Interaction of human immunodeficiency virus type 1 envelope glycoprotein gp120 with a galactoglycerolipid associated...

The expression of a molecule recognized by anti-galactosyl ceramide antibodies (MAb) O1 on the surface membrane of human spermatozoa was investigated by biochemical and immunochemical methods. Indirect immunofluorescence shows that this molecule is preferentially localized on the middle piece of the sperm tail. Immuno-thin-layer chromatography has identified it as a glycolipid related but not identical to galactosylceramide. Consistent with a structure similar to galactosylceramide, the sperm glycolipid is capable of binding gp120. An improved ELISA has been utilized to demonstrate the specificity of binding of the antibodies and gp120 to the isolated lipid fraction. Identity of the binding site of the two ligands to the glycolipid is suggested by competition assays. On the basis of preliminary biochemical analysis this glycolipid was tentatively classified as a galactosylalkylacylglycerolipid (GalAAG), the nonsulfated form of the seminolipid, a glycolipid known to be present in the testis and germ cells of mammals. These data indicate that human sperm express a glycolipid similar in structure to the receptor for HIV described on the CD4- neural and colonic epithelial cell lines, and moreover suggest that this glycolipid could also function as HIV receptor and possibly be implicated in its transmission.