Fig. 5. Microscopic images of GFP staining of human foreskin fibroblasts (HFFs) transfected with the DNAs (10 mg per 10⁵ cells) of Towne_BAC, DUL32, and rescued-UL32 at 10 days posttransfection. Viral infection can be visualized by using GFP staining because all BAC-DNAs contain a GFP expression cassette.