FIG. 6.

Demonstration of cell-cell fusion events at 9 h after VZV infection. HELF cells were seeded on glass coverslips and stained with orange CellTracker (CMRA), washed, and then inoculated with green-CellTracker-labeled uninfected HELF cells (a through c) or infected HELF cells (d through l). Cells were fixed at 4 h (d through f) or 9 h (g through i and j through l) after infection and stained for gE protein (blue; monoclonal antibody and secondary anti-mouse Alexa Fluor 647 conjugate). Nuclei were stained with Hoechst 22358 (d through l, gray). Cells were analyzed for the mixing of green and red fluorescent signals in the cytoplasm that would indicate fusion of newly infected cells with an input cell. The thin white arrows in panels g through i point to a cell (red and green cytoplasm) that seems to have partially fused with fused input cells. The adjacent output cell (arrowhead) has not yet fused (only red fluorescence). Scale bars are 50 μm.