The primary receptor for human immunodeficiency virus (HIV) is the CD4 molecule; however, in vitro evidence suggests that a neutral glycolipid, galactosyl ceramide (GalCer) or a derivative molecule, 3' sulfogalactosyl ceramide (GalS), may serve as an alternative receptor for HIV type 1 (HIV-1) in cells of neural and colonic origin. Biochemical studies have demonstrated that recombinant gp120 envelope protein binds to GalCer/GalS in both solid- phase enzyme-linked immunosorbent assay and high-performance thin-layer chromatography overlays. We have used the SK-N-MC cell line, a CD4-negative, GalCer/GalS-positive cell line previously characterized as susceptible to HIV-1 infection, to identify virus isolates with either a positive infection phenotype, HIV(HxB2), or a negative infection phenotype, HIV-189.6. Using a solid-phase virus binding assay, we determined the level of restriction in HIV-189.6 infection to be at the level of virus-glycolipid binding. Furthermore, using HIV-1(HxB2)-HIV-189.6 chimeras, we have identified a 193-amino-acid fragment from the envelope region of HIV-1(HxB2) containing the V3, V4, and V5 regions which confers a positive infection phenotype on the HIV-189.6 background. Recombinant viruses which separate this 193- amino-acid fragment into two distinct chimeras are each able to confer a positive infection phenotype on the background of HIV(89.6), suggesting that a stable GalCer/GalS-envelope interaction is dependent on the conformation of the envelope protein in the context of the viral membrane. Alternatively, the GalCer/GalS-gp120 bond may involve multiple sites on the oligomeric envelope protein.
ASJC Scopus subject areas
- Insect Science