Apoptosis resulting from valproate, ganciclovir, and PFA. BCBL-1 cells were incubated in the absence or presence of valproate (0.6 mM) for 3 or 4 days. Where indicated, ganciclovir (GCV) or PFA was present throughout the incubation at the indicated concentration (μM). Cells were assessed for the percentage of apoptotic cells using the TUNEL assay with flow cytometry. (A) The percentage of the total cells that were apoptotic after a 3-day incubation is graphically shown for each condition. ▪ indicates cells not treated with an antiviral agent; ▧, 2 μM GCV; □, 20 μM GCV; ▨, 100 μM PFA; and ▦, 750 μM PFA. (B) Representative flow cytometric profiles are shown for cells incubated in the absence (filled curve) and presence (open curve) of valproate in combination with the indicated antiviral agent. (C) Cells were fixed and processed for dual immunofluorescence looking at the early lytic viral protein PPF and for TUNEL. Filters were used that selectively detected either the red using Alexa Fluor 567 (PPF) or green using fluorescein isothiocyanate (FITC) (TUNEL) fluorescence. Where indicated, ganciclovir was present at 20 μM.