Immunogenicity and structures of a rationally designed prefusion MERS-CoV spike antigen

Proc Natl Acad Sci U S A. 2017 Aug 29;114(35):E7348-E7357. doi: 10.1073/pnas.1707304114. Epub 2017 Aug 14.

Abstract

Middle East respiratory syndrome coronavirus (MERS-CoV) is a lineage C betacoronavirus that since its emergence in 2012 has caused outbreaks in human populations with case-fatality rates of ∼36%. As in other coronaviruses, the spike (S) glycoprotein of MERS-CoV mediates receptor recognition and membrane fusion and is the primary target of the humoral immune response during infection. Here we use structure-based design to develop a generalizable strategy for retaining coronavirus S proteins in the antigenically optimal prefusion conformation and demonstrate that our engineered immunogen is able to elicit high neutralizing antibody titers against MERS-CoV. We also determined high-resolution structures of the trimeric MERS-CoV S ectodomain in complex with G4, a stem-directed neutralizing antibody. The structures reveal that G4 recognizes a glycosylated loop that is variable among coronaviruses and they define four conformational states of the trimer wherein each receptor-binding domain is either tightly packed at the membrane-distal apex or rotated into a receptor-accessible conformation. Our studies suggest a potential mechanism for fusion initiation through sequential receptor-binding events and provide a foundation for the structure-based design of coronavirus vaccines.

Keywords: X-ray crystallography; coronavirus; cryo-EM; neutralizing antibody; peplomer.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, N.I.H., Intramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Animals
  • Antibodies, Neutralizing / immunology*
  • Antibodies, Viral / immunology
  • Coronaviridae / immunology
  • Coronavirus Infections / virology
  • Crystallography, X-Ray / methods
  • Humans
  • Immunity, Humoral / immunology
  • Immunoglobulin G / metabolism
  • Mice, Inbred BALB C
  • Middle East Respiratory Syndrome Coronavirus / immunology
  • Protein Binding
  • Protein Conformation
  • Receptors, Virus / metabolism
  • Spike Glycoprotein, Coronavirus / immunology*
  • Structure-Activity Relationship
  • Vaccination
  • Viral Vaccines / immunology

Substances

  • Antibodies, Neutralizing
  • Antibodies, Viral
  • Immunoglobulin G
  • Receptors, Virus
  • Spike Glycoprotein, Coronavirus
  • Viral Vaccines

Associated data

  • PDB/5W9H
  • PDB/5W9P
  • PDB/5VYH
  • PDB/5VZR