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Role of reticuloendotheliosis virus envelope glycoprotein in superinfection interference
1McArdle Laboratory for Cancer Research, University of Wisconsin-Madison 53706.
Abstract:
Cells expressing specific proviruses are resistant to superinfection by viruses of the same subgroup. To investigate the role of the reticuloendotheliosis virus (REV) envelope glycoprotein (env-gp) in the establishment of resistance to superinfection, we constructed plasmids that express either the wild-type env-gp or an env-gp derivative that lacks part of the transmembrane (TM) protein. After transfection, transient expression of the wild-type env gene resulted in syncytium formation in a mammalian cell line permissive for virus replication, whereas synthesis of the TM-defective env-gp did not result in syncytium formation. Several stable cell lines expressing either the normal or TM-defective env-gp were isolated. Expression of the normal env-gp in the absence of expression of other viral genes induced resistance to infection by REV. Immunofluorescence analysis of cells expressing the TM-defective env derivative and an examination of the glycosylation pattern of this peptide indicated that it is not translocated to the cell surface but resides primarily in the rough endoplasmic reticulum. However, these cells were also resistant to REV infection. Thus, interaction between the env derivative and the cellular component that functions as a receptor for the virus can occur in the endoplasmic reticulum and renders the cell immune to superinfection.
Insights
Cells resistant to viral superinfection can be achieved by expressing the reticuloendotheliosis virus (REV) envelope glycoprotein (env-gp). Even a defective env-gp, retained in the endoplasmic reticulum, can induce resistance, suggesting early-stage viral interactions.
Area of Science:
- Virology
- Cell Biology
- Molecular Biology
Background:
- Cells expressing specific proviruses exhibit resistance to superinfection by homologous viruses.
- The reticuloendotheliosis virus (REV) envelope glycoprotein (env-gp) is implicated in this resistance mechanism.
Purpose of the Study:
- To investigate the role of REV env-gp in establishing resistance to viral superinfection.
- To determine if a modified env-gp lacking transmembrane (TM) protein can induce resistance.
Main Methods:
- Construction of plasmids expressing wild-type or TM-defective REV env-gp.
- Transfection of mammalian cell lines and isolation of stable cell lines.
- Analysis of syncytium formation, env-gp localization (immunofluorescence), and glycosylation patterns.
Main Results:
- Wild-type env-gp expression induced syncytium formation and resistance to REV infection.
- TM-defective env-gp did not cause syncytium formation but was retained in the rough endoplasmic reticulum.
- Cells expressing TM-defective env-gp also exhibited resistance to REV infection.
Conclusions:
- REV env-gp expression alone confers resistance to superinfection.
- Interaction between a defective env-gp and cellular receptors can occur in the endoplasmic reticulum, leading to resistance.
- This suggests that viral entry or receptor interaction can be blocked at an early stage of viral infection within the cell.