Glycoprotein E of the Japanese Encephalitis Virus forms virus-like particles and induces Syncytia when expressed by a baculovirus.

　　 Du R, Yin F, Wang M, Hu Z, Wang H, Deng F.

      J Gen Virol. 2015 Jan 15. pii: vir.0.000052. doi: 10.1099/vir.0.000052. [Epub ahead of print]

　   Abstract

　　The prM glycoprotein is thought to be a chaperon for the proper folding, membrane association and assembly of the envelope protein (E) of flaviviruses. The prM-E and E proteins of the Japanese encephalitis virus (JEV) were expressed in insect cells by using both the baculovirus-expression system and the transient expression method. Protein expression was analysed by Western blots, and the cytopathic effect was observed by microscopy. In the baculovirus-expression system, the E protein, with or without the prM protein induced syncytial formation in Sf9 cells. Transient expression of prM-E also induced syncytia in Sf9 cells. Immno-fluorescence revealed that in presence of prM, E proteins were ER-like in distribution, while in the absence of prM, E proteins were located on the cell surface. Sucrose gradient sedimentation and Western blot analysis indicated that the E protein expressed with or without the prM protein was secreted into the culture medium in particulate form. And the formation of virus-like particles (VLPs) in the medium was confirmed by electron microscopy (EM) and immuno-electron microscopy (IEM). The results suggest that E protein of JEV in the absence of prM retained its fusion ability, by either cell surface expression or formation of VLPs. Moreover, based on the observation that co-expression of prM-E in Sf9 cells induce considerable syncytial formation, a novel, safe and simple antiviral screening approach is proposed when studying inhibitory antibodies, peptides or small molecules targeting to JEV E protein.

　　http://www.ncbi.nlm.nih.gov/pubmed/25593161