Purification step, yield, and flagellin bioactivity^a of candidate vaccines.

a<p>flagellin bioactivity was assessed by measuring secreted IL-8 with a sandwich ELISA (BD Biosciences) as previously described <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0020928#pone.0020928-Song1" target="_blank">[9]</a>. HEK293 cells in 96-well plates (n = 9) were stimulated with 278 ng/ml of each vaccine candidate for 16–18 hours at 37°C. IL-8 concentrations in medium were calculated from an IL-8 standard curve, and expressed as means ± SDs. IL-8 levels of cell control samples were < = 30 pg/ml.