Elucidating the role of RXRA in the myeloid lineage in post-infectious basal ganglia encephalitis

项目摘要 儿童感染化脓性链球菌（A组链球菌; GAS）与基础 神经节脑炎（BGE）后遗症，表现为运动[Sydenham舞蹈病（SC）]或精神病 [链球菌感染相关的儿童自身免疫性神经精神障碍（PANDAS）] 症状人类和动物研究表明，异常的细胞（Th 17淋巴细胞）和体液 （自身抗体）适应性免疫反应，通常产生对抗复发性S。化脓性感染， 靶向脑并引起神经血管损伤、抗体进入脑、神经炎症（小胶质细胞 活化和巨噬细胞浸润）和神经回路功能障碍。然而，并不是所有的孩子都能在... 感染性BGE，尽管频繁的GAS感染表明存在遗传风险因素， 他们发展疾病。通过对82名患者和146名对照的基因组DNA进行全外显子组测序， 通过生物信息学分析，我们已经在大约20个基因中确定了可能的候选遗传变异， 与感染后BGE的疾病风险相关。BGE风险最高的基因之一RXRA（编码 视黄酸X受体α）是先天性和适应性免疫应答的关键调节剂。我们发现 Rxra mRNA和蛋白水平在活化的小胶质细胞和浸润的巨噬细胞中上调， 小鼠反复鼻内GAS感染后的大脑。在这里，我们将测试的假设，RXRA，确定由 全外显子组测序，调节骨髓谱系中的几种先天免疫应答（小胶质细胞和 巨噬细胞），包括活化、抗原呈递、细胞因子产生和吞噬作用， 复发性GAS后脑中神经血管损伤和神经回路功能障碍的关键 感染.我们已经产生了在骨髓谱系（小胶质细胞和巨噬细胞）中缺乏Rxra功能的小鼠。 对于我们的第一个目标，我们将测试小胶质细胞/巨噬细胞中Rxra对其活化、抗原 使用PET成像、单细胞RNA测序和免疫荧光技术， 在我们的感染后BGE小鼠模型中进行验证。与此同时，我们将对人类进行体外研究， 在SC/PANDAS/PANS患者中鉴定的携带RXRA基因无义突变的小胶质细胞， 测试GAS暴露后的活化和吞噬能力。对于我们的第二个目标，我们将研究 消除骨髓细胞中Rxra功能对神经血管损伤（即血脑屏障）的后果 功能障碍）、消除兴奋性突触和神经元回路功能障碍 反复鼻内GAS感染后的测序研究、病理学、生理学和行为学测定 在对照或骨髓特异性Rxra缺陷小鼠中。这些原理验证研究有可能揭示 疾病发病机制的新机制，并开发潜在的生物标志物或新的治疗方法，以帮助 家庭的诊断和治疗策略，其中目前有几个有限的临床疗效。

PROJECT SUMMARY Childhood infections with Streptococcus pyogenes (Group A Streptococcus; GAS) are associated with basal ganglia encephalitis (BGE) sequelae that present with either movement [Sydenham’s chorea (SC)] or psychiatric [Pediatric Autoimmune Neuropsychiatric Disorders Associated with Streptococcal infections (PANDAS)] symptoms. Human and animal studies have shown that aberrant cellular (Th17 lymphocytes) and humoral (autoantibodies) adaptive immune responses, generated normally to fight recurrent S. pyogenes infections, target the brain and elicit neurovascular damage, antibody entry into the brain, neuroinflammation (microglial activation and macrophage infiltration) and neural circuit dysfunction. However, not all children develop post- infectious BGE despite frequent GAS infections suggesting the presence of genetic risk factors that predispose them to develop disease. Through whole-exome sequencing of genomic DNA from 82 patients and 146 controls followed by bioinformatics analysis, we have identified candidate genetic variants in ~20 genes that are likely associated with disease risk for post-infectious BGE. One of the top BGE risk genes, RXRA (encoding for Retinoid X Receptor Alpha), is a key regulator of both innate and adaptive immune responses. We have found that Rxra mRNA and proteins levels are upregulated in activated microglia and infiltrating macrophages in the brain after recurrent intranasal GAS infections in mice. Here, we will test the hypothesis that RXRA, identified by whole-exome sequencing, regulates several innate immune responses in the myeloid lineage (microglia and macrophages) ranging from activation, antigen presentation, cytokine production and phagocytosis, that are critical for both neurovascular damage and neuronal circuit dysfunction in the brain after recurrent GAS infections. We have generated mice lacking Rxra function in the myeloid lineage (microglia and macrophages). For our first objective, we will test the requirement of Rxra in microglial/macrophages for their activation, antigen presentation, cytokine production and phagocytosis in vivo using PET imaging, single cell RNA sequencing and validation in our mouse model for post-infectious BGE. In parallel, we will perform in vitro studies with the human microglia cells, carrying the nonsense mutations in the RXRA gene identified in SC/PANDAS/PANS patients, to test activation and phagocytic ability following GAS exposure. For our second objective, we will examine the consequences of eliminating Rxra function in the myeloid cell for neurovascular damage (i.e. blood-brain barrier dysfunction), elimination of excitatory synapses and neuronal circuitry dysfunction using single cell RNA sequencing studies, pathological, physiological and behavioral assays after recurrent intranasal GAS infections in control or myeloid-specific Rxra deficient mice. These proof-of-principle studies have the potential to uncover novel mechanisms of disease pathogenesis and develop potential biomarkers or new therapeutics to assist in diagnostic and treatment strategies for families, of which there are currently few with limited clinical efficacy.