Figure 2. Characterization of recombinant influenza viruses.

(A) Multiple-cycle growth curves of recombinant viruses on MDCK cells. MDCK cells were infected at a multiplicity of infection (MOI) of 0.001. The virus titers were measured by TCID₅₀. The data shown are means ± SD for triplicate wells at each time point. Statistical significance (p>0.05). (B) SDS-PAGE analysis of expression of NA proteins in recombinant viruses. Concentrated viruses were resuspended with SDS-PAGE sample loading buffer, incubated at 37°C for 30 min, and heated at 100°C for 1 min. The protein was separated by 12% SDS-PAGE, gels were stained with coomassie brilliant blue G250.