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. 2021 Nov 9;95(23):e02379-20. doi: 10.1128/JVI.02379-20

FIG 2.

FIG 2

Competitive HAI assay using sera from preimmune animals infected with seasonal and pandemic H1N1 virus strains. (A to C) The extent of HAI titer reduction through competitive HAI. HAI titer of antisera from ferret infected with H1N1 seasonal (Chile/83 and Sing/86) and pandemic (CA/09) influenza virus strains following preabsorption with the corresponding rHAΔSA protein representing seasonal (Chile/83 and Sing/86) or pandemic (CA/09) virus strains. Differences in HAI titer were analyzed using a paired t test (***, P < 0.0001). Dotted lines represent the 1:40 HAI titer threshold. (D) The fold change in HAI activity for the same serum samples following preabsorption with rHAΔSA protein representing seasonal (Chile/83 and Sing/86) or pandemic (CA/09) virus strains. The dotted line represents the 4-fold change in the HAI titer.