Fig 1.

Role of HN in initiating the activation of F: requirement for site II stimulation for F activation. Monolayers of 293T cells coexpressing NDV wt HN and wt F were allowed to bind to receptor-bearing RBCs at 4°C in the absence (A) or presence (B) of 2 mM zanamivir. Upon transfer to 37°C, medium without (A) or with (B) 2 mM zanamivir was added. Values on the y axis reflect quantitation of RBCs that were released, bound, or fused. The values are means ± standard deviation (SD) of experiments performed in triplicate.