Entry and replication of Japanese encephalitis virus in cultured neurogenic cells

Abstract

The entry mode and growth pattern of Japanese encephalitis (JE) virus in mouse neuroblastoma N18TG2 cells and mouse neuroblastoma x rat glioma NG108-15 hybrid cells were studied by electron microscopy. At two minutes after inoculation, JE virions adsorbed onto and directly penetrated through the plasma membrane of the hybrid cells, whereas virions did not adsorb nor entered the neuroblastoma cells. Correspondingly, the hybrid cells showed assembling progeny JE virions in the cistemae of rough endoplasmic reticulum (RER) 1 day postinoculation (p.i.) although virions were rarely found on the following days during the experiment. On the other hand, progeny virions did not assemble in the RER cisternae of the neuroblastoma cells throughout the experiment. The morphologic observations, therefore, suggest that (a) the hybrid cells express JE-virus receptors which facilitate the viral attachment onto and entry into the cells, while the neuroblastoma cells do not and (b) JE virus replicates very poorly after the entry into the hybrid cells while it does not replicate at all in the neuroblastoma cells. The virus titrations of the media of the neuroblastoma and hybrid cell cultures showed only titers indicative of residual virus of the inoculum that progressively decreased during the experiment. The present results show therefore that of the two neurogenic cell culture lines studied only the hybrid cell line can be used for the study of viral entry and replication, although it is not suited for virus production. Possible reasons for the poor replication of JE virus in the hybrid cells are discussed.