FIG 5.

Functionality of GhV-F⁽⁺¹⁾ variants in syncytium formation and virus infectivity assays. Human U87 glioblastoma cells were transfected in duplicate with plasmids encoding the GhV-F⁽⁺¹⁾ variants and GhV-G proteins at a 1:1 ratio. (A) Cells were fixed and stained with Giemsa at 30 h posttransfection. Representative images are shown. (B) Quantification of fusogenicity of GhV-F and GhV-G proteins. The images were quantified by manually counting nuclei in syncytia in each field using ImageJ software. Results are presented as means and SD from 10 fields per condition. (C) GhVpp infectivity. Purified GhVpp were produced as described for Fig. 4, and 5 μl was used to infect U87 cells. Infections were performed in triplicate. Infected cells were lysed and assayed for Renilla luciferase activity at 24 hpi. Activity was measured in relative luciferase units (RLU), and data are presented as means and SD. Statistical significance of differences between values for the GhV-F′ pseudotypes and the other groups was determined by a two-tailed Student t test followed by the Holm step-down procedure for multiple comparisons (*, P < 0.01).