Metabolic reprogramming tips vaccinia virus infection outcomes by stabilizing interferon-γ induced IRF1

Area of Science:

• Immunology and Virology
• Cellular Metabolism and Gene Regulation

Background:

• Interferon (IFN)-stimulated genes (ISGs) are crucial for antiviral defense, but their regulation beyond primary signaling is not fully understood.
• Aberrant ISG expression is observed in diseases, suggesting uncharacterized regulatory mechanisms.
• Cellular metabolism, particularly glucose vs. galactose utilization, influences cell identity and susceptibility to viruses.

Purpose of the Study:

• To investigate how cellular metabolism (aerobic glycolysis vs. oxidative phosphorylation) impacts ISG expression and function.
• To identify novel regulatory pathways controlling key ISG proteins, such as IRF1.
• To determine the functional consequences of metabolic regulation on viral replication.

Main Methods:

• Cultured human, mouse, and cat cells in glucose-rich (glycolysis) or galactose-rich (oxidative phosphorylation) media.
• Stimulated cells with interferons (IFN-α, IFN-γ) and analyzed ISG RNA and protein expression.
• Utilized proteasome inhibition and knockout (KO) of IRF1 to dissect regulatory mechanisms.
• Assessed viral replication of vaccinia virus (poxvirus) and herpesvirus under different conditions.

Main Results:

• Glucose and galactose media differentially regulated ISG RNA and protein expression, with greater differences between treatments than between metabolites.
• Interferon-priming led to distinct protein expression: IRF1 upregulated in IFN-γ/glucose, IFITM3 upregulated in galactose.
• Metabolic regulation of IRF1 was conserved across species and dependent on proteasome activity.
• Glucose/IFN-γ decreased vaccinia virus replication, dependent on IRF1; galactose conditions showed less impact.
• A late-stage block in viral replication affecting herpes- and poxvirus titers was observed in specific metabolic conditions.

Conclusions:

• Cellular metabolism, specifically glucose vs. galactose utilization, represents a novel regulatory layer for key ISG proteins like IRF1.
• This metabolic control influences antiviral defense efficacy and viral replication outcomes.
• The findings suggest that the interferon response incorporates subprograms that can adapt to changing metabolite levels during infection and proliferation.