CHEMOKINE-MEDIATED NEUROPROTECTION AND REPAIR DURING WNV ENCEPHALITIS

描述（由申请人提供）：这项竞争性更新的长期实验目的是评估趋化因子及其受体在西尼罗河病毒脑炎小鼠模型中促进病毒清除、免疫病理和修复的功能作用。小鼠西尼罗河病毒感染是一种广为接受的黄病毒脑炎模型，在免疫功能低下或失调的个体中，低剂量强毒株皮下感染可导致神经侵袭性疾病。因此，小鼠实验研究已经确定了决定人类西尼罗河病毒脑炎神经发病机制和结果的病毒和宿主因素，包括决定浸润免疫细胞进入和命运的几种趋化因子受体。在已发表的研究中，我们已经确定趋化因子CXCL12和CXCL10分别以区域特异性的方式控制白细胞进入血脑屏障（BBB）和中枢神经系统（CNS）实质。在初步研究中，我们还观察到西尼罗河病毒感染导致神经源区BrDU掺入增加，这表明成人神经发生受到病毒感染的影响。此外，我们已经确定TLR3信号影响神经前体细胞转录因子Pax6和nestin在几个大脑区域的表达，提供了病毒感染和已知调节趋化因子表达和神经发生的先天免疫分子激活之间的联系。本提案旨在了解血脑屏障运输的保护性与致病性白细胞和病毒进入的免疫学基础。由于趋化因子上调也会招募神经前体细胞进行修复，我们将进一步评估趋化因子如何影响wnv损伤的中枢神经系统内的神经发生。我们将在三个方面解决这些问题：1)确定在西尼罗河病毒脑炎期间负责保护性白细胞与致病性白细胞跨血脑屏障迁移的促炎途径。该目的将确定白细胞进入血脑屏障和特定中枢神经系统区域内运输的分子线索。此外，我们将确定CXCR4在血脑屏障T细胞亚群进入中的作用；2)确定西尼罗河病毒进入血脑屏障的分子机制及其作用。该目的将采用体外和体内方法来确定西尼罗河病毒对中枢神经系统内皮和病毒入侵的影响；3)研究趋化因子受体介导的西尼罗河病毒脑炎期间神经保护和修复策略。这一目的将确定西尼罗河病毒感染如何影响成人中枢神经系统中神经细胞的产生以及控制这一过程的趋化因子。总之，这些研究将扩展我们目前对趋化因子及其受体在西尼罗河病毒脑炎期间如何控制中枢神经系统炎症并最终修复的理解。

DESCRIPTION (provided by applicant): The long term experimental objective of this competitive renewal is to evaluate the functional roles of chemokines and their receptors in contributing to viral clearance, immunopathology and repair in a murine model of WNV encephalitis. Murine WNV infection is well-accepted flavivirus encephalitis model whereby subcutaneous infection with low inoculum of virulent strains leads to neuroinvasive disease in individuals with depressed or dysregulated immune function. Thus, murine experimental studies have identified viral and host factors that determine the neuropathogenesis and outcome of WNV encephalitis in humans, including several chemokine receptors that determine the entry and fate of infiltrating immune cells. In published studies we have determined that the chemokines CXCL12 and CXCL10 control leukocyte access to the central nervous system (CNS) parenchyma at the blood-brain barrier (BBB) and within the CNS parenchyma in a region-specific manner, respectively. In preliminary studies we have also observed that WNV infection led to increased BrDU incorporation within neurogenic zones, suggesting that adult neurogenesis is affected by viral infection. In addition, we have determined that TLR3 signaling affects the expression of neural precursor cell transcription factors Pax6 and nestin in several brain regions, providing a link between viral infection and activation of innate immune molecules known to regulate both chemokine expression and neurogenesis. The present proposal seeks to understand the immunological basis of BBB trafficking for protective versus pathogenic leukocytes and for virus entry. Because chemokine up-regulation also recruits neural precursor cells for repair, we will additionally evaluate how chemokines influence neurogenesis within the WNV-damaged CNS. We will address these questions in three aims: 1) Identify the proinflammatory pathways responsible for the migration of protective versus pathogenic leukocytes across the BBB during WNV encephalitis. This aim will determine molecular cues for leukocyte entry at the BBB and trafficking within specific CNS regions. Additionally, we will determine the role of CXCR4 in T cell subset entry at the BBB; 2) Identify molecular mechanisms involved in WNV entry and effects at the BBB. This aim will use in vitro and in vivo approaches to determine WNV effects on CNS endothelium and viral invasion; and 3) Examine chemokine receptor-mediated strategies for neuroprotection and repair during WNV encephalitis. This aim will determine how WNV infection affects the generation of neural cells in the adult CNS and the chemokines that control this process. Together, these studies will extend our current understanding of how chemokines and their receptors control CNS inflammation and ultimately repair during WNV encephalitis. PUBLIC HEALTH RELEVANCE: Viral encephalitis is an emerging global health threat without effective therapeutic strategies. In particular, the arthropod-borne flaviviruses, West Nile (WNV), Japanese encephalitis (JEV), Tick-borne encephalitis (TBEV, Murray Valley encephalitis (MVEV) and St. Louis encephalitis (SLEV) viruses, cause outbreaks of encephalitis worldwide, with a total annual case rate of over 50,000 (www.who.int). Among the important questions regarding the neuropathogenesis of flavivirus encephalitis is whether individuals that develop neuroinvasive disease do so because of impaired virologic control in the periphery and/or because of fundamental differences in blood-brain barrier (BBB) biology and whether viral-mediated effects on endogenous repair mechanisms alter functional outcomes. In addition, although central nervous system infections (CNS) with these cytopathic neurotropic viruses require the parenchymal penetration of T lymphocytes for virus clearance, there are also data suggesting that the presence of these immune cells within the CNS induces immunopathologic damage. Thus, understanding the mechanisms that govern the entry of virus and leukocyte subsets at the BBB is essential for developing treatments that can prevent neuroinvasion in patients at risk and promote appropriate antiviral immune responses within the CNS after neuroinvasion has occurred. The present proposal seeks to understand the immunological basis of BBB trafficking for protective versus pathogenic leukocytes and for virus entry and to additionally evaluate adult neurogenesis within the WNV-damaged CNS. These studies will extend our current understanding of the molecular mechanisms that control CNS inflammation and repair during WNV encephalitis. Further, the data obtained from these experiments may identify potential targets for therapeutic treatment of humans with flavivirus encephalitides.