VZV in the enteric nervous system: pathogenesis and consequences

描述（由申请人提供）：肠神经系统（ENS）可以在没有大脑或脊髓输入的情况下控制肠道的行为。功能正常的ENS对生命至关重要，当其异常时，会引起不适，并可能导致胃肠道运动、分泌和炎症紊乱的病理生理学或严重程度。我们最近发现，水痘带状疱疹病毒（VZV）在大多数经历过天然水痘或接种过水痘疫苗的人肠道神经元中建立潜伏期。此外，VZV与免疫功能低下个体中致命性假性梗阻的发生有关。无论是VZV进入ENS的途径，还是其在肠神经元（“肠带状疱疹”）中重新激活的频率或后果，以前都没有被探索过。目前的建议旨在验证以下假设：内脏传入神经的运输将VZV传导到ENS，无细胞病毒粒子在肠神经元中建立潜伏期，非结构性VZV ORF61蛋白必须在神经元中表达才能使VZV表现出溶解性感染或从潜伏期中重新激活。虽然VZV对人类细胞表现出明显的偏好，但我们已经开发了动物模型，允许在体外和体内研究ENS的VZV感染。根据条件的不同，VZV在从豚鼠或小鼠分离的肠神经元中重现潜伏性、溶解性和再激活性感染，当引入肠道时，VZV在豚鼠ENS中原位建立潜伏期。该提案有3个具体目标：(1)VZV能否通过感觉神经纤维从皮肤传播到ENS ？初步的研究已经确定了背路神经节中的神经元，它既投射到皮肤，也投射到肠道。我们将确定当VZV被引入皮肤时，是否在ENS中建立潜伏感染，以及VZV感染的神经末梢是否释放感染性无细胞VZV，通过突触间隙将潜伏感染转移到目标神经元。(2)病毒血症能否引起肠神经元潜伏性VZV感染？我们将确定感染VZV的T淋巴细胞是否释放无感染细胞的VZV，以及它们是否可以直接在肠神经元中或通过粘膜上皮或皮肤感染间接建立潜伏期。初步研究表明，静脉注射VZV感染的外周血单个核细胞后，豚鼠肠神经元中存在VZV DNA。(3) VZV ORF61蛋白的表达是否为肠神经元溶解性感染的必要条件？我们将研究缺乏ORF61的VZV突变体建立溶性感染肠神经元或从潜伏期重新激活的能力。肠道神经元中VZV的未预料到的再激活可能有助于肠易激综合征、炎症性肠病、特发性胃轻瘫和慢性肠假性梗阻等胃肠道疾病的发病机制，这一可能性增强了了解ENS VZV感染的意义。

DESCRIPTION (provided by applicant): The enteric nervous system (ENS) can control the behavior of the bowel without input from brain or spinal cord. A functioning ENS is essential for life and, when abnormal, causes discomfort and may contribute to the pathophysiology or severity of disorders of gastrointestinal motility, secretion, and inflammation. We have recently discovered that varicella zoster virus (VZV) establishes latency within human enteric neurons in most individuals who have experienced natural varicella or received varicella vaccine. VZV, moreover, has been linked to the occurrence of lethal pseudoobstruction in immunocompromised individuals. Neither the route by which VZV gains access to the ENS, nor the frequency or consequences of its reactivation in enteric neurons ("enteric zoster") has previously been explored. The current proposal is designed to test the hypotheses that transport in visceral afferent nerves conducts VZV to the ENS, that cell- free virions establish latency in enteric neurons, and that the non-structural VZV ORF61 protein must be expressed in neurons to enable VZV to manifest lytic infection or to reactivate from latency. Although VZV displays a marked preference for human cells, we have developed animal models that permit VZV infection of the ENS to be studied in vitro and in vivo. Depending on conditions, VZV recapitulates latent, lytic, and reactivating infection in enteric neurons isolated from guinea pigs or mice and, when introduced to the bowel, VZV establishes latency in the guinea pig ENS in situ. The proposal has 3 specific aims: (1) Can VZV travel from the skin to the ENS in sensory nerve fibers? Preliminary studies have identified neurons in dorsal route ganglia that project both to skin and gut. We will determine whether latent infection is established in the ENS when VZV is introduced to the skin and whether VZV-infected nerve terminals release infectious cell-free VZV that crosses synaptic gaps to transfer latent infection to target neurons. (2) Can a viremia establish latent VZV infection of enteric neurons? We will determine whether VZV-infected T lymphocytes release infectious cell-free VZV and whether they can establish latency directly in enteric neurons or indirectly via infections of the mucosal epithelium or skin. Preliminary studies have shown that VZV DNA is present in guinea pig enteric neurons following the iv injection of VZV-infected peripheral blood mononuclear cells. (3) Is VZV ORF61 protein expression necessary for the manifestation of lytic infection in enteric neurons? We will study the ability of a VZV mutant that lacks ORF61 to establish lytic infection of enteric neurons or reactivate from latency. The significance of understanding VZV infection of the ENS is enhanced by the possibility that unsuspected reactivation of VZV in enteric neurons might contribute to the pathogenesis of GI disorders such as irritable bowel syndrome, inflammatory bowel disease, idiopathic gastroparesis, and chronic intestinal pseudoobstruction.