Vector samples were diluted in 0.14 M NaCl, 0.05 M Tris-HCl buffer pH 8.2 (Tris-buffered saline, TBS), and adsorbed onto carbon-coated Formvar membranes on grids, and incubated with primary antibody (monoclonal anti-CAR or anti-gp64 antibody) at a dilution of 1:50 in TBS for 1 h at room temperature (RT). After rinsing with TBS, the grids were postincubated with 20-nm colloidal gold-tagged goat anti-mouse immunoglobulin G antibody (British Biocell International Ltd., Cardiff, UK; diluted to 1:50 in TBS) for 30 min at RT. After rinsing with TBS, the specimens were negatively stained with 1% uranyl acetate in H2O for 1 min at RT, rinsed again with TBS, and examined under a JEM1400 JEOL electron microscope equipped with an Orius-Gatan digitalized camera (Gatan, Grandchamp, France).