Cos7 cells grown on glass coverslips in 24-well plates were transfected with 0.8 mg of plasmid DNA using Lipofectamine (Invitrogen, Germany). 48 hours after transfection the cells were fixed and permeabilized with ice cold methanol. Primary antibodies were then added. Unbound primary antibody was removed by three washing steps using PBS. Binding of the primary antibody was detected with the appropriate secondary antibody conjugated with FITC (fluorescein isothiocyanate) (Dako, Germany). Counterstaining of cell nuclei was done with DAPI (4',6diamidino-2-phenylindole). Images were collected using a Zeiss Axioplan 2 fluorescence microscope fitted with a Visitron Systems charge-coupled device camera (Puchheim, Germany). Images were processed using MetaView software and Adobe Photoshop. Antibodies: gB-specific human mab C23 (TI-23) [41] , gN-specific murine mab 14-16A [71] , gH-specific murine mab SA4 [72] , murine anti-HA (Sigma Aldrich, Germany) and murine anti-GST (BIOZOL, Germany).