FIG 6.
pH1N1 mutant virus growth kinetics in human A549 cells. (A and B) Human A549 cells were infected (MOI of 0.1) in triplicates with the recombinant viruses encoding different variants of NS1 and PA proteins (NS1MUT/PAMUT, NS1MUT/PAWT, NS1WT/PAMUT, and NS1WT/PAWT) and incubated at 33°C (A) or 37°C (B). Virus titers in infected cell TCS were determined at the indicated hours postinfection by an immunofocus assay. *, P < 0.05 (NS1MUT/PAMUT versus NS1MUT/PAWT, NS1MUT/PAMUT versus NS1MUT/PAWT, and NS1MUT/PAMUT versus NS1WT/PAWT) using Student's t test (n = 3 per time point); ns, not significant (P > 0.05). (C and D) Human A549 cells were infected (MOI of 0.1) in triplicates with viruses isolated from two patients (ACU009 and ACU022) infected during the 2015–2016 season (43) and with the A/California/04/2009 strain and incubated at 33°C (C) or 37°C (D). Virus titers in infected cell TCS were determined at the indicated hours postinfection by an immunofocus assay. *, P < 0.05 (virus isolates ACU009 and ACU022 versus A/California/04/2009).