Development of a Universal Type A Influenza Viral RdRp-Induced Reporter System with Potential for Antiviral Drug Screening

The reemergence of new influenza strains and the rise of drug-resistant variants highlighted the urgent need for continuous development of novel antiviral therapies. Previously, reporter virus-based assays were commonly used for the screening of anti-influenza drugs. However, developing reporter viruses tailored to various influenza strains proved to be a time-consuming and labor-intensive process. In this study, we developed a universal MDCK cell-based reporter system that used viral RdRp activity to assess the efficacy of antiviral drugs against live influenza virus. This system employed Gaussia luciferase (Gluc) expression, driven by an RNA polymerase II (Pol-II) promoter and influenza virus RNA promoters recognized by polymerases from different influenza A virus (IAV) subtypes, facilitating transcription and translation of Gluc. The direct correlation between Gluc activity and viral RNA replication was confirmed. The drug evaluation results demonstrated a positive correlation between Gluc expression and the inhibitory effects of RdRp inhibitors when assessed with H1N1, H3N2, and H9N2 viruses. The study established a sensitive and rapid assay for researching and developing drugs targeting influenza RdRp without modifying the viruses, which will accelerate the development of next-generation antivirals and facilitate rapid testing of emerging influenza variants.