title: Longitudinal profile of immunoglobulin G (IgG), IgM, and IgA antibodies against the severe acute respiratory syndrome (SARS) coronavirus nucleocapsid protein in patients with pneumonia due to the SARS coronavirus.
abstract: By using a recombinant severe acute respiratory syndrome coronavirus (SARS-CoV) nucleocapsid protein-based enzyme-linked immunosorbent assay (ELISA) and serum specimens serially collected (from day 0 to day 240 after symptom onset) from patients with pneumonia due to SARS-CoV, we analyzed the longitudinal profiles of immunoglobulin G (IgG), IgM, and IgA antibodies against the SARS-CoV nucleocapsid protein in patients with pneumonia due to SARS-CoV. For IgG, the median optical density at 450 nm (OD450) turned positive at day 17 and a biphasic response was observed. At day 240, all patients were still positive for anti-nucleocapsid protein IgG antibody. For IgM, the median OD450 turned positive at day 20.5, peaked at about day 80, and fell to below the baseline level at about day 180. At day 240, 36% of the patients were still positive for anti-nucleocapsid protein IgM antibody. For IgA, the median OD450 turned positive at day 17, peaked at about day 50, and fell to below the baseline level at about day 180. At day 240, 36% of the patients were still positive for anti-nucleocapsid protein IgA antibody. The time of seroconversion detected by the recombinant SARS-CoV nucleocapsid protein-based ELISA and that detected by indirect immunofluorescence assay were similar. The median times of seroconversion for IgG, IgM, and IgA detected by the indirect immunofluorescence assay were 17 days (17 days by ELISA), 16.5 days (20.5 days by ELISA), and 17.5 days (17 days by ELISA), respectively, after disease onset. One, four, and one of the six patients who died did not produce any IgG, IgM, and IgA antibodies against the nucleocapsid protein of SARS-CoV, respectively, although these antibodies were detected in all six patients by the indirect immunofluorescence assay. Further studies should be performed to see whether SARS-CoV nucleocapsid protein antibody positivity has any prognostic significance.
authors.affiliation: Department of Microbiology, The University of Hong Kong, Hong Kong.
authors.forename: Patrick C Y
authors.initials: PC
authors.lastname: Woo
authors.forename: Susanna K P
authors.initials: SK
authors.lastname: Lau
authors.forename: Beatrice H L
authors.initials: BH
authors.lastname: Wong
authors.forename: Kwok-hung
authors.initials: KH
authors.lastname: Chan
authors.forename: Chung-ming
authors.initials: CM
authors.lastname: Chu
authors.forename: Hoi-wah
authors.initials: HW
authors.lastname: Tsoi
authors.forename: Yi
authors.initials: Y
authors.lastname: Huang
authors.forename: J S Malik
authors.initials: JS
authors.lastname: Peiris
authors.forename: Kwok-yung
authors.initials: KY
authors.lastname: Yuen
mesh_terms: D000914:Antibodies, Viral / Q000097:blood*; D000086462:Coronavirus Nucleocapsid Proteins; D004797:Enzyme-Linked Immunosorbent Assay; D005455:Fluorescent Antibody Technique; D006801:Humans; D007070:Immunoglobulin A / Q000097:blood; D007074:Immunoglobulin G / Q000097:blood; D007075:Immunoglobulin M / Q000097:blood; D019590:Nucleocapsid Proteins / Q000276:immunology*; D011014:Pneumonia / Q000209:etiology*; D011379:Prognosis; D011994:Recombinant Proteins / Q000276:immunology; D045473:Severe acute respiratory syndrome-related coronavirus / Q000276:immunology*; D045169:Severe Acute Respiratory Syndrome / Q000150:complications* / Q000276:immunology; D013997:Time Factors
chemical_list: D000914:Antibodies, Viral; D000086462:Coronavirus Nucleocapsid Proteins; D007070:Immunoglobulin A; D007074:Immunoglobulin G; D007075:Immunoglobulin M; D019590:Nucleocapsid Proteins; D011994:Recombinant Proteins