FIG 1.

Analysis of Syto-stained HSV-1 virions by FACS. Vero cells were infected with wild-type HSV-1 at an MOI of 5 for 18 hpi. Extracellular virions were stained with 1 μM Syto 13 and analyzed by flow cytometry. (A) Schematic description of the gating strategy. Note that aggregated particles were first excluded by gating them out in the SSC versus FSC plots and by specific flow cytometry parameters (see Materials and Methods). (B) The graphs on the left for each condition (dot plots) show the fluorescence profiles of all nonaggregated particles, while only Syto 13⁺ samples (fluorescence above the buffer control) were considered on the right (histograms). Percentages denote the amount of Syto 13-positive particles relative to the starting population, which includes inert particles inherently present in the FACS buffer (24). Meanwhile, the mean fluorescence signal (MFI) is only that of the Syto 13⁺ viral particles.