N-linked oligosaccharides of simian immunodeficiency virus envelope glycoproteins are dispensable for the interaction with the CD4 receptor.

In contrast to others groups, we have previously shown that N-linked glycans of HIV-1 and HIV-2 envelope glycoproteins do not play a major role in the gp-CD4 interaction. In order to clarify these inconsistencies, we investigated the role of N-glycans in the interaction of SIV with the CD4 receptor. The inhibition of binding of radiolabeled SIV envelope glycoprotein (gp140) to CD4+ cells by increasing concentrations of soluble CD4 shows that the interaction occurred with high affinity (K0.5 = 1.4 x 10(-8) M). Treating SIV gp140 with endo F-N glycanase, with or without detergent, reduced its molecular mass from 140 to 75 KDa. This indicates that N-glycan represents about 50% of molecular mass of the glycoprotein. Interestingly, the fact that deglycosylated SIV gp140 as its native form bound significantly and specifically to CD4 receptor indicates that oligosaccharides of SIV gp140 are not required for the gp-CD4 interaction.