Pathway of rubella virus infectious entry into Vero cells

Abstract

The mechanism and the kinetics of rubella virus (RV) penetration into Vero cells were studied. By using pronase or acid treatment to inactivate virus which had adsorbed to cell membrane but had not been internalized, it was found that a period of 7 h was required in order for all of the adsorbed virus to enter the host cells. Lysosomotropic agents (monensin, methylamine, ammonium chloride and chloroquine) were used to study the mechanism by which RV penetrates host cells. Virus replication was inhibited if treatment of cells with these compounds was performed for at least 9 h after infection. However, if extracellular adsorbed virions were eliminated by acid treatment following removal of the lysosomotropic compounds, RV replication was completely inhibited by treatment with these drugs for any time period after adsorption. This indicated that the prolonged period of treatment with these compounds necessary to inhibit virus replication is due to the slow rate of RV internalization. None of the compounds had any effect on infection initiated by transfection of RV RNA, confirming that these drugs were exerting their inhibitory activity at penetration. The inhibition of RV replication by lysosomotropic compounds indicates that RV penetrates host cells by the endosomal pathway.

Rubella Virus Replication and Links to Teratogenicity

“…Early biochemical studies by Katow and Sugiura (70) showed that exposure of the RV E1 and E2 glycoproteins to pH 6.0 or less induced a conformational change within the glycoproteins that favored the fusion of the viral envelope to the endosomal membrane. This hypothesis was further supported by more recent studies which demonstrated the inhibition of viral replication following the use of lysosomotropic agents (116). Preliminary viral attachment and penetration studies by thin-section electron microscopy (TSEM) indicate that at physiological pH of 7.4, RV enters predominantly via the endocytic route.…”

Effects of Endocytosis Inhibitory Drugs on Rubella Virus Entry into VeroE6 Cells

“…Inhibition of RV infection by lysotrophic compound also supports this speculation (26). On the basis of these observations, we investigated whether entry of RV into cells is mediated by a clathrin dependent pathway.…”

Analysis of Rubella Virus Capsid Protein-Mediated Enhancement of Replicon Replication and Mutant Rescue

“…While wt replicon replication can proceed without the presence of C, C is more efficient in its role in the initial phases of RNA replication than is the NotI domain, explaining the enhancement of wt replicon replication. In the context of virus infection, since rubella virus enters the cell by receptor-mediated endocytosis (23), following fusion of the virion membrane with an endosomal membrane, C protein in the capsid could remain bound to the virion RNA and subsequently recruit the replicase protein that is translated from the virion RNA by directly binding to it. This would localize the initial replication complex to the endosomal membrane, the site of RNA synthesis in rubella virus-infected cells (17).…”