Characterization of live-attenuated Japanese encephalitis vaccine virus SA14-14-2

Author:

Dong Yang  Xiao-Feng Li  Qing Ye  Hong-Jiang Wang  Yong-Qiang Deng  Shun-Ya Zhu  Yu Zhang  Shi-Hua Li  Cheng-Feng Qin  

Journal:

Vaccine

Issue Date:

2014

Abstract(summary):

Highlights • The in vitro and in vivo stability of live JE vaccine SA14-14-2 was investigated. • SA14-14-2 is phenotypic and genetic stable after serial passaging in Vero cells. • Passaging of SA14-14-2 in mouse brain results in adaptive mutations and virulence reversion. • Four adaptive mutations in E protein, F107L, K138E, T226R and I270T, are associated with virulence. Abstract The live attenuated Japanese encephalitis (JE) vaccine SA14-14-2 was licensed decades ago and now approved for clinical use in most JE endemic countries. Large-scale clinical trials demonstrate ideal safety and efficacy profile of this Chinese vaccine. The SA14-14-2 vaccine was derived from a virulent strain SA14 after hundreds of serial passaging in cells and animals, concern about virulence reversion remains exist. In the present study, to study the in vitro and in vivo genetic and attenuation stability of the vaccine virus, SA14-14-2 was serially passaged in Vero cells and mouse brain followed by sequence comparison and attenuation phenotype analysis. The results showed that no significant mutation was acquired after serial passaging in Vero cells except a single Ser66Leu mutation within capsid protein, which had no effect on viral virulence in mice. Importantly, serial passaging of SA14-14-2 in suckling mouse brain resulted in emergence of adaptive mutations and increased virulence in mice. Population and plaque-purified clone consensus sequence analysis showed four adaptive mutations in envelope (E) protein, F107L, K138E, T226R and I270T, sequentially occurred and become predominant during serial passaging in suckling mouse brain. Especially, these adaptive mutations were close related with the enhanced neurovirulence and neuroinvasiveness in mice. Our results provide experimental evidence of highly genetic and attenuation stability of SA14-14-2 following passaging in Vero cells, and reveal the potential virulence reversion during passaging in mouse brain in association with critical adaptive mutations in E protein. These findings are important for quality control and evaluation of live JE vaccines and will help understand the attenuation mechanism of flavivirus vaccine.

Page:

2675-2675