OBJECTIVETo investigate the change of viral titers under different conditions in cultured cells persistently-infected with different strains of Japanese encephalitis virus (JEV) and find out the factors that influence viral multiplication.

METHODSJEV JaGAr-01 and Nakayama wild strains were used to infect human hepatoma cell line KN73 respectively, and the persistent infection model was established. Viral titers were examined by plaque methods using BHK cells. Human nerve fibroblastoma cell line IMR-32 was infected with the strains of the virus that can cause persistent infection, and the thermal sensitivity of the viral strains was measured at 30 degrees C and 37 degrees C. KN73 cells persistently infected with JEV were infected with two JEV strains respectively, and viral superinfection was studied. To explore the replication of the persistently-infected viruses, KN73 and IMR-32 cells were infected with the viral strains.

RESULTSTwo persistently infected viral strains did not show any thermal difference. The results of superinfection were that the viral titers of JaGAr-01 strains were 1.3 and 8.8 percent of the control, respectively, and the viral titers of Nakayama strain were 80 and 1.7 percent of the control, respectively. JaGAr-01 wild strains, Nakayama wild strains and their persistently-infected strains infected KN73 and IMR-32 respectively. The replication of the persistently-infected strains was obviously lower than the wild strains in KN73 cells, however, in IMR-32 cells their replication was similar.

CONCLUSIONSThe two strains of JEV were not found to be temperature-mutant. It is possible that mutant viruses containing DI particles exist in JEV persistently-infected strains. In different cells there may be different host factors hindering the replication of the persistently-infected strains.

Animals ; Cell Line ; Encephalitis Virus, Japanese ; genetics ; physiology ; Encephalitis, Japanese ; virology ; Humans ; Virus Cultivation ; Virus Replication

Japanese encephalitis virus (JEV) is a pathogenic mosquito-borne flavivirus which is responsible for outbreaks of severe viral encephalitis. The cellular entry of JEV is a prerequisite for Japanese encephalitis, so the understanding of its underlying mechanisms will provide more approaches for treating such disease. In recent years, increasing research has been conducted to investigate the mechanisms of cellular entry of JEV, and the results of research on other flavivirus have expanded the research directions for JEV. More methods will be used to suppress JEV infection because of the development of E protein antibodies and the discovery of several inhibitors of the cellular entry process. This review will summarize the recent advances in the mechanisms of JEV cellular entry and membrane fusion.
Animals ; Biomedical Research ; trends ; Encephalitis Virus, Japanese ; genetics ; physiology ; Encephalitis, Japanese ; virology ; Humans ; Virus Internalization

China ; Encephalitis Virus, Japanese ; genetics ; immunology ; isolation & purification ; Encephalitis, Japanese ; virology ; Humans ; Research ; trends

To explore the spatial distribution mechanism of Japanese encephalitis virus (JEV), PhyML v3.0 was used to build phylogenetic tree using JEV sequences in the dataset. PAUP v4.0 and Migrapyhla softz ware were then used to analyze the migration events. The results showed that a total of 95 migration events were observed during the dispersal of JEV throughout Asia. Further analysis revealed that Thailand, and several Chinese provinces (including Shandong, Shanghai, Sichuan and Yunnan), were the main migration sources of JEV. JEV spread from these migration sources as follows: from Thailand to Australia, Cambodia, Tibet and India; from Shanghai to eastern coastal Asian regions and Yunnan; from Shandong to Korea, Zhejiang, Hubei, Shanxi and Liaoning; from Sichuan mainly to inland regions of China, as well as Vietnam and Japan; and from Yunnan to Zhejiang. This study indicated that frequent migration events occurred during the dispersal of JEV in the Asia and Pacific regions, and that Thailand, Shandong, Shanghai, Sichuan and Yunnan were the sources of JEV dispersal.
Asia ; epidemiology ; China ; epidemiology ; Encephalitis Virus, Japanese ; classification ; genetics ; isolation & purification ; physiology ; Encephalitis, Japanese ; epidemiology ; transmission ; virology ; Phylogeny

The biological and genetic characteristics of a highly neurovirulent JE virus strain SA4 were studied. Mice were inoculated intracerebrally with strain SA4 and SA14, and observed for 14 days, respectively. On different days, mice brains were harvested for titrations of the virus content in the brains. Full-length genome of SA4 was sequenced and compared with SA14 as well as other JE virus strains in the world. The results indicated that the mice inoculated by SA4 induced sickness and death more rapidly (24 hours faster) than those induced by the SA14. The virus titers in the brains of mice infected with SA4 were 0.5-1.0 lg PFU/mL higher than that infected with SA14. The sequence comparison indicated that the nucleotide and amino acid homology between SA4 and the other 21 JE strains were 84.6%-99.0% and 95.2%-99.7% respectively. Comparison with strain SA14 revealed that there were 17 amino acid differences between the two strains, of which 5 were in the E protein region. The results demonstrate that strain SA4 is a highly neurovirulent strain. The substitutions of the 17 amino acids in the SA4 strain can be the molecular basis for the biological characteristics of high neurovirulence.
Animals ; Brain ; virology ; Encephalitis Virus, Japanese ; classification ; genetics ; isolation & purification ; pathogenicity ; Encephalitis, Japanese ; mortality ; virology ; Genotype ; Humans ; Mice ; Sequence Analysis ; Viral Envelope Proteins ; genetics ; Virulence

PrME and NS1 gene were the two main immuneprotect proteins of Japanese encephalitis virus (JEV), and they were also N-linked glycosylation proteins. To clear the effect of N-glycosylation on JEV immunity, the N-glycosylation site of prME and NS1 gene were eliminated by site-directed mutant PCR, subtituting the N to Q. And the the mutant genes were subcloned into eukaryotic expression plasmid. Four-weeks female mice were immuned with the wildtype and mutant gene by twice. The antibodies against prME were detected by ELISA and the neutralization antibodies were tested by viral neutralizing assay. The immunoprotection were determined by attack with JEV virulent strain. Compare with the wild-type gene immuned-groups, one N-glycan eliminated prME gene could induce a little higher ELISA antibody, neutralization antibody and immunoprotection, but the immunity of gene with both N-glycan absence was decreased. The similar status were observed in the wildtype and mutant NS1 groups. Thus these results show that the N-linked glycosylation in the prME and NS1 gene were correlated with the immunity, one glycan absent would enhance the immunity but both two loss would impair it.
Animals ; Antibodies, Viral ; immunology ; Encephalitis Virus, Japanese ; genetics ; immunology ; metabolism ; Encephalitis, Japanese ; immunology ; virology ; Female ; Glycosylation ; Humans ; Mice ; Mice, Inbred BALB C ; Viral Nonstructural Proteins ; genetics ; immunology ; metabolism

To conduct sequencing of full-length genomes of two Japanese encephalitis virus strains (JEV) newly isolated in 2009 in China and analyze the characteristics of complete nucleotide sequences. The complete genomic sequences were obtained by RT-PCR and sequencing directly. Bioinformatics was used to analyze the nucleic acid data, deduced amino acid sequence and phylogenetic trees. The result of sequence analysis showed that the genomes of YN0911 and YN0967 strains were both 10965nt in length, which coded 3432 amino acid polyprotein. The homology of genome ranged from 83.3% to 98.9% in nt and from 94.8% to 99.7% in aa, respectively, when compared with selected JEV strains in GenBank. There were 13 amino acid divergences which were not the key virulence sites in E protein when compared with vaccine strain SA14-14-2. There were 11nt deletions in the 3' UTR region. Phylogenetic analyses based on C/ PrM, E gene and full-length genome all showed that YN0911 and YN0967 strains belonged to genotype I. The result also showed that two new JEVs had close phylogenetic relationship with the strains from Viet Nam, Sichuan Province, Guizhou Province, Guangxi Province, China. This study indicated that JEV strains newly isolated in 2009 in China were the members of JEV genotype I. The key virulence sites in E protein did not change.
Amino Acid Sequence ; Base Sequence ; China ; Encephalitis Virus, Japanese ; classification ; genetics ; isolation & purification ; Encephalitis, Japanese ; virology ; Genome, Viral ; genetics ; Humans ; Molecular Sequence Data ; Phylogeny ; Sequence Analysis, DNA

OBJECTIVETo construct infectious Japanese encephalitis virus (JEV) based on the in vitro-ligated cDNA template of the vaccine strain SA14-14-2, and identify the virus.

METHODSFull-length genomic cDNA of JEV SA14-14-2 strain was ligated and then RNA was transcribed in vitro, the infective virus was obtained by transfecting the RNA into Vero cells and identified.

RESULTSThe infective clone of JEV was constructed, the virulence was weaker than the wild virus.

CONCLUSIONIt was possible to construct infectious clone from the production strain of live attenuated Japanese B encephalitis vaccine.

Animals ; Animals, Newborn ; Base Sequence ; Cells, Cultured ; Cercopithecus aethiops ; Cloning, Molecular ; DNA, Complementary ; genetics ; Encephalitis Virus, Japanese ; genetics ; immunology ; pathogenicity ; Encephalitis, Japanese ; pathology ; virology ; Genome, Viral ; Japanese Encephalitis Vaccines ; immunology ; Mice ; RNA, Viral ; genetics ; Vaccines, Attenuated ; immunology ; Vero Cells ; Virulence

Japanese encephalitis virus(JEV)is one of the leading cause of viral encephalitis in Asia. The phenotypic and genotypic characteristics of isolated virus strains are reviewed in this paper. Studies on the biological characteristics of the isolates showed that different isolates existed apparent differences in virus plaque morphology, neuroinvasive pathogenicity in mice, protective antigenicity and hemagglutination property. In China, only genotype III JEV strains were isolated before 1977. But since 1977, both genotype I and I JEV strains were isolated and the genotype I virus, which was isolated from mosquitoes mostly, has become the dominant strain. Study on the genomic sequence indicated that there was only a few amino acid difference (< or = 43%) between the two genotype isolates. Comparison between both genotype isolates and widely used live vaccine strain SA14-14-2 revealed that there were only < or = 3% amino acid differences, most of which were the SA14-14-2 unique attenuating sites. These results indicate that the SA14-14-2 live vaccine is able to protect people against infection of the both genotype I and Ill JEV strains.
Animals ; China ; Culicidae ; virology ; Encephalitis Virus, Japanese ; classification ; genetics ; immunology ; isolation & purification ; Encephalitis, Japanese ; immunology ; prevention & control ; virology ; Genome, Viral ; genetics ; Genotype ; Humans ; Japanese Encephalitis Vaccines ; immunology ; Mice ; Phenotype ; Species Specificity ; Vaccines, Attenuated ; immunology

In order to reveal the phenotypic characteristics of 17 JE virus strains isolated from different years, plaque sizes, mice neurovirulence and mice neuroinvasiveness of the isolates were studied and compared. BHK21 cell monolayers were used for testing the plaque sizes. The virus neurovirulence was tested in 9-11g mice inoculated intracerebrally and the virus neuroinvasiveness was tested in 9-11g and 14-16g by subcutaneous inoculation. Results showed that all the viruses produced clear plaques on the BHK21 cell monolayers with different sizes and all the virus strains appeared high neurovirulence in the mice with higher than lg8. 0/0.03 mL virus titers, while no apparent difference among them. The neuroinvasiveness (subcutaneous virulence) tested in the 9-11g mice had shown a little difference, but when tested in the 12-14 g mice,the difference was apparent. The results demonstrated that JEV in nature were highly neurovirulent with no apparent difference. However the neuroinvasiveness of the JEV in nature was greatly different, which didn't relate to the years of isolation and genotypes, but most of the viruses isolated from patients showed higher neuroinvasiveness.
Animals ; Cell Line ; China ; Culicidae ; virology ; Encephalitis Virus, Japanese ; genetics ; isolation & purification ; pathogenicity ; Encephalitis, Japanese ; virology ; Genotype ; Humans ; Mice ; Phenotype ; Viral Plaque Assay ; Virulence