FIG. 2.

Deprivation of Gln, Arg, or Met results in enhanced ICP0⁻ virus plating efficiency. Twenty-four-hour-old Vero cell monolayers were incubated in media lacking 1 of the 15 amino acids included in the DMEM formulation. Each day for 4 days, monolayers were infected with 5 to 100 PFU of wild-type (KOS) (A) or ICP0⁻ (n212) (B) virus in complete DMEM. After a 1-h infection, monolayers were overlaid with complete DMEM containing methyl cellulose and incubated for 5 days at 37°C. Plaques were counted and multiplied by a dilution factor of 1 to 20 to normalize all plaque counts to infection with 100 PFU/plate. Bars represent the average numbers of PFU/plate in three independent experiments, and error bars represent the standard deviations.