ALPHA(1)-ACID GLYCOPROTEIN BINDS HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1 (HIV-1) ENVELOPE GLYCOPROTEIN VIA N-LINKED GLYCANS

In the present study, we demonstrate a specific low-affinity interacti on between recombinant precursor gp160 (rgp160) or surface unit gp120 (rgp120) of human immunodeficiency virus type 1 (HIV-1) and alpha(1)-a cid glycoprotein (AGP), a human glycoprotein displaying complex type N -glycans. Binding of rgp160/rgp120 to agarose-coupled AGP was dose-dep endent, saturable, calcium-, pH- and temperature-dependent. Binding wa s inhibited by soluble AGP, asialo-AGP, fetuin, beta-D-GlcNAc(47)-BSA, alpha-D-Man(20)-BSA, mannan, complex-type asialo-agalacto-tetraantena ry precursor oligosaccharide from human AGP and oligomannose 9 from po rcine thyroglobulin; fully deglycosylated AGP was not inhibitory. The three AGP glycoforms separated on immobilized ConA bound rgp160 to the same extent as did unfractionated AGP. These findings extend our prev ious results on the carbohydrate-binding properties of HIV-1 envelope (Env) glycoprotein in that they demonstrate the involvement of AGP gly can moieties in the binding to rgp160/rgp120. Preincubation of rgp160 with AGP or mannan significantly reduced its binding to monocyte-deriv ed macrophages (MDM), suggesting that AGP may play a role in preventin g binding of soluble or virus-bound Env glycoprotein to CD4(+) monocyt ic cells.