A novel pre-fusion conformation-specific neutralizing epitope on the respiratory syncytial virus fusion protein

Abstract

Respiratory syncytial virus (RSV) remains a major human pathogen, infecting the majority of infants before age two and causing re-infection throughout life. Despite decades of RSV research, there is no licensed RSV vaccine. Most candidate vaccines studied to date have incorporated the RSV fusion (F) surface glycoprotein, because the sequence of F is highly conserved among strains of RSV. To better define the human B cell response to RSV F, we isolated from a single donor 13 new neutralizing human monoclonal antibodies (mAbs) that recognize the RSV F protein in the pre-fusion conformation. Epitope binning studies showed that the majority of neutralizing mAbs targeted a new antigenic site on the globular head domain of F, designated here antigenic site VIII, which occupies an intermediate position between the previously defined major antigenic sites II and site Ø. Antibodies to site VIII competed for binding with antibodies to both of those adjacent neutralizing sites. The new mAbs exhibited unusual breadth for pre-fusion F-specific antibodies, cross-reacting with F proteins from both RSV subgroups A and B viruses. We solved the X-ray crystal structure of one site VIII mAb, hRSV90, in complex with pre-fusion RSV F protein. The structure revealed a large footprint of interaction for hRSV90 on RSV F, in which the heavy chain and light chain both have specific interactions mediating binding to site VIII, the heavy chain overlaps with site Ø, and the light chain interacts partially with site II.

Infants Infected with Respiratory Syncytial Virus Generate Potent Neutralizing Antibodies that Lack Somatic Hypermutation

“…There was also a more modest preference for the VH1-18:VK2-30, VH1-18:VL3-21, and VH5-51:VL6-57 gene pairs (Figure 1E). The VH1-18:VK2-30 gene pair was present in 8.5% of RSV F-reactive antibodies isolated from adults and is associated with recognition of site V on preF (Gilman et al, 2016; Mousa et al, 2017). Overall, the results demonstrate that RSV infection induces B cell responses with higher levels of SHM in infants ≥ 6 mo.…”

“…Although the secondary structure elements that form site III are present on both preF and postF, they adopt a different spatial arrangement in postF that results in higher affinity binding to preF (Corti et al, 2013). Antigenic site V, located between sites Ø and III, was recently identified and shown to be the target of additional preF-specific antibodies that are potently neutralizing (Gilman et al, 2016; Mousa et al, 2017). A preF-specific antibody that targets site Ø and contains Fc modifications to extend serum half-life (MEDI8897) is currently in late-phase clinical trials (Griffin et al, 2017; Zhu et al, 2017).…”

Respiratory syncytial virus entry and how to block it

“…As a result of tremendous advances in monoclonalantibody-isolation technology, during the past 10 years, hundreds of human-derived antibodies directed against the RSV F and G proteins have been isolated and characterized [127][128][129][130][131][132] . Some of the F-directed antibodies are 10-50-fold more potent than palivizumab, and many of them recognize epitopes located exclusively on the prefusion conformation.…”

Tailored Design of Protein Nanoparticle Scaffolds for Multivalent Presentation of Viral Glycoprotein Antigens

“…11-501, 5TPN res. 27-509) 23,37,38 . A C3-symmetric specified docking search was first performed, and output was assessed by the previously described RPX scoring method for symmetric docking 26 .…”