Human DBR1 defines a new pathway of intrinsic antiviral immunity in the CNS

描述（由申请人提供）：儿童单纯疱疹病毒1型（HSV-1）脑炎（HSE）是由HSV-1原发性感染引起的一种危及生命的并发症，HSV-1是一种在大多数儿童中引起无害感染的常见病毒。HSE的发病机制尚不清楚，直到我们最近发现该疾病可能是由单基因突变导致的，该突变损害了一些儿童中枢神经系统（CNS）中tlr3依赖的IFN-介导的对HSV-1的免疫。我们描述了10例患者，每个患者都携带TLR3通路基因的纯合或杂合突变。我们还证实，患者特异性诱导多能干细胞（iPSC）衍生的TLR3缺陷神经元和少突胶质细胞对HSV-1感染高度敏感，这表明TLR3- ifn介导的中枢神经系统内在抗HSV-1免疫受损是TLR3免疫先天缺陷患者HSE发病机制的基础。因此，其他儿童的HSE可能是由中枢神经系统的单基因先天错误引起的——对HSV-1的内在免疫，可能但不一定与TLR3-IFN回路有关。令人惊讶的是，在最近通过全外显子组测序（WES）研究的100名HSE儿童中，有4名携带编码人类脱分支酶1 （DBR1）的基因纯合（2名患者）或杂合（2名患者）错义突变。人类DBR1被认为在从pre-mRNA中切除的颈部内含子的快速周转中起关键作用。与此观察结果相关，另外7名被研究的HSE儿童在编码5‘-3’外核糖核酸酶1 （XRN1）的基因上携带杂合无义（2例）或错义（5例）突变，XRN1是在宿主mrna前衰变途径中与DBR1密切相关的分子。DBR1和XRN1都有特定的中枢神经系统表达模式。虽然酵母菌Xrn1被认为是一种重要的抗病毒分子，但DBR1和Xrn1如何控制人类中枢系统的抗hsv -1免疫还完全不清楚。我们假设人类DBR1和XRN1定义了一种新的、中枢系统特异性的内在抗hsv -1免疫机制。本应用程序的目的是在分子和细胞水平上测试这一假设。建议的工作将

DESCRIPTION (provided by applicant): Childhood herpes simplex virus 1 (HSV-1) encephalitis (HSE) is a life-threatening complication of primary infection by HSV-1, a common virus that causes innocuous infections in most children. The pathogenesis of HSE remained unclear until we recently showed that the disease may result from single-gene mutations impairing TLR3-dependent, IFN-¿/¿-mediated immunity to HSV-1 in the central nervous system (CNS), in some children. We described 10 patients, each carrying homozygous or heterozygous mutations in a TLR3 pathway gene. We also demonstrated that patient-specific induced pluripotent stem cells (iPSC)-derived TLR3-deficient neurons and oligodendrocytes were highly susceptible to HSV-1 infection, suggesting that impaired TLR3-IFN-mediated CNS intrinsic anti-HSV-1 immunity underlies the pathogenesis of HSE in patients with inborn errors of TLR3 immunity. HSE in other children may therefore result from a collection of single-gene inborn errors of CNS- intrinsic immunity against HSV-1, probably but not necessarily related to the TLR3-IFN circuit. Surprisingly, out of the 100 HSE children recently studied by whole exome sequencing (WES), four carry homozygous (two patients) or heterozygous (two patients) missense mutations in the gene encoding human debranching enzyme 1 (DBR1). Human DBR1 has been proposed to play a key role in the rapid turnover of lariat introns excised from pre-mRNA. Related to this observation, seven other HSE children studied carry heterozygous nonsense (two patients) or missense (five patients) mutations in the gene encoding 5'-3' exoribonuclease 1 (XRN1), a molecule closely connected to DBR1 in a host pre-mRNA decay pathway. Both DBR1 and XRN1 have particular CNS expression patterns. Although yeast Xrn1 is known as an essential antiviral molecule, it is completely unknown how DBR1 and XRN1 can control anti-HSV-1 immunity in the human CNS. We hypothesize that human DBR1 and XRN1 define a new, CNS-specific mechanism of intrinsic anti-HSV-1 immunity. The goal of the present application is to test this hypothesis at the molecular and cellular levels. The proposed work will be focused on the exploration of the specific role of DBR1 and its related genes (mainly XRN1) in CNS-intrinsic anti-viral immunity. The preliminary results further showed that dermal fibroblasts from one patient homozygous for a DBR1 I120T mutation express only very low levels of DBR1 protein and enhanced HSV-1 susceptibility, as comparing to the healthy controls tested. We will test fibroblasts from all patients carrying mutations in DBR1 or XRN1. We will investigate the antiviral activity of DBR1 and XRN1, indirectly via TLR3- or IFN-mediated immunity, or directly via the suppression of viral RNA recombination by DBR1 or XRN1, in in vitro assays. We will investigate anti-HSV-1 immune responses and HSV-1 susceptibility, both IFN-dependent or not, in patients' fibroblasts and iPSC-derived neurons deficient for DBR1 or XRN1, in comparison with those with impaired TLR3-, IFN-mediated immunity. This research will shed light on a novel molecule and cellular mechanism of the HSE pathogenesis, which will open new therapeutic avenues.