The Institute of Basic Medical Sciences, National Cheng Kung University, Tainan, Taiwan.
PLoS One. 2011;6(11):e27082. doi: 10.1371/journal.pone.0027082. Epub 2011 Nov 1.
Enterovirus 71 (EV71) has emerged as a neuroinvasive virus responsible for several large outbreaks in the Asia-Pacific region while virulence determinant remains unexplored.
In this report, we investigated increased virulence of unadapted EV71 clinical isolate 237 as compared with isolate 4643 in mice. A fragment 12 nucleotides in length in stem loop (SL) II of 237 5'-untranslated region (UTR) visibly reduced survival time and rate in mice was identified by constructing a series of infectious clones harboring chimeric 5'-UTR. In cells transfected with bicistronic plasmids, and replicon RNAs, the 12-nt fragment of isolate 237 enhanced translational activities and accelerated replication of subgenomic EV71. Finally, single nucleotide change from cytosine to uridine at base 158 in this short fragment of 5'-UTR was proven to reduce viral translation and EV71 virulence in mice. Results collectively indicated a pivotal role of novel virulence determinant C158 on virus translation in vitro and EV71 virulence in vivo.
These results presented the first reported virulence determinant in EV71 5'-UTR and first position discovered from unadapted isolates.
肠道病毒 71 型（EV71）已成为一种神经侵袭性病毒，在亚太地区引发了几次大规模疫情，但其毒力决定因素仍未得到探索。
本报告研究了未经适应的 EV71 临床分离株 237 与分离株 4643 相比在小鼠中的毒力增强。通过构建一系列携带嵌合 5'-UTR 的感染性克隆，鉴定出 237 5'-UTR 茎环（SL）II 中长 12 个核苷酸的片段明显缩短了小鼠的存活时间和存活率。在转染双顺反子质粒和复制子 RNA 的细胞中，分离株 237 的 12-nt 片段增强了亚基因组 EV71 的翻译活性并加速了其复制。最后，证明 5'-UTR 这个短片段中第 158 位碱基由胞嘧啶变为尿嘧啶的单核苷酸变化降低了病毒在小鼠中的翻译和 EV71 的毒力。结果表明，新型毒力决定因素 C158 在病毒体外翻译和 EV71 体内毒力中起着关键作用。
这些结果首次报道了 EV71 5'-UTR 中的毒力决定因素，也是首次从未经适应的分离株中发现的位置。
