Dengue E-protein was assessed in suspension HepG2 cells by intracellular staining and fluorescence activated cell sorter (Becton Dickinson, USA) and an Alexa-647 conjugated (AlexaFluor conjugation kit, Invitrogen, USA) monoclonal antibody (4G2, ATCC). Cells were scraped and permeabilized using BD FACS Perm/Wash solution (Becton Dickinson, USA) and acquisition and analysis was performed using CellQuest software (Becton Dickinson, USA).