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.