Ambivalent role of miR-124-3p on Influenza A Virus in vitro: Enhancing replication by attenuating innate immunity while causing defects in virion production

Abstract

<p><strong>Background: </strong>Small non-coding RNAs have emerged as promising therapeutics in recent studies and clinical trials. These molecules have demonstrated potential in targeting various diseases, and ongoing research continues to uncover novel targets and therapeutic agents. Among these, miR-124-3p was shown to have broad-spectrum antiviral properties, including effectiveness against Influenza A virus (IAV) <em>in vitro.</em> However, the exact antiviral mechanism of miR-214-3p remains unclear as the miRNA was shown to have immunoinhibitory effect upon bacterial infection in previous studies. This observation appears to be seemed contradictory with the results observed in IAV infection. The aim of our study was to clarify the role of miR-124-3p in IAV, specifically WSN strain, replication <em>in vitro</em>.</p><p><br></p><p><strong>Methodology: </strong>We assess miR-124-3p’s effect on cell’s immunity, viral proteins, and viral replication through different quantitative assays.</p><p><br></p><p><strong>Results: </strong>Our findings revealed that the introduction of miR-124-3p through transfection, along with subsequent Sendai Virus, resulted in a widespread suppression of genes responsible for triggering an anti-viral response. Paradoxically, viral load of IAV was significantly decreased for cells transfected with miR-124-3p. Through subsequent sequence analysis, 2 and 1 possible target sites at the coding sequence of NA and HA respectively consisting of a G:U wobble and 3’ compensatory site of miR-124-3p were identified, suggesting that IAV virion production was affected due to inefficient production of surface proteins essential for egression and propagation. To verify this possibility, the target sequence was subcloned into 3’ UTR of a luciferase reporter and a luciferase assay was subsequently performed. We observed a significant reduction in luciferase reporter activity signifying that there is direct interaction between miR-124-3p and the targets identified.</p><p><br></p><p><strong>Conclusion: </strong>Our finding of a miRNA attenuating Influenza Viral Production thorough non-canonical binding to viral mRNA CDS suggests there is high flexibility in designing IAV-targeting siRNAs or miRNAs.</p>