FIG. 1.

Schematic of the construction of UL20-null viruses. (A) The top line represents the prototypic arrangement of the HSV-1 genome with the unique long (UL) and unique short (US) regions flanked by the terminal repeat (TR) and internal repeat (IR) regions. (B) Shown below is an expanded genomic region between map units 0.25 and 0.3 containing the UL19, UL20, UL20.5, UL21, and UL22 genes. (C) The recombination plasmid, pΔ20-EGFP, which contains UL20 flanking sequences for recombination with the viral genome, was generated by inserting a CMV-EGFP gene cassette (E) between the BamHI restriction sites flanking the UL20 gene (D).