To confirm the relevance of STING cleavage by the DENV-NS2B3 on the inhibition of type I IFN production upon DENV infection, we transduced Sting 2/2 MEFs with lentiviruses expressing either WT human STING (STING-WT) or a mutant (uncleavable) version, that harbors the mouse STING sequence at the NS2B3-cleavage site (STING-MUT) ( Figure 1B and 1F) . Twenty-four hours after transduction MEFs were infected with DENV-2 at an MOI of 1 (strains 16681 and NGC) or mock treated and the levels of IFNb, IFNa and viral RNA were measured by qRT-PCR after total RNA extraction from the cells at different times post infection ( Figure 5A-5F) . A schematic representation of the lentiviruses used is shown in figure 5G . For these experiments, as shown in figure 5A and 5D, MEFs expressing the uncleavable version of STING (STING-MUT) expressed significantly higher levels of IFNb mRNA when compared to MEFs expressing WT STING (STING-WT) or to the control MEFs (GFP) confirming that the cleavage of STING by DENV-NS2B3 is necessary for the inhibition of IFNb production in infected cells. The induction of IFNb was detected as early as 2 hpi. Infection with the two DENV-2 strains also induced higher levels of IFNa mRNA in MEFs expressing STING-MUT than in the MEFs expressing STING-WT and the GFP control ( Figure 5B and 5E ). Under these experimental conditions, the replication of the mouse adapted DENV-2 (NGC) was increased in Sting 2/2 MEFs expressing wild type STING as compared with STING-MUT ( Figure 5F ). In the case of 16681 strain, a significant increase of replication was observed only with Sting 2/2 MEFs (GFP) at 48 hpi., and no significant difference was observed in MEFs expressing the two versions of STING, presumably due to a high level of lentiviral-expressed STING that could overwhelm the ability of this non mouse-adapted DENV strain to replicate in this system ( Figure 5C ).