The effects of autophagy on the replication of Nelson Bay orthoreovirus
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RESEARCH
Open Access
The effects of autophagy on the replication of Nelson Bay orthoreovirus Xiao-Li Tao1,2, Wei Zhao2, Wei Tong2, Xiao-Fang Wang2, Li-Li Dou2, Jiang-Man Chen2, Nian Liu2, Ying Lu2, Yi-Bo Zhang2, Xu-Peng Jin2, Yan-Fei Shen2, Hong-Yan Zhao2, Hong Jin1* and Yong-Gang Li2*
Abstract Background: Nelson Bay orthoreovirus (NBV) was first isolated over 40 years ago from a fruit bat in Australia. Normally, NBV does not cause human diseases, but recently several NBV strains have been associated with human respiratory tract infections, thus attracting clinical attention. Autophagy, an evolutionarily conserved process in eukaryotic cells, degrades intracellular substrates, participates in multiple physiological processes, and maintains cellular homeostasis. In addition, autophagy is intimately involved in viral infection. Methods: A new strain of NBV, isolated from a patient with a respiratory tract infection who returned to Japan from Bali, Indonesia, in 2007, was used in this study. NBV was rescued using a reverse genetics system involving cotransfection of BHK cells with 11 plasmids (pT7-L1 MB, pT7-L2 MB, pT7-L3 MB, pT7-M1 MB, pT7-M2 MB, pT7-M3 MB, pT7-S1 MB, pT7-S2 MB, pT7S3 MB, pT7-S4 MB, and pcDNA3.1-T7), yielding NBV-MB. Recovered viruses were confirmed by immunofluorescence. The effect of NBV-MB on autophagy was evaluated by measuring the LC3-I/II proteins by immunoblot analysis after infection of BHK cells. Furthermore, after treatment with rapamycin (RAPA), 3-methyladenine (3-MA), chloroquine (CQ), or plasmid (GFPLC3) transfection, the changes in expression of the LC3 gene and the amount of LC3-I/II protein were examined. In addition, variations in viral titer were assayed after treatment of BHK cells with drugs or after transfection with plasmids pCAGM3 and pCAGS3, which encode virus nonstructural proteins μNS and σNS, respectively. Results: NBV-MB infection induced autophagy in host cells; however, the level of induction was dependent on viral replication. Induction of autophagy increased viral replication. By contrast, inhibiting autophagy suppressed NBV replication, albeit not significantly. The NBV-MB nonstructural protein μNS was involved in the induction of autophagy with viral infection. Conclusions: NBV-MB infection triggered autophagy. Also, the NBV nonstructural protein μNS may contribute to augmentation of autophagy upon viral infection. Keywords: Autophagy, Nelson Bay, Orthoreovirus replication, μNS
Background Orthoreoviruses are double-stranded nonenveloped RNA viruses belonging to family Reoviridae. Their genomes consist of ten dsRNA segments, which are classified on the basis of size as large (L1–L3), medium (M1–M3), and small (S1–S4). Based on the ability to induce cell-to-cell fusion in infected cells, orthoreoviruses are divided into * Correspondence: [email protected]; [email protected] 1 Department of Pathogenic Microbiology, College of Basic Medical Sciences, China Medical University, No. 77, Puhe Road, Shenyang North New Area, Shenyang City 110013, Liaoning Province, People’
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