Equine herpesvirus-1 (EHV-1), which causes encephalomyelitis in horses, shows endotheliotropism in the central nervous system of horses, and generally does not infect neurons. However, little is known about the mechanism underlying the resistance of neuron to EHV-1, due to the lack of convenient cell culture systems. In this study, we examined EHV-1 infection in immortalized Rn33B rat neuronal cells, which differentiate into neurons when cultured under nonpermissive conditions. Because murine cell lines are resistant to EHV-1 infections due to the lack of functional entry receptors for EHV-1, we used an Rn33B-derived cell line that stably expresses the equine MHC class 1 molecule, which acts as EHV-1 entry receptor (Rn33B-A68B2M cells). EHV-1 infected undifferentiated Rn33B-A68B2M cells more efficiently than differentiated cells, resulting in the production of progeny virus in the former but not in the latter. By contrast, both differentiated and undifferentiated cells infected with herpes simplex virus-1 produced infectious viral progeny. While EHV-1 infection induced stronger expression of IFN alpha gene in differentiated cells than in undifferentiated cells, downstream IFN responses, including phosphorylation of STAT1 (signal transducer and activator of transcription 1) and expression of IFN-stimulated genes, were not activated regardless of whether cells were differentiated or not. These results suggest that neuronal differentiation of RN33B-A68B2M cells reduced their susceptibility to EHV-1, which is not due to different IFN responses. This culture system may be useful as an in vitro model for studying neuron-specific resistance to EHV-1, by investigating viral and host factors responsible for the difference in susceptibility between differentiated and undifferentiated cells.

中文翻译：

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表达马主要组织相容性类别1的大鼠永生神经元细胞系Rn33B对马疱疹病毒1感染的敏感性取决于分化。

马疱疹病毒1（EHV-1）引起马脑脊髓炎，在马的中枢神经系统中表现出内吞性，通常不感染神经元。然而，由于缺乏方便的细胞培养系统，关于神经元对EHV-1的抗性的机制了解甚少。在这项研究中，我们研究了永生化的Rn33B大鼠神经元细胞中的EHV-1感染，该细胞在非允许条件下培养时会分化为神经元。由于鼠细胞系由于缺乏EHV-1的功能性进入受体而对EHV-1感染具有抗性，因此我们使用了Rn33B衍生的细胞系，该细胞系稳定表达马MHC 1类分子，该分子充当EHV-1进入受体（Rn33B-A68B2M细胞）。EHV-1感染的未分化Rn33B-A68B2M细胞比分化细胞更有效，导致前者产生子代病毒，而后者则不。相比之下，单纯疱疹病毒1感染的分化和未分化细胞均产生感染性病毒后代。尽管EHV-1感染在分化细胞中诱导的IFNα基因表达比未分化细胞强，但下游IFN反应（包括STAT1的磷酸化（信号转导和转录激活因子1）和IFN刺激基因的表达）均未激活细胞是否分化。这些结果表明，RN33B-A68B2M细胞的神经元分化降低了其对EHV-1的敏感性，这不是由于不同的IFN反应。该培养系统可用作研究神经元对EHV-1的特异性抗药性的体外模型，