FIG 6.

Substitutions at residue 145 impact HI titers. HI titers were measured against H3 viruses carrying amino acid substitutions at residue 145 using swine antisera generated against OH/04 (cyan), NY/11 possessing HA residue 145 N (red) or IA/14 possessing HA residue 145 K (light green). For each panel, two sets of sera were tested independently. The first set of sera was tested 3 times in duplicates. Confirmatory tests were run on a second set of sera, which was tested once in duplicates. The serum reactivities of all H3 mutant viruses to the respective swine antisera are depicted as fold change (log₂ HI titer for mutant virus/log₂ HI titer for homologous virus). Plotted data represent means ± standard deviations (SD). Colors are based on the antigenic cluster designation for swine H3N2 IAVs.