It has recently been shown that cargo internalised via caveolae can be delivered to acidic early-endosomes [17] . Caveolaemediated endocytosis is dependent on the integrity of lipid-rafts, and like other raft mediated endocytic pathways can be inhibited by cholesterol depletion [8, 20] . The effect of cholesterol depletion on BTV-1 infection was investigated using methyl-b-cyclodextrin (MbCD) which binds and extracts cholesterol from the plasma membrane. BHK cells were mock-treated or treated with MbCD for 0.5 h at 37uC. The cells were then incubated with filipin which binds cholesterol and can be detected by fluorescence microscopy. Filipin fluorescence was detected at the plasma membrane and within the cytosol of mock-treated cells (Fig. 3A) . In contrast, although fluorescence was detected within the cytosol, the intense plasma membrane fluorescence generated by filipin binding was greatly reduced by MbCD, indicating extensive and selective cholesterol depletion from the cell surfaces (Fig. 3B) .