Indirect immunofluorescent assay of the VP19c protein in DEV infected DEF cells. Mock infected DEF cells probed with the VP19c antibody (A). DEV infected DEF cells probed with the preimmune sera (D) or VP19c antibody (G). Cells were labeled with FITC-conjugated goat anti-rabbit immunoglobulin G and counterstained with DAPI to visualize the nuclei (B, E, H). Then FITC and DAPI were merged (C, F, I). (Images were acquired by using 60 × objective).