Human Immunodeficiency Virus Type 1 V1-V2 Envelope Loop Sequences Expand and Add Glycosylation Sites over the Course of Infection, and These Modifications Affect Antibody Neutralization Sensitivity

Abstract

Over the course of infection, human immunodeficiency virus type 1 (HIV-1) continuously adapts to evade the evolving host neutralizing antibody responses. Changes in the envelope variable loop sequences, particularly the extent of glycosylation, have been implicated in antibody escape. To document modifications that potentially influence antibody susceptibility, we compared envelope variable loops 1 and 2 (V1-V2) from multiple sequences isolated at the primary phase of infection to those isolated around 2 to 3 years into the chronic phase of infection in nine women with HIV-1 subtype A. HIV-1 sequences isolated during chronic infection had significantly longer V1-V2 loops, with a significantly higher number of potential N-linked glycosylation sites, than the sequences isolated early in infection. To assess the effects of these V1-V2 changes on antibody neutralization and infectivity, we created chimeric envelope sequences, which incorporated a subject's V1-V2 sequences into a common subtype A envelope backbone and then used them to generate pseudotyped viruses. Compared to the parent virus, the introduction of a subject's early-infection V1-V2 envelope variable loops rendered the chimeric envelope more sensitive to that subject's plasma samples but only to plasma samples collected >6 months after the sequences were isolated. Neutralization was not detected with the same plasma when the early-infection V1-V2 sequences were replaced with chronic-infection V1-V2 sequences, suggesting that changes in V1-V2 contribute to antibody escape. Pseudotyped viruses with V1-V2 segments from different times in infection, however, showed no significant difference in neutralization sensitivity to heterologous pooled plasma, suggesting that viruses with V1-V2 loops from early in infection were not inherently more neutralization sensitive. Pseudotyped viruses bearing chimeric envelopes with early-infection V1-V2 sequences showed a trend in infecting cells with low CD4 concentrations more efficiently, while engineered viruses with V1-V2 sequences isolated during chronic infection were moderately better at infecting cells with low CCR5 concentrations. These studies suggest that changes within the V1-V2 envelope domains over the course of an infection influence sensitivity to autologous neutralizing antibodies and may also impact host receptor/ coreceptor interactions.

The Thai Phase III HIV Type 1 Vaccine Trial (RV144) Regimen Induces Antibodies That Target Conserved Regions Within the V2 Loop of gp120

“…It has a highly conserved length among early or transmitted/founder isolates and length and glycosylation of the V2 loop are commonly associated with escape from neutralizing antibodies. 30,35,65 Furthermore, V2 contains a putative a 4 b 7 integrin-binding motif of uncertain significance. 39 Although 1454 KARASAVVAS ET AL.…”

“…[22][23][24][25][26][27][28] Sequence variation within the V1/V2 loops alters neutralization resistance and viral escape is associated with V2 loop mutations. [29][30][31][32][33] Compared to viruses circulating in chronically infected persons, transmitted viruses (subtypes A and C) appear to have shorter V1/V2 regions and fewer N-linked glycosylation sites. 30,[34][35][36] The V2 loop contains a putative a 4 b 7 integrin binding motif (LDI/V) at amino acid (aa) residues 179-181 (HBX2 numbering system) that was shown to interact with the gut mucosal homing receptor.…”

“…[29][30][31][32][33] Compared to viruses circulating in chronically infected persons, transmitted viruses (subtypes A and C) appear to have shorter V1/V2 regions and fewer N-linked glycosylation sites. 30,[34][35][36] The V2 loop contains a putative a 4 b 7 integrin binding motif (LDI/V) at amino acid (aa) residues 179-181 (HBX2 numbering system) that was shown to interact with the gut mucosal homing receptor. 23,24 Under physiological conditions, the a 4 b 7 receptor facilitates the migration of lymphocytes to the gut and some have postulated that HIV-1 exploits this interaction to infect lymphocytes localized at mucosal tissues.…”

“…Antibodies against the V2 loop target several conserved residues that are sensitive to glycosylation patterns and changes within the loop alter the efficiency by which antibodies neutralize HIV-1. 26,30,41,48 T cell peptide epitope mapping studies with peripheral blood mononuclear cells (PBMCs) from HIV-1-uninfected RV144 vaccine recipients using the interferon-gamma ELISpot assay demonstrated preferential CD4 + T cell responses to the V2 loop region compared to other regions of gp120. 49 Antibody epitope mapping studies were undertaken to assess whether there was a similar preferential targeting of regions within gp120.…”

Partial Enzymatic Deglycosylation Preserves the Structure of Cleaved Recombinant HIV-1 Envelope Glycoprotein Trimers

“…During the course of this study, we found that KNH1144 SOSIP gp140 trimers from which the MPER was deleted (SOSIP.664) adopt a monodisperse distribution in the absence of detergent. 5 This property makes them more suitable than SOSIP.681 trimers for BN-PAGE, biophysical analyses, and EM studies. We confirmed that Endo H removed similar amounts of glycans from KNH1144 SOSIP.664 and SOSIP.681 trimers, as judged by SDS-PAGE analysis (not shown).…”