FIG. 3.

The half time to peak yield of different subtypes of influenza virus in Vero cells is reduced by inclusion of the NS gene segment of Eng53/v-a. The HA and NA genes of contemporary human H1N1 and H3N2 viruses, contemporary avian H6N1 and H9N2 viruses, and PR8 were rescued on the master strains PR8 and PR8 containing the NS gene segment of Eng53/v-a (PR8/Eng-NS). Vero cell monolayers were infected with each virus at a MOI of 0.01, and the numbers of PFU in culture supernatants were determined at 12-h intervals. The average half times to peak titer shown were calculated from three independent experiments conducted with each virus; the error bars indicate the 95% confidence intervals.