Structural Superimposition

Abstact

Enterovirus D68 (EV-D68) is a picornavirus that causes biennial outbreaks of respiratory disease in young children that can progress to rare but severe complications, including acute flaccid myelitis (AFM). EV-D68 virus-like particles (VLPs) elicit potent neutralizing antibodies that are protective in animal models. Here, we report the isolation and characterization of monoclonal antibodies elicited by EV-D68 VLPs in nonhuman primates (NHPs). We identified five potently neutralizing mAbs targeting overlapping epitopes near the capsid fivefold axis of symmetry formed by pentamers of viral protein 1. Cryo-electron microscopy structures of mAbs 1E11 and 5H03 in complex with VLP revealed epitopes on the capsid that bridge the sialic acid binding site and the proteinaceous entry receptor major facilitator superfamily domain-containing protein 6 binding site. We further characterized the mechanisms by which these mAbs neutralize EV-D68 and found that mAbs can disrupt multiple steps in the EV-D68 life cycle, including promoting premature uncoating. Antibodies elicited by VLP immunization of NHP protected as well as a best-in-class human mAb in a mouse challenge model, although single-amino acid mutations in the capsid enabled viral escape. Our results demonstrate that EV-D68 VLP-elicited mAbs target major viral sites of vulnerability, provide insight into their mechanisms of neutralization, and reinforce the potential for VLP-based vaccines as a countermeasure for EV-D68.