Identification of a critical neutralization determinant of severe acute respiratory syndrome (SARS)-associated coronavirus: importance for designing SARS vaccines

Virology. 2005 Mar 30;334(1):74-82. doi: 10.1016/j.virol.2005.01.034.

Abstract

The spike (S) protein of severe acute respiratory syndrome-associated coronavirus (SARS-CoV) is not only responsible for receptor binding, but also a major antigenic determinant capable of inducing protective immunity. In this study, we demonstrated that the receptor-binding domain (RBD) of S protein is an important immunogenic site in patients with SARS and rabbits immunized with inactivated SARS-CoV. Serum samples from convalescent SARS patients and immunized rabbits had potent neutralizing activities against infection by pseudovirus expressing SARS-CoV S protein. Depletion of RBD-specific antibodies from patient or rabbit immune sera by immunoadsorption significantly reduced serum-mediated neutralizing activity, while affinity-purified anti-RBD antibodies had relatively higher potency neutralizing infectivity of SARS pseudovirus, indicating that the RBD of S protein is a critical neutralization determinant of SARS-CoV during viral infection and immunization. Two monoclonal antibodies (1A5 and 2C5) targeting at the RBD of S protein were isolated from mice immunized with inactivated SARS-CoV. Both 1A5 and 2C5 possessed potent neutralizing activities, although they directed against distinct conformation-dependant epitopes as shown by ELISA and binding competition assay. We further demonstrated that 2C5, but not 1A5, was able to block binding of the RBD to angiotensin-converting enzyme 2 (ACE2), the functional receptor on targeted cells. These data provide important information for understanding the antigenicity and immunogenicity of SARS-CoV and for designing SARS vaccines.

MeSH terms

  • Animals
  • Antibodies, Monoclonal / isolation & purification
  • Antibodies, Viral / blood
  • Antibodies, Viral / isolation & purification
  • Antigens, Viral / chemistry
  • Antigens, Viral / genetics
  • Epitopes / chemistry
  • Epitopes / genetics
  • Humans
  • Membrane Glycoproteins / chemistry
  • Membrane Glycoproteins / genetics
  • Membrane Glycoproteins / immunology
  • Mice
  • Mice, Inbred BALB C
  • Neutralization Tests
  • Protein Structure, Tertiary
  • Rabbits
  • SARS Virus / genetics
  • SARS Virus / immunology*
  • Severe Acute Respiratory Syndrome / immunology
  • Severe Acute Respiratory Syndrome / prevention & control
  • Severe Acute Respiratory Syndrome / virology
  • Spike Glycoprotein, Coronavirus
  • Viral Envelope Proteins / chemistry
  • Viral Envelope Proteins / genetics
  • Viral Envelope Proteins / immunology
  • Viral Vaccines / genetics
  • Viral Vaccines / immunology*

Substances

  • Antibodies, Monoclonal
  • Antibodies, Viral
  • Antigens, Viral
  • Epitopes
  • MHV surface projection glycoprotein
  • Membrane Glycoproteins
  • Spike Glycoprotein, Coronavirus
  • Viral Envelope Proteins
  • Viral Vaccines
  • spike glycoprotein, SARS-CoV