-1和HTLV-2的情况下，称为Tax 1和Tax 2的转录激活蛋白是病毒复制所必需的，但也是通过CREB和NF：B途径的细胞启动子。HTLV-1 Tax 1蛋白的体外活性已被广泛评价，特别是在其作为癌蛋白发挥功能的能力方面。Tax 2似乎缺乏这种能力，这可能部分解释了HTLV-2的低致病性。此外，据报道Tax 2表现出CREB和NF：B的弱反式激活。本实验室的初步实验表明，Tax 2蛋白在大肠杆菌中表达，表达量为1000 μ g/ml。大肠杆菌（或在稳定转导的Jurkat细胞中）是外周血单核细胞（PBMC）的β趋化因子的有效诱导剂，并且观察到下调CCR 5共受体表达并改善PBMC活力和淋巴增殖能力。此外，Tax 2显示抑制HIV-1感染的PBMC和淋巴细胞中HIV-1 p24抗原的释放。假设：HTLV-2及其调节基因产物Tax 2有可能通过增加淋巴细胞活力和增殖、诱导β趋化因子以及下调CC趋化因子受体来改变先天宿主免疫反应。由此产生的影响可能会改变宿主在与其他病原体（包括HIV-1）共感染期间的反应。具体目标：（1）为了确认和验证Tax 2的体外功能，将野生型HTLV-2（wtHTLV-2）与Tax 2缺陷型HTLV-2感染性克隆（TaxHTLV-2）就其影响PBMC增殖能力和β趋化因子的加工的能力进行比较。作为子目标，将比较CD 4+与CD 8 + T细胞亚群中β趋化因子表达的相对水平。(2)通过比较重组Tax 2蛋白与一组Tax 2突变体的能力，确定Tax 2介导的抗病毒趋化因子诱导机制。突变蛋白将包括NF-κ B激活区、CREB结合区和核定位区的改变。(3)提示HTLV-2 Tax 2蛋白在HIV-1/HTLV-2合并感染期间可能作为免疫调节剂发挥主导作用。本研究的总体目标是了解Tax 2在调节HTLV-2感染个体的淋巴细胞功能中的作用，并暗示其在HIV-1/HTLV-2合并感染患者中修饰HIV-1感染中的作用。该项目探索了一种新的方法，研究一种病毒（HTLV-2）的辅助蛋白改变宿主细胞库中第二种相关病毒（HIV-1）的生物生命周期的潜力。我们希望这项拟议中的研究将促进我们对影响全国数千名退伍军人的逆转录病毒感染动态的理解。 公共卫生相关性： 拟议研究与退伍军人健康和/或医疗保健问题的相关性：HIV流行对VA医疗保健系统产生了重大影响[http://www.hiv.va.gov/vahiv? page= print-data-2005]。自1998年以来，退伍军人事务部通过免疫学病例登记处（ICR）跟踪向艾滋病毒患者提供的护理。ICR的数据来自VA的电子病历系统，其中包括有关临床状况和医疗保健利用的广泛信息。2005财政年度，估计有26 000名感染艾滋病毒的退伍军人在退伍军人事务部设施登记接受治疗。许多感染艾滋病毒的退伍军人不愿意坚持HAART治疗，因为担心与毒性有关。由于这些原因，HIV感染者迫切需要与较低毒性和治疗失败率相关的任何新的治疗策略。拟议的研究将侧重于探索艾滋病毒感染者免疫治疗的可能策略。

DESCRIPTION (provided by applicant) The human T leukemia virus type 1 (HTLV-1) and its genetic counterpart, HTLV-2, are the first-described human retroviruses. Unlike human immunodeficiency virus (HIV-1), infections with HTLV-1 and HTLV-2 are generally silent and asymptomatic for the entire lifetime of an individual. The differential pathology seen between HIV-1 and HTLV-1 and HTLV-2 is most likely attributable to differences in viral accessory genes regulating viral replication, latency, and transport within the host cell. In the case of HTLV-1 and HTLV-2, the transcriptional activating proteins, known as Tax1 and Tax2, are essential for viral replication, but are also cellular promoters via the CREB and NF:B pathways. The in vitro activity of the HTLV-1 Tax1 protein has been evaluated extensively, especially in the context of its ability to function as an oncoprotein. Tax2 seems to lack this ability, which may account in part for the low pathogenecity of HTLV-2. Tax2 has additionally been reported to exhibit poor transactivation of both CREB and NF:B. Nonetheless, preliminary experiments conducted in our laboratory indicate that Tax2 protein expressed in E. coli (or in stably transduced Jurkat cells) is a potent inducer of beta chemokines by peripheral blood mononuclear cells (PBMCs), and was observed to down-regulate CCR5 co-receptor expression and improve PBMC viability and lymphoproliferative capacity. Additionally, Tax2 was shown to inhibit HIV-1 p24 antigen release in HIV-1 infected PBMCs and lymphoid cells. Hypothesis: HTLV-2 and its regulatory gene product, Tax2, have the potential to modify innate host immune responses though increased lymphocyte viability and proliferation, induction of beta chemokines, and down-regulation of CC-chemokine receptors. The resultant effects could alter host responses during co- infection with other pathogens, including HIV-1. Specific Aims: (1) To confirm and validate the in vitro function of Tax2, wild type HTLV-2 (wtHTLV-2) will be compared with a Tax2-deficient HTLV-2 infectious clone ( TaxHTLV-2) with respect to their ability to affect PBMC proliferative capacity and elaboration of the beta chemokines. As a subaim, relative levels of beta chemokine expression in CD4+ vs. CD8+ T cell subsets will be compared. (2) To determine a mechanism of Tax2-mediated-induction of antiviral chemokines by comparing the ability of a recombinant Tax2 protein with a panel of Tax2 mutants. Mutant proteins will include alterations in the NF-KB activating region, CREB binding region, and nuclear localization region. (3) To implicate a possible dominant role of the HTLV-2 Tax2 protein as a possible immunomodulator during HIV-1/HTLV-2 co- infection. The overall goal of this research is to develop an understanding of the role of Tax2 in modulating lymphocyte function in HTLV-2 infected individuals, and to implicate its role in modifying HIV-1 infection in patients with HIV-1/HTLV-2 co-infections. The project explores a novel approach of examining the potential of an accessory protein of one virus (HTLV-2) to alter the biologic life cycle of a second, related virus (HIV-1) in the host cell reservoirs. We expect that the proposed research will advance our understanding of the dynamics of retroviral infections which affect thousands of Veteran's nationwide. PUBLIC HEALTH RELEVANCE: Relevance of the proposed research to veterans health and/or healthcare issues: The HIV epidemic has had a major impact on the VA healthcare system [http://www.hiv.va.gov/vahiv?page=prin-data-2005]. Since 1998, the VA has tracked the care provided to patients with HIV disease through the Immunology Case Registry (ICR). Data for the ICR are drawn from the VA's electronic medical record system, which includes a broad range of information on clinical condition and health care utilization. There were an estimated of 26,000 HIV infected veterans enrolled at VA facilities for treatment during FY2005. Many HIV infected veterans are reluctant to adhere to HAART therapy because of concerns related to toxicity. For these reasons, any new strategies for therapy associated with lower rates of toxicity and treatment failure are critically needed for HIV infected individuals. The proposed studies will focus on exploring possible strategies for immune based therapy of HIV infected patients.