New insights into the interaction between the gp120 and the HIV receptor in human sperm (human.sperm/gp120/galactoglycerolipid/antigalactosylceramide/seminolipid/spermatogonia)

The human immunodeficiency virus (HIV) can infect some cell types which lac k CD4. Galactosylceramide, a glycolipid present in the nervous system and c olonic epithelial cells, has been implicated in the virus entry in these ce lls. Our data demonstrate that the HIV surface glycoprotein gp120 binds to the galactosyl-alkyl-acylglycerol (GalAAG), a glycolipid structurally relat ed to galactosylceramide present on the surface membrane of the spermatozoa . In this paper, we review our previous data and further confirm the specif icity of the interaction between this galactoglycerolipid and the gp120. Co nsistent with the structural similarity to galactosylceramide, the sperm Ga lAAG is capable of specifically binding the gp120. The specificity of the b inding of antibodies anti-galactosylceramide and the gp120 to the sperm ext ract and to the purified GalAAG fraction prepared from the same extract has been demonstrated utilizing an ELISA assay which favors sensitivity and sp ecificity. Immunofluorescence and immunoelectron microscopy data show a dif ferent localization for the GalAAG and its sulfated form the seminolipid (S GalAAG). The GalAAG is preferentially localized in the equatorial segment a nd the middle piece of the sperm tail, while the seminolipid is widely dist ributed on the membrane of the spermatozoa. These data indicate that human sperm express on their surface membrane a glycolipid similar in structure t o galactosylceramide, the receptor for HIV identified in the CD4(-) cells, that could function as a HIV receptor and possibly be implicated in its tra nsmission. (C) 1998 Elsevier Science Ireland Ltd. All rights reserved.