INTERACTION OF HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 ENVELOPE GLYCOPROTEIN GP120 WITH A GALACTOGLYCEROLIPID ASSOCIATED WITH HUMAN SPERM

The expression of a molecule recognized by anti-galactosyl ceramide an tibodies (MAb) O1 on the surface membrane of human spermatozoa was inv estigated by biochemical and immunochemical methods. Indirect immunofl uorescence shows that this molecule is preferentially localized on the middle piece of the sperm tail, Immune-thin-layer chromatography has identified it as a glycolipid related but not identical to galactosylc eramide. Consistent with a structure similar to galactosylceramide, th e sperm glycolipid is capable of binding gp120. An improved ELISA has been utilized to demonstrate the specificity of binding of the antibod ies 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 glycolip id was tentatively classified as a galactosylalkylacylglycerolipid (Ga lAAG), the nonsulfated form of the seminolipid, a glycolipid known to be present in the testis and germ cells of mammals. These data indicat e that human sperm express a glycolipid similar in structure to the re ceptor for HIV described on the CD4(-) neural and colonic epithelial c ell Lines, and moreover suggest that this glycolipid could also functi on as HIV receptor and possibly be implicated in its transmission.