A Single Nucleotide in Stem Loop II of 5′-Untranslated Region Contributes to Virulence of Enterovirus 71 in Mice

Abstract

BackgroundEnterovirus 71 (EV71) has emerged as a neuroinvasive virus responsible for several large outbreaks in the Asia-Pacific region while virulence determinant remains unexplored.Principal FindingsIn 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.ConclusionsThese results presented the first reported virulence determinant in EV71 5′-UTR and first position discovered from unadapted isolates.

Enterovirus 71 infection of motor neuron-like NSC-34 cells undergoes a non-lytic exit pathway

“…Previous studies have identified a number of mutations in the viral genome that were shown to be involved in increased virulence in animal models, to confer a replicative advantage in vitro , or to correlate with CNS involvement in patients22464748495051525354555657. However, upon analysis of the viral genome of S41, C2 and MS, none of these mutations could explain the increased neurovirulence of S41 compared to C2 and MS in the AG129 mouse model.…”

Identification of molecular determinants of cell culture growth characteristics of Enterovirus 71

“…Yeh et al [19] constructed a series of infectious clones containing chimeric 5′-NTR regions and mapped a genetic determinant of EV-A71 virulence to nt. 158 within a fragment comprising 12 nucleotides in the stem loop (SL) II structure of EV-A71 clinical isolate 237.…”

“…A single nucleotide change from cytosine to uridine at position 158 (USLIIM-C158U) caused an alteration in the RNA secondary structure of SL II which led to reduced viral translation and virulence in mice. Mice infected with the USLIIM-C158U mutant was observed to have prolonged average survival time and survival rate as compared with infection with the wild-type USLIIM (40% vs. 0%, P  < 0.005) [19]. In this study, we are investigating if the EV-A71 sub-genotype B4, strain 41 (5865/Sin/000009) has the same or a different virulence determinant from sub-genotype B1 (clinical isolate 237) and the BrCr prototype strain [17].…”

Genome Sequence of Enterovirus D68 from St. Louis, Missouri, USA

“…To our knowledge, no amino acids have been associated with virulence or increased infectivity of EV-D68; therefore, we cannot associate the changes we observed in these genomes to phenotypic traits. Because changes in the 5′ untranslated region have the potential to affect the rate of replication ( 8 – 10 ), it is possible that minor genome changes are responsible for the rapid spread and high severity of disease in 2014. Correlation between clinical features of patients in conjunction with additional genomic analysis might provide further insight into the pathogenetic determinants of this strain.…”