Herpesvirus-encoded microRNAs (miRNAs) have been discovered in infected cells; however, lack of a suitable animal model has hampered functional analyses of viral miRNAs in vivo. Marek’s disease virus (MDV) (Gallid alphaherpesvirus 2, GaHV-2) genome contains 14 miRNA precursors, which encode 26 mature miRNAs, grouped into three clusters. In this study, the role of MDV-encoded cluster 3 miRNAs, also known as mdv1-miR-M8-M10, in pathogenesis was evaluated in chickens, the natural host of MDV. Our results show that deletion of cluster 3 miRNAs did not affect virus replication and plaque size in cell culture, but increased early cytolytic replication of MDV in chickens. We also observed that deletion of cluster 3 miRNAs resulted in significantly higher virus reactivation from peripheral blood lymphocytes. In addition, pathogenesis studies showed that deletion of cluster 3 miRNAs resulted in more severe atrophy of lymphoid organs and reduced mean death time, but did not affect the incidence of MDV-associated visceral tumors. We confirmed these results by generating a cluster 3 miRNA revertant virus in which the parental MDV phenotype was restored. To the best of our knowledge, our study provides the first evidence that MDV cluster 3 miRNAs play an important role in modulating MDV pathogenesis.

中文翻译：

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马立克氏病病毒簇3 miRNA限制病毒的早期细胞溶解复制和发病机理

在感染的细胞中发现了疱疹病毒编码的microRNA（miRNA）。但是，缺乏合适的动物模型阻碍了体内病毒miRNA的功能分析。马立克氏病病毒（MDV）（Gallid alpha疱疹病毒在图2中，GaHV-2基因组包含14个miRNA前体，它们编码26个成熟的miRNA，分为三个簇。在这项研究中，评估了MDV天然宿主鸡中MDV编码的簇3 miRNA（也称为mdv1-miR-M8-M10）在发病中的作用。我们的结果表明，删除簇3 miRNA不会影响病毒在细胞培养中的复制和噬菌斑大小，但会增加鸡MDV的早期细胞溶解复制。我们还观察到，删除簇3 miRNA会导致外周血淋巴细胞的病毒重新激活明显更高。此外，发病机制研究表明，删除簇3 miRNA导致淋巴器官更为严重的萎缩并缩短了平均死亡时间，但并未影响与MDV相关的内脏肿瘤的发生率。我们通过产生簇3 miRNA回复病毒证实了这些结果，其中父母MDV表型已恢复。据我们所知，我们的研究提供了第一个证据，证明MDV簇3 miRNA在调节MDV发病机理中起重要作用。