Membrane glycolipids and human immunodeficiency virus infection of primary macrophages

The membrane glycolipids galactosylceramide (GalCer) and sulfatide (SGalCer) have been reported to act as receptors of human immunodeficiency virus (HIV) on CD4- cell lines. We show here that these glycolipids are present on CD4+ cells purified from human blood and on in vitro-differentiated monocyte-derived macrophages (MDMs). We investigated the role they could play in HIV infection. Glycolipids of MDMs were characterized at the molecular level by immunolabeling and thin-layer chromatography immune overlay, using a panel of human-, rabbit-, or murine-specific antibodies. GalCer and SGalCer were expressed at the surface of MDMs as assessed by indirect immunofluorescence and flow cytometry analysis, and they could be characterized with specific antibodies in the cellular glycolipid extracts in addition to GM1, GM3, and GD1b gangliosides. Recombinant 125-I-labeled gp160 specifically bound to GalCer, SGalCer, GM1, and GM3 as well as to phospholipids (phosphatidylethanolamine and phosphatidylserine) from MDM extracts. Anti-SGalCer monoclonal antibodies (MAbs), but not anti-GalCer antibodies, entailed limited (30-40%) but significant inhibition of gp160 binding to MDMs. However, the four human anti-SGalCer MAbs and the three murine or rabbit ant-GalCer antibodies tested did not inhibit HIV infection of MDMs, in contrast to CD4 antibody anti-Leu3a tested in parallel. These findings suggests that although HIV envelope glycoprotein can bind to SGalCer and GalCer from CD4+ MDM extracts, these glycolipids do not apparently act as HIV coreceptors nor are they involved in HIV infection of these cells.