FIG 5.
Three representative P9 viral clones exhibited enhanced replication in MDCK and A549 cells. Viable virus output from MDCK (A) or A549 (C) cells infected with three viruses derived from the P9 infection (L2, N9, and L18) and parental rH1N1 viruses, at an MOI of 0.001, was determined by TCID50 assay at 12, 24, 36, 48, 60, and 72 hpi. The values are expressed as means ± SD (n = 3). An asterisk indicates that the value of the corresponding virus was significantly different from that of the rH1N1 virus (P < 0.05 by ANOVA). (B) Western blots for viral NP detection in MDCK cells at 12 and 24 hpi; β-actin was used as a loading control. The Western blot results are representative of three independent experiments.