title: Structural basis for nonneutralizing antibody competition at antigenic site II of the respiratory syncytial virus fusion protein.
abstract: Palivizumab was the first antiviral monoclonal antibody (mAb) approved for therapeutic use in humans, and remains a prophylactic treatment for infants at risk for severe disease because of respiratory syncytial virus (RSV). Palivizumab is an engineered humanized version of a murine mAb targeting antigenic site II of the RSV fusion (F) protein, a key target in vaccine development. There are limited reported naturally occurring human mAbs to site II; therefore, the structural basis for human antibody recognition of this major antigenic site is poorly understood. Here, we describe a nonneutralizing class of site II-specific mAbs that competed for binding with palivizumab to postfusion RSV F protein. We also describe two classes of site II-specific neutralizing mAbs, one of which escaped competition with nonneutralizing mAbs. An X-ray crystal structure of the neutralizing mAb 14N4 in complex with F protein showed that the binding angle at which human neutralizing mAbs interact with antigenic site II determines whether or not nonneutralizing antibodies compete with their binding. Fine-mapping studies determined that nonneutralizing mAbs that interfere with binding of neutralizing mAbs recognize site II with a pose that facilitates binding to an epitope containing F surface residues on a neighboring protomer. Neutralizing antibodies, like motavizumab and a new mAb designated 3J20 that escape interference by the inhibiting mAbs, avoid such contact by binding at an angle that is shifted away from the nonneutralizing site. Furthermore, binding to rationally and computationally designed site II helix-loop-helix epitope-scaffold vaccines distinguished neutralizing from nonneutralizing site II antibodies.
authors: Vanderbilt Vaccine Center, Vanderbilt University Medical Center, Nashville, TN 37232.
authors: Jarrod J
authors: JJ
authors: Mousa
authors: Chemical and Physical Biology Program, Vanderbilt University Medical Center, Nashville, TN 37232.
authors: Marion F
authors: MF
authors: Sauer
authors: Chemical and Physical Biology Program, Vanderbilt University Medical Center, Nashville, TN 37232.
authors: Alexander M
authors: AM
authors: Sevy
authors: Department of Pathology, Microbiology, and Immunology, Vanderbilt University, Nashville, TN 37232.
authors: Jessica A
authors: JA
authors: Finn
authors: Vanderbilt Vaccine Center, Vanderbilt University Medical Center, Nashville, TN 37232.
authors: John T
authors: 0000-0001-5545-6871
authors: JT
authors: Bates
authors: Department of Pathology, Microbiology, and Immunology, Vanderbilt University, Nashville, TN 37232.
authors: Gabriela
authors: G
authors: Alvarado
authors: Vanderbilt Vaccine Center, Vanderbilt University Medical Center, Nashville, TN 37232.
authors: Hannah G
authors: HG
authors: King
authors: Vanderbilt Vaccine Center, Vanderbilt University Medical Center, Nashville, TN 37232.
authors: Leah B
authors: LB
authors: Loerinc
authors: Integral Molecular, Inc., Philadelphia, PA 19104.
authors: Rachel H
authors: RH
authors: Fong
authors: Integral Molecular, Inc., Philadelphia, PA 19104.
authors: Benjamin J
authors: BJ
authors: Doranz
authors: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037.
authors: Bruno E
authors: BE
authors: Correia
authors: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037.
authors: Oleksandr
authors: O
authors: Kalyuzhniy
authors: Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305.
authors: Xiaolin
authors: X
authors: Wen
authors: Department of Structural Biology, Stanford University School of Medicine, Stanford, CA 94305.
authors: Theodore S
authors: TS
authors: Jardetzky
authors: Department of Immunology and Microbial Science, The Scripps Research Institute, La Jolla, CA 92037.
authors: William R
authors: WR
authors: Schief
authors: Department of Cell and Developmental Biology, Vanderbilt University Medical Center, Nashville, TN 37232.
authors: Melanie D
authors: MD
authors: Ohi
authors: Department of Chemistry, Vanderbilt University, Nashville, TN 37232.
authors: Jens
authors: J
authors: Meiler
authors: Vanderbilt Vaccine Center, Vanderbilt University Medical Center, Nashville, TN 37232; james.crowe@vanderbilt.edu.|Department of Pathology, Microbiology, and Immunology, Vanderbilt University, Nashville, TN 37232.|Department of Pediatrics, Vanderbilt University School of Medicine, Nashville, TN 37232.
authors: James E
authors: 0000-0002-0049-1079
authors: JE
authors: Crowe
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000276:immunology / Q000494:pharmacology; D061067:Antibodies, Monoclonal, Humanized / Q000276:immunology; D057134:Antibodies, Neutralizing / Q000737:chemistry / Q000276:immunology*; D000914:Antibodies, Viral / Q000276:immunology*; D000998:Antiviral Agents / Q000494:pharmacology; D002460:Cell Line; D018360:Crystallography, X-Ray; D018604:Epitope Mapping; D000939:Epitopes / Q000276:immunology; D006801:Humans; D051379:Mice; D016296:Mutagenesis; D000069455:Palivizumab / Q000494:pharmacology; D022261:Respiratory Syncytial Virus Vaccines / Q000737:chemistry / Q000276:immunology; D018113:Respiratory Syncytial Virus, Human / Q000187:drug effects / Q000276:immunology*; D014760:Viral Fusion Proteins / Q000276:immunology*
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D057134:Antibodies, Neutralizing; D000914:Antibodies, Viral; D000998:Antiviral Agents; D000939:Epitopes; C526850:F protein, human respiratory syncytial virus; D022261:Respiratory Syncytial Virus Vaccines; D014760:Viral Fusion Proteins; C506968:motavizumab; D000069455:Palivizumab
keywords: F protein; human respiratory syncytial virus; neutralizing antibodies