Impact of NA mutations on sialidase activity.

Shown is the NA activity of Egyptian H5N1 viruses carrying different mutations against MUNANA (A-G) and fetuin (H). The experiments were done in three independent runs. The relative NA activity of different virus dilutions (y-axis) is compared to rg-AL (A-G). The p-values shown in the graphs refer to the statistical significance of the 50% NA-activity (shown as dashed lines) of indicated viruses compared to rg-AL (A-G). The activity of different viruses against fetuin in ELLA assay was calculated after adjustment of the absorbance (OD490) of rg-AL to 100%. The results are expressed as relative mean and standard deviation of three replicates (H). Asterisks refer to statistical compared to rg-AL at p value < 0.05. Viruses were adjusted to 32 HA units using chicken erythrocytes (and similar results were obtained after adjusting titers to plaque forming units).