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Suppression of interferon-induced antiviral activity in cells expressing hepatitis C virus proteins
Abstract:
To elucidate the mechanism of the persistent nature of hepatitis C virus (HCV) infection, we examined whether the expression of HCV proteins affect the antiviral activity of interferon (IFN). Antiviral activity of IFN in HepG2 cells expressing all HCV (type 1b) proteins was much lower than vector control (VC) HepG2 cells when encephalomyocarditis virus (EMCV) was used as a challenge virus. Lesser sensitivity to IFN was also observed in cells expressing NS3, NS4, and NS5 and in cells expressing only NS5A. In contrast, HepG2 cells expressing core, E1, E2, NS2, and NS3 proteins were equally sensitive to IFN as VC cells. We then tested the antiviral activity by IFN in two human amnion-derived FL cell lines expressing NS5A from two different clones, one with an intact sequence of IFN sensitivity-determining region (ISDR) and the other with a mutated ISDR sequence. They were almost equally insensitive to IFN treatment when EMCV was challenged. HCV thus has functional protein(s), possibly NS5A, to suppress IFN-induced antiviral activity and plays an important role in virus-cell interaction and regulation of viral replication.
Insights
Hepatitis C virus (HCV) proteins, particularly NS5A, can suppress interferon's (IFN) antiviral activity. This finding helps explain persistent HCV infections and guides future therapeutic strategies.
Area of Science:
- Virology
- Immunology
- Hepatology
Background:
- Hepatitis C virus (HCV) infection often persists, suggesting viral mechanisms to evade host defenses.
- Interferon (IFN) is a key antiviral cytokine, but its efficacy against HCV can be limited.
Purpose of the Study:
- To investigate how specific HCV proteins influence the antiviral response to IFN.
- To identify viral factors contributing to persistent HCV infection.
Main Methods:
- HCV proteins were expressed in HepG2 and FL cell lines.
- Antiviral activity of IFN was assessed using encephalomyocarditis virus (EMCV) as a challenge.
- IFN sensitivity was compared between cells expressing different HCV proteins and controls.
Main Results:
- Cells expressing all HCV proteins, or NS3, NS4, NS5, or NS5A alone, showed reduced sensitivity to IFN.
- Cells expressing NS5A, regardless of ISDR sequence integrity, were insensitive to IFN.
- HCV core, E1, E2, NS2, and NS3 proteins did not affect IFN sensitivity.
Conclusions:
- HCV possesses functional proteins, likely NS5A, that suppress IFN-induced antiviral activity.
- This suppression mechanism is crucial for HCV-cell interactions and viral replication, contributing to persistent infections.