Mannose Binding Lectin in Neuroinflammation and NeuroAIDS

描述（由申请方提供）：人类免疫缺陷病毒-1（HIV-1）在中枢神经系统（CNS）早期被检测到，并引起神经炎症，导致神经元损伤和死亡的开始和扩展。仅在美国，约100万HIV-1感染者中有40%可能获得HIV-1相关的CNS损伤。HIV-1神经发病机制和中枢神经系统损伤的先天免疫机制尚未得到充分研究。甘露糖结合凝集素（MBL）是由MBL 2基因编码的活性相蛋白，其通过识别存在于病原体（例如病毒、细菌）表面的甘露糖残基并通过激活MBL相关的丝氨酸蛋白酶（MASP）来启动补体途径，从而发动针对感染风险的先天免疫应答。MBL与HIV-1 gp 41/120的高甘露糖N-连接聚糖残基结合，并增强细胞因子应答和巨噬细胞介导的HIV-1调理作用。因此，较低的MBL表达或功能可导致神经炎症和病毒蛋白和免疫复合物在脑中的异常积累，从而导致神经毒性和神经认知障碍。最近，在约1000例HIV-1感染儿童中，我们发现导致非功能性MBL表达的MBL 2遗传变异的存在与CNS损伤的更快进展相关。虽然MBL 2变异体对HIV-1易感性和疾病进展的影响是已知的，但它们与CNS损伤进展的相关性是一个新发现。拟议的研究旨在通过研究MBL表达和功能与HIV-1相关神经炎症和CNS损伤的易感性和进展的关系来扩展这一新发现。我们的总体假设是MBL的低表达和改变的功能损害MBL介导的补体激活、相关的细胞因子应答、清道夫调理作用功能，并导致对HIV-1感染和神经炎症的易感性增加、病毒/补体蛋白或自身抗原在脑中的积累，最终导致神经认知障碍。此外，变体MBL 2/MASP-2等位基因改变CNS中MBL的表达和功能。对于这些研究，我们将确定来自HIV神经行为研究中心的HIV感染受损/未受损成人（N=2385）的配对CSF/血浆中的MBL、MASP和补体蛋白水平。（HNRC，UCSD）;和尸检脑组织（N=45），来自National NeuroAIDS Tissue Consortium（NNTC，Rockville，MD），使用高灵敏度多重ELISA，HIV感染期间的先天免疫应答微阵列分析，定量PCR验证，基因分型，荧光染色和荧光显微镜技术。这些研究将有助于了解MBL和相关先天免疫补体生物标志物在HIV相关神经炎症和神经认知障碍中的新作用;并可能为开发有效治疗药物（如重组人MBL）提供途径。公共卫生相关性：拟议的研究将确定甘露糖结合凝集素的新作用，补体介导的先天免疫和病原体吞噬作用的重要组成部分，在大脑中的HIV-1感染和相关的神经炎症，病毒蛋白积累和神经认知障碍的易感性。

DESCRIPTION (provided by applicant): Human immunodeficiency virus-1 (HIV-1) is detected early in central nervous system (CNS) and causes neuroinflammation leading to the initiation and expansion of neuronal injury and death. In USA alone, 40% of about 1 million HIV-1 infected individuals are likely to acquire HIV-1 related CNS impairment. The innate immune mechanisms underlying HIV-1 neuropathogenesis and CNS impairment have been understudied. Mannose binding lectin (MBL), coded by MBL2 gene, is an active phase protein that mounts innate immune response against risk of infections by recognizing mannose residues present on the surface of pathogens (e.g. viruses, bacteria) and initiating the complement pathway by activating MBL- associated serine proteases (MASPs). MBL binds to high mannose N-linked glycan residues of HIV-1 gp41/120 and elicits cytokine responses and macrophage mediated HIV-1 opsonization. Thus, lower MBL expression or function can result in neuroinflammation and anomalous accumulation of viral proteins and immune complexes in brain leading to neurotoxicity and neurocognitive impairment. Recently, in about 1000 HIV-1 infected children we showed that the presence of MBL2 genetic variants resulting in expression of non-functional MBL was associated with more rapid progression of CNS impairment. Although effects of MBL2 variants on susceptibility of HIV-1 and disease progression are known; their association with the progression of CNS impairment is a new finding. The proposed research seeks to extend this new finding by studying the association of MBL expression and function to the susceptibility and progression of HIV-1 related neuroinflammation and CNS impairment. Our overarching hypothesis is that lower expression and altered function of MBL impairs MBL-mediated complement activation, related cytokine responses; scavenger opsonization function and leads to increased susceptibility to HIV-1 infection and neuroinflammation, accumulation of viral/complement proteins or autoantigens in brain, and eventually neurocognitive impairment. Additionally, variant MBL2/MASP-2 alleles alter expression and function of MBL in CNS. For these studies, we will determine the MBL, MASPs and complement protein levels in paired CSF/plasma from HIV infected impaired/unimpaired adults (N=2385) from HIV Neurobehavioral Research Center (HNRC, UCSD); and post-mortem brain tissues (N=45) from National NeuroAIDS Tissue Consortium (NNTC, Rockville, MD) using highly sensitive multiplex ELISAs, innate immune response microarray analyses during HIV infection, quantitative PCR validation, genotyping, immunohistostaining and fluorescence microscopy techniques. These studies will help to understand the novel role of MBL and related innate immunity complement biomarkers in HIV related neuroinflammation and neurocognitive impairment; and might suggest avenues for development of effective therapeutics such as recombinant human MBL. PUBLIC HEALTH RELEVANCE: Proposed studies will determine the novel role of mannose binding lectin, an important component of complement-mediated innate immunity and pathogen phagocytosis, in susceptibility of HIV-1 infection in brain and related neuroinflammation, viral protein accumulation and neurocognitive impairment.