HIV-1 Tat genetic variation impacts NeuroAIDS

 描述(由申请人提供)：HIV-1已证明有能力导致不利的神经并发症。高效抗逆转录病毒疗法(HAART)的引入提高了存活率，减少了病毒载量，增加了CD4T细胞计数，减少了机会性感染，并减少了最严重的HIV相关神经认知障碍(HAD)形式-HIV相关痴呆(HAD)。然而，所有形式的手的总体流行率都有所增加，这可能是因为艾滋病毒-1感染者持续感染的寿命更长。除了在中枢神经系统内激活抗病毒免疫反应外，HIV-1蛋白的产生还通过直接和间接机制导致神经毒性。特别令人感兴趣的是HIV-1反式激活蛋白Tat，它除了驱动病毒转录外，还作为一种细胞外神经毒性蛋白，激活星形胶质细胞和小胶质细胞，并影响血脑屏障(BBB)的结构和功能。除了受感染的淋巴细胞外，受感染的单核细胞、小胶质细胞和星形胶质细胞也会释放TAT。尽管HAART的广泛使用，位于中枢神经系统的HIV-1感染细胞仍然可以持续产生TAT，这表明在HAART时代，对这种蛋白质的神经学脆弱性仍然存在。此外，患有HAD的人的脑提取液中TAT的mRNA水平也升高。HIV-1还表现出广泛的序列变异，在许多宿主特异性和共病压力下形成的准种，同时保持对复制和传染性以及致病至关重要的功能。关于B亚型TAT基因变异和手部的研究已经证明：(I)在没有或存在HAD的情况下，来自患者的TAT序列显示关于神经损伤和起源组织的序列聚集，(Ii)来自手部患者的脑源性TAT序列之间的非同义和同义突变率显著高于从没有神经系统疾病的患者中分离的TAT序列，以及(Iii)第74和100位的变异与从脑源性序列分离的TAT序列相关。重要的是，来自HAD患者的HIV-1TAT与更大的神经元死亡有关。总之，这些报告表明，HIV-1TAT的遗传多样性可能有助于HAND的建立和严重程度。有鉴于此，这项应用的假设是，患者来源的HIV蛋白TAT的遗传变异与神经损伤有明确的联系。为了探索这一假说，其具体目的是：(1)识别和表征具有明确程度的神经认知障碍的患者的HIV-1 Tat基因的多态；(2)在蛋白质-蛋白质分子模型中检测HIV-1 Tat基因的多态对结构的影响；以及(3)检测Tat基因的多态对血脑屏障和中枢神经系统细胞的功能影响。这些研究将有助于确定HIV-1 Tat基因的多态性如何影响中枢神经系统的功能和手部的发育，并为开发手部的诊断分析和潜在的预防和治疗策略提供有用的信息。

 DESCRIPTION (provided by applicant): HIV-1 has demonstrated the ability to cause adverse neurological complications. The introduction of highly active antiretroviral therapy (HAART) has resulted in improved survival, reduced viral loads, increased CD4 T- cell counts, reduced opportunistic infections, and has resulted in a decrease in the most severe form of HIV- associated neurocognitive disorders (HAND), HIV-associated dementia (HAD). However, the overall prevalence of all forms of HAND has increased, potentially because HIV-1-infected individuals are living longer with persistent infection. In addition to activating an antiviral immne response within the CNS, the production of HIV-1 proteins leads to neurotoxicity through direct and indirect mechanisms. Of particular interest is the HIV-1 transactivator protein Tat, which in addition to driving viral transcription also functions as an extracellular neurotoxic protein, activator of astrocytes and microglial cells, and impacts the structure and function of the blood-brain barrier (BBB). Tat is released by infected monocytes, microglial cells, and astrocytes in addition to infected lymphocytes. Tat can be continually produced by HIV-1-infected cells located in the CNS despite the widespread use of HAART, demonstrating that neurologic vulnerability to this protein persists in the HAART era. In addition, mRNA levels for Tat are elevated in brain extracts from individuals with HAD. HIV-1 also displays extensive sequence variation with the quasispecies shaped by many host-specific and comorbidity pressures, while simultaneously maintaining functions that are critical to replication and infectivity as well as pathogenesis. Studies with respect to subtype B Tat genetic variation and HAND have demonstrated (i) Tat sequences from patients in the absence or presence of HAD showed clustering of sequences with respect to neurological impairment as well as tissue of origin, (ii) nonsynonymous versus synonymous mutation rates among brain-derived Tat sequences from patients with HAND were significantly greater than those isolated from patients without neurological disease, and (iii) variation at positions 74 and 100 were correlated to Tat sequences isolated from brain-derived sequences. Importantly, HIV-1 Tat derived from HAD patients has been associated with greater neuronal death. Together, these reports suggest that genetic diversity of HIV-1 Tat likely contributes to the establishment and severity of HAND. Given this, the hypothesis of this application is that patient-derived genetic variants of the HIV- protein Tat are specifically linked with neurologic impairment. To explore this hypothesis, the Specific Aims are to: (1) identify and characterize polymorphisms in HIV-1 Tat from patients with defined degrees of neurocognitive impairment; (2) examine the structural impact of HIV-1 Tat polymorphisms in protein-protein molecular models; and (3) examine the functional impact of the Tat polymorphisms on the BBB and cells of the CNS. These studies will contribute to defining how HIV-1 Tat polymorphisms affect the function of the CNS and the development of HAND and provide information useful in development of diagnostic assays of HAND and potential preventative and treatment strategies.