HIV-1 envelope trimer elicits higher neutralizing antibody responses than monomeric gp120

Division of Molecular Medicine, Children's Hospital, Boston, MA 02115, USA.
Proceedings of the National Academy of Sciences (Impact Factor: 9.67). 07/2012; 109(30):12111-6. DOI: 10.1073/pnas.1204533109
Source: PubMed


HIV-1 envelope glycoprotein is the primary target for HIV-1-specific antibodies. The native HIV-1 envelope spike on the virion surface is a trimer, but trimeric gp140 and monomeric gp120 currently are believed to induce comparable immune responses. Indeed, most studies on the immunogenicity of HIV-1 envelope oligomers have revealed only marginal improvement over monomers. We report here that suitably prepared envelope trimers have nearly all the antigenic properties expected for native viral spikes. These stable, rigorously homogenous trimers have antigenic properties markedly different from those of monomeric gp120s derived from the same sequences, and they induce potent neutralizing antibody responses for a cross-clade set of tier 1 and tier 2 viruses with titers substantially higher than those elicited by the corresponding gp120 monomers. These results, which demonstrate that there are relevant immunologic differences between monomers and high-quality envelope trimers, have important implications for HIV-1 vaccine development.

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Available from: Joseph Nkolola, May 11, 2014
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    • "The CZA97.012 protein derives from a subtype C sequence and has been studied in multiple immunization and other experiments (Go et al., 2014; Kovacs et al., 2012; Nkolola et al., 2010). Like the BG505 WT.SEKS gp140, it has a knocked-out cleavage site, but also includes foldon domains near the C-termini of the gp41 ECTO subunits to artificially drive oligomerization (Go et al., 2014; Kovacs et al., 2012; Nkolola et al., 2010). The CZA97.012 gp140 was expressed in 293T cells and purified via its C-terminal His-tag followed by SEC, as previously described (Chung et al., 2014). "
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    ABSTRACT: A highly glycosylated, trimeric envelope glycoprotein (Env) mediates HIV-1 cell entry. The high density and heterogeneity of the glycans shield Env from recognition by the immune system, but paradoxically, many potent broadly neutralizing antibodies (bNAbs) recognize epitopes involving this glycan shield. To better understand Env glycosylation and its role in bNAb recognition, we characterized a soluble, cleaved recombinant trimer (BG505 SOSIP.664) that is a close structural and antigenic mimic of native Env. Large, unprocessed oligomannose-type structures (Man8-9GlcNAc2) are notably prevalent on the gp120 components of the trimer, irrespective of the mammalian cell expression system or the bNAb used for affinity purification. In contrast, gp41 subunits carry more highly processed glycans. The glycans on uncleaved, non-native oligomeric gp140 proteins are also highly processed. A homogeneous, oligomannose-dominated glycan profile is therefore a hallmark of a native Env conformation and a potential Achilles' heel that can be exploited for bNAb recognition and vaccine design. Copyright © 2015 The Authors. Published by Elsevier Inc. All rights reserved.
    Cell Reports 06/2015; 11(10). DOI:10.1016/j.celrep.2015.05.017 · 8.36 Impact Factor
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    • "It is worth considering that the Env-protein based vaccines tested so far in clinical trials have utilized gp120 Env monomers or a truncated form of gp160 (HVTN 505), although the spikes present on the infectious virion are constituted by trimers of gp160, which differ from monomeric gp120 Env in terms of antigenic properties and conformational epitopes displayed (57). This further emphasizes the concept that vaccine design should be more “pathogenesis-driven” in order to effectively target key virus molecules, a notion to carefully consider in future vaccine development. "
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    ABSTRACT: Many attempts have been made or are ongoing for HIV prevention and HIV cure. Many successes are in the list, particularly for HIV drugs, recently proposed also for prevention. However, no eradication of infection has been achieved so far with any drug. Further, a residual immune dysregulation associated to chronic immune activation and incomplete restoration of B and T cell subsets, together with HIV DNA persistence in reservoirs, are still unmet needs of the highly active antiretroviral therapy, causing novel "non-AIDS related" diseases that account for a higher risk of death even in virologically suppressed patients. These "ART unmet needs" represent a problem, which is expected to increase by ART roll out. Further, in countries such as South Africa, where six millions of individuals are infected, ART appears unable to contain the epidemics. Regretfully, all the attempts at developing a preventative vaccine have been largely disappointing. However, recent therapeutic immunization strategies have opened new avenues for HIV treatment, which might be exploitable also for preventative vaccine approaches. For example, immunization strategies aimed at targeting key viral products responsible of virus transmission, activation, and maintenance of virus reservoirs may intensify drug efficacy and lead to a functional cure providing new perspectives also for prevention and future virus eradication strategies. However, this approach imposes new challenges to the scientific community, vaccine developers, and regulatory bodies, such as the identification of novel immunological and virological biomarkers to assess efficacy end-points, taking advantage from the natural history of infection and exploiting lessons from former trials. This review will focus first on recent advancement of therapeutic strategies, then on the progresses made in preventative approaches, discussing concepts, and problems for the way ahead for the development of vaccines for HIV treatment and prevention.
    Frontiers in Immunology 09/2014; 5:417. DOI:10.3389/fimmu.2014.00417
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    • "In other studies, gp120, native-like SOSIP trimers, or uncleaved gp140s have been covalently immobilized and Fab or IgG used in solution [11,12,67-70]. Even when there is potential for more complex binding, simple Langmuir models have generally been fitted to the binding data [11,12,67-69]. These approaches have shortcomings. "
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    ABSTRACT: Background 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. Results 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. Conclusions 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.
    Retrovirology 05/2014; 11(1):41. DOI:10.1186/1742-4690-11-41 · 4.19 Impact Factor
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