DENV-infected Vero cells or C6/36 cells were fixed and permeablilized with 80% acetone at 220 o C for 10 min. The presence of virus was detected by D29 Fab-IgG, h3H5 and h4G2 at 1 mg/ml, followed by staining with FITC-conjugated antihuman IgG (ZyMax, Invitrogen). Cells were mounted with MOWIOL (Sigma) and images were captured using a fluorescent microscope (Olympus).