Sun Chao, Yang Decheng, Gao Rongyuan, Liang Te, Wang Haiwei, Zhou Guohui, Yu Li
Division of Livestock Infectious Diseases, State Key Laboratory of Veterinary Biotechnology, Harbin Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Harbin, PRChina.
J Gen Virol. 2016 Apr;97(4):901-911. doi: 10.1099/jgv.0.000406. Epub 2016 Jan 20.
The 5' untranslated region (5'UTR) of foot-and-mouth disease virus (FMDV) contains an internal ribosome entry site (IRES) that facilitates translation initiation of the viral ORF in a 5' (m7GpppN) cap-independent manner. IRES elements are responsible for the virulence phenotypes of several enteroviruses. Here, we constructed a chimeric virus in which the IRES of FMDV was completely replaced with that of bovine rhinitis B virus (BRBV) in an infectious clone of serotype O FMDV. The resulting IRES-replaced virus, FMDV(BRBV), replicated as efficiently as WT FMDV in hamster-derived BHK-21 cells, but was restricted for growth in porcine-derived IBRS-2, PK-15 and SK-6 cells, which are susceptible to WT FMDV. To identify the genetic determinants of FMDV underlying this altered cell tropism, a series of IRES-chimeric viruses were constructed in which each domain of the FMDV IRES was replaced with its counterpart from the BRBV IRES. The replication kinetics of these chimeric viruses in different cell lines revealed that the growth restriction phenotype in porcine-derived cells was produced after the replacement of domain 3 or 4 in the FMDV IRES. Furthermore, the change in FMDV cell tropism due to IRES replacement in porcine-derived cells was mainly attributed to a decline in cell-specific IRES translation initiation efficiency. These findings demonstrate that IRES domains 3 and 4 of FMDV are novel cell-specific cis-elements for viral replication in vitro and suggest that IRES-mediated translation determines the species specificity of FMDV infection in vivo.
口蹄疫病毒（FMDV）的5'非翻译区（5'UTR）包含一个内部核糖体进入位点（IRES），该位点以不依赖于5'（m7GpppN）帽的方式促进病毒开放阅读框的翻译起始。IRES元件负责几种肠道病毒的毒力表型。在此，我们构建了一种嵌合病毒，其中在O型FMDV的感染性克隆中，FMDV的IRES被牛鼻炎B病毒（BRBV）的IRES完全取代。产生的IRES取代病毒FMDV(BRBV)在仓鼠来源的BHK-21细胞中复制效率与野生型FMDV相同，但在对野生型FMDV敏感的猪来源的IBRS-2、PK-15和SK-6细胞中生长受到限制。为了确定FMDV这种细胞嗜性改变背后的遗传决定因素，构建了一系列IRES嵌合病毒，其中FMDV IRES的每个结构域都被BRBV IRES的对应结构域取代。这些嵌合病毒在不同细胞系中的复制动力学表明，在FMDV IRES的结构域3或4被取代后，猪来源细胞中出现了生长限制表型。此外，猪来源细胞中由于IRES取代导致的FMDV细胞嗜性变化主要归因于细胞特异性IRES翻译起始效率的下降。这些发现表明，FMDV的IRES结构域3和4是体外病毒复制的新型细胞特异性顺式元件，并表明IRES介导的翻译决定了FMDV在体内感染的物种特异性。
