Classical swine fever virus (CSFV), a positive-sense RNA virus, hijacks cell host proteins for its own replication. Rab18, a small Rab GTPase, regulates intracellular membrane-trafficking events between various compartments in cells and is involved in the life cycle of multiple viruses. However, the effect of Rab18 on the production of CSFV remains uncertain. In this study, we showed that knockdown of Rab18 by lentiviruses inhibited CSFV production, while overexpression of Rab18 by lentiviruses enhanced CSFV production. Subsequent experiments revealed that the negative-mutant Rab18-S22 N inhibited CSFV infection, while the positive-mutant Rab18-Q67 L enhanced CSFV infection. Furthermore, we showed that CSFV RNA replication and virion assembly, measured by real-time fluorescence quantitative PCR (RT-qPCR), indirect immunofluorescence assay (IFA), and confocal microscopy, were reduced in cells lacking Rab18 expression. In addition, co-immunoprecipitation, GST-pulldown, and confocal microscopy assays revealed that Rab18 bound to the viral protein NS5A. Further, NS5A was shown to be redistributed in Rab18 knockdown cells. Taken together, these findings demonstrate Rab18 as a novel host factor required for CSFV RNA replication and particle assembly by interaction with the viral protein NS5A.

中文翻译：

---

Rab18与经典猪瘟病毒NS5A结合，并介导猪脐静脉内皮细胞中病毒的复制和组装。

古典猪瘟病毒（CSFV）是一种正向RNA病毒，劫持了细胞宿主蛋白以进行自身复制。Rab18是一种小的Rab GTP酶，调节细胞内各个区室之间的细胞内膜运输事件，并参与多种病毒的生命周期。但是，Rab18对CSFV产生的影响仍不确定。在这项研究中，我们表明慢病毒敲除Rab18抑制了CSFV的产生，而慢病毒Rab18的过表达增强了CSFV的产生。随后的实验表明，负突变Rab18-S22 N抑制了CSFV感染，而正突变Rab18-Q67 L增强了CSFV感染。此外，我们还显示，通过实时荧光定量PCR（RT-qPCR），间接免疫荧光测定（IFA）对CSFV RNA复制和病毒体装配进行了测定，和共聚焦显微镜，减少了缺乏Rab18表达的细胞。此外，共免疫沉淀，GST下拉和共聚焦显微镜分析显示，Rab18与病毒蛋白NS5A结合。此外，显示NS​​5A在Rab18敲低细胞中重新分布。综上所述，这些发现证明Rab18是通过与病毒蛋白NS5A相互作用而成为CSFV RNA复制和颗粒组装所需的新型宿主因子。