Fig 8.

Chimeric receptor binding proteins with mutation at NDV HN site II: expression, neuraminidase activity, and binding avidity. (A) FACS analysis of cell surface expression from cells transfected with the chimeric proteins described. The results are presented as percentages of NDV HN cell surface expression. (B) Neuraminidase activity of the receptor binding proteins, expressed in relative fluorescence intensity units (RFU) in the absence (clear bar) or presence (black bar) of 2 mM zanamivir. (C) A panel of RBCs with different degrees of receptor depletion was used to quantify HAD on cell monolayers expressing HPIV3-NDV R516A HN or NiV-NDV R516A HN in the absence or presence of 2 mM zanamivir at 4°C. The binding of each depleted RBC preparation (y axis) is expressed as a percentage of that of the control (i.e., of the amount of untreated, nondepleted RBCs bound to cells expressing the corresponding receptor binding protein). Data represent the means of results from triplicate monolayers from 3 representative experiments, with bars denoting standard deviations.