Glycosylation Patterns of HIV-1 gp120 Depend on the Type of Expressing Cells and Affect Antibody Recognition
ABSTRACT Human immunodeficiency virus type 1 (HIV-1) entry is mediated by the interaction between a variably glycosylated envelope glycoprotein (gp120) and host-cell receptors. Approximately half of the molecular mass of gp120 is contributed by N-glycans, which serve as potential epitopes and may shield gp120 from immune recognition. The role of gp120 glycans in the host immune response to HIV-1 has not been comprehensively studied at the molecular level. We developed a new approach to characterize cell-specific gp120 glycosylation, the regulation of glycosylation, and the effect of variable glycosylation on antibody reactivity. A model oligomeric gp120 was expressed in different cell types, including cell lines that represent host-infected cells or cells used to produce gp120 for vaccination purposes. N-Glycosylation of gp120 varied, depending on the cell type used for its expression and the metabolic manipulation during expression. The resultant glycosylation included changes in the ratio of high-mannose to complex N-glycans, terminal decoration, and branching. Differential glycosylation of gp120 affected envelope recognition by polyclonal antibodies from the sera of HIV-1-infected subjects. These results indicate that gp120 glycans contribute to antibody reactivity and should be considered in HIV-1 vaccine design.
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ABSTRACT: A highly glycosylated, trimeric envelope glycoprotein (Env) mediates HIV-1 cell entry. The high density and heterogeneity of the glycans shield Env from recognition by the immune system, but paradoxically, many potent broadly neutralizing antibodies (bNAbs) recognize epitopes involving this glycan shield. To better understand Env glycosylation and its role in bNAb recognition, we characterized a soluble, cleaved recombinant trimer (BG505 SOSIP.664) that is a close structural and antigenic mimic of native Env. Large, unprocessed oligomannose-type structures (Man8-9GlcNAc2) are notably prevalent on the gp120 components of the trimer, irrespective of the mammalian cell expression system or the bNAb used for affinity purification. In contrast, gp41 subunits carry more highly processed glycans. The glycans on uncleaved, non-native oligomeric gp140 proteins are also highly processed. A homogeneous, oligomannose-dominated glycan profile is therefore a hallmark of a native Env conformation and a potential Achilles' heel that can be exploited for bNAb recognition and vaccine design. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.Cell Reports 06/2015; DOI:10.1016/j.celrep.2015.05.017 · 7.21 Impact Factor
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ABSTRACT: Plasmacytoid dendritic cells (pDCs) play a vital role in activation of anti-HIV-1 immunity, and suppression of pDCs might mitigate immune responses against HIV-1. HIV-1 gp120 high-mannose has been attributed immunosuppressive roles in human myeloid DCs, but no receptors for high-mannose have so far been reported on human pDCs. Here we show that upon activation with HIV-1 or by a synthetic compound triggering the same receptor in human pDCs as single-stranded RNA, human pDCs upregulate the mannose receptor (MR, CD206). To examine the functional outcome of this upregulation, inactivated intact or viable HIV-1 particles with various degrees of mannosylation were cultured with pDCs. Activation of pDCs was determined by assaying secretion of IFN-alpha, viability, and upregulation of several pDC-activation markers: CD40, CD86, HLA-DR, CCR7, and PD-L1. The level of activation negatively correlated with degree of mannosylation, however, subsequent reduction in the original mannosylation level had no effect on the pDC phenotype. Furthermore, two of the infectious HIV-1 strains induced profound necrosis in pDCs, also in a mannose-independent manner. We therefore conclude that natural mannosylation of HIV-1 is not involved in HIV-1-mediated immune suppression of pDCs.Molecular Immunology 06/2014; 59(2):180–187. DOI:10.1016/j.molimm.2014.02.009 · 3.00 Impact Factor
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ABSTRACT: Neutralization properties of human immunodeficiency virus (HIV-1) are often defined using pseudoviruses grown in transformed cells, which are not biologically relevant HIV-1 producer cells. Little information exists on how these viruses compare to viruses produced in primary lymphocytes, particularly for globally relevant HIV-1 strains. Therefore, replication-competent chimeras encoding envelope variants from the dominant HIV-1 subtypes (A, C, and D) obtained early after infection were generated and the neutralization properties explored. Pseudoviruses generated in 293T cells were the most sensitive to antibody neutralization. Replicating viruses generated in primary lymphocytes were most resistant to neutralization by plasma antibodies and most monoclonal antibodies (b12, 4E10, 2F5, VRC01). These differences were not associated with differences in envelope content. Surprisingly, the virus source did not impact neutralization sensitivity of most viruses to PG9. These findings suggest that producer cell type has a major effect on neutralization sensitivity, but in an antibody dependent manner.Virology 02/2012; 427(1):25-33. DOI:10.1016/j.virol.2012.02.001 · 3.28 Impact Factor