Programmed cell death induced by Japanese encephalitis virus YL vaccine strain or its recombinant envelope protein in varied cultured cells.

OBJECTIVE: The Japanese encephalitis virus YL vaccine strain (JEV-YL) was investigated as regards its organ tropism and the role of recombinant envelope glycoprotein in the induction of apoptosis was explored. METHODS: Threevaried cell lines (HepG2, Vero and C6) were infected with JEV-YL or transfected with eukaryotic expression plasmids (pcE, pcF1R2, pcF1R1 and pcF2R2) which contain different parts of the envelope gene and phenotypic properties were examined by flow cytometry and DNA fragmentation analysis. RESULTS: After JEV-YL infection, smaller plaque was produced on HepG2 cells than on Vero cells, whereas no cytopathic effect was observed on C6 cells; moreover, by apoptosis and DNA fragmentation assays, the hallmark cytopathic effects were detected in HepG2 and Vero cells but not in C6 cells. Furthermore, cells used in our study transfected with recombinant core plasmid, pcE, which include full-length E gene but the deleted forms (pcF1R2, pcF1R1 and pcF2R2) did not have similar results as JEV-YLs. CONCLUSIONS: The JEV-YL vaccine strain had changed cell tropism to liver cells different from other virulent strains which have neural tropism, and in this study we proved that the transient-expressed entire E protein of JEV-YL could induce apoptosis and the mutations of E protein may change the organ tropism of JEV-YL.

Expression of recombinant envelope protein of Japanese encephalitis virus YL strain in Escherichia coli possesses hemagglutination activity.

The nucleotide sequence of glycoprotein E of YL vaccine strain was cloned, sequenced and expressed in E. coli. Phylogenetic analysis of envelope (E) amino acid sequences of 18 JEVs in GenBank showed that the vaccine strain YL closer to the virulent strain HVI which is a Taiwanese isolate. We found only two amino acid mutations (K-138 and G-389) of E protein might lead viral attenuation in YL. In this study, we used pRSET vector system to construct three recombinant plasmids (pRSET/F1R1, pRSET/F2R2 and pRSET/F1R2), which encoded and expressed different or overlapping amino acid region of E protein. The antigenicity and hemagglutination activity of these recombinant proteins were examined by western blotting and hemagglutination test, respectively. Our results demonstrated that the recombinant protein of pRSET/F1R2 possesses predominant antigenicity and hemagglutination activity.