Influenza A Virus NS1 Inhibits RIPLET Activation of Duck RIG-I Signaling.

Area of Science:

• Immunology
• Virology
• Molecular Biology

Background:

• Retinoic acid-inducible gene I (RIG-I) is vital for detecting viral RNA and initiating immune responses against influenza A viruses (IAVs).
• RIG-I activation in mammals depends on ubiquitination by E3 ubiquitin ligases TRIM25 and RIPLET.

Purpose of the Study:

• To investigate the role of duck RIPLET in RIG-I activation in avian cells.
• To determine if avian influenza virus non-structural protein 1 (NS1) can inhibit duck RIG-I activation.

Main Methods:

• Dual luciferase assays to measure IFN-β promoter activity.
• Quantitative PCR (qPCR) to analyze immune gene expression and viral RNA levels.
• Co-immunoprecipitation and confocal microscopy to study protein interactions.

Main Results:

• Duck RIPLET enhances RIG-I activation and IFN-β promoter activity in chicken cells.
• Co-expression of duck RIG-I and RIPLET reduces viral RNA and upregulates immune genes during low pathogenic avian influenza (LPAI) H6N2 infection.
• Duck RIG-I and RIPLET interact and colocalize in the cytoplasm.
• IAV NS1 proteins inhibit duck RIPLET-mediated RIG-I activation, with avian strains showing the strongest inhibition.

Conclusions:

• Duck RIPLET is a key E3 ubiquitin ligase for RIG-I activation in avian systems.
• The RIG-I immune pathway is susceptible to inhibition by IAV NS1 proteins across different strains.
• Understanding these interactions is crucial for developing strategies against avian influenza.