Figure 2. Effect of ISG15 on cytotoxicity and virus growth after infection of MEFs with virulent and E3L deletion VACV mutant viruses.

A. ISG15−/−, PKR−/− or wild type cells were mock-infected or infected at 0.1 PFU/cell with WR or VVΔE3L. At different times p.i, the CPE in the cells was examined by phase-contrast microscopy. B. Virus growth of WR and VVΔE3L infected (0.1 PFU/cell) ISG15+/+, or ISG15 −/−, or PKR−/− cells. At different times cells were harvested and virus yields were determined by plaque assay for WR or by immunostaining for VVΔE3L.