FIG 2.

Isolation of HA mutants with increased heat stability. (A) Schematic diagram of the selection strategy used. The mutant virus library was subjected to three consecutive rounds of heat treatment, resulting in the selection of variants with increased heat stability. Likewise, the parental virus was subjected to three rounds of heat treatment (not shown here). (B) The mutant virus library and parental stock of H5HA-N224K+Q226L/CA04 underwent three consecutive heat treatments at 50°C for the indicated times. Shown are the means and standard deviations at each time point (plaque assay in AX4 cells in triplicate).