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Figure 2 | Virology Journal

Figure 2

From: Mutations at positions 186 and 194 in the HA gene of the 2009 H1N1 pandemic influenza virus improve replication in cell culture and eggs

Figure 2

Yield of A/CA/04/2009, A/PR/8/34, and reverse genetics viruses bearing the A/CA/04/2009 NA and selected HA genes, as described in Fig. 1. A. Infectious titer of virus produced by MDCK cell monolayers infected at an MOI of 0.05 in 6-well plates, as determined by focus formation assay (FFA) on MDCK cells [21]. Cells were incubated at 37°C for the indicated times, after which 200 μl of the culture medium was sampled and stored at 4°C for infectious titer determination on MDCK cells using a slight modification of previously described FFA methods [21]. Data shown are the mean and standard deviation (S.D.) from one of three representative experiments. B. HA titers of MDCK-derived virus samples collected from the experiment in panel A, determined using standard methods [22]. Data shown are from one of three representative experiments. C. Infectious titers of virus produced by twelve- to fourteen-day-old embryonated chicken eggs infected with 100 μl of the indicated virus stocks containing 10,000 infectious units (as determined by FFA). The eggs were incubated for 72 hrs at 34°C after infection, and titers were determined as described for panel A. Mean and S.D. from four independent experiments are shown, with 2-4 eggs used for each virus in each experiment. D. HA titers of egg-derived virus samples collected from the experiment in panel C. Mean and S.D. from four independent experiments are shown.

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