HIV-1 Tat genetic variation impacts NeuroAIDS

 描述（由申请人提供）：HIV-1已证明能够引起不良神经系统并发症。高效抗逆转录病毒疗法（HAART）的引入已经导致存活率提高、病毒载量降低、CD 4 T细胞计数增加、机会性感染减少，并且已经导致最严重形式的HIV相关神经认知障碍（HAND）、HIV相关痴呆（HAD）的减少。然而，所有形式的HAND的总体流行率都有所增加，这可能是因为HIV-1感染者在持续感染的情况下寿命更长。除了激活CNS内的抗病毒免疫应答外，HIV-1蛋白的产生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反式激活蛋白达特，其除了驱动病毒转录之外还作为细胞外神经毒性蛋白、星形胶质细胞和小胶质细胞的激活剂起作用，并且影响血脑屏障（BBB）的结构和功能。除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释放达特。达特可由位于CNS中的HIV-1感染的细胞持续产生，尽管HAART被广泛使用，这表明在HAART时代神经系统对这种蛋白质的脆弱性仍然存在。此外，达特的mRNA水平在患有HAD的个体的脑提取物中升高。HIV-1还显示出广泛的序列变异，其准种由许多宿主特异性和共病压力形成，同时保持对复制和感染性以及发病机制至关重要的功能。关于亚型B达特遗传变异和HAND的研究已经证明（i）来自不存在或存在HAD的患者的达特序列显示关于神经损伤以及起源组织的序列聚类，（ii）来自HAND患者的脑来源的达特序列中的非同义突变率与同义突变率显著大于从没有神经疾病的患者分离的那些，和（iii）位置74和100处的变异与从脑衍生序列分离的达特序列相关。重要的是，来自HAD患者的HIV-1达特与更大的神经元死亡相关。总之，这些报告表明，HIV-1达特的遗传多样性可能有助于HAND的建立和严重程度。鉴于此，本申请的假设是HIV-蛋白达特的患者来源的遗传变体与神经损伤特异性相关。为了探索这一假设，具体目的是：（1）鉴定和表征具有确定程度的神经认知障碍患者的HIV-1达特多态性;（2）在蛋白质-蛋白质分子模型中检查HIV-1达特多态性的结构影响;（3）检查达特多态性对BBB和CNS细胞的功能影响。这些研究将有助于确定HIV-1达特多态性如何影响中枢神经系统的功能和HAND的发展，并为HAND的诊断检测和潜在的预防和治疗策略的发展提供有用的信息。

 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.