FIG. 4.

Spread of virus infection. Replicate monolayers of HFFF₂ cells were infected with 0.01 PFU/cell of HSV-1 strain 17⁺ (WT) or K5ΔZ, FRΔUL37, KΔUL36, or ARΔUL36 mutant virus. (A) Unfused cells; (B) cells after treatment with PEG and dimethyl sulfoxide at 1 h postinfection to induce syncytium formation. The cells were fixed and labeled at 24 h postinfection. Viral DNA was visualized by FISH using Cy3-labeled probe (red), nuclei were stained with DAPI (blue), and cell cytoplasm was stained with CellMask deep red (yellow). Bars, 50 μm in all panels.