Evaluation of inapparent nosocomial severe acute respiratory syndrome coronavirus infection in Vietnam by use of highly specific recombinant truncated nucleocapsid protein-based enzyme-linked immunosorbent assay.

Abstract

Severe acute respiratory syndrome (SARS) is a recently emerged human disease associated with pneumonia. Inapparent infection with SARS coronavirus (CoV) is not well characterized. To develop a safe, simple, and reliable screening method for SARS diagnosis and epidemiological study, two recombinant SARS-CoV nucleocapsid proteins (N' protein and (N)Delta(121) protein) were expressed in Escherichia coli, purified by affinity chromatography, and used as antigens for indirect, immunoglobulin G enzyme-linked immunosorbent assays (ELISA). Serum samples collected from healthy volunteers and SARS patients in Vietnam were used to evaluate the newly developed methods. The N' protein-based ELISA showed a highly nonspecific reaction. The (N)Delta(121) protein-based ELISA, with a nonspecific reaction drastically reduced compared to that of the nearly-whole-length N' protein-based ELISA, resulted in higher rates of positive reactions, higher titers, and earlier detection than the SARS-CoV-infected cell lysate-based ELISA. These results indicate that our newly developed SARS-CoV (N)Delta(121) protein-based ELISA is not only safe but also a more specific and more sensitive method to diagnose SARS-CoV infection and hence a useful tool for large-scale epidemiological studies. To identify inapparent SARS-CoV infections, serum samples collected from health care workers (HCWs) in Vietnam were screened by the (N)Delta(121) protein-based ELISA, and positive samples were confirmed by a virus neutralization test. Four out of 149 HCWs were identified to have inapparent SARS-CoV infection in Vietnam, indicating that subclinical SARS-CoV infection in Vietnam is rare but does exist.

• Authors: Fuxun Yu, Mai Quynh Le, Shingo Inoue, Hong Thi Cam Thai, Futoshi Hasebe, Maria Del Carmen Parquet, Kouichi Morita
• Journal: Clinical and diagnostic laboratory immunology (Clin Diagn Lab Immunol) Vol. 12 Issue 7 Pg. 848-54 (Jul 2005) ISSN: 1071-412X [Print] United States
• PMID: 16002634 (Publication Type: Evaluation Study, Journal Article, Research Support, Non-U.S. Gov't)

Chemical References

• Antibodies, Viral
• Nucleocapsid Proteins

Topics

• Antibodies, Viral (blood)
• Cross Infection (epidemiology, immunology, virology)
• Enzyme-Linked Immunosorbent Assay
• Humans
• Nucleocapsid Proteins (immunology)
• Severe acute respiratory syndrome-related coronavirus (genetics, immunology)
• Seroepidemiologic Studies
• Severe Acute Respiratory Syndrome (epidemiology, immunology)
• Vietnam