Structures of respiratory syncytial virus G antigen bound to broadly neutralizing antibodies

Fedechkin, Stanislav O.; George, Natasha L; Wolff, Jacob T.; Kauvar, Lawrence M.; DuBois, Rebecca M.

doi:10.1126/sciimmunol.aar3534

Cited by 61 publications

(63 citation statements)

References 43 publications

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“…It is reasonable to suggest that the CX3C motif is essential for the formation of the cystine noose, which presumably is a relatively rigid structural feature. In contrast, recent structural analyses of the binding of RSV G NAbs to the CCR indicated that the structure around the rigid cystine noose is relatively flexible and can display distinct conformations when targeted by different NAbs (55,56). Despite the flexibility of the conserved region surrounding the CX3C motif, our results show that the integrity of this motif is essential for both the induction of an efficient G-specific cross-subgroup neutralizing antibody response and the neutralization of RSV by these antibodies.…”

Section: Discussioncontrasting

confidence: 82%

Effects of Alterations to the CX3C Motif and Secreted Form of Human Respiratory Syncytial Virus (RSV) G Protein on Immune Responses to a Parainfluenza Virus Vector Expressing the RSV G Protein

Liang

Kabatova

Kabát

et al. 2019

J Virol

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Human respiratory syncytial virus (RSV) is a major pediatric respiratory pathogen. The attachment (G) and fusion (F) glycoproteins are major neutralization and protective antigens. RSV G is expressed as membrane-anchored (mG) and -secreted (sG) forms, both containing a central fractalkine-like CX3C motif. The CX3C motif and sG are thought to interfere with host immune responses and have been suggested to be omitted from a vaccine. We used a chimeric bovine/human parainfluenza virus type 3 (rB/HPIV3) vector to express RSV wild-type (wt) G and modified forms, including sG alone, mG alone, mutants with ablated CX3C, and G with enhanced packaging into vector virions. In hamsters, these viruses replicated to similar titers. When assayed with a complement-enhanced neutralization assay in Vero cells, sG did not reduce the serum RSV-or PIV3-neutralizing antibody (NAb) responses, whereas ablating CX3C drastically reduced the RSV NAb response. Protective efficacy against RSV challenge was not reduced by sG but was strongly dependent on the CX3C motif. In ciliated human airway epithelial (HAE) cells, NAbs induced by wt G, but not by wt F, completely blocked RSV infection in the absence of added complement. This activity was dependent on the integrity of the CX3C motif. In hamsters, the rB/HPIV3 expressing wt G conferred better protection against RSV challenge than that expressing wt F. Codon optimization of the wt G further increased its immunogenicity and protective efficacy. This study showed that ablation of the CX3C motif or sG in an RSV vaccine, as has been suggested previously, would be ill advised. IMPORTANCE Human RSV is the leading viral cause of severe pediatric respiratory illness. An RSV vaccine is not yet available. The RSV attachment protein G is an important protective and neutralization antigen. G contains a conserved fractalkine-like CX3C motif and is expressed in mG and sG forms. sG and the CX3C motif are thought to interfere with host immune responses, but this remains poorly characterized. Here, we used an attenuated chimeric bovine/human parainfluenza virus type 3 (rB/HPIV3) vector to express various modified forms of RSV G. We demonstrated that strong antibody and protective responses could be induced by G alone, and that this was highly dependent on the integrity of the CX3C motif. There was no evidence that sG or the CX3C motif impaired immune responses against RSV G or the rB/HPIV3 vector. rB/HPIV3 expressing wt RSV G provides a bivalent vaccine against RSV and HPIV3.

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Section: Discussioncontrasting

confidence: 82%

Effects of Alterations to the CX3C Motif and Secreted Form of Human Respiratory Syncytial Virus (RSV) G Protein on Immune Responses to a Parainfluenza Virus Vector Expressing the RSV G Protein

Liang

Kabatova

Kabát

et al. 2019

J Virol

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“…1B). Similar to RSV G-antibody structures determined previously (16,46), antibody 3G12 binds to a conformational epitope comprising RSV G residues 160 to 179, 182, and 189, revealing additional interactions beyond the linear epitope residues 167 to 176 ( Fig. 1).…”

Section: Resultssupporting

confidence: 72%

“…Most of the anti-G bnmAbs that have been studied to date bind with high affinity to RSV G (K D [binding dissociation constant] ϭ 1.1 pM to 3.3 nM) and bind to linear epitopes within the RSV G CCD as determined by linear epitope mapping techniques (17,21,40,45). Recently, two studies elucidated four high-resolution crystal structures of antibody-RSV G CCD complexes (16,46). Unexpectedly, all four antibodies have additional interactions outside their linear epitopes, revealing a previously unappreciated role of the disulfide-stabilized cysteine noose in forming conformational epitopes and contributing to high-affinity antibody binding.…”

mentioning

confidence: 99%

Conformational Flexibility in Respiratory Syncytial Virus G Neutralizing Epitopes

Fedechkin

George

Castrejon

et al. 2020

J Virol

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Respiratory syncytial virus (RSV) is a top cause of severe lower respiratory tract disease and mortality in infants and the elderly. Currently, no vaccine or effective treatment exists for RSV. The RSV G glycoprotein mediates viral attachment to cells and contributes to pathogenesis by modulating host immunity through interactions with the human chemokine receptor CX3CR1. Antibodies targeting the RSV G central conserved domain are protective in both prophylactic and postinfection animal models. Here, we describe the crystal structure of the broadly neutralizing human monoclonal antibody 3G12 bound to the RSV G central conserved domain. Antibody 3G12 binds to a conformational epitope composed of highly conserved residues, explaining its broad neutralization activity. Surprisingly, RSV G complexed with 3G12 adopts a distinct conformation not observed in previously described RSV G-antibody structures. Comparison to other structures reveals that the RSV G central conserved domain is flexible and can adopt multiple conformations in the regions flanking the cysteine noose. We also show that restriction of RSV G flexibility with a proline mutation abolishes binding to antibody 3G12 but not antibody 3D3, which recognizes a different conformation of RSV G. Our studies provide new insights for rational vaccine design, indicating the importance of preserving both the global structural integrity of antigens and local conformational flexibility at antigenic sites, which may elicit a more diverse antibody response and broader protection against infection and disease. IMPORTANCE Respiratory syncytial virus (RSV) causes severe respiratory infections in infants, young children, and the elderly, and currently, no licensed vaccine exists. In this study, we describe the crystal structure of the RSV surface glycoprotein G in complex with a broadly neutralizing human monoclonal antibody. The antibody binds to RSV G at a highly conserved region stabilized by two disulfide bonds, but it captures RSV G in a conformation not previously observed, revealing that this region is both structured and flexible. Importantly, our findings provide insight for the design of vaccines that elicit diverse antibodies, which may provide broad protection from infection and disease. KEYWORDS X-ray crystallography, broadly neutralizing antibodies, protein structurefunction, respiratory syncytial virus R espiratory syncytial virus (RSV) is a globally prevalent virus that affects the airways and lungs. Infants and young children are at the highest risk of severe outcomes from RSV infection, with 33.1 million episodes of lower respiratory tract infection and approximately 3.2 million hospital visits and 118,200 deaths per year worldwide in children under the age of 5 years due to RSV (1). RSV is also a major cause of illness in adults older than 65 years of age and immunocompromised individuals, with an

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“…The cystine noose present in these structures adopts a conserved fold that is also observed in the fourth subdomain of the tumour necrosis factor receptor (TNFR) 51 . In the past year, two groups determined four high-resolution X-ray crystal structures of neutralizing antibodies bound to human RSV G-derived peptides 52,53 . Although the cystine noose was structurally conserved with minor flexibility at the tip of the noose, multiple conformations of the highly conserved amino-terminal flanking region were observed, suggesting that this region is flexible and generally unstructured (FIg.…”

Section: Neutrophilmentioning

confidence: 99%

“…However, a different prefusion-specific antibody, REGN2222, which recognizes antigenic site V, recently failed to reach its clinical end points in a phase III study 135 , and the reasons for the failure are not yet known. Other prefusion-specific antibodies are also in preclinical development, as are antibodies directed against the G protein that inhibit viral attachment 52,53 . Cocktails of antibodies against F and G, or against two different antigenic sites on F, are also being considered and may lead to synergistic effects and reduced viral escape.…”

Section: Clinical Interventionsmentioning

confidence: 99%

Respiratory syncytial virus entry and how to block it

2019

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AlveoliSmall air sacs in the lung that provide rapid gas exchange with blood. BronchiolitisInflammation of the bronchioles that reduces air passage. FormalinAn aqueous solution of formaldehyde.Abstract | Respiratory syncytial virus (RSV) is a leading cause of lower respiratory tract disease in young children and elderly people. Although the virus was isolated in 1955, an effective RSV vaccine has not been developed, and the only licensed intervention is passive immunoprophylaxis of high-risk infants with a humanized monoclonal antibody. During the past 5 years, however, there has been substantial progress in our understanding of the structure and function of the RSV glycoproteins and their interactions with host cell factors that mediate entry. This period has coincided with renewed interest in developing effective interventions, including the isolation of potent monoclonal antibodies and small molecules and the design of novel vaccine candidates. In this Review , we summarize the recent findings that have begun to elucidate RSV entry mechanisms, describe progress on the development of new interventions and conclude with a perspective on gaps in our knowledge that require further investigation.

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Structures of respiratory syncytial virus G antigen bound to broadly neutralizing antibodies

Cited by 61 publications

References 43 publications

Effects of Alterations to the CX3C Motif and Secreted Form of Human Respiratory Syncytial Virus (RSV) G Protein on Immune Responses to a Parainfluenza Virus Vector Expressing the RSV G Protein

Effects of Alterations to the CX3C Motif and Secreted Form of Human Respiratory Syncytial Virus (RSV) G Protein on Immune Responses to a Parainfluenza Virus Vector Expressing the RSV G Protein

Conformational Flexibility in Respiratory Syncytial Virus G Neutralizing Epitopes

Respiratory syncytial virus entry and how to block it

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