FIG. 4.

Kinetics of viral RNA accumulation. MDCK cells were infected at 10 PFU/ml with wild-type and PA mutant viruses. At the times indicated, cells were collected, total RNA was isolated, and the accumulation of the different viral RNA species of segment 7 was determined by real-time RT-PCR amplification, as described in Ma-terials and Methods. (A) mRNA. (B) Top, vRNA. Bottom, cRNA. RNA levels are indicated as the mean ± half of the standard deviation values from duplicates samples from at least seven independent experiments.