Broad diversity of neutralizing antibodies isolated from memory B cells in HIV-infected individuals

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Passive transfer of broadly neutralizing human antibodies against HIV-1 protects macaques against infection. However, HIV-1 uses several strategies to escape antibody neutralization, including mutation of the gp160 viral surface spike, a glycan shield to block antibody access to the spike, and expression of a limited number of viral surface spikes, which interferes with bivalent antibody binding. The latter is thought to decrease antibody apparent affinity or avidity, thereby interfering with neutralizing activity. To test the idea that increasing apparent affinity might enhance neutralizing activity, we engineered bispecific anti–HIV-1 antibodies (BiAbs) that can bind bivalently by virtue of one scFv arm that binds to gp120 and a second arm to the gp41 subunit of gp160. The individual arms of the BiAbs preserved the binding specificities of the original anti-HIV IgG antibodies and together bound simultaneously to gp120 and gp41. Heterotypic bivalent binding enhanced neutralization compared with the parental antibodies. We conclude that antibody recognition and viral neutralization of HIV can be improved by heteroligation.

Section: Resultsmentioning

confidence: 99%

Section: Bivalent Scfv-fc Recapitulates Binding and Neutralizing Propmentioning

confidence: 99%

Enhanced HIV-1 neutralization by antibody heteroligation

Mouquet

Warncke

Scheid

et al. 2012

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“…It also can expose conserved epitopes hidden by large glycans to elicit an immune response that recognizes HA variants in higher titer. This strategy opens a new direction for vaccine design and, together with other different vaccine strategies (27)(28)(29)(30) and recent discoveries of HAneutralizing antibodies (31)(32)(33)(34)(35)(36), should facilitate the development of vaccines against viruses such as influenza, hepatitis C virus, and HIV.…”

Section: Discussionmentioning

confidence: 99%

Glycans on influenza hemagglutinin affect receptor binding and immune response

Wang

Chen

Tseng

et al. 2009

283

256

Recent cases of avian influenza H5N1 and the swine-origin 2009 H1N1 have caused a great concern that a global disaster like the 1918 influenza pandemic may occur again. Viral transmission begins with a critical interaction between hemagglutinin (HA) glycoprotein, which is on the viral coat of influenza, and sialic acid (SA) containing glycans, which are on the host cell surface. To elucidate the role of HA glycosylation in this important interaction, various defined HA glycoforms were prepared, and their binding affinity and specificity were studied by using a synthetic SA microarray. Truncation of the N-glycan structures on HA increased SA binding affinities while decreasing specificity toward disparate SA ligands. The contribution of each monosaccharide and sulfate group within SA ligand structures to HA binding energy was quantitatively dissected. It was found that the sulfate group adds nearly 100-fold (2.04 kcal/mol) in binding energy to fully glycosylated HA, and so does the biantennary glycan to the monoglycosylated HA glycoform. Antibodies raised against HA protein bearing only a single N-linked GlcNAc at each glycosylation site showed better binding affinity and neutralization activity against influenza subtypes than the fully glycosylated HAs elicited. Thus, removal of structurally nonessential glycans on viral surface glycoproteins may be a very effective and general approach for vaccine design against influenza and other human viruses.flu vaccine ͉ glycan binding ͉ glycosylation T he highly pathogenic H5N1 and the 2009 swine-origin influenza A (H1N1) viruses have caused global outbreaks and raised a great concern that further changes in the viruses may occur to bring about a deadly pandemic (1, 2). Important contributions to our understanding of influenza infections have come from the studies on hemagglutinin (HA), a viral coat glycoprotein that binds to specific sialylated glycan receptors in the respiratory tract, allowing the virus to enter the cell (3-6). To cross the species barrier and infect the human population, avian HA must change its receptorbinding preference from a terminally sialylated glycan that contains ␣2,3 (avian)-linked to ␣2,6 (human)-linked sialic acid motifs (7), and this switch could occur through only two mutations, as in the 1918 pandemic (8). Understanding the factors that affect influenza binding to glycan receptors is thus critical for developing methods to control any future crossover influenza strains that have pandemic potential.HA is a homotrimeric transmembrane protein with an ectodomain composed of a globular head and a stem region (3). Both regions carry N-linked oligosaccharides (9), which affect the functional properties of HA (10, 11). Among different subtypes of influenza A viruses, there is extensive variation in the glycosylation sites of the head region, whereas the stem oligosaccharides are more conserved and required for fusion activity (11). Glycans near antigenic peptide epitopes interfere with antibody recognition (12), and glycans near the proteolytic ...

“…In the last several years, however, a number of broadly neutralizing Abs (bNAbs) have been isolated from HIV-1-infected individuals (1)(2)(3)(4)(5)(6). Structural knowledge of such Abs in complex with the viral envelope (Env) glycoprotein gp120 (2,3,(7)(8)(9)(10) has raised the hope that immunogen design can be facilitated through a process of reverse vaccinology (11).…”

mentioning

confidence: 99%

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

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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.