Immunofluorescent staining of Gag in a HIV-1-infected macrophage. Monocyte-derived-macrophages were infected with HIV-1 NLAD8 pseudotyped with VSV-G. At day 7 post-infection, cells were fixed, permeabilized and stained with a rabbit antiserum anti-HIV-1 p17 (AIDS Research and Reference Reagent Program, Division of AIDS, NIAID, NIH, from Dr. Paul Spearman) revealed by goat anti-rabbit antibodies conjugated to Alexa Fluor 488. A three dimensional reconstruction built from an 8 μm thick section (0.5 μm between planes) is presented. It has been generated using the Nikon A1R Confocal laser microscope system. The macrophages often appear with this typical shape in "sunny side up egg" where the nucleus is a small part of the "yolk". The Gag staining appears rich and complex; there is a diffuse cytosolic staining, some structures with intense staining located in the "yolk" which may correspond to the viral assembly compartments, and very small dots scattered everywhere which could correspond to free virions or Gag multimers (the microscope resolution is not good enough to estimate their precise size). Scale bar, 5 μm.