Multiple amino acid variations in the nonstructural proteins of swine Japanese encephalitis virus alter its virulence in mice

Abstract

In a previous study, we performed serial brain-to-brain passages of swine Japanese encephalitis virus in mice and sequenced the complete genomes of the F5 and F20 passaged mouse-adapted variants. In the current study, we analyzed the differences between their genome sequences and found 12 amino acid substitutions in the nonstructural proteins. We also assessed the growth characteristics of these two variants in mammalian cells in vitro and in vivo. Our investigations revealed that the F20 variant had enhanced growth characteristics and modified virulence compared with the F5 variant. We therefore conclude that multiple amino acid substitutions in the nonstructural proteins of swine Japanese encephalitis virus alter its virulence in mice.

Fitness adaptations of Japanese encephalitis virus in pigs following vector-free serial passaging

“…Our data demonstrate that JEV passaging in pigs induced virus adaptations associated with enhanced viremia, nasal shedding, clinical scores and innate immune responses. This can be interpreted as an increase in viral fitness and relates to previous observations found with other Flaviviruses following passaging in vertebrates such as West Nile virus (WNV) in chicks [62], Zika virus (ZIKV) in mice [63][64][65] and also JEV in mice [66]. However, JEV passaging in suckling mice was also reported to result in attenuation [67].…”

North American Birds as Potential Amplifying Hosts of Japanese Encephalitis Virus

“…Recently, in vitro and in vivo experiments with a JEV swine isolate from China revealed that multiple amino acid substitutions in the nonstructural proteins altered viral virulence in mice. 33 Perhaps minor virus alterations in the JEV genome have led to past and possibly future changes in avian virulence, as has been demonstrated for WNV. 34 Historically, human JEV outbreaks have most often been associated with genotype III viruses; however, in the past two decades, substantially more human infections have been caused by genotype I viruses, and the distribution of these two epidemic genotypes overlaps.…”

An amino acid substitution (V3I) in the Japanese encephalitis virus NS4A protein increases its virulence in mice, but not its growth rate in vitro

“…Recently, we reported that amino acid position 123 of the E protein determined the growth properties and pathogenicity of JEV (Tajima et al, 2010). Several additional studies have shown that mutations in other coding and non-coding regions are also critical for virus replication and pathogenesis in the mouse model (Mori et al, 2005;Chambers et al, 2007;Kim et al, 2008;Wu et al, 2011).…”

“…The E protein is thought to play major roles in determining viral pathogenicity by defining cell tropism and mediating entry into susceptible cells (Lindenbach et al, 2007;Gubler et al, 2007). Since the early 1990s, various attempts have been made to clarify the molecular basis of JEV virulence by comparing the nucleotide sequences of virus strains with different degrees of virulence (Nitayaphan et al, 1990;Aihara et al, 1991;Cecilia & Gould, 1991;Hasegawa et al, 1992;Sumiyoshi et al, 1995;Chen et al, 1996;Ni & Barrett, 1996, 1998Arroyo et al, 2001;Wu et al, 2003;Lee et al, 2004;Chambers et al, 2007;Pujhari et al, 2011;Wu et al 2011). Some of these reports have suggested that nucleotide substitutions in the E protein may alter the virulence of JEV.…”