The highly neurotropic rabies virus (RABV) enters peripheral neurons at axon termini and requires long distance axonal transport and trans-synaptic spread between neurons for the infection of the central nervous system (CNS). Recent 3D imaging of field RABV-infected brains revealed a remarkably high proportion of infected astroglia, indicating that highly virulent field viruses are able to suppress astrocyte-mediated innate immune responses and virus elimination pathways. While fundamental for CNS invasion, in vivo field RABV spread and tropism in peripheral tissues is understudied. Here, we used three-dimensional light sheet and confocal laser scanning microscopy to investigate the in vivo distribution patterns of a field RABV clone in cleared high-volume tissue samples after infection via a natural (intramuscular; hind leg) and an artificial (intracranial) inoculation route. Immunostaining of virus and host markers provided a comprehensive overview of RABV infection in the CNS and peripheral nerves after centripetal and centrifugal virus spread. Importantly, we identified non-neuronal, axon-ensheathing neuroglia (Schwann cells, SCs) in peripheral nerves of the hind leg and facial regions as a target cell population of field RABV. This suggests that virus release from axons and infected SCs is part of the RABV in vivo cycle and may affect RABV-related demyelination of peripheral neurons and local innate immune responses. Detection of RABV in axon-surrounding myelinating SCs after i.c. infection further provided evidence for anterograde spread of RABV, highlighting that RABV axonal transport and spread of infectious virus in peripheral nerves is not exclusively retrograde. Our data support a new model in which, comparable to CNS neuroglia, SC infection in peripheral nerves suppresses glia-mediated innate immunity and delays antiviral host responses required for successful transport from the peripheral infection sites to the brain.

中文翻译：

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顺行病毒在外周神经元中传播后狂犬病病毒对神经胶质细胞的感染

高度嗜神经狂犬病病毒 (RABV) 在轴突末端进入外周神经元，需要长距离轴突运输和神经元之间的跨突触传播才能感染中枢神经系统 (CNS)。最近对野 RABV 感染大脑的 3D 成像显示感染星形胶质细胞的比例非常高，这表明高毒力野病毒能够抑制星形胶质细胞介导的先天免疫反应和病毒消除途径。虽然是 CNS 侵袭的基础，但体内野 RABV 在外周组织中的传播和趋向性尚未得到充分研究。在这里，我们使用三维光片和共聚焦激光扫描显微镜来研究野外 RABV 克隆在通过自然（肌内；后腿）和人工（颅内）接种途径。病毒和宿主标记的免疫染色提供了向心和离心病毒传播后中枢神经系统和外周神经中 RABV 感染的全面概述。重要的是，我们将后腿和面部区域的外周神经中的非神经元、轴突鞘神经胶质细胞（雪旺细胞，SCs）鉴定为野兔病毒的靶细胞群。这表明从轴突和受感染的 SCs 释放的病毒是 RABV 体内循环的一部分，可能会影响 RABV 相关的外周神经元脱髓鞘和局部先天免疫反应。ic 感染后在轴突周围有髓鞘的 SCs 中检测到 RABV 进一步提供了 RABV 顺行传播的证据，强调 RABV 轴突运输和传染性病毒在周围神经中的传播并不完全是逆行。我们的数据支持一种新模型，在该模型中，与 CNS 神经胶质细胞相比，外周神经中的 SC 感染抑制了胶质细胞介导的先天免疫，并延迟了从外周感染部位成功转移到大脑所需的抗病毒宿主反应。