Replication kinetics of recombinant viruses rgG1-WT, rgG1-NP-V41I, rgG1-NP-D210E, and rgG1-NP-V41I-D210E in MDCK cells at 33°C (A) or 37°C (B). Confluent monolayers of the various cell lines were inoculated with rgG1-WT, rgG1-NP-V41I, rgG1-NP-D210E, or rgG1-NP-V41I-D210E viruses. Cultured supernatants were harvested at 12, 24, 48, 72, and 96 hpi. Virus titers were determined by TCID50 assay using MDCK cells. Results are presented as mean ± SEM and are representative of three independent experiments. *, p < 0.05 and **, p < 0.001, compared the value of rgG1-NP-D210E with rgG1-WT.