Table 1. Hemagglutination inhibition reactions of reassortant viruses containing single or multiple mutations.

Reference virus	Pass.	Subtype	Ferret antisera
			A/Anhui/1/2013
A/Anhui/1/2013 (reassortant virus)	E4	H7N9	320
Mutated viruses
S128N	E3	H7N9	320
L177I	E3	H7N9	320
N47H	E3	H7N9	320
133NGS	E3	H7N9	160
133NGS+S128N	E2	H7N9	80
133NGS+S128N+L177I	E2	H7N9	160
133NGS+S128N+N47H	E2	H7N9	160

Abbreviation: Hemagglutination inhibition assay, HI. Two independent experiments were performed for the seven reassortant viruses in this study. HI titers of two testing results were same indicating good inner laboratory reproducibility of antigenic analysis in this study.