Programmed Cell Death Induced by Japanese Encephalitis Virus YL Vaccine Strain or Its Recombinant Envelope Protein in Varied Cultured Cells

Abstract

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.

Tumor necrosis factor receptor‐1‐induced neuronal death by TRADD contributes to the pathogenesis of Japanese encephalitis

“…Caspase 3 is an effector caspase that function as a central regulator of apoptosis (Slee et al 2001). JEV infection triggers apoptosis in different transformed cell lines, resulting in caspase 3 activation, cytochrome c release, and exposure of phosphatidylserine on the outer leaflet of the plasma membrane (Liao et al 1997;Chen et al 2006). Mouse embryonic stem cell-derived neurons and neuroblastoma cells rapidly undergo apoptosis within 2-3 days after JEV infection (Yang et al 2004).…”

Recombinant core proteins of Japanese encephalitis virus as activators of the innate immune response

“…Because of JEV replication, products will accumulate in the cytosol during replication, and the endosomal TLR in phagocytic cells can detect viral products by phagocytosis of infected cell or debris from lysed cells. Our previous study has shown that the transient-expressed JEV E protein induced apoptosis in Vero cells [6][7][8] and that the core protein could cause cells to undergo necrosis (data not shown). In this study, the recombinant capsid protein may play as a ligand of TLR and trigger the pro-inflammatory mediators release in the absence of viral infection or cause necrotic cells to yield endogenous host-derived products such as heat shock proteins, and initiate inflammation and immune response, in contrast to apoptotic cell death, which does not trigger inflammation.…”

“…The JEV polyprotein is cleaved by both host and viral proteases to yield at least 10 distinct products in the order of three structural proteins (core, M, and E), and seven nonstructural proteins (NS1, NS2A, NS2B, NS3, NS4A, NS4B, and NS5) [5,6]. The envelope glycoprotein (E), with the presence of a hypervariable region, appears to play a major role in inducing protective immunity and determining viral pathogenicity by defining cellular tropism and triggering apoptosis in infected cells [6][7][8]. By contrast, the wellconserved core is a small protein (14 kDa) and possesses multiple functions involved in the formation of the viral nucleocapsid as well as affliction of viral RNA replication [9].…”

Mosquito Cell-Derived Japanese Encephalitis Virus-Like Particles Induce Specific Humoral and Cellular Immune Responses in Mice

“…Candidate JEV VLP-based vaccines produced through DNA transfection into mammalian cells or stable cell lines provide effective protection against JEV in animals [19][20][21][22][23]. However, the expression of toxic E glycoproteins could limit the generation of stable cell lines capable of producing higher yields of VLPs in mammalian cells [24][25][26]. Nonetheless, JEV GI VLPs produced from stable mammalian cell lines have been shown to induce immunity against GI and GIII JEV in mice and swine [27].…”