FIG 6.

Stability at 50°C of selected HA mutants. Shown are the virus titers (A and B) and HA titers (C and D) of the HA mutants selected from the mutant virus library screen and the parental H5HA-N224K+Q226L/CA04 virus after three rounds of treatment at 50°C. HA mutants further characterized for fusion and receptor-binding activity are shown in panels A and C. The mutants that were not characterized further are shown in panels B and D. A “+” indicates that the HA protein encodes the respective amino acid change(s) in the background of H5HA-N224K+Q226L.