Characterization And Analysis Of The Passaged Virus Of The Field Japanese Encephalitis Virus Strain CSF.XZ-2D Isolated From Swine

Japanese encephalitis (JE) is a viral zoonosis caused by Japanese encephalitis virus(JEV).JEV infection causes serious nervous system disorders in both human and domesticanimals.JEV is transmitted by mosquitoes and the epidemic disease occurs mainly insummer and autumn seasons.Porcine is regarded as the most important reservoir forJEV.Regardless of age and variety,pigs are susceptible to JEV but, the mortality rate is nothigh..JEV infection also causes porcine reproductive failure, such as abortion, stillbirth andorchitis, resulting in huge economic losses in pig farming.To investigate the features of JEV currently prevalent in Henan province, thecerebrospinal fluid (CSF) samples collected from aborted fetuses were blind passaged onBHK-21cells. A field isolate, namely as CSF.XZ-2D, was finally isolated andcharacterized by RT-PCR, gene cloning, DNA sequencing, immunofluorescence assay(IFA), and animal experiments. The phylogenetic analysis based on JEV genes of both Eand M showed that the isolate CSF.XZ-2D belongs to genotype III. Subsequently, thegenetic stability of E gene of JEV isolate CSF.XZ-2D passaged in BHK-21cells (babyhamster kidney cell line) was studied. The results showed that the E gene is becomingstable after25passages in BHK-21cells. After serial subcultivation, two stable amino acid(aa) mutations happened at the sites E271(Eâ†'V) and E278(Vâ†'L). No mutations wereobserved at part of the virulence correlated aa sites, such as E107, E138, E176, E177andE315, same to those of vaccine strain SA14-14-2. However, mutations at the other twovirulence correlated aa sites of E279(Kâ†'Mâ†'K) and E312(Kâ†'Râ†'Kâ†'R) happenedrepeatedly. Whether these mutations are correlated to the virulence variation andadaptability of JEV to host cells needs to be further studied.In this work, the viral features and genetic stability of the JEV isolate CSF.XZ-2Dpassaged on BHK-21cell line were primarily studied and this study will provide animportant basis for further understanding of the prevalence of JEV in pig populations inHenan province.