Investigation of herpes simplex virus -1 neurotropism in SCID DRG xenografts

描述(申请人提供)：单纯疱疹病毒-1(HSV-1)是一种人类甲型疱疹病毒，在初次感染后在周围神经节建立终身潜伏感染。HSV-1感染通常是良性的，尽管其神经毒力和神经侵袭能力是HSV-1导致人类有害疾病的主要机制，特别是在新生儿和免疫低下的宿主中。我们的总体目标是建立一种体内研究HSV-1在人感觉神经节中的神经发病机制的模型。我们将利用我们建立的研究水痘-带状疱疹病毒(VZV)神经发病机制的系统，评估严重联合免疫缺陷(SCID)小鼠人背根神经节(DRG)移植瘤中HSV-1的感染情况。HSV-1感染的生物学与VZV相似，因为HSV-1和VZV在初次感染后均在感觉神经节内建立潜伏期。在SCIDhu DRG模型中对VZV的研究提供了第一次机会来检查人类甲型疱疹病毒在体内构成人DRG的细胞内的复制。DRG异种移植模型有可能在实验系统中揭示HSV-1在体内自然宿主组织微环境中的神经发病特征，这将大大增加对啮齿动物模型的观察。实验将针对三个具体目标：(1)我们将确定HSV-1在SCID小鼠体内接种人DRG异种移植后的过程，鉴定DRG内哪些细胞类型允许HSV-1基因表达，神经元和/或卫星细胞是否被生产性感染，以及HSV-1是否经历了我们在VZV感染的DRG异种移植中观察到的人类神经元向持久性的过渡模式；(2)我们将通过对重组HSV-1毒株的评估来研究HSV-1基因的功能，特别是我们将检查在初始感染和在DRG持续感染期间对HSV-1胸苷激酶(TK)的需求，以及它们进入DRG的能力；(3)如果HSV-1被证明能够在DRG移植瘤中持续存在，我们将评估该模型是否可用于通过移植潜伏感染的DRG异种移植瘤来研究HSV-1的重新激活，并用触发神经细胞信号通路的药物来增加HSV-1在啮齿动物模型中的重新激活。本工作旨在论证在SCID小鼠体内应用DRG异种移植的可行性，以探讨HSV-1在感觉神经节组织微环境中分化的人感觉神经元和非神经元细胞中神经发病的分子机制。除了对基本病毒-宿主相互作用的新见解外，这样的模型对于研究抗病毒药物和用于治疗或预防这种常见病毒引起的人类疾病的HSV-1减毒活疫苗候选具有潜在价值。公共卫生相关性：单纯疱疹病毒1型(HSV-1)可引起口腔和生殖器损害以及脑炎。这些感染在美国仍然是一个重要的公共卫生问题。HSV-1的严重并发症可能发生在健康人和那些患有损害免疫系统的疾病的人身上。我们的目标是开发一个模型来研究HSV-1如何感染人类神经细胞，这将对开发新药和疫苗具有潜在价值。

DESCRIPTION (provided by applicant): Herpes simplex virus-1 (HSV-1) is human alphaherpesvirus that establishes a lifelong latent infection in peripheral nerve ganglia following primary infection. HSV-1 infections are generally benign, although its capacity for neurovirulence and neuroinvasiveness are the primary mechanisms through which HSV-1 can cause harmful disease in humans, especially in neonates and immunocompromised hosts. Our overall objective is to develop a model for examining HSV-1 neuropathogenesis in human sensory ganglia in vivo. We will evaluate HSV-1 infection of human dorsal root ganglion (DRG) xenografts in mice with severe combined immunodeficiency (SCID), exploiting the system that we created to investigate varicella- zoster virus (VZV) neuropathogenesis. The biology of HSV-1 infection is similar to VZV in that both HSV-1 and VZV establish latency within sensory ganglia following primary infection. Studies of VZV in the SCIDhu DRG model have provided the first opportunity to examine replication of a human alphaherpesvirus within cells that comprise human DRG in vivo. The DRG xenograft model has the potential to reveal characteristics of HSV-1 neuropathogenesis in the natural human host tissue microenvironment in vivo in an experimental system that will add substantially to observations from rodent models. Experiments will address three specific aims: (1) we will define the course of events that follows HSV-1 inoculation of human DRG xenografts in SCID mice, identifying what cell types within DRG are permissive for HSV-1 gene expression, whether neurons and/or satellite cells become productively infected and whether HSV-1 undergoes the pattern of transition to persistence in human neurons that we have observed in VZV-infected DRG xenografts; (2) we will investigate HSV-1 gene functions through the evaluation of recombinant HSV-1 strains, in particular we will examine the requirement for HSV-1 thymidine kinase (TK) during initial infection and persistence in DRG, and gD mutants for their capacity for viral entry; (3) if HSV-1 is shown to establish persistence in DRG xenografts, we will assess whether this model can be used to study HSV-1 reactivation by explanting latently-infected DRG xenografts and treating with agents that trigger neural cell signaling pathways and increase HSV-1 reactivation in rodent models. This work is intended to demonstrate the feasibility of using DRG xenografts in SCID mice to explore the molecular mechanisms of HSV-1 neuropathogenesis in differentiated human sensory neurons and non-neuronal cells within their sensory ganglia tissue microenvironment in vivo. In addition to new insights about basic virus-host interactions, such a model has potential value for studying antiviral drugs and live attenuated HSV-1 vaccine candidates to treat or prevent human disease caused by this common virus. PUBLIC HEALTH RELEVANCE: Herpes Simplex Virus 1 (HSV-1) causes oral and genital lesions and encephalitis. These infections remain an important public health problem in the United States. Serious complications from HSV-1 can occur in healthy people and in those who have diseases that impair their immune systems. Our goal is to develop a model to study how HSV-1 infects human nerve cells that will have potential value for developing new drugs and vaccines.