T lymphocyte-induced glial activation during CNS immune reconstitution disease

描述（由申请方提供）：免疫重建炎症综合征（IRIS）已成为开始联合抗逆转录病毒治疗（cART）后管理HIV感染的主要临床并发症。IRIS最常见于治疗开始时重度T细胞淋巴细胞减少症的患者，通常存在机会性感染。cART诱导的淋巴细胞减少的逆转恢复了宿主防御，但由于特异性记忆T细胞的差异性扩增，恢复的T细胞库通常具有有限的多样性并且对特定抗原高度应答。各种各样的机会致病菌已与IRIS和异质性的临床表现进行了观察。然而，独立于潜在的病原体或甚至在没有可识别的机会性感染的情况下，IRIS的特征在于过度的免疫激活，具有升高的重建活化T细胞的频率。专门攻击大脑的免疫恢复被称为中枢神经系统（CNS）-IRIS，由于其临床严重性，它特别具有挑战性。尽管如此，导致CNS-IRIS的神经免疫病理机制仍知之甚少。我们实验室在该资助的前一个资助期内获得的结果表明，来自外周免疫系统的脑浸润性病毒特异性T淋巴细胞激活了常驻小胶质细胞，包括那些在远离病灶病毒感染的广泛区域中的细胞。基于这些发现，在这种竞争性更新应用中要测试的中心假设是，补充但失调的T淋巴细胞通过提供促进驻留小胶质细胞过度活化和神经毒性介质过度产生的信号来驱动CNS免疫重建疾病（IRD）。在拟议的研究中，我们将首先确定携带疱疹病毒脑感染的淋巴细胞减少小鼠的T细胞重建是否过度激活驻留的小胶质细胞。这将通过将CD 3（+）T细胞过继转移到淋巴细胞减少动物中，然后评估小胶质细胞活化来实现。然后，我们将确定Foxp 3（+）调节性T细胞（Treg）失调如何导致CNS-IRD。这些研究将使用表达Foxp 3-DTR（白喉毒素受体）的转基因小鼠，以确定在过继转移到感染的淋巴细胞减少动物中之前，从CD 3（+）T细胞中清除Tcl 3的效果。最后一组实验将确定T细胞重建增强神经退行性变的机制。识别T淋巴细胞和小胶质细胞之间驱动过度活跃的神经免疫反应的精确相互作用对HIV医学领域至关重要。新的治疗方法（例如，因此，迫切需要靶向不同神经致病途径的Treg免疫疗法。然而，靶向机制仍然知之甚少，因为它们很难通过临床研究来解决。在此应用中，我们建议填补这一知识空白，通过研究实验CNS-IRD使用T细胞再增殖的淋巴细胞减少小鼠宿主窝藏机会性病毒脑感染。

DESCRIPTION (provided by applicant): Immune reconstitution inflammatory syndrome (IRIS) has emerged as a major clinical complication in the management of HIV infection following the initiation of combination antiretroviral therapy (cART). IRIS is most commonly seen in patients with severe T cell lymphopenia at the initiation of treatment, often in the presence of an opportunistic infection. cART-induced reversal of lymphopenia restores host defense, but the T- cell repertoire that comes back is often of limited diversity and hyper-responsive to particular antigens due to differential expansion of specific memory T-cells. A wide variety of opportunistic pathogens have been associated with IRIS and heterogeneous clinical manifestations are observed. However, independent of the underlying pathogen or even in the absence of identifiable opportunistic infection, IRIS is characterized by excessive immune activation with elevated frequencies of reconstituting activated T-cells. Immune recovery which specifically attacks the brain is termed central nervous system (CNS)-IRIS and it is particularly challenging due to its clinical severity. Still, the neuroimmunopathogenic mechanisms resulting in CNS-IRIS are poorly understood. Results obtained in our laboratory over the previous funding period of this grant have shown that brain-infiltrating, virus-specific T lymphocytes from the peripheral immune system activate resident microglial cells, including those in widespread areas distal to focal viral infection. Building upon these findings, the central hypothesis to be tested in this competitive renewal application is that replenished yet dysregulated T-lymphocytes drive CNS-immune reconstitution disease (IRD) by providing signals which promote hyper-activation of resident microglia and the overproduction of neurotoxic mediators. In the proposed studies, we will first determine whether T-cell reconstitution of lymphopenic mice harboring herpesvirus brain infection hyper-activates resident microglial cells. This will be achieved through adoptive transfer of CD3(+) T-cells into lymphopenic animals followed by assessment of microglial activation. We will then determine how Foxp3(+) regulatory T-cell (Treg) dysregulation contributes to CNS-IRD. These studies will employ Foxp3-DTR (diphtheria toxin receptor) expressing transgenic mice to determine the effect of depleting Tregs from CD3(+) T-cells prior to adoptive transfer into infected, lymphopenic animals. The final set of experiments will determine mechanisms by which T-cell reconstitution potentiates neurodegeneration. Identification of the precise interactions between T lymphocytes and microglia which drive hyperactive neuroimmune responses is vitally important to the field of HIV medicine. Novel therapeutic approaches (e.g., Treg immunotherapy) which target distinct neuropathogenic pathways are urgently needed. However, the mechanisms to target are still poorly understood because they are difficult to address through clinical studies. In this application, we propose to fill this gap in knowledge by studying experimental CNS-IRD using T-cell repopulation of lymphopenic murine hosts harboring opportunistic viral brain infection.