Mutation at a Single Position in the V2 Domain of the HIV-1 Envelope Protein Confers Neutralization Sensitivity to a Highly Neutralization-Resistant Virus

Abstract

Understanding the determinants of neutralization sensitivity and resistance is important for the development of an effective human immunodeficiency virus type 1 (HIV-1) vaccine. In these studies, we have made use of the swarm of closely related envelope protein variants (quasispecies) from an extremely neutralizationresistant clinical isolate in order to identify mutations that conferred neutralization sensitivity to antibodies in sera from HIV-1-infected individuals. Here, we describe a virus with a rare mutation at position 179 in the V2 domain of gp120, where replacement of aspartic acid (D) by asparagine (N) converts a virus that is highly resistant to neutralization by multiple polyclonal and monoclonal antibodies, as well as antiviral entry inhibitors, to one that is sensitive to neutralization. Although the V2 domain sequence is highly variable, D at position 179 is highly conserved in HIV-1 and simian immunodeficiency virus (SIV) and is located within the LDI/V recognition motif of the recently described ␣4␤7 receptor binding site. Our results suggest that the D179N mutation induces a conformational change that exposes epitopes in both the gp120 and the gp41 portions of the envelope protein, such as the CD4 binding site and the MPER, that are normally concealed by conformational masking. Our results suggest that D179 plays a central role in maintaining the conformation and infectivity of HIV-1 as well as mediating binding to ␣4␤7.A major goal in human immunodeficiency virus type 1 (HIV-1) vaccine research is the identification of immunogens able to elicit protective immunity from HIV-1 infection. Results from the recent RV144 clinical trial in Thailand (53) have provided evidence that immunization with vaccines containing the recombinant HIV-1 envelope glycoprotein gp120 (6, 7) can protect humans from HIV infection when incorporated in a prime/boost immunization regimen. Although the level of protection observed in the RV144 trial (31%) was modest, it represents a significant advance in HIV-1 vaccine research and has rekindled the efforts to identify improved subunit vaccine antigens that might achieve even higher levels of protection. In these studies, we have sought to understand the molecular determinants of neutralization sensitivity and resistance in HIV-1 envelope proteins for the purpose of developing improved vaccine antigens.In previous studies (47), we have described a novel method of mutational analysis of the HIV-1 envelope protein, termed swarm analysis, for identification of mutations that confer sensitivity and/or resistance to broadly neutralizing antibodies (bNAbs). This method makes use of the natural amino acid sequence virus variation that occurs in each HIV-infected individual to establish panels of closely related envelope proteins that differ from each other by a limited number of amino acid substitutions. We have previously used this method to identify a novel amino acid substitution in gp41 that conferred sensitivity to neutralization by monoclonal and polyclonal antibodies as we...

Polyclonal B Cell Responses to Conserved Neutralization Epitopes in a Subset of HIV-1-Infected Individuals

“…entirely solvent exposed and may be involved in trimer packing. This is in fact a very common phenomenon that has also been reported in several recent studies (9,74,78,100,101,112). Our observation that a relatively larger fraction of gp41 MPER mutants than of gp120 mutants cause global sensitivity (compare Fig.…”

Unliganded HIV-1 gp120 core structures assume the CD4-bound conformation with regulation by quaternary interactions and variable loops

“…These regions reside near the trimer axis and contribute to spike stability (38). Our results explain why many of the diverse biological properties of HIV-1 strains (e.g., CD4 dependence or sensitivity to inhibition) can be determined by the structure of these loops (39)(40)(41). Changes in gp41 can also influence the transition of gp120 into an NBD-556-binding conformation.…”

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

“…[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.…”