DENV-infected Vero cells were harvested 5 days post-infection and lysed with cold lysis buffer (1.5% Triton X-100, 0.2 mM Phenylmethylsulfonyl Fluoride (PMSF), 1 mg/ml pepstatin A and 75 mM KCl in PBS) for 40 min on ice. An equal volume of 56 loading dye was added to the cell lysate before 12% SDS-PAGE and transferred onto nitrocellulose membranes. Blocked membranes were probed with dengue-specific antibodies at RT for 1 hr and detected with HRP-conjugated anti-human IgG-Fc or antimouse IgG-Fc secondary antibody and developed with chemiluminescence (Supersignal West Pico Chemiluminescent Substrate, Pierce).