An efficiently cleaved HIV-1 clade C Env selectively binds to neutralizing antibodies.
Ontology highlight
ABSTRACT:
SUBMITTER: Boliar S
PROVIDER: S-EPMC4379091 | biostudies-literature |
REPOSITORIES: biostudies-literature
Similar Datasets
Project description:A desirable but as yet unachieved property of a human immunodeficiency virus type 1 (HIV-1) vaccine candidate is the ability to induce broadly neutralizing antibodies (bNAbs). One approach to the problem is to create trimeric mimics of the native envelope glycoprotein (Env) spike that expose as many bNAb epitopes as possible, while occluding those for non-neutralizing antibodies (non-NAbs). Here, we describe the design and properties of soluble, cleaved SOSIP.664 gp140 trimers based on the subtype A transmitted/founder strain, BG505. These trimers are highly stable, more so even than the corresponding gp120 monomer, as judged by differential scanning calorimetry. They are also homogenous and closely resemble native virus spikes when visualized by negative stain electron microscopy (EM). We used several techniques, including ELISA and surface plasmon resonance (SPR), to determine the relationship between the ability of monoclonal antibodies (MAbs) to bind the soluble trimers and neutralize the corresponding virus. In general, the concordance was excellent, in that virtually all bNAbs against multiple neutralizing epitopes on HIV-1 Env were highly reactive with the BG505 SOSIP.664 gp140 trimers, including quaternary epitopes (CH01, PG9, PG16 and PGT145). Conversely, non-NAbs to the CD4-binding site, CD4-induced epitopes or gp41ECTO did not react with the trimers, even when their epitopes were present on simpler forms of Env (e.g. gp120 monomers or dissociated gp41 subunits). Three non-neutralizing MAbs to V3 epitopes did, however, react strongly with the trimers but only by ELISA, and not at all by SPR and to only a limited extent by EM. These new soluble trimers are useful for structural studies and are being assessed for their performance as immunogens.
| S-EPMC3777863 | biostudies-literature
Project description:The development of soluble envelope glycoprotein (Env) mimetics displaying ordered trimeric symmetry has ushered in a new era in HIV-1 vaccination. The recently reported native, flexibly linked (NFL) design allows the generation of native-like trimers from clinical isolates at high yields and homogeneity. As the majority of infections world-wide are of the clade C subtype, we examined responses in non-human primates to well-ordered subtype C 16055 trimers administered in soluble or high-density liposomal formats. We detected superior germinal center formation and enhanced autologous neutralizing antibodies against the neutralization-resistant (tier 2) 16055 virus following inoculation of liposome-arrayed trimers. Epitope mapping of the neutralizing monoclonal antibodies (mAbs) indicated major contacts with the V2 apex, and 3D electron microscopy reconstructions of Fab-trimer complexes revealed a horizontal binding angle to the Env spike. These vaccine-elicited mAbs target the V2 cap, demonstrating a means to accomplish tier 2 virus neutralization by penetrating the dense N-glycan shield.
| S-EPMC5528178 | biostudies-literature
Project description:Although vaccines are important in preventing viral infections by inducing neutralizing antibodies (nAbs), HIV-1 has proven to be a difficult target and escapes humoral immunity through various mechanisms. We sought to test whether HIV-1 Env mimics may serve as immunogens.Using random peptide phage display libraries, we identified the epitopes recognized by polyclonal antibodies of a rhesus monkey that had developed high-titer, broadly reactive nAbs after infection with a simian-human immunodeficiency virus (SHIV) encoding env of a recently transmitted HIV-1 clade C (HIV-C). Phage peptide inserts were analyzed for conformational and linear homology using computational analysis; some peptides mimicked various domains of the original HIV-C Env, such as conformational V3 loop epitopes and the conserved linear region of the gp120 C-terminus. Next, we devised a novel prime/boost strategy to test the immunogenicity of such phage-displayed peptides and primed mice only once with HIV-C gp160 DNA followed by boosting with mixtures of recombinant phages.This strategy, which was designed to focus the immune system on a few Env epitopes (immunofocusing), not only induced HIV-C gp160 binding antibodies and cross-clade nAbs, but also linked a conserved HIV Env region for the first time to the induction of nAbs: the C-terminus of gp120. The identification of conserved antigen mimics may lead to novel immunogens capable of inducing broadly reactive nAbs.
| S-EPMC2597739 | biostudies-literature
Project description:The trimeric envelope glycoproteins (Env) on the surface of HIV-1 virions are the targets for neutralizing antibodies (NAbs). No candidate HIV-1 immunogen has yet induced potent, broadly active NAbs (bNAbs). Part of the explanation may be that previously tested Env proteins inadequately mimic the functional, native Env complex. Trimerization and the proteolytic processing of Env precursors into gp120 and gp41 profoundly alter antigenicity, but soluble cleaved trimers are too unstable to serve as immunogens. By introducing stabilizing mutations (SOSIP), we constructed soluble, cleaved Env trimers derived from the HIV-1 subtype A isolate BG505 that resemble native Env spikes on virions both structurally and antigenically.We used surface plasmon resonance (SPR) to quantify antibody binding to different forms of BG505 Env: the proteolytically cleaved SOSIP.664 trimers, cleaved gp120-gp41ECTO protomers, and gp120 monomers. Non-NAbs to the CD4-binding site bound only marginally to the trimers but equally well to gp120-gp41ECTO protomers and gp120 monomers, whereas the bNAb VRC01, directed to the CD4bs, bound to all three forms. In contrast, bNAbs to V1V2 glycan-dependent epitopes bound preferentially (PG9 and PG16) or exclusively (PGT145) to trimers. We also explored the antigenic consequences of three different features of SOSIP.664 gp140 trimers: the engineered inter-subunit disulfide bond, the trimer-stabilizing I559P change in gp41ECTO, and proteolytic cleavage at the gp120-gp41ECTO junction. Each of these three features incrementally promoted native-like trimer antigenicity. We compared Fab and IgG versions of bNAbs and validated a bivalent model of IgG binding. The NAbs showed widely divergent binding kinetics and degrees of binding to native-like BG505 SOSIP.664. High off-rate constants and low stoichiometric estimates of NAb binding were associated with large amounts of residual infectivity after NAb neutralization of the corresponding BG505.T332N pseudovirus.The antigenicity and structural integrity of cleaved BG505 SOSIP.664 trimers render these proteins good mimics of functional Env spikes on virions. In contrast, uncleaved gp140s antigenically resemble individual gp120-gp41ECTO protomers and gp120 monomers, but not native trimers. Although NAb binding to functional trimers may thus be both necessary and sufficient for neutralization, the kinetics and stoichiometry of the interaction influence the neutralizing efficacy of individual NAbs.
| S-EPMC4067080 | biostudies-literature
Project description:BackgroundAntigenicity of HIV-1 envelope proteins (Envs) of both lab-adapted and primary isolates expressed on the cell surface rarely match with in vitro neutralization of viruses, pseudo-typed with corresponding Envs. Often, both neutralizing and non-neutralizing antibodies bind to Envs expressed on the cell membrane. This could be due to the lack of efficient cleavage of Env expressed on the cell surface. Naturally occurring, efficiently cleaved Envs with appropriate antigenic properties are relatively rare. Given viral diversity it is essential to increase the pool of candidate Envs suitable for immunogen design. Previously, it has been reported that JRFL Env is the only clade B Env, which is efficiently cleaved on the cell surface and retains desirable antigenic properties. JRCSF is a clade B Env isolated from the same patient as JRFL. JRCSF Env has not been explored aggressively for designing immunogen as the binding characteristics of JRCSF Env to broadly neutralizing antibodies on the cell surface and its cleavage status are unknown.ResultsAlthough JRCSF preferentially binds to most of the other gp120-directed neutralizing antibodies and cleavage dependent antibody, PGT151 efficiently, it binds poorly to CD4-binding-site-directed (CD4-bs-directed) neutralizing antibodies on cell surface. Membrane bound form of modified JRCSF Env containing the N197D mutation binds to CD4-bs-directed neutralizing antibodies better than JRFL, without debilitating its ability to bind quaternary epitope-directed neutralizing antibodies or exposing the CD4i antibody epitopes. In comparison to JRFL (E168K), JRCSF Env binds more efficiently to PG9/PGT145 class of V1/V2-directed conformational antibodies. Biochemical, cell surface staining and gp120 shedding experiments suggest that JRCSF is efficiently cleaved on the cell surface.ConclusionsBinding of JRCSF Env expressed on cell surface to the various HIV-1 Env-directed antibodies has not been reported earlier. Here, for the first time, we report that compared to JRFL, JRCSF displays epitopes for a larger number of broadly neutralizing antibodies and is also efficiently cleaved when expressed on the cell surface. Thus, considering the diversity of viral Envs and the discovery of conformation dependent glycan-directed antibodies in HIV-1 infected individuals, an innately cleaved JRCSF Env as present on the viral membrane and displaying those distinct epitopes may be an important candidate for immunogen design.
| S-EPMC5117575 | biostudies-literature
Project description:HIV-1 conceals epitopes of its envelope glycoproteins (Env) recognized by antibody (Ab)-dependent cellular cytotoxicity (ADCC)-mediating antibodies. These Abs, including anti-coreceptor binding site (CoRBS) and anti-cluster A antibodies, preferentially recognize Env in its "open" conformation. The binding of anti-CoRBS Abs has been shown to induce conformational changes that further open Env, allowing interaction of anti-cluster A antibodies. We explored the possibility that CoRBS Abs synergize with anti-cluster A Abs to engage Fc-gamma receptors to mediate ADCC. We found that binding of anti-CoRBS and anti-cluster A Abs to the same gp120 is required for interaction with soluble dimeric FcγRIIIa in enzyme-linked immunosorbent assays (ELISAs). We also found that Fc regions of both Abs are required to optimally engage FcγRIIIa and mediate robust ADCC. Taken together, our results indicate that these two families of Abs act together in a sequential and synergistic fashion to promote FcγRIIIa engagement and ADCC.IMPORTANCE The "open" CD4-bound conformation of HIV-1 envelope glycoproteins is the primary target of antibody-dependent cellular cytotoxicity (ADCC)-mediating antibodies present in HIV-positive (HIV+) sera, such as anti-coreceptor binding site and anti-cluster A antibodies. Here we report that the binding of these two families of antibodies is required to engage FcγRIIIa and mediate ADCC.
| S-EPMC6340017 | biostudies-literature
Project description:Vaccine efforts to combat HIV are challenged by the global diversity of viral strains and shielding of neutralization epitopes on the viral envelope glycoprotein trimer. Even so, the isolation of broadly neutralizing Abs from infected individuals suggests the potential for eliciting protective Abs through vaccination. This study reports a panel of 58 mAbs cloned from a rhesus macaque (Macaca mulatta) immunized with envelope glycoprotein immunogens curated from an HIV-1 clade C-infected volunteer. Twenty mAbs showed neutralizing activity, and the strongest neutralizer displayed 92% breadth with a median IC50 of 1.35 μg/ml against a 13-virus panel. Neutralizing mAbs predominantly targeted linear epitopes in the V3 region in the cradle orientation (V3C) with others targeting the V3 ladle orientation (V3L), the CD4 binding site (CD4bs), C1, C4, or gp41. Nonneutralizing mAbs bound C1, C5, or undetermined conformational epitopes. Neutralization potency strongly correlated with the magnitude of binding to infected primary macaque splenocytes and to the level of Ab-dependent cellular cytotoxicity, but did not predict the degree of Ab-dependent cellular phagocytosis. Using an individualized germline gene database, mAbs were traced to 23 of 72 functional IgHV alleles. Neutralizing V3C Abs displayed minimal nucleotide somatic hypermutation in the H chain V region (3.77%), indicating that relatively little affinity maturation was needed to achieve in-clade neutralization breadth. Overall, this study underscores the polyfunctional nature of vaccine-elicited tier 2-neutralizing V3 Abs and demonstrates partial reproduction of the human donor's humoral immune response through nonhuman primate vaccination.
| S-EPMC7887735 | biostudies-literature
Project description:Broadly neutralizing antibodies (bNAbs) against HIV-1 Env V1V2 arise in multiple donors. However, atomic-level interactions had previously been determined only with antibodies from a single donor, thus making commonalities in recognition uncertain. Here we report the cocrystal structure of V1V2 with antibody CH03 from a second donor and model Env interactions of antibody CAP256-VRC26 from a third donor. These V1V2-directed bNAbs used strand-strand interactions between a protruding antibody loop and a V1V2 strand but differed in their N-glycan recognition. Ontogeny analysis indicated that protruding loops develop early, and glycan interactions mature over time. Altogether, the multidonor information suggested that V1V2-directed bNAbs form an 'extended class', for which we engineered ontogeny-specific antigens: Env trimers with chimeric V1V2s that interacted with inferred ancestor and intermediate antibodies. The ontogeny-based design of vaccine antigens described here may provide a general means for eliciting antibodies of a desired class.
| S-EPMC4833398 | biostudies-literature
Project description:Standardized assessments of HIV-1 vaccine-elicited neutralizing antibody responses are complicated by the genetic and antigenic variability of the viral envelope glycoproteins (Envs). To address these issues, suitable reference strains are needed that are representative of the global epidemic. Several panels have been recommended previously, but no clear answers have been available on how many and which strains are best suited for this purpose. We used a statistical model selection method to identify a global panel of reference Env clones from among 219 Env-pseudotyped viruses assayed in TZM-bl cells with sera from 205 HIV-1-infected individuals. The Envs and sera were sampled globally from diverse geographic locations and represented all major genetic subtypes and circulating recombinant forms of the virus. Assays with a panel size of only nine viruses adequately represented the spectrum of HIV-1 serum neutralizing activity seen with the larger panel of 219 viruses. An optimal panel of nine viruses was selected and augmented with three additional viruses for greater genetic and antigenic coverage. The spectrum of HIV-1 serum neutralizing activity seen with the final 12-virus panel closely approximated the activity seen with subtype-matched viruses. Moreover, the final panel was highly sensitive for detection of many of the known broadly neutralizing antibodies. For broader assay applications, all 12 Env clones were converted to infectious molecular clones using a proviral backbone carrying a Renilla luciferase reporter gene (Env.IMC.LucR viruses). This global panel should facilitate highly standardized assessments of vaccine-elicited neutralizing antibodies across multiple HIV-1 vaccine platforms in different parts of the world.An effective HIV-1 vaccine will need to overcome the extraordinary genetic variability of the virus, where most variation occurs in the viral envelope glycoproteins that are the sole targets for neutralizing antibodies. Efforts to elicit broadly cross-reactive neutralizing antibodies that will protect against infection by most circulating strains of the virus are guided in part by in vitro assays that determine the ability of vaccine-elicited antibodies to neutralize genetically diverse HIV-1 variants. Until now, little information was available on how many and which strains of the virus are best suited for this purpose. We applied robust statistical methods to evaluate a large neutralization data set and identified a small panel of viruses that are a good representation of the global epidemic. The neutralization properties of this new panel of reference strains should facilitate the development of an effective HIV-1 vaccine.
| S-EPMC3958090 | biostudies-literature
Project description:HIV-1 is relatively resistant to antibody-mediated neutralization; however, rare antibodies to the exterior envelope glycoprotein, gp120, and the transmembrane glycoprotein, gp41, can neutralize a broad array of isolates. Two antibodies, 2F5 and 4E10, are directed against the gp41 membrane proximal external region (MPER); however, the kinetic neutralization signature of these antibodies remains unresolved. Previously, we reported that the fully cleaved, cell surface envelope glycoproteins (Env) derived from the primary isolate, JR-FL, are well recognized exclusively by gp120-directed neutralizing ligands and not by nonneutralizing gp120 antibodies. However, the gp120 nonneutralizing antibodies can recognize HIV spikes that are rendered fully cleavage defective by site-directed mutagenesis. Here, we extended such analysis to gp41 neutralizing and nonneutralizing antibodies and, relative to the rules of gp120-specific antibody recognition, we observed marked contrasts. Similar to gp120 recognition, the nonneutralizing gp41 cluster 1 or cluster 2 antibodies bound much more efficiently to cleavage-defective spikes when compared to their recognition of cleaved spikes. In contrast to gp120 neutralizing antibody recognition, the broadly neutralizing gp41 antibodies 2F5 and 4E10, like the nonneutralizing gp41 antibodies, did not efficiently recognize the predominantly cleaved, primary isolate JR-FL spikes. However, if the spikes were rendered cleavage defective, recognition by both the neutralizing and nonneutralizing ligand markedly increased. CD4 interaction with the cleaved spikes markedly increased recognition by most nonneutralizing gp41 antibodies, whereas such treatment had a minimal increase of 2F5 and 4E10 recognition. These data indicate again the profound influence that cleavage imposes on the quaternary packing of primary isolate spikes and have important implications for soluble trimer candidate immunogens.
| S-EPMC3159124 | biostudies-literature