Genomic changes in an attenuated genotype I Japanese encephalitis virus and comparison with virulent parental strain
Genotype I Japanese encephalitis virus (JEV) strain SCYA201201 was previously isolated from brain tissues of aborted piglets. In this study, we obtained an attenuated SCYA201201-0901 strain by serial passage of strain SCYA201201-1 in Syrian baby hamster kidney cells, combined with multiple plaque purifications and selection for virulence in mice. We investigated the genetic changes associated with attenuation by comparing the entire genomes of SCYA201201-0901 and SCYA201201-1. Sequence comparisons identified 14 common amino acid substitutions in the coding region, with two nucleotide point mutations in the 5′-untranslated region (UTR) and another three in the 3′-UTR, which differed between the attenuated and virulent strains. In addition, a total of 13 silent nucleotide mutations were found after attenuation. These substitutions, alone or in combination, may be responsible for the attenuated phenotype of the SCYA201201-0901 strain in mice. This information will contribute to our understanding of attenuation and of the molecular basis of virulence in genotype I strains such as SCYA201201-0901, as well as aiding the development of safer JEV vaccines.
KeywordsJapanese encephalitis virus Virulence attenuation Genetic analysis Mutation site Adaptation
This work was supported by the National Program on Key Research Project of China (2016YFD0500403). We thank lady Qingjun Li for helpful advice.
RW and SJC conceived and designed the study. QZ, XTW, and YPW collected the samples. YF, QGY, YH, XPM, and YYZ carried out the experiments. XFH and YYZ drafted the manuscript.
Compliance with ethical standards
Conflicts of interest
Authors declare that there were no conflict of interests.
Research involving human participants and/or animals
All procedures performed in the present study involving animals were approved by the Institutional Animal Care and Use Committee of Sichuan Agriculture University (Approval Number BK2014-047), Sichuan, China and followed the guidelines of the National Institutes of Health.
All authors read and approved the final manuscript.