FIG 4.

Investigation of the conformational stability of prefusion CDV F variants. (A) Vero cells were transfected with standard- or variant-expressing plasmid DNA. Immunofluorescence (IF) and flow cytometry were performed as described in the legend to Fig. 1H. In some experiments, brief heat shocks (10 min at the indicated temperatures) were performed prior to IF. (B) Syncytium formation assay. Cell-cell fusion induction after cotransfection of Vero-cSLAM cells with plasmid DNA encoding mutant CDV F proteins and CDV H. In some experiments, the cells were incubated overnight at 30 or 25°C. Representative fields of view were captured with a confocal microscope (Olympus FluoView FV1000) 24 h (30°C) or 48 h (25°C) posttransfection.