The involvement of dynamin in BTV-1 entry and infection was investigated using a DN mutant of the 'aa' splice variant of dynamin-2 [3, 54, 55] . BHK cells were transiently transfected to express GFP-wt 'aa' dynamin-2, or GFP-DN 'aa' dynamin-2. At 12 h post-transfection, the cells were incubated with Alexa-568 labelled transferrin for 15 minutes or with BTV-1 for 0.5 h. The cells were then fixed and processed for confocal microscopy (Fig. 4) . Virus was detected using PM10 (anti-VP5) and an Alexa-568 conjugated secondary antibody. Cells expressing wt or DNdynamin-2 were identified by the GFP fusion tag and are shown in green. The cells expressing GFP-DN-dynamin-2 showed transferrin uptake at a lower frequency than cells expressing the wt construct ( Fig. 4A-D and 4I) indicating a block to clathrinmediated endocytosis. In contrast, BTV-1 was taken up normally by cells expressing DN-dynamin-2 ( Fig. 4E-H and 4I ).