title: Design and characterization of epitope-scaffold immunogens that present the motavizumab epitope from respiratory syncytial virus.
abstract: Respiratory syncytial virus (RSV) is a major cause of respiratory tract infections in infants, but an effective vaccine has not yet been developed. An ideal vaccine would elicit protective antibodies while avoiding virus-specific T-cell responses, which have been implicated in vaccine-enhanced disease with previous RSV vaccines. We propose that heterologous proteins designed to present RSV-neutralizing antibody epitopes and to elicit cognate antibodies have the potential to fulfill these vaccine requirements, as they can be fashioned to be free of viral T-cell epitopes. Here we present the design and characterization of three epitope-scaffolds that present the epitope of motavizumab, a potent neutralizing antibody that binds to a helix-loop-helix motif in the RSV fusion glycoprotein. Two of the epitope-scaffolds could be purified, and one epitope-scaffold based on a Staphylococcus aureus protein A domain bound motavizumab with kinetic and thermodynamic properties consistent with the free epitope-scaffold being stabilized in a conformation that closely resembled the motavizumab-bound state. This epitope-scaffold was well folded as assessed by circular dichroism and isothermal titration calorimetry, and its crystal structure (determined in complex with motavizumab to 1.9 Å resolution) was similar to the computationally designed model, with all hydrogen-bond interactions critical for binding to motavizumab preserved. Immunization of mice with this epitope-scaffold failed to elicit neutralizing antibodies but did elicit sera with F binding activity. The elicitation of F binding antibodies suggests that some of the design criteria for eliciting protective antibodies without virus-specific T-cell responses are being met, but additional optimization of these novel immunogens is required.
authors.affiliation: Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA. mclellanja@mail.nih.gov
authors.forename: Jason S
authors.initials: JS
authors.lastname: McLellan
authors.forename: Bruno E
authors.initials: BE
authors.lastname: Correia
authors.forename: Man
authors.initials: M
authors.lastname: Chen
authors.forename: Yongping
authors.initials: Y
authors.lastname: Yang
authors.forename: Barney S
authors.initials: BS
authors.lastname: Graham
authors.forename: William R
authors.initials: WR
authors.lastname: Schief
authors.forename: Peter D
authors.initials: PD
authors.lastname: Kwong
mesh_terms: D000595:Amino Acid Sequence; D000911:Antibodies, Monoclonal / Q000276:immunology*; D061067:Antibodies, Monoclonal, Humanized; D002151:Calorimetry; D002460:Cell Line; D002942:Circular Dichroism; D000939:Epitopes / Q000737:chemistry* / Q000276:immunology; D006801:Humans; D008958:Models, Molecular; D008969:Molecular Sequence Data; D012136:Respiratory Syncytial Viruses / Q000276:immunology*; D013205:Staphylococcal Protein A / Q000737:chemistry
chemical_list: D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; D000939:Epitopes; D013205:Staphylococcal Protein A; C506968:motavizumab