Crystal Structure of HIV-1 Primary Receptor CD4 in Complex with a Potent Antiviral Antibody

Freeman, Michael; Seaman, Michael S.; Rits-Volloch, Sophia; Hong, Xinguo; Kao, Chia-Ying; Ho, David D.; Chen, Bing

doi:10.1016/j.str.2010.09.017

Cited by 67 publications

(73 citation statements)

References 52 publications

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“…Based on the known structure of the complex of iMab Fab with human CD4 (29), these substitutions are expected to abrogate iMab binding to CD4. Indeed, binding of PG9-ΔiMab to CD4 molecules expressed on the surface of TZM-bl cells was undetectable by flow cytometry at concentrations up to 48 nM (10 μg/mL).…”

Section: Resultsmentioning

confidence: 99%

“…Fig. 4 shows the gp120 trimer (41) together with a superimposition of the known CD4 structure (42) bound by iMab Fab (29), along with the known structure of PG9 scFv (8) connected by a 15-aa linker. The data shown in Fig.…”

Section: Resultsmentioning

confidence: 99%

“…IMab was chosen because of its established safety record (well tolerated without serious adverse events) and anti-HIV-1 activity (>1 log reduction in viral load) in infected patients in phase 1a, 1b, 2a, and 2b clinical trials (25,26,28). This monoclonal Ab binds to domain 2 of human CD4, on a face opposite to the site of gp120 and MHC class II binding, and potently inhibits HIV-1 entry via a noncompetitive mechanism after virus attachment (29,30). The effect of iMab on humoral responses to vaccination in vivo, as a surrogate of CD4-MHC II interactions, is currently under investigation in a clinical trial of HIV-uninfected individuals.…”

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confidence: 99%

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Bispecific antibodies directed to CD4 domain 2 and HIV envelope exhibit exceptional breadth and picomolar potency against HIV-1

Pace

Song

Ochsenbauer

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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In the absence of an effective HIV-1 vaccine, passive immunization using broadly neutralizing Abs or Ab-like molecules could provide an alternative to the daily administration of oral antiretroviral agents that has recently shown promise as preexposure prophylaxis. Currently, no single broadly neutralizing Ab (bNAb) or combination of bNAbs neutralizes all HIV-1 strains at practically achievable concentrations in vivo . To address this problem, we created bispecific Abs that combine the HIV-1 inhibitory activity of ibalizumab (iMab), a humanized mAb directed to domain 2 of human CD4, with that of anti-gp120 bNAbs. These bispecific bNAbs (BibNAbs) exploit iMab’s potent anti–HIV-1 activity and demonstrated clinical efficacy and safety to anchor and thereby concentrate a second broadly neutralizing agent at the site of viral entry. Two BibNabs, PG9-iMab and PG16-iMab, exhibit exceptional breadth and potency, neutralizing 100% of the 118 viruses tested at low picomolar concentrations, including viruses resistant to both parental mAbs. The enhanced potency of these BibNAbs was entirely dependent on CD4 anchoring, not on membrane anchoring per se, and required optimal Ab geometry and linker length. We propose that iMab-based BibNAbs, such as PG9-iMab and PG16-iMab, are promising candidates for passive immunization to prevent HIV-1 infection.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Bispecific antibodies directed to CD4 domain 2 and HIV envelope exhibit exceptional breadth and picomolar potency against HIV-1

Pace

Song

Ochsenbauer

et al. 2013

Proc. Natl. Acad. Sci. U.S.A.

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“…[26][27][28][29][30][31][32][33][34][35] Multiple screens for HIV-1 inhibitors relied on in vitro assays, which used viral proteins or their fragments, or on HIV-1 infections/replication as a readout. In vitro screening has identified competitive inhibitors of assembly of the gp41 HR1-and HR2-derived peptides into the 6HB.…”

Section: Introductionmentioning

confidence: 99%

High-Throughput HIV–Cell Fusion Assay for Discovery of Virus Entry Inhibitors

Marin

Giroud

et al. 2015

ASSAY and Drug Development Technologies

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HIV-1 initiates infection by merging its envelope membrane with the target cell membrane, a process that is mediated by the viral Env glycoprotein following its sequential binding to CD4 and coreceptors, CXCR4 or CCR5. Although HIV-1 fusion has been a target for antiviral therapy, the virus has developed resistance to drugs blocking the CCR5 binding or Env refolding steps of this process. This highlights the need for novel inhibitors. Here, we adapted and optimized an enzymatic HIV-cell fusion assay, which reports the transfer of virus-encapsulated b-lactamase into the cytoplasm, to high-throughput screening (HTS) with a 384-well format. The assay was robustly performed in HTS format and was validated by the pilot screen of a small library of pharmacologically active compounds. Several hits identified by screening included a prominent cluster of purinergic receptor antagonists. Functional studies demonstrated that P2X1 receptor antagonists selectively inhibited HIV-1 fusion without affecting the fusion activity of an unrelated virus that enters cells through an endocytic route. The inhibition of HIV-cell fusion by P2X1 antagonists was not through downmodulation of the cell surface expression of CD4 or coreceptors, thus implicating P2X1 receptor in the HIV-1 fusion step. The ability of these antagonists to inhibit viruses regardless of their coreceptor (CXCR4 or CCR5) preference indicates that fusion is blocked at a late step downstream of coreceptor binding. A future large-scale screening campaign for HIV-1 fusion inhibitors, using the above functional readout, will likely reveal novel classes of inhibitors and suggest potential targets for antiviral therapy.

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“…The antibodies were purified by affinity chromatography using GammaBind-plus resin (GE Healthcare), followed by gel-filtration chromatography. Fab preparations by papain digestion were carried out as described (41). SPR binding assays, immunoprecipitation, and Western blot, flow cytometry, and antibody neutralization assays were carried out following the detailed protocols published previously (10) and as described in SI Materials and Methods.…”

Section: Methodsmentioning

confidence: 99%

Antigenicity-defined conformations of an extremely neutralization-resistant HIV-1 envelope spike

Cai

Karaca-Griffin

Chen

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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The extraordinary genetic diversity of the HIV-1 envelope spike [Env; trimeric (gp160) 3 , cleaved to (gp120/gp41) 3 ] poses challenges for vaccine development. Envs of different clinical isolates exhibit different sensitivities to antibody-mediated neutralization. Envs of difficult-to-neutralize viruses are thought to be more stable and conformationally homogeneous trimers than those of easyto-neutralize viruses, thereby providing more effective concealment of conserved, functionally critical sites. In this study we have characterized the antigenic properties of an Env derived from one of the most neutralization-resistant HIV-1 isolates, CH120.6. Sequence variation at neutralizing epitopes does not fully account for its exceptional resistance to antibodies. The full-length, membrane-bound CH120.6 Env is indeed stable and conformationally homogeneous. Its antigenicity correlates closely with its neutralization sensitivity, and major changes in antigenicity upon CD4 engagement appear to be restricted to the coreceptor site. The CH120.6 gp140 trimer, the soluble and uncleaved ectodomain of (gp160) 3 , retains many antigenic properties of the intact Env, consistent with a conformation close to that of Env spikes on a virion, whereas its monomeric gp120 exposes many nonneutralizing or strain-specific epitopes. Thus, trimer organization and stability are important determinants not only for occluding many epitopes but also for conferring resistance to neutralization by all but a small set of antibodies. Env preparations derived from neutralization-resistant viruses may induce irrelevant antibody responses less frequently than do other Envs and may be excellent templates for developing soluble immunogens.HIV-1 gp160 | neutralizing antibodies | vaccine design

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Crystal Structure of HIV-1 Primary Receptor CD4 in Complex with a Potent Antiviral Antibody

Cited by 67 publications

References 52 publications

Bispecific antibodies directed to CD4 domain 2 and HIV envelope exhibit exceptional breadth and picomolar potency against HIV-1

Bispecific antibodies directed to CD4 domain 2 and HIV envelope exhibit exceptional breadth and picomolar potency against HIV-1

High-Throughput HIV–Cell Fusion Assay for Discovery of Virus Entry Inhibitors

Antigenicity-defined conformations of an extremely neutralization-resistant HIV-1 envelope spike

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