FIG 5.

Substitutions at residue 145 modulate serum reactivity. Antibody responses to H3 viruses carrying amino acid substitutions at residue 145 was determined by ELISA using swine antisera generated against OH/04 (A), NY/11 possessing HA residue 145 N (B), or IA/14 possessing HA residue 145 K (C). Two sets of sera were tested independently. The first set of sera was tested 2 times in duplicates. The second set of sera was tested only once in duplicate. Plotted data represent means ± standard deviations (SD). O.D., optical density.