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.
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.
Yu
Fuxun
F
Department of Virology, Institute of Tropical Medicine, Nagasaki University, 1-12-4 Sakamoto, Nagasaki 852-8523, Japan.
Le
Mai Quynh
MQ
Inoue
Shingo
S
Thai
Hong Thi Cam
HT
Hasebe
Futoshi
F
Del Carmen Parquet
Maria
M
Morita
Kouichi
K
D000914:Antibodies, Viral / Q000097:blood*; D003428:Cross Infection / Q000453:epidemiology / Q000276:immunology* / Q000821:virology; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D019590:Nucleocapsid Proteins / Q000276:immunology*; D045473:Severe acute respiratory syndrome-related coronavirus / Q000235:genetics / Q000276:immunology*; D016036:Seroepidemiologic Studies; D045169:Severe Acute Respiratory Syndrome / Q000453:epidemiology / Q000276:immunology*; D014744:Vietnam
D000914:Antibodies, Viral; D019590:Nucleocapsid Proteins