Marked Depletion of Glycosylation Sites in HIV-1 gp120 under Selection Pressure by the Mannose-Specific Plant Lectins ofHippeastrumHybrid andGalanthus nivalis

Abstract

The plant lectins from Hippeastrum hybrid (HHA) and Galanthus nivalis (GNA) are 50,000-D tetramers showing specificity for ␣-(1,3) and/or ␣-(1,6)-mannose oligomers. They inhibit HIV-1 infection at a 50% effective concentration of 0.2 to 0.3 g/ml. Escalating HHA or GNA concentrations (up to 500 g/ml) led to the isolation of three HIV-1(III B ) strains in CEM T cell cultures that were highly resistant to HHA and GNA, several other related mannose-specific plant lectins, and the monoclonal antibody 2G12, modestly resistant to the mannose-specific cyanovirin, which is derived from a blue-green alga, but fully susceptible to other HIV entry inhibitors as well as HIV reverse transcriptase inhibitors. These mutant virus strains were devoid of up to seven or eight of 22 glycosylation sites in the viral envelope glycoprotein gp120 because of mutations at the Asn or Thr/Ser sites of the N-glycosylation motifs. In one of the strains, a novel glycosylation site was created near a deleted glycosylation site. The affected glycosylation sites were predominantly clustered in regions of gp120 that are not involved in the direct interaction with either CD4, CCR5, CXCR4, or gp41. The mutant viruses containing the deleted glycosylation sites were markedly more infectious in CEM T-cell cultures than wild-type virus.

Consistent Patterns of Change during the Divergence of Human Immunodeficiency Virus Type 1 Envelope from That of the Inoculated Virus in Simian/Human Immunodeficiency Virus-Infected Macaques

“…The one exception was animal L97191, which had the highest viral load set point but whose viral population was only 0.3% divergent from the inoculum at 32 wpi. In contrast, only one of the four animals with low viral set points (Ͻ10 4 RNA copies/ml) developed quasispecies that diverged from the inoculum. The control animals and those that received ineffective vaccines (DNA-DNA or DNA-protein) tended to be the animals with higher viral loads and greater divergence of their quasispecies.…”

“…Six of the seven macaques with high viral set points (Ͼ10 4 RNA copies/ml) developed quasispecies that diverged from the inoculum ( Table 1). The one exception was animal L97191, which had the highest viral load set point but whose viral population was only 0.3% divergent from the inoculum at 32 wpi.…”

“…In contrast, macaques that received DNA priming and either DNA or protein boosting neither controlled viremia nor maintained their CD4 ϩ T-cell counts. Eleven macaques from this study were chosen as representative of each vaccine group; seven of the animals were not protected from CD4 ϩ T-cell decline and had high viral load set points (Ͼ10 4 RNA copies/ml), and four of the animals were protected from CD4 ϩ T-cell decline and had lower viral load set points (Ͻ10 4 RNA copies/ml) ( Table 1).…”

An oligosaccharide-based HIV-1 2G12 mimotope vaccine induces carbohydrate-specific antibodies that fail to neutralize HIV-1 virions

“…Glycosylation on gp120 can account for Ͼ50% of the molecular mass (28), and it is known that multiple N-linked glycosylation sites are associated with 2G12 binding (11,29). 2G12-resistant viruses have been shown to associate with mutations in these glycosylation sites (30,31), and a recent study using such viruses has suggested that the antibody's antiviral efficacy across clades may be narrower than originally claimed (32). Sequence analysis indicated that three glycosylation sites (N295, N332, and N392) were critical for interaction while several others contributed to binding (12).…”

Fundamental Difference in the Content of High-Mannose Carbohydrate in the HIV-1 and HIV-2 Lineages

“…GNA and HHA inhibit the replication of HIV-1 and SIVmac251, and uncloned, resistant populations of virus have been selected (3,14). In this report, we define two N-linked sites in the external surface glycoprotein gp120 and one in the transmembrane glycoprotein gp41 whose mutation imparts high-level resistance to the inhibitory effects of GNA and HHA to cloned SIVmac239.…”