Relative rates of non-pneumonic SARS coronavirus infection and SARS coronavirus pneumonia

Lancet. 2004 Mar 13;363(9412):841-5. doi: 10.1016/S0140-6736(04)15729-2.

Abstract

Background: Although the genome of severe acute respiratory syndrome coronavirus (SARS-CoV) has been sequenced and a possible animal reservoir identified, seroprevalence studies and mass screening for detection of subclinical and non-pneumonic infections are still lacking.

Methods: We cloned and purified the nucleocapsid protein and spike polypeptide of SARS-CoV and examined their immunogenicity with serum from patients with SARS-CoV pneumonia. An ELISA based on recombinant nucleocapsid protein for IgG detection was tested with serum from 149 healthy blood donors who donated 3 years previously and with serum positive for antibodies against SARS-CoV (by indirect immunofluorescence assay) from 106 patients with SARS-CoV pneumonia. The seroprevalence of SARS-CoV was studied with the ELISA in healthy blood donors who donated during the SARS outbreak in Hong Kong, non-pneumonic hospital inpatients, and symptom-free health-care workers. All positive samples were confirmed by two separate western-blot assays (with recombinant nucleocapsid protein and recombinant spike polypeptide).

Findings: Western-blot analysis showed that the nucleocapsid protein and spike polypeptide of SARS-CoV are highly immunogenic. The specificity of the IgG antibody test (ELISA with positive samples confirmed by the two western-blot assays) was 100%, and the sensitivity was 94.3%. Three of 400 healthy blood donors who donated during the SARS outbreak and one of 131 non-pneumonic paediatric inpatients were positive for IgG antibodies, confirmed by the two western-blot assays (total, 0.48% of our study population).

Interpretation: Our findings support the existence of subclinical or non-pneumonic SARS-CoV infections. Such infections are more common than SARS-CoV pneumonia in our locality.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Blood Donors
  • Blotting, Western
  • China / epidemiology
  • Coronavirus / genetics
  • Coronavirus / isolation & purification*
  • Cross Infection / epidemiology
  • Cross Infection / immunology
  • Enzyme-Linked Immunosorbent Assay
  • Humans
  • Immunoglobulin G / analysis
  • Immunoglobulin G / immunology
  • Membrane Glycoproteins / analysis
  • Nucleocapsid Proteins / genetics
  • Nucleocapsid Proteins / immunology
  • Pneumonia, Viral / epidemiology*
  • Pneumonia, Viral / immunology
  • Pneumonia, Viral / virology
  • Recombinant Proteins / analysis
  • Recombinant Proteins / immunology
  • Seroepidemiologic Studies
  • Severe Acute Respiratory Syndrome / epidemiology*
  • Severe Acute Respiratory Syndrome / immunology
  • Severe Acute Respiratory Syndrome / virology
  • Spike Glycoprotein, Coronavirus
  • Viral Envelope Proteins / analysis

Substances

  • Immunoglobulin G
  • Membrane Glycoproteins
  • Nucleocapsid Proteins
  • Recombinant Proteins
  • Spike Glycoprotein, Coronavirus
  • Viral Envelope Proteins
  • spike glycoprotein, SARS-CoV