T lymphocyte-induced glial activation during CNS immune reconstitution disease

描述（由申请人提供）：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HIV感染管理的主要临床并发症。IRIS最常见于治疗开始时出现严重T细胞淋巴细胞减少的患者，通常伴有机会性感染。cart诱导的淋巴细胞减少逆转恢复了宿主防御，但由于特异性记忆T细胞的差异扩增，返回的T细胞库通常具有有限的多样性和对特定抗原的高度反应。各种各样的机会性病原体与IRIS有关，并且观察到不同的临床表现。然而，与潜在的病原体无关，甚至在没有可识别的机会性感染的情况下，IRIS的特征是过度的免疫激活，激活的t细胞重组的频率升高。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。然而，导致CNS-IRIS的神经免疫致病机制尚不清楚。我们实验室在之前的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淋巴细胞激活了驻留的小胶质细胞，包括那些位于局灶性病毒感染远端的广泛区域的小胶质细胞。基于这些发现，在这个竞争性更新应用中需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激活和神经毒性介质过度产生的信号来驱动中枢神经系统免疫重建疾病（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细胞重构是否会过度激活驻留的小胶质细胞。这将通过将CD3(+) t细胞过继转移到淋巴细胞减少的动物中，然后评估小胶质细胞的激活来实现。然后，我们将确定Foxp3（+）调节性t细胞（Treg）失调如何导致CNS-IRD。这些研究将使用表达Foxp3-DTR（白喉毒素受体）的转基因小鼠来确定在将CD3(+) t细胞过继转移到感染的淋巴细胞减少的动物之前，从CD3(+) t细胞中消耗Tregs的效果。最后一组实验将确定t细胞重构增强神经退行性变的机制。确定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。迫切需要针对不同神经致病途径的新型治疗方法（例如Treg免疫疗法）。然而，靶向的机制仍然知之甚少，因为它们很难通过临床研究来解决。在这项应用中，我们建议通过利用t细胞在淋巴细胞减少的小鼠宿主中进行机会性病毒脑感染的实验CNS-IRD来填补这一知识空白。

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.