The envelope glycoprotein gp120 of the human immunodeficiency virus (HIV), the causative agent of AIDS, contains approx 24 potential sites forN-glycosylation (Asn-X-Ser/Thr, X≠Pro) (1), all of which are utilized and constitute about 50% of the molecular mass (2). Binding of gp120 to the CD4 molecule is an initial step in viral infection of cells bearing the CD4 molecule on the surface, and fusion of HIV-infected cells with uninfected CD4-positive cells (3).
