Figure 6: Comparison of the growth rate of H3N2 A/Guangdong/ST798/2008 strains carrying either 526R or 526K PB2 in mixed cultures.

(a) MDCK cells or (b) A549 cells were infected at an MOI of 0.001 with a mixture (1:1) of wild-type (WT) (PB2-526R) and variant (PB2 R526K) A/Guangdong/ST798/2008 and sequentially passaged four times. At each passage viral RNA was isolated from cell culture supernatants at 48 h post infection, and the PB2 gene amplified by RT-PCR and sequenced. The genetic code for WT PB2-526R is AGA; variant PB2 526K is AAA. The DNA sequence chromatograms shown are from one of the three MDCK (a) and one of the four A549 (b) experiments in which 526R outgrew 526K. Experiments were repeated four times.