Activation of the innate immune response represents one of the most important cellular mechanisms to limit virus replication and spread in cell culture. Here, we examined the effect of adenoviral gene expression on the antiviral response in adenovirus-transformed cell lines; HEK293, HEK293SF and AGE1.HN. We demonstrate that the expression of the early region protein 1A in these cell lines impairs their ability to activate antiviral genes by the IFN pathway. This property may help in the isolation of newly emerging viruses and the propagation of interferon-sensitive virus strains.
Received 30 October 2015 Accepted 4 December 2015The IFN pathway of the innate immune response plays an important role in the control of viral infections. Once a cell detects viral components via its intracellular pathogen recognition receptors, type I IFNs (IFN-a/b) are synthesized and secreted, which act in an auto-and paracrine fashion and lead to the expression of IFN-stimulated genes (ISGs). Some of these ISGs, such as the myxovirus resistance A protein (MxA), possess direct antiviral activities (Haller et al., 2009). Viruses have developed efficient strategies to inhibit the IFN response (García-Sastre, 2011) and escape these antiviral mechanisms. Still, suppression of the antiviral response by chemical inhibitors, expression of viral antagonists or knockdown of antiviral proteins can improve permissiveness for emerging virus strains and increase yields in vaccine production (McSharry et al., 2015;Stewart et al., 2014;van Wielink et al., 2011;Young et al., 2003;Zhu et al., 2014). Inhibition of the IFN pathway can also support the propagation of IFN-sensitive viruses, like the influenza A virus (IAV) deletion strain that lacks its non-structural protein 1 (delNS1). The delNS1 strain is attenuated in IFN-competent cells and hence, is considered as a live vaccine for both animals (Richt & García-Sastre, 2009;Wang et al., 2008) and humans (Mössler et al., 2013;Wressnigg et al., 2009). So far, only a few cell lines, such as Vero cells, which are unable to produce IFN, support the propagation of IFN-sensitive viruses (Barrett et al., 2009;Emeny & Morgan, 1979;Stewart et al., 2014). However, not all viruses replicate in these African green monkey cells and some properties of the virus, such as the glycan structures of viral surface proteins, can be altered by propagation in cells that do not originate from natural host organisms (Dumont et al., 2015;Genzel et al., 2012; Schwarzer et al., 2009). Thus, there is a need to provide flexible host cell systems for the propagation of IFN-sensitive viruses.In this study, we examined the effect of adenovirus early region protein 1A (E1A) and 1B (E1B) expression on the antiviral response and permissiveness for IFN-sensitive viruses in the adenovirus-transformed (Ad t ) cell lines, AGE1.HN (Niklas et al., 2011), HEK293 and HEK293SF [a derivative of HEK293 cells growing in serum-free (SF) medium and adapted to the proliferation in suspension (Cô té et al., 1998)].
IAV efficiently replicates in adeno...