Scanning electron microscopy imaging of HIV-1 capsids in the cytoplasm and at the nuclear membrane of infected cells. (A) Schematic representation of the mature HIV-1 capsid shell. The HIV-1 capsid is an assembly of approximately 1,500 CA monomers arranged into a hexagonal array of hexamers. Dimensions are derived from microscopy observations of mature virions or isolated cores. (B-D) Images show the backscattered gold signal corresponding to specific labelling with a mouse monoclonal anti-p24 antibody (183-H12-5C AIDS Reagent Program) followed with goat anti-mouse IgG H&L conjugated 10 nm gold (British Biocell International) in HIV-1 infected P4-CCR5 cells. HIV-1 capsids are typically conical- or cylindrical-shaped, ca 100-150 nm long, and heavily labelled with 10-30 immunogold particles. The bulk of antibodies likely induces some distortions in size and shape of capsids. In panels B and D, capsids are located at the nuclear membrane: nuclear pore complexes appear as bright rings with dark lumen.