ABSTRACT
Prevention efforts for respiratory syncytial virus (RSV) have been advanced due to the recent isolation and characterization of antibodies that specifically recognize the prefusion conformation of the RSV fusion (F) glycoprotein. These potently neutralizing antibodies are in clinical development for passive prophylaxis and have also aided the design of vaccine antigens that display prefusion-specific epitopes. To date, prefusion-specific antibodies have been shown to target two antigenic sites on RSV F, but both of these sites are also present on monomeric forms of F. Here we present a structural and functional characterization of human antibody AM14, which potently neutralized laboratory strains and clinical isolates of RSV from both A and B subtypes. The crystal structure and location of escape mutations revealed that AM14 recognizes a quaternary epitope that spans two protomers and includes a region that undergoes extensive conformational changes in the pre- to postfusion F transition. Binding assays demonstrated that AM14 is unique in its specific recognition of trimeric furin-cleaved prefusion F, which is the mature form of F on infectious virions. These results demonstrate that the prefusion F trimer contains potent neutralizing epitopes not present on monomers and that AM14 should be particularly useful for characterizing the conformational state of RSV F-based vaccine antigens.
Subject(s)
Antibodies, Neutralizing/ultrastructure , Antibodies, Viral/ultrastructure , Epitopes, B-Lymphocyte/ultrastructure , Respiratory Syncytial Viruses/immunology , Antibodies, Neutralizing/chemistry , Antibodies, Neutralizing/immunology , Antibodies, Viral/chemistry , Antibodies, Viral/immunology , Antigens, Viral/immunology , Cell Line , Chromatography, Gel , Crystallography, X-Ray , Enzyme-Linked Immunosorbent Assay , Epitope Mapping , Epitopes, B-Lymphocyte/chemistry , Epitopes, B-Lymphocyte/immunology , Flow Cytometry , Glycoproteins/chemistry , Glycoproteins/immunology , Glycoproteins/ultrastructure , Humans , Protein Structure, Quaternary , Surface Plasmon ResonanceABSTRACT
Human respiratory syncytial virus (RSV) is the main cause of lower respiratory tract infections in young children. The RSV fusion protein (F) is highly conserved and is the only viral membrane protein that is essential for infection. The prefusion conformation of RSV F is considered the most relevant target for antiviral strategies because it is the fusion-competent form of the protein and the primary target of neutralizing activity present in human serum. Here, we describe two llama-derived single-domain antibodies (VHHs) that have potent RSV-neutralizing activity and bind selectively to prefusion RSV F with picomolar affinity. Crystal structures of these VHHs in complex with prefusion F show that they recognize a conserved cavity formed by two F protomers. In addition, the VHHs prevent RSV replication and lung infiltration of inflammatory monocytes and T cells in RSV-challenged mice. These prefusion F-specific VHHs represent promising antiviral agents against RSV.
Subject(s)
Antibodies, Neutralizing/immunology , Respiratory Syncytial Virus Infections/immunology , Respiratory Syncytial Virus, Human/immunology , Single-Domain Antibodies/immunology , Viral Fusion Proteins/immunology , Animals , Camelids, New World/immunology , Chlorocebus aethiops , Humans , Mice , Monocytes/immunology , Monocytes/virology , Protein Binding , Respiratory Syncytial Virus Infections/virology , Respiratory Syncytial Virus, Human/physiology , T-Lymphocytes/immunology , T-Lymphocytes/virology , Vero Cells , Virus Replication/immunologyABSTRACT
This corrects the article DOI: 10.1038/ncomms14158.