Expression of Dengue virus as determined by immunofluorescent staining with mouse anti-Dengue virus-2. Cells were counterstained with Evans Blue, but different filtration systems available on the different microscopes variably blocked visualization of the background of cells fluorescing red. Transfection efficiencies were generally in the range of 0.01% to 1% and in the background of each photograph in this figure are numerous non-fluorescent cells, best visualized on an Apple Macintosh. In the experiments here, cells were photographed variously with either 40X or 60X objectives. A, Dengue 2 wild type virus (48 hrs); B, ΔprM-E (48 hrs);C, ΔC-prM-E (48 hrs); D, Dengue 2 wild type (8 days); E, ΔprM-E (8 days); F, ΔC-prM-E (8 days).