Influenza A virus H1N1-derived circNP37 positively regulates viral replication by sponging host miR-361-5p

RNA viruses, such as respiratory syncytial virus and SARS-CoV-2, can generate viral circular RNAs (circRNAs), which may play important roles during viral infection. However, whether influenza A viruses have this ability to generate viral circRNAs remains unknown. In this study, we discovered that the negative-strand RNA of the H1N1 nucleoprotein (NP) gene can generate a circRNA, designated circNP37. Furthermore, we demonstrated that circNP37 positively regulated viral replication by competitively sponging host miR-361-5p which inhibited polymerase basic protein 2 (PB2) expression. These results were confirmed using in vivo experiments. Compared with wild-type virus, infection with circNP37 knockout virus resulted in a reduced viral load in the lungs. This study demonstrates, for the first time, the existence and biological function of H1N1-derived circNP37. These findings help us better understand the mechanisms of influenza virus replication and pathogenicity. HighlightsO_LINegative-strand RNA of the H1N1 nucleoprotein gene can generate a circRNA C_LIO_LICircNP37 plays important roles in viral replication and viral-host interactions C_LIO_LICircNP37 positively regulates replication by competitively sponging host miR-361-5p C_LI eTOC BlurbO_LIIn this study, we found that influenza A virus H1N1 infection can generate virus-derived circRNA, circNP37. We also demonstrated that circNP37 positively regulate viral PB2 gene expression and viral replication via sponge host miR-361-5p during viral infection. C_LI