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Published on: September 14, 2014
Improved epitope resolution of the prefusion trimer-specific antibody AM14 bound to the RSV F glycoprotein
Wayne Harshbarger1, Priyanka D Abeyrathne1, Sai Tian1
1GSK, Vaccine Design and Cellular Immunology, Rockville, MD, USA.
Insights
This study reveals the precise structure of the Respiratory Syncytial Virus (RSV) F glycoprotein bound to the AM14 antibody. These findings enhance understanding of RSV vaccine antigen structure and quality control.
Area of Science:
- Virology
- Structural Biology
- Immunology
Background:
- Respiratory syncytial virus (RSV) is a leading cause of infant respiratory infections, making RSV vaccines a public health priority.
- The RSV F glycoprotein, particularly its prefusion form (PreF), is a key target for neutralizing antibodies and vaccine development.
- The DS-Cav1 antigen is a stabilized prefusion F protein under investigation for RSV vaccines.
Purpose of the Study:
- To determine the high-resolution structure of the AM14 antibody bound to the RSV prefusion F glycoprotein (DS-Cav1).
- To elucidate the molecular details of the AM14 epitope on the RSV F trimer.
- To provide insights into RSV vaccine design and quality assessment.
Main Methods:
- X-ray crystallography and cryo-electron microscopy (cryo-EM) were employed to resolve the structure of the AM14-DS-Cav1 complex.
- High-resolution structures were obtained at 3.6 Å (X-ray) and 3.4 Å (cryo-EM).
- Analysis of side-chain densities allowed for precise mapping of the antibody-epitope interface.
Main Results:
- High-resolution structures revealed detailed interactions between the AM14 antibody and the prefusion RSV F glycoprotein.
- The structures enabled accurate mapping of the AM14 epitope, which spans two F protomers on the trimer.
- The findings rationalize AM14's binding to specific RSV F mutants and highlight flexibility in key antigenic residues.
Conclusions:
- The determined structures provide a comprehensive understanding of the AM14 epitope on the RSV F trimer.
- This structural information is crucial for the rational design and quality control of RSV prefusion F-based vaccines.
- The study advances the development of effective strategies against RSV infections.
Abstract:
Respiratory syncytial virus (RSV) is the most common cause of acute lower respiratory tract infections resulting in medical intervention and hospitalizations during infancy and early childhood, and vaccination against RSV remains a public health priority. The RSV F glycoprotein is a major target of neutralizing antibodies, and the prefusion stabilized form of F (DS-Cav1) is under investigation as a vaccine antigen. AM14 is a human monoclonal antibody with the exclusive capacity of binding an epitope on prefusion F (PreF), which spans two F protomers. The quality of recognizing a trimer-specific epitope makes AM14 valuable for probing PreF-based immunogen conformation and functionality during vaccine production. Currently, only a low-resolution (5.5 Å) X-ray structure is available of the PreF-AM14 complex, revealing few reliable details of the interface. Here, we perform complementary structural studies using X-ray crystallography and cryo-electron microscopy (cryo-EM) to provide improved resolution structures at 3.6 Å and 3.4 Å resolutions, respectively. Both X-ray and cryo-EM structures provide clear side-chain densities, which allow for accurate mapping of the AM14 epitope on DS-Cav1. The structures help rationalize the molecular basis for AM14 loss of binding to RSV F monoclonal antibody-resistant mutants and reveal flexibility for the side chain of a key antigenic residue on PreF. This work provides the basis for a comprehensive understanding of RSV F trimer specificity with implications in vaccine design and quality assessment of PreF-based immunogens.
