T lymphocyte-induced glial activation during CNS immune reconstitution disease

描述(由申请人提供)：随着联合抗逆转录病毒疗法(CART)的开始，免疫重建炎症综合征(IRIS)已成为艾滋病毒感染管理中的主要临床并发症。虹膜最常见于治疗开始时患有严重T淋巴细胞减少症的患者，通常是在机会性感染的情况下。CART诱导的淋巴细胞减少逆转可以恢复宿主防御，但由于特定记忆T细胞的不同扩张，恢复的T细胞谱系通常是有限的多样性和对特定抗原的高反应性。各种机会性病原体都与IRIS有关，临床表现也各不相同。然而，独立于潜在的病原体，甚至在没有可识别的机会性感染的情况下，IRIS的特征是过度免疫激活，并提高重建激活的T细胞的频率。特异性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，这一过程特别具有挑战性。尽管如此，导致CNS-IRIS的神经免疫病理机制仍然知之甚少。我们实验室在这笔赠款的前一个资助期所获得的结果表明，来自外周免疫系统的脑渗透的病毒特异性T淋巴细胞激活驻留的小胶质细胞，包括局部病毒感染远端广泛区域的小胶质细胞。基于这些发现，在这一竞争性更新应用中要检验的中心假设是，补充但调节失调的T淋巴细胞通过提供促进常驻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细胞重建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症动物体内，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)失调是如何导致CNS-IRD的。这些研究将使用表达白喉毒素受体(Foxp3-DTR)的转基因小鼠来确定在过继转移到受感染的淋巴细胞减少的动物之前，耗尽CD3(+)T细胞中的Tregs的效果。最后一组实验将确定T细胞重建加强神经退化的机制。准确识别T淋巴细胞和小胶质细胞之间的相互作用是驱动过度活跃的神经免疫反应的关键，这对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的治疗方法(例如，Treg免疫治疗)。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，我们建议通过研究实验性CNS-IRD来填补这一知识空白，该研究使用携带机会性病毒脑感染的淋巴细胞减少小鼠宿主的T细胞再繁殖。

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.