Reconstitution of interferon regulatory factor 7 expression restores interferon beta induction in Huh7 cells

ABSTRACT Abundance of essential components of double-stranded RNA (dsRNA) recognition and the subsequent interferon (IFN) response vary widely between primary human hepatocytes (PHHs) and commonly used cell culture models based on derivatives of Huh7 cells, supporting replication of all hepatitis viruses. We used RNA sequencing to compare the innate immune response in hepatoma cells with primary cells and non-neoplastic immortalized hepatocytes (PH5CH). Stimulation with the dsRNA analog poly(I:C) in Huh7 and Huh7.5, either by supernatant feeding or by transfection, resulted in an induction of interferon-stimulated genes widely comparable to that of PHH and PH5CH, but Huh7 and Huh7.5 lacked efficient production of IFN-β. We identified interferon regulatory factor 7 (IRF7) as a critical component missing in Huh7-derived cells. Upon reconstitution of IRF7 expression, IFNB induction was restored to the levels observed in PHH upon stimulation with poly(I:C). In contrast to PH5CH cells, for which IRF3 was sufficient for full IFN induction, the lack of IRF7 could not be compensated by increased IRF3 expression in Huh7-derived cells. We further found significant IFNB induction upon Sendai virus and hepatitis delta virus infections in Huh7.5 cells reconstituted with IRF7, but not in hepatitis A or hepatitis C virus-infected cells, widely representing the characteristics of the IFN response observed in other models and in vivo . Our data suggest that the reconstitution of IRF7 expression in Huh7 cells can aid a more physiological analysis of cell intrinsic immune responses to hepatotropic viruses in future studies. IMPORTANCE Current in vitro studies often rely on Huh7-based hepatoma cells, which, although permissive for hepatitis viruses, lack critical components for double-stranded RNA recognition. We used RNA sequencing to compare the cell intrinsic innate immune responses of hepatoma cells with more authentic cellular models. We discovered that Huh7-derived cells, which are known to show very limited induction of IFNB upon pathogen recognition receptor stimulation, lack expression of interferon regulatory factor 7 (IRF7), an essential component for robust type I interferon induction. By reconstituting IRF7, we were able to restore the interferon response to levels observed in primary human hepatocytes. Our study not only identifies a key missing link in the Huh7/Huh7.5 innate immune response but also offers a way to enhance the physiological relevance of these cells in future studies. Our findings pave the way for more accurate modeling of the human hepatic response to viral infections, potentially improving the understanding and management of hepatitis.