FIG 4.

Cell population-based infections with OP7 seed viruses. (A) Infectivity and vRNA content of OP7 and PP seed viruses (from Fig. 3A and C, respectively). Infectious virus titers were quantified by a TCID₅₀ assay, and purified vRNAs from virions were quantified by real-time RT-qPCR. Data were used to calculate fractions of infectious virus and numbers of vRNAs per virion based on the virus particle concentration (derived from the HA titer). Normalization of vRNAs per virion was based on PR8-RKI virus (as a reference). (B) Outcome of high-MOI experiments using the seed viruses shown in panel A. MDCK cells, infected at an MOI of 10, were assayed for the per-cell vRNA content at 12 hpi. Infectivity and vRNAs per virion are given for produced virions. Infection experiments with PR8-RKI and PR8-NIBSC viruses were performed in independent experiments (n = 3) and once with each OP7 and PP seed virus. Error bars indicate standard deviations of depicted mean values.