Hemagglutinin amino acid substitutions in A/Vietnam/1203/04-like (H5N1) recombinant viruses generated in this study

aAmino acid numbering is based on H3 HA (Nobusawa et al., 1991, Virology, 182, 475–485).
Note: Underlined HA mutations caused an unstable phenotype. The genetic stability of recombinant H5N1 viruses was monitored by plaque assay and by sequencing of the HA and NA genes after transfection and after one passage in MDCK cells. Influenza virus was defined as genetically stable if it was able to replicate efficiently in the cell line used, maintain a homogeneous plaque phenotype, and did not contain additional subpopulations based on the sequence analysis of the HA and NA genes after one passage in MDCK cells. If different subpopulations were identified, those viruses were designated as unstable.