FIG. 4.

Alignment of HA1 amino acid sequences of the swine H3N2 influenza viruses from 1970 to 2006. The underlined residues are antigenic sites (lowercase letters indicate discrete antigenic sites), residues in green are potential glycosylation sites, and residues in yellow shade denote the receptor-binding sites. Swine influenza viruses of different lineages are indicated by different colors, as shown in Fig. 1.