Experiments were performed using BSR, BFAE, CPT-Tert or C6/36 cells cultured in two-well glass chamber slides (Lab-Tek, Nalge Nunc International). Cells were either transfected with appropriate plasmids or infected with various BTV strains at a MOI between 0.01 and 1.5. Cells were washed with PBS and fixed with 5% formaldehyde for 15 minutes. The fixed cells were then processed as described previously [39] and incubated with the appropriate antisera. Secondary antibodies were conjugated with Alexa Fluor 488 (Invitrogen, Molecular Probes) or Alexa Fluor 594 (Invitrogen, Molecular Probes). Slides were mounted using VECTASHIELD Mounting Medium with DAPI (49,6-diamidino-2-phenylindole, Vector Laboratories). Slides were analysed and images collected using a Leica TCS SP2 confocal microscope.