To determine whether impairment of cholesterol efflux by HIV-1 infection leads to cholesterol accumulation and foam cell formation, we loaded macrophages (uninfected or infected with Nef-expressing or ΔNef HIV-1) with lipids by incubating with acetylated LDL (AcLDL) in the presence of apoA-I and stained cellular lipids with Oil Red O (Figure 6). This evidence concerns the gene APOA1 and HIV-1 infection.