A Development-Specific Mechanism of Pathogenesis in HSV Encephalitis

 描述(由申请人提供)：成人感染单纯疱疹病毒(HSV)通常是亚临床的，但在新生儿中，HSV是死亡和发病的重要原因。尽管发育中的大脑和成人之间的免疫反应差异与新生儿疾病严重程度的增加有关，但这种差异的确切原因尚不清楚。单纯疱疹病毒蛋白γ34.5常被描述为单纯疱疹病毒中枢神经系统感染过程中的“神经毒力因子”，因为发现该基因的缺失会导致病毒显著减弱，从而减少神经元的复制。先前的研究表明，单纯疱疹病毒PKR34.5蛋白是通过多个结构域来对抗宿主细胞启动的I型干扰素反应的核心，这些结构域的功能是：(1)通过γ受体对抗宿主翻译抑制；(2)抑制坦克结合激酶途径；(3)通过结合其起始蛋白的结构域抑制自噬反应。包括单纯疱疹病毒在内的许多嗜神经病毒抑制自噬是神经元发病的关键功能，神经元利用自噬作为控制病毒复制和避免潜在破坏性细胞溶解反应的方法。在成年单纯疱疹病毒脑炎的小鼠模型中，缺乏BBD的γ34.5突变体HSV-1不能抑制自噬，并且在成年小鼠中神经严重减弱。自噬在出生后在新生儿的大脑中上调，它在神经发育中也发挥着关键作用。我的初步数据表明，与成人不同，在新生儿脑炎模型中，γ34.5的Beclin-1结合功能对于单纯疱疹病毒的发病是必不可少的。然而，从γ-1中删除整个HSV34.5基因仍然会导致新生儿大脑的神经衰减。因此，我假设γ34.5赋予 HSV通过一种不同于抑制自噬的机制在新生儿中发挥神经毒力。尽管自噬似乎在成人单纯疱疹病毒性脑炎模型中发挥了细胞保护作用，但自噬在新生儿大脑独特环境中的作用尚未被研究。研究新生儿缺氧缺血损伤的研究小组最近的工作表明，自噬功能失调可能导致新生儿大脑中凋亡细胞死亡的增加。我的初步数据表明，激活的自噬标记与新生儿大脑感染区域的细胞凋亡之间存在关联。因此，我假设，与成人不同，自噬并不能保护新生儿的大脑免受HSV感染，激活的自噬会导致更多的细胞凋亡。我将使用几种突变病毒阐明新生儿和成人神经发病的关键决定因素，这些突变病毒在γ34.5区对宿主细胞相互作用至关重要。使用野生的 在新感染的新生儿中枢神经系统中，我将研究自噬的激活以及自噬在细胞凋亡中的作用。

 DESCRIPTION (provided by applicant): Infection with herpes simplex virus (HSV) in adults is often subclinical, but in the newborn HSV is a significant cause of mortality and morbidity. Although differences in the immune response between the developing brain and the adult have been implicated in the increased severity of disease in the neonate, the precise reasons for this difference are unknown. The HSV protein γ34.5 is often described as the "neurovirulence factor" during HSV central nervous system (CNS) infection due to the finding that the deletion of this gene results in a significantly attenuated virus that has decreased replication in neurons. Prior studies have shown that the HSV γ34.5 protein is central to countering the type-I interferon response initiated by the host cell through multiple domains that function to (i) counter host-translational arrest through PKR, (ii) inhibit the TANK-binding kinase pathway, and (iii) inhibit te autophagic response through a domain that binds its initiating protein, beclin-1. Inhibition of autophagy by many neurotropic viruses, including HSV, is a critical function for pathogenesis in neurons, which use autophagy as a method to control viral replication and avoid a potentially devastating cytolytic response. In a murine model of adult HSV encephalitis, a beclin-1 binding domain (BBD) deficient γ34.5 mutant HSV-1 is unable to inhibit autophagy and is severely neuroattenuated in adult mice. Autophagy is up-regulated in the neonatal brain after birth and it also plays a critical role in neurodevelopment. My preliminary data suggests that unlike in the adult, the beclin-1-binding function of γ34.5 is dispensable for the pathogenesis of HSV in a model of neonatal encephalitis. However, deletion of the entire γ34.5 gene from HSV-1 still results in neuroattenuation in the neonatal brain. Therefore, I hypothesize that γ34.5 confers the neurovirulence of HSV in the neonate through a mechanism that is distinct from the inhibition of autophagy. Although autophagy appears to play a cytoprotective role in an adult model of HSV encephalitis, the role of autophagy in the unique environment of the neonatal brain has not yet been investigated. Recent work by groups investigating neonatal hypoxic-ischemic injury has demonstrated that dysregulated autophagy may contribute to increased apoptotic cell death in the neonatal brain. My preliminary data suggests an association between markers of activated autophagy and apoptosis in infected regions of the neonatal brain. Thus, I hypothesize that unlike in the adult, autophagy does not protect the newborn brain from HSV infection and activated autophagy leads to increased apoptotic cell death. I will elucidate the critical determinants of neuropathogenesis in the neonate compared to the adult using several mutant viruses that have been deleted in the γ34.5 regions critical for host-cell interaction. Using wild type and autophagy knockout mice, I will investigate the activation of autophagy in the infected neonatal CNS and the contribution of autophagy to apoptotic cell death.