FIG. 5.

One-step growth curve of recombinants and parental viruses in MDBK cells. Confluent MDBK cells were infected with viruses at an MOI of 5 PFU per cell. After 1 h of adsorption at 4°C, residual input viruses were removed. The cultures were washed three times with phosphate-buffered saline, and 5 ml of medium was added to each flask before further incubation (37°C). At indicated time intervals, replicate cultures were frozen. Virus yields were determined by titration on MDBK cells. Each data point represents the average of duplicate samples obtained from separate infections.