IFNB1 and infection: To validate the results described using p55-C1B and IFNβ promoter assays in a primary cell model, we measured IFNα/β production upon infection of MDDCs either with DENV or a Semliki forest virus (SFV) expressing the DENV NS2B3 protease complex or the mutant version of the protease (NS2B3-S135A) as a control [23], [25].