FIG 2.

Viral polymerase activity and growth kinetics. (A) Polymerase activities of the viral RNP complex in a minigenome assay. The luciferase reporter plasmid p-Luci and internal control plasmid Renilla were transfected into 293T cells, together with PB2, PB1, PA, and NP plasmids. After 24 h, cell lysates were used to measure firefly and Renilla luciferase activities. The values shown are means ± standard deviations of results for three independent experiments and were standardized to the activity of rDK1, rSY, or rJS285 (as 100%), respectively. The value of each reassortant virus was compared with that of the corresponding parental virus. *, P < 0.05; **, P < 0.01. (B to D) Viral growth kinetics in MDCK and A549 cells. Cells were inoculated at a multiplicity of infection of 0.01, and virus titers in supernatants were determined as the number of 50% tissue culture infectious doses (TCID₅₀) per ml in MDCK cells at the indicated time points. Averages of triplicate experiments are shown, with error bars representing the standard deviations. *, the value for the corresponding virus was significantly different (P < 0.05, based on analysis of variance) from that of the rDK1 (B), rSY (C), or rJS285 (D) virus, respectively.