Reduction in Interferon-Stimulated Genes Contributes to High-Yield Production of Influenza Virus in Suspension MDCK Cells

Compared with the traditional vaccine produced in embryonated chicken eggs, cell-based manufacturing represented by the Madin-Darby canine kidney (MDCK) cell line has a larger production scale and reduces the risk of egg shortage in a pandemic. Establishing a culture system that enables high production of the influenza virus is a key issue in influenza vaccine production. Here, a serum-free suspension culture of MDCK (sMDCK) cells was obtained from adherent MDCK (aMDCK) cells by direct adaptation. Viral infection experiments showed that viral yields of influenza A/B virus in sMDCK cells were higher than in aMDCK cells. Transcriptome analysis revealed that numerous interferon-stimulated genes (ISGs) exhibited reduced expression in sMDCK cells. To further clarify the mechanism of high viral production in sMDCK cells, we demonstrated the antiviral role of RIG-I and IFIT3 in MDCK cells by knockdown and overexpression experiments. Furthermore, suppression of the JAK/STAT pathway enhances the viral accumulation in aMDCK cells instead of sMDCK cells, suggesting the reduction in the JAK/STAT pathway and ISGs promotes viral replication in sMDCK cells. Taken together, we elucidate the relationship between the host innate immune response and the high viral productive property of sMDCK cells, which helps optimize cell production processes and supports the production of cell-based influenza vaccines.