NS2B/NS3 mutations enhance the infectivity of genotype I Japanese encephalitis virus in amplifying hosts

• Published in: PLoS pathogens Vol. 15; no. 8; p. e1007992
• Main Authors: Fan, Yi-Chin, Liang, Jian-Jong, Chen, Jo-Mei, Lin, Jen-Wei, Chen, Yi-Ying, Su, Kuan-Hsuan, Lin, Chang-Chi, Tu, Wu-Chun, Chiou, Ming-Tang, Ou, Shan-Chia, Chang, Gwong-Jen J., Lin, Yi-Ling, Chiou, Shyan-Song
• Format: Journal Article
• Language: English
• Published: United States Public Library of Science 05.08.2019; Public Library of Science (PLoS)
• Subjects: Amplification; Animals; Aquatic insects; Biology and Life Sciences; Chickens; Culex; Development and progression; Encephalitis; Encephalitis Virus, Japanese - genetics; Encephalitis Virus, Japanese - pathogenicity; Encephalitis, Japanese - epidemiology; Encephalitis, Japanese - genetics; Encephalitis, Japanese - virology; Epidemics; Female; Gene mutation; Genes; Genetic aspects; Genotype; Genotypes; Health aspects; High temperature; Hogs; Host-virus relationships; Infection; Infectivity; Japanese encephalitis; Juveniles; Medicine and Health Sciences; Mosquito Vectors; Mosquitoes; Mutation; Poultry; Preventive medicine; Replication; RNA Helicases - genetics; Serine Endopeptidases - genetics; Swine; Vaccines; Vector-borne diseases; Viral genetics; Viral Nonstructural Proteins - genetics; Viremia; Viremia - transmission; Virus diseases; Virus Replication; Viruses; Zika virus; Taiwan; United States > US
• ISSN: 1553-7374; 1553-7366; 1553-7374
• DOI: 10.1371/journal.ppat.1007992

Genotype I (GI) virus has replaced genotype III (GIII) virus as the dominant Japanese encephalitis virus (JEV) in the epidemic area of Asia. The mechanism underlying the genotype replacement remains unclear. Therefore, we focused our current study on investigating the roles of mosquito vector and amplifying host(s) in JEV genotype replacement by comparing the replication ability of GI and GIII viruses. GI and GIII viruses had similar infection rates and replicated to similar viral titers after blood meal feedings in Culex tritaeniorhynchus. However, GI virus yielded a higher viral titer in amplifying host-derived cells, especially at an elevated temperature, and produced an earlier and higher viremia in experimentally inoculated pigs, ducklings, and young chickens. Subsequently we identified the amplification advantage of viral genetic determinants from GI viruses by utilizing chimeric and recombinant JEVs (rJEVs). Compared to the recombinant GIII virus (rGIII virus), we observed that both the recombinant GI virus and the chimeric rJEVs encoding GI virus-derived NS1-3 genes supported higher replication ability in amplifying hosts. The replication advantage of the chimeric rJEVs was lost after introduction of a single substitution from a GIII viral mutation (NS2B-L99V, NS3-S78A, or NS3-D177E). In addition, the gain-of-function assay further elucidated that rGIII virus encoding GI virus NS2B-V99L/NS3-A78S/E177E substitutions re-gained the enhanced replication ability. Thus, we conclude that the replication advantage of GI virus in pigs and poultry is the result of three critical NS2B/NS3 substitutions. This may lead to more efficient transmission of GI virus than GIII virus in the amplifying host-mosquito cycle.