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Mapping the complete glycoproteome of virion-derived HIV-1 gp120 provides insights into broadly neutralizing antibody binding

View Article: PubMed Central - PubMed

ABSTRACT

The surface envelope glycoprotein (SU) of Human immunodeficiency virus type 1 (HIV-1), gp120SU plays an essential role in virus binding to target CD4+ T-cells and is a major vaccine target. Gp120 has remarkably high levels of N-linked glycosylation and there is considerable evidence that this “glycan shield” can help protect the virus from antibody-mediated neutralization. In recent years, however, it has become clear that gp120 glycosylation can also be included in the targets of recognition by some of the most potent broadly neutralizing antibodies. Knowing the site-specific glycosylation of gp120 can facilitate the rational design of glycopeptide antigens for HIV vaccine development. While most prior studies have focused on glycan analysis of recombinant forms of gp120, here we report the first systematic glycosylation site analysis of gp120 derived from virions produced by infected T lymphoid cells and show that a single site is exclusively substituted with complex glycans. These results should help guide the design of vaccine immunogens.

No MeSH data available.


Visual representation of the HIV-1BaL gp120 secondary structure.Residue numbers for N-linked glycosylation sites are listed as both sequential numbering with respect to the experimentally deduced BaL sequence, and with the numbering with respect to the reference HIVHXB2 indicated in brackets. Individual sites are indicated as orange circles, with the sequential site number (1–24) shown within the circle. The three consensus sites of HXB2CG not present in this swarm are indicated with empty circles. The general type of glycosylation (high mannose, complex, hybrid) observed at each site is indicated by colour coding, with the key given within the figure.
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f5: Visual representation of the HIV-1BaL gp120 secondary structure.Residue numbers for N-linked glycosylation sites are listed as both sequential numbering with respect to the experimentally deduced BaL sequence, and with the numbering with respect to the reference HIVHXB2 indicated in brackets. Individual sites are indicated as orange circles, with the sequential site number (1–24) shown within the circle. The three consensus sites of HXB2CG not present in this swarm are indicated with empty circles. The general type of glycosylation (high mannose, complex, hybrid) observed at each site is indicated by colour coding, with the key given within the figure.

Mentions: Our work constitutes the first systematic glycoproteomic analysis of any virion-derived gp120 to include site specific analysis. Other workers23 have previously applied glycoproteomic methods to viral gp120 but the focus of their work was the development of an automated spectral-aligning strategy and they only reported on five glycosylation sites. As shown in Fig 5, the virion-derived gp120 we studied has 24 N-glycosylation sites. Compared to the canonical HIV-1HXB2 strain, it is missing 3 N-glycosylation sites in and near the V2 loop and has an additional site in the V1 loop (Fig. 5). Thirteen sites are exclusively occupied with oligomannose glycans (Fig.5; dark green annotations). An additional seven sites are almost entirely oligomannose together with a trace (<0.3%) of non-sialylated complex structures (Asn-129) or low levels (<1%) of hybrid structures (Asn-140, Asn-143, Asn-279, Asn-292, Asn-298 and Asn-304). Complex-type glycans are found in substantial amounts at four sites. Two of these, Asn-200 and Asn-460, additionally carry hybrid structures, although oligomannose glycans are not present. A single site, Asn-357, carries oligomannose, complex and hybrid glycans. All three glycan classes are present at this site in comparable amounts. Finally, one site, Asn-135, is exclusively occupied with sialylated multiantennary complex glycans.


Mapping the complete glycoproteome of virion-derived HIV-1 gp120 provides insights into broadly neutralizing antibody binding
Visual representation of the HIV-1BaL gp120 secondary structure.Residue numbers for N-linked glycosylation sites are listed as both sequential numbering with respect to the experimentally deduced BaL sequence, and with the numbering with respect to the reference HIVHXB2 indicated in brackets. Individual sites are indicated as orange circles, with the sequential site number (1–24) shown within the circle. The three consensus sites of HXB2CG not present in this swarm are indicated with empty circles. The general type of glycosylation (high mannose, complex, hybrid) observed at each site is indicated by colour coding, with the key given within the figure.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC5015092&req=5

f5: Visual representation of the HIV-1BaL gp120 secondary structure.Residue numbers for N-linked glycosylation sites are listed as both sequential numbering with respect to the experimentally deduced BaL sequence, and with the numbering with respect to the reference HIVHXB2 indicated in brackets. Individual sites are indicated as orange circles, with the sequential site number (1–24) shown within the circle. The three consensus sites of HXB2CG not present in this swarm are indicated with empty circles. The general type of glycosylation (high mannose, complex, hybrid) observed at each site is indicated by colour coding, with the key given within the figure.
Mentions: Our work constitutes the first systematic glycoproteomic analysis of any virion-derived gp120 to include site specific analysis. Other workers23 have previously applied glycoproteomic methods to viral gp120 but the focus of their work was the development of an automated spectral-aligning strategy and they only reported on five glycosylation sites. As shown in Fig 5, the virion-derived gp120 we studied has 24 N-glycosylation sites. Compared to the canonical HIV-1HXB2 strain, it is missing 3 N-glycosylation sites in and near the V2 loop and has an additional site in the V1 loop (Fig. 5). Thirteen sites are exclusively occupied with oligomannose glycans (Fig.5; dark green annotations). An additional seven sites are almost entirely oligomannose together with a trace (<0.3%) of non-sialylated complex structures (Asn-129) or low levels (<1%) of hybrid structures (Asn-140, Asn-143, Asn-279, Asn-292, Asn-298 and Asn-304). Complex-type glycans are found in substantial amounts at four sites. Two of these, Asn-200 and Asn-460, additionally carry hybrid structures, although oligomannose glycans are not present. A single site, Asn-357, carries oligomannose, complex and hybrid glycans. All three glycan classes are present at this site in comparable amounts. Finally, one site, Asn-135, is exclusively occupied with sialylated multiantennary complex glycans.

View Article: PubMed Central - PubMed

ABSTRACT

The surface envelope glycoprotein (SU) of Human immunodeficiency virus type 1 (HIV-1), gp120SU plays an essential role in virus binding to target CD4+ T-cells and is a major vaccine target. Gp120 has remarkably high levels of N-linked glycosylation and there is considerable evidence that this &ldquo;glycan shield&rdquo; can help protect the virus from antibody-mediated neutralization. In recent years, however, it has become clear that gp120 glycosylation can also be included in the targets of recognition by some of the most potent broadly neutralizing antibodies. Knowing the site-specific glycosylation of gp120 can facilitate the rational design of glycopeptide antigens for HIV vaccine development. While most prior studies have focused on glycan analysis of recombinant forms of gp120, here we report the first systematic glycosylation site analysis of gp120 derived from virions produced by infected T lymphoid cells and show that a single site is exclusively substituted with complex glycans. These results should help guide the design of vaccine immunogens.

No MeSH data available.