Clade-Specific Differences between Human Immunodeficiency Virus Type 1 Clades B and C: Diversity and Correlations in C3-V4 Regions of gp120

A recombinant human monoclonal antibody, IgG1 b12 (b12), recognizes a conformational epitope on human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (Env) gp120 that overlaps the CD4 binding domain. Although b12 is able to broadly neutralize HIV-1 subtype B, C, and D viruses, many HIV-1 CRF01_AE viruses are resistant to b12-mediated neutralization. In this report, we examined the molecular mechanisms underlying the low neutralization susceptibility of CRF01_AE viruses to b12, using recently established CRF01_AE Env recombinant viruses. Our results showed that two potential N-linked glycosylation (PNLG) sites in the V2 and C2 regions of Env gp120 played an important role in regulating the susceptibility of CRF01_AE Env to b12. The locations of these PNLG sites correspond to amino acid positions 186 and 197 in HXB2 Env gp120; thus, they are designated N186 and N197 in this study. Removal of N186 significantly conferred the b12 susceptibility of 2 resistant CRF01_AE Env clones, 65CC4 and 107CC2, while the introduction of N186 reduced the b12 susceptibility of a susceptible CRF01_AE Env clone, 65CC1. In addition, removal of both N186 and N197 conferred the b12 susceptibility of 3 resistant CRF01_AE Env clones, 45PB1, 62PL1, and 101PL1, whereas the removal of either N186 or N197 was not sufficient to confer the b12 susceptibility of these CRF01_AE Env clones. Finally, removal of N197 conferred the b12 susceptibility of 2 resistant CRF01_AE Env clones lacking N186, 55PL1 and 102CC2. Taken together, we propose that two PNLG sites, N186 and N197, in Env gp120 are important determinants of the b12 resistance of CRF01_AE viruses.

Section: Discussionmentioning

confidence: 99%

Two N-Linked Glycosylation Sites in the V2 and C2 Regions of Human Immunodeficiency Virus Type 1 CRF01_AE Envelope Glycoprotein gp120 Regulate Viral Neutralization Susceptibility to the Human Monoclonal Antibody Specific for the CD4 Binding Domain

Utachee¹,

Nakamura²,

Isarangkura-na-ayuthaya

et al. 2010

“…In addition to the C3 chimeras, we constructed viruses chimeric for the C3 through V4 regions, which have been proposed to be in close proximity and to interact with one another (9). Significantly, in all four individuals, the introduction of the autologous C3-V4 into a heterologous parent virus resulted in an increase in sensitivity to neutralization, with two of the chimeras (63/88/63-C3-V4 and 88/63/88-C3-V4) reaching titers observed in autologous neutralization of the parent virus (Fig.…”

Section: What Are the Likely Targets Of The Autologous Neutralizing Rmentioning

confidence: 99%

“…As mentioned, the C3 region of subtype C viruses appears to be under strong diversifying pressure (8). Furthermore, the ␣2-helix of subtype C viruses is more solvated and shows greater amphipathicity than its subtype B counterpart (9), despite high sequence entropy at the polar faces. Although it is not clear whether these structural and diversity differences in subtype C reflect subtype-specific properties of NAbs, unique mutations within the ␣2-helix were linked with resistance to neutralization by donor plasma (34).…”

mentioning

confidence: 93%

“…The V4 region in subtype C viruses is generally shorter and significantly more positively charged than in subtype B viruses (9,21,23). Increased length in the V4 region in subtype C viruses correlated with resistance to neutralization in linked donor plasma but less so for heterologous plasma, suggesting that changes in V4 may be driven by type-specific NAbs (34).…”

mentioning

confidence: 99%

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The C3-V4 Region Is a Major Target of Autologous Neutralizing Antibodies in Human Immunodeficiency Virus Type 1 Subtype C Infection

Moore¹,

Gray²,

Choge³

et al. 2008

141

159

The early autologous neutralizing antibody response in human immunodeficiency virus type 1 (HIV-1) subtype C infections is often characterized by high titers, but the response is type specific with little to no cross-neutralizing activity. The specificities of these early neutralizing antibodies are not known; however, the type specificity suggests that they may target the variable regions of the envelope. Here, we show that cross-reactive anti-V3 antibodies developed within 3 to 12 weeks in six individuals but did not mediate autologous neutralization. Using a series of chimeric viruses, we found that antibodies directed at the V1V2, V4, and V5 regions contributed to autologous neutralization in some individuals, with V1V2 playing a more substantial role. However, these antibodies did not account for the total neutralizing capacity of these sera against the early autologous virus. Antibodies directed against the C3-V4 region were involved in autologous neutralization in all four sera studied. In two sera, transfer of the C3-V4 region rendered the chimera as sensitive to antibody neutralization as the parental virus. Although the C3 region, which contains the highly variable ␣2-helix was not a direct target in most cases, it contributed to the formation of neutralization epitopes as substitution of this region resulted in neutralization resistance. These data suggest that the C3 and V4 regions combine to form important structural motifs and that epitopes in this region are major targets of the early autologous neutralizing response in HIV-1 subtype C infection.

“…The length of the C3 region is approximately 54 amino acids (HxB2 numbering, amino acids 332 to 384) and contains at least 3 N-linked glycans (12). The alpha-2 helix, which spans 18 amino acids from positions 335 to 352, has a very conserved amphipathic structure among subtype C strains, with most variation occurring at the solvent-exposed hydrophilic face (7). The higher diversity in the alpha-2 helix of subtype C viruses compared to subtype B viruses (6) supports the experimental findings that this region is commonly targeted by autologous neutralizing antibodies (21,24).…”

mentioning

confidence: 99%

Isolation of a Monoclonal Antibody That Targets the Alpha-2 Helix of gp120 and Represents the Initial Autologous Neutralizing-Antibody Response in an HIV-1 Subtype C-Infected Individual

Gray

Moody

Wibmer

et al. 2011

The C3-V4 region is a major target of autologous neutralizing antibodies in HIV-1 subtype C infection. We previously identified a Center for AIDS Program of Research in South Africa (CAPRISA) participant, CAP88, who developed a potent neutralizing-antibody response within 3 months of infection that targeted an epitope in the C3 region of the HIV-1 envelope (P. L. Moore et al., PLoS Pathog. 5:e1000598, 2009). Here we showed that these type-specific antibodies could be adsorbed using recombinant gp120 from the transmitted/founder virus from CAP88 but not by gp120 made from other isolates. Furthermore, this activity could be depleted using a chimeric gp120 protein that contained only the C3 region from the CAP88 viral envelope engrafted onto the unrelated CAP63 viral envelope (called 63-88C3). On the basis of this, a differential sorting of memory B cells was performed using gp120s made from 63-88C3 and CAP63 labeled with different fluorochromes as positive and negative probes, respectively. This strategy resulted in the isolation of a highly specific monoclonal antibody (MAb), called CAP88-CH06, that neutralized the CAP88 transmitted/founder virus and viruses from acute infection but was unable to neutralize CAP88 viruses isolated at 6 and 12 months postinfection. The latter viruses contained 2 amino acid changes in the alpha-2 helix of C3 that mediated escape from this MAb. One of these changes involved the introduction of an N-linked glycan at position 339 that occluded the epitope, while the other mutation (either E343K or E350K) was a charge change. Our data validate the use of differential sorting to isolate a MAb targeting a specific epitope in the envelope glycoprotein and provided insights into the mechanisms of autologous neutralization escape.