Inhibition of cell-to-cell infection and syncytia formation. Uninfected 1G5 T cells were pretreated for 24 h with either (A) mock, (B) 10-6 M ddC, or with ddC and (B) 2 mg/ml or (C) 4 mg/ml S. fusiforme, or with S. fusiforme only at (D) 2 mg/ml or (E) 4 mg/ml. 1G5 cells were cocultivated at 1:1 ratio with CEM cells that were infected with NL4-3 at 0.01 moi. 24 h after cocultivation, cells were examined for syncytium formation using Leica DM IL Fluo microscope, ×20 magnification (A-F). Cell cultures were monitored for luciferase expression, and % inhibition was calculated from maximal luciferase expression from untreated 1G5 cells (1.9 × 105 RLU, not shown), which was plotted and is indicated on top of each bar (H). Data are mean +/- SD of triplicates. Uninfected adherent GHOST  cells were ddC treated and cocultivated at 1:1 ratio with HIV infected 1G5 cells for 24 h, and examined for syncytia formation by green fluorescence (G). Image shows fluorescence micrograph taken of a green fluorescent giant cell, which was superimposed on the same field phase contrast black and white image.