Figure 8.

Replication levels and viral RNA synthesis of the recombinant viruses. (A) In vitro growth characterization of the wild-type and mutant viruses in DF-1 cells. DF-1 cells were infected with the indicated viruses at a multiplicity of infection (MOI) of 0.01, and the virus titers were determined at the indicated time points. Asterisks indicate a statistically significant difference in the titers of the chimeric virus and the parental virus. (B and C) Viral RNA synthesis in rNDV-NP_E402A- and rNDV-WT-infected cells. DF-1 cells were infected with rNDV-WT or rNDV-NP_E402A at a MOI of 0.01, and total RNA was purified from infected cells at 12, 24, and 36 h post-infection. Levels of RNA corresponding to the nucleoprotein (B) and phosphoprotein (C) segments of Newcastle disease virus were measured in virus-infected cells by quantitative real-time PCR. RNA levels were normalized to those of GAPDH. P-values were calculated based on a two-tailed, unpaired t-test (95% confidence levels). *P = 0.01–0.05; **P = 0.001–0.01; ***P = 0.0001–0.001. n = 3.