Raising endosomal pH may prevent receptor recycling, which could deplete the cell surfaces of attachment receptors and thereby reduce infection. However, the pattern of virus uptake by concanamycin-A treated cells (detected at 0.5 h post-uptake by confocal microscopy using the PM10 antibody) was indistinguishable from mock-treated cells (data not shown), indicating that the inhibitory effect of concanamycin-A on infection was not due to a failure of the virus to be internalised.