Fig. 5.

Reverse-genetics analysis of the impact of selected SARS-CoV nsp7 and nsp8 mutations. Plaque phenotypes of viable but crippled mutants with engineered nsp7 and nsp8 mutations are illustrated on the Left. Plaque assays were performed with early progeny virus, harvested from cells at 18 h post full-length RNA transfection (Materials and Methods). On the Right, growth curves are shown for crippled nsp7 and nsp8 mutants and the WT parental virus. For these experiments, mutant virus was harvested from transfected cells at 42 h p.t. After titration of these virus stocks, fresh Vero-E6 cells were infected (M.O.I., 5), and virus production at the given time points was measured by plaque assay. Graphs display mean titers and SDs derived from three independent experiments. Nonviable mutants and mutants with a phenotype similar to WT virus are listed at the Bottom.