Phylogenetic analysis of the nucleotide sequences of the HA coding region of A(H3N2).

<p>Sequences of randomly selected samples from this study (n = 62) (designated A/Thailand/CU and denoted in colored dots) and those identified in Thailand from the databases during 2016–2017 (n = 29) were compared to the A(H3N2) vaccine and reference strains of known clades reported by the WHO and others (squares). The phylogenetic tree was constructed using the maximum likelihood method and HKY+G model with 1,000 bootstrap replicates implemented in MEGA (version 6). Branch values of >70% are indicated at the nodes. Dominant epitope (A-E) determined for each sequence are marked with different colored dots (A = yellow, B = pink, C = purple, D = green, and E = blue). The signature amino acid substitutions (colored) occurring on the antigenic epitopes are also shown. Scale bar represents approximately 0.5% nucleotide difference between close relatives. Residue numbers are specific for HA1 (color-coded by epitope) and HA2 (dark blue). The vaccine strain A/Hong Kong/4801/2014 belonged to 3C.2a clade. Shaded area (Group V) highlights strains of interest.