FIG. 1.

Proteasome inhibitors prevent VACV replication. (A, B) Plaque formation. BS-C-1 monolayers were incubated with VACV at 4°C. After 1 h, the virus inoculum was removed and replaced with medium containing 0.5% methylcellulose with or without the indicated concentrations of MG132 or epoxomicin. At 24 h after infection, the cells were stained with crystal violet and the plaques counted. (C) Virus yields. HeLa cells were incubated with VACV (3 PFU/cell) for 1 h at 4°C. The inoculum was removed and the cells were washed and incubated with fresh medium in the presence of DMSO, MG132, or epoxomicin. At the indicated times, the cells were harvested and lysed by freezing and thawing and the virus titers determined by plaque assay in BS-C-1 cells without proteasome inhibitors. (D) Cytotoxicity assay. HeLa cells were incubated with medium containing DMSO, 10 μM MG132, or 2 μM epoxomicin for either 12 or 24 h and assayed for the release of lactate dehydrogenase.