Fig. 4.

Quantification of band intensities at the strip test line. (A–F) Intensities of the bands shown in Fig. 3 were quantified by ImageJ software. The intensities of the bands in the α2,3 Sia strips (blue circle) and α2,6 Sia strips (red triangle) were expressed relative to the maximum values for each virus, and plotted as a function of virus HAU titer. (A) Human H1N1 strain. (B) Human H3N2 strain. (C and D) Bird H5N1 strains. (E and F) H5N1 mutant strains with increased human-type receptor affinity. For the human H3N2 strain (B), the intensity values were calculated relative to the maximum values for the human H1N1 strain (A) that was analyzed at the same time. Each data point is the mean±SD of three independent experiments. (G and H) Scatter plots of virus binding affinity (x-axis) versus test line band intensity (y-axis) on α2,3 Sia strips (G) and α2,6 Sia strips (H). Virus binding affinity was measured as absorbance (630 nm) in virus binding assays. (For interpretation of the references to color in this figure legend, the reader is referred to the web version of this article.)