FIG. 2.

tsH5-4 is defective in infectious virus production at 39.5°C. (A) Plaque assay of tsH5-4. Confluent BSC40 cells were infected with equivalent amounts of virus (either wt or tsH5-4) and maintained at the indicated temperature. After 2 days, the medium was removed and the cells were stained with crystal violet. (B) Twenty-four-hour viral yield of tsH5-4. Confluent BSC40 cells were infected with either wt or tsH5-4 virus at the indicated MOI and maintained at the indicated temperature. At 24 h p.i., the cells were harvested and disrupted and viral yield was analyzed by titer determination on BSC40 cells at 31.5°C. Each infection was performed in duplicate, and the average is shown in the bar graph.