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Modulation of virion incorporation of Ebolavirus glycoprotein: effects on attachment, cellular entry and
Andrea Marzi1, Anja Wegele, Stefan Pöhlmann
1Institute for Clinical and Molecular Virology, University Erlangen-Nürnberg, 91054 Erlangen, Germany.
Abstract:
The filoviruses Ebolavirus (EBOV) and Marburgvirus (MARV) cause severe hemorrhagic fever in humans and are potential agents of biological warfare. The envelope glycoprotein (GP) of filoviruses mediates viral entry into cells and is an attractive target for therapeutic intervention and vaccine design. Here, we asked if the efficiency of virion incorporation of EBOV-GP impacts attachment and entry into target cells and modulates susceptibility to neutralizing antibodies. In order to control the level of EBOV-GP expression, we generated cell lines expressing the GPs of the four known EBOV subspecies in an inducible fashion. Regulated expression of GP on the cell surface allowed production of reporter viruses harboring different amounts of GP. A pronounced reduction of virion incorporation of EBOV-GP had relatively little effect on virion infectivity, suggesting that only a few copies of GP might be sufficient for efficient engagement of cellular receptors. In contrast, optimal interactions with cellular attachment factors like the DC-SIGN protein required incorporation of high amounts of GP. Antibody-mediated neutralization of virions bearing high amounts of GP was slightly more efficient than neutralization of virions harboring low amounts of GP, suggesting that the efficiency of GP incorporation into virions might modulate susceptibility to neutralizing antibodies. Finally, regulated expression of GP in permissive 293 cells did not reduce EBOV-GP-driven infection but diminished vesicular stomatitis virus GP (VSV-G) and amphotropic murine leukemia virus (A-MLV) GP mediated entry in a dose-dependent manner. Therefore, intracellular GP does not seem to downmodulate expression of its receptor(s) but might alter expression and/or function of molecules involved in VSV-G and A-MLV-GP-dependent entry. Our results suggest that the efficiency of virion incorporation of GP could impact EBOV attachment to target cells and might modulate control of viral spread by the humoral immune response.
Insights
The amount of Ebolavirus glycoprotein (GP) on a virus affects how well it attaches to cells and how susceptible it is to antibodies. Low GP levels are sufficient for infection, but high levels are needed for optimal attachment to certain factors.
Area of Science:
- Virology
- Immunology
- Molecular Biology
Background:
- Filoviruses, including Ebolavirus (EBOV) and Marburgvirus (MARV), are significant public health threats due to causing severe hemorrhagic fever.
- The filovirus envelope glycoprotein (GP) is crucial for viral entry into host cells, making it a key target for antiviral therapies and vaccine development.
- Understanding how GP incorporation into virions influences infectivity and immune response is vital for controlling filovirus outbreaks.
Purpose of the Study:
- To investigate whether the efficiency of Ebolavirus glycoprotein (EBOV-GP) incorporation into virions impacts viral attachment, entry into target cells, and susceptibility to neutralizing antibodies.
- To determine the relationship between EBOV-GP expression levels and viral infectivity and interaction with cellular attachment factors.
- To explore the effect of EBOV-GP expression on the entry mediated by other viral glycoproteins.
Main Methods:
- Generated inducible cell lines expressing EBOV GPs from four subspecies to control GP expression levels.
- Produced reporter viruses with varying amounts of incorporated EBOV-GP by regulating cell surface GP expression.
- Assessed virion infectivity, attachment to cellular factors (e.g., DC-SIGN), and neutralization by antibodies.
- Evaluated the impact of regulated GP expression on entry mediated by heterologous viral glycoproteins (VSV-G, A-MLV GP).
Main Results:
- Reduced EBOV-GP incorporation had minimal impact on virion infectivity, suggesting a low threshold for cellular receptor engagement.
- Optimal interaction with attachment factors like DC-SIGN required high levels of EBOV-GP incorporation.
- Virions with higher EBOV-GP content showed slightly increased susceptibility to antibody-mediated neutralization.
- Regulated EBOV-GP expression did not affect EBOV-GP-driven infection but dose-dependently reduced entry mediated by VSV-G and A-MLV GP.
Conclusions:
- The efficiency of EBOV-GP incorporation into virions plays a role in viral attachment to target cells.
- GP incorporation levels may modulate the effectiveness of neutralizing antibodies in controlling viral spread.
- Intracellular GP expression might influence the function of cellular molecules involved in the entry of other viruses.
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