Fig 3.

Chimeric proteins containing the NiV G stalk domain and the NDV globular head are efficiently expressed and can activate NiV F-mediated fusion. (A) Schematic diagram of chimera NiV-NDV. The stalk region is derived from residues 1 to 180 or residues 1 to 186 of NiV G, and the globular head is derived from residues 124 to 571 of NDV HN. (B) FACS analysis of cell surface expression from cells transfected with the chimeric proteins shown in Fig. 1A. The results are presented as percentages of NDV HN cell surface expression. (C) Receptor binding in the absence (□) or presence (■) of 2 mM zanamivir. (D) Neuraminidase activity of the receptor binding proteins, expressed in relative fluorescence intensity units (RFU) in the absence (□) or presence (■) of 2 mM zanamivir. The values in panels B, C, and D are means ± the standard deviations (SD) of results from samples assessed in triplicate and are representative of the experiment repeated at least three times. (E) Cell-to-cell fusion promoted by the chimeric proteins coexpressed with NiV F is observed in the top panel by syncytium formation using visible microscopy and in the bottom panel by redistribution of RFP (red fluorescent protein) using fluorescence microscopy.