Figure 3

Fusogenic activity of RVFV Gn and Gc proteins. A) Insect cells were infected with a baculovirus expressing RVFV N, Gn and Gc for 24 hours and a monoclonal antibody against baculovirus gp64 were added to the media. After 2 hours the media was replaced with low pH media (pH 5.0) for two minutes and then replaced with normal media (right, upper panel). As controls, infected cells expressing RVFV proteins were kept at normal pH media of 6.5 (left, upper panel). As negative control, infected insect cells expressing BTV VP2 protein were included and pH shift was performed (right, lower panel) or the media was kept at neutral pH (left, lower panel). Pictures were taken at 200× magnification. B) Quantification of fusion capacity. The number of syncytia per field was counted by visual microscopy at 400× magnification and the average and standard deviation were calculated. Each assay was performed in triplicate.