Mannose Binding Lectin in Neuroinflammation and NeuroAIDS

描述(申请人提供)：人类免疫缺陷病毒-1(HIV-1)是在中枢神经系统(CNS)早期发现的，会引起神经炎症，导致神经元损伤和死亡的起始和扩大。仅在美国，约100万HIV-1感染者中就有40%可能患上HIV-1相关的中枢神经系统损害。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MBL2基因编码的一种活跃期蛋白，通过识别病原体(如病毒、细菌)表面的甘露糖残基，并通过激活MBL相关丝氨酸蛋白酶(MASP)来启动补体途径，从而增强对感染风险的天然免疫应答。MBL与HIV-1gp41/120的高甘露糖N-连接糖基结合，诱导细胞因子反应和巨噬细胞介导的HIV-1调理。因此，MBL的低表达或低功能可导致神经炎症和病毒蛋白和免疫复合体在脑内的异常积聚，从而导致神经毒性和神经认知功能障碍。最近，在大约1000名感染HIV-1的儿童中，我们发现MBL2基因变异的存在导致非功能性MBL的表达与中枢神经系统损害的进展更快相关。虽然MBL2变异对HIV-1易感性和疾病进展的影响是已知的，但它们与中枢神经系统损害进展的关联是一个新的发现。这项拟议的研究试图通过研究MBL的表达和功能与HIV-1相关神经炎症和中枢神经系统损伤的易感性和进展的关系来扩展这一新发现。我们的主要假设是，MBL的低表达和功能改变损害了MBL介导的补体激活，相关的细胞因子反应；清道夫调理功能，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内积聚，最终导致神经认知障碍。此外，MBL2/MASP-2变异等位基因改变了MBL在中枢神经系统中的表达和功能。在这些研究中，我们将使用高灵敏度的多重ELISA、HIV感染过程中的先天免疫反应微阵列分析、定量PCR验证、基因分型、免疫组织化学染色和荧光显微镜技术，检测来自HIV神经行为研究中心(HNRC，UCSD)的HIV感染者/未受损成年人(N=2385)以及美国国家神经艾滋病组织联合会(NNTC，Rockville，MD)的死后脑组织(N=45)的脑脊液/血浆配对中的MBL、MASPs和补体蛋白水平。这些研究将有助于理解MBL和相关的天然免疫补体生物标记物在HIV相关的神经炎症和神经认知障碍中的新作用；并可能为开发有效的治疗方法，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在脑内感染HIV-1及其相关神经炎、病毒蛋白积累和神经认知障碍的易感性中的新作用。甘露糖结合凝集素是补体介导的先天免疫和病原体吞噬作用的重要组成部分。

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.