Kinetics of Severe Acute Respiratory Syndrome (SARS) Coronavirus-Specific Antibodies in 271 Laboratory-Confirmed Cases of SARS

Abstract

The sensitivities and specificities of an immunofluorescence assay and an enzyme immunoassay for detection of antibodies specific for severe acute respiratory syndrome coronavirus (SARS-CoV) were compared for 148 laboratory-confirmed SARS cases. The appearance and persistence of SARS-CoV-specific antibodies were assessed, with immunoglobulin G detected in 59% of samples collected within 14 days and persisting for 60 to 95 days after the onset of illness. (2-4, 7, 9, 10), although data on the performance of various antibody detection assays and the persistence of SARS-CoV-specific antibodies are lacking.The first aim of this study was to compare the sensitivities and specificities of a commercial immunofluorescence assay (IFA; Euroimmun AG, Lübeck, Germany) and a recombinant double-nucleocapsid antigen sandwich enzyme-linked immunosorbent assay (ELISA; Wantai Biological Pharmacy Enterprise Company, Ltd., Beijing, China) for SARS-CoV-specific immunoglobulin G (IgG) and IgM in patients for whom SARS-CoV RNA had been detected by reverse transcriptase PCR (RT-PCR). The second aim was to assess the timing of the appearance and persistence of SARS-CoV-specific antibodies after the onset of disease.Three hundred four patients fitting the SARS clinical case definition (fever of 38°C or higher, cough or shortness of breath, new pulmonary infiltrates on chest radiography, and close contact with a person with a suspected or probable case) were hospitalized at Ditan Hospital, Beijing, China, between 26 March and 31 May 2003. Probable cases were regarded as laboratory confirmed if SARS-CoV-specific IgG and/or IgM was detected by IFA within 3 weeks of the onset of illness and/or SARS-CoV RNA was detected by RT-PCR within 2 weeks. SARS-CoV infection was laboratory confirmed in 271 of 304 (89.1%) cases, with 33 individuals testing SARS-CoV negative (10.9%; 27 of these had alternative laboratory diagnoses). The mean age of the 271 individuals with laboratoryconfirmed cases was 36 Ϯ 16 years, and they included 92 (33.9%) health care workers and 32 patients with significant underlying illnesses. SARS acquisition in the hospital setting, in either health care workers, inpatients, or hospital visitors, occurred in 112 (41.3%) cases, and a further 62 individuals acquired SARS following exposure at home to family members or friends with hospital-acquired infections. The clinical features were similar to those reported elsewhere (data not shown) (1,3,5,10,11).Comparison of IFA and ELISA for detection of SARS-CoVspecific IgG and IgM. Testing was performed for 148 patients for whom SARS-CoV was detected in respiratory or fecal samples by RT-PCR. SARS-CoV IgM was detected for 117 (79%) people and SARS-CoV IgG was detected for 145 (98%) people by IFA, while IgM was detected for 133 (90%) people and IgG was detected for 120 (82%) people by ELISA. Controls included 105 asymptomatic close contacts of individuals with SARS cases (medical workers) and 90 individuals with chronic hepatitis B (30 cases), hepatitis C (30 cases), or human immunodef...

Effects of severe acute respiratory syndrome (SARS) coronavirus infection on peripheral blood lymphocytes and their subsets

“…Of the 148 SARS-CoV RT-PCR positive samples, SARS-CoV IgG was detected in 145 (98%) and SARS-CoV IgM in 117 (79%) using IFA. 12 There were 33/304 (10.9%) that were negative on SARS testing. An alternative laboratory diagnosis was made in 27/33, of which the most common were acute influenza B (13 cases) and Klebsiella pneumoniae infection (nine cases).…”

Longitudinal Analysis of Severe Acute Respiratory Syndrome (SARS) Coronavirus-Specific Antibody in SARS Patients

“…Second, we did not use any antibody test other than IFA, such as an enzyme-linked immunosorbent assay, to determine the antibody response and compare the results with those determined by IFA. However, some previous studies have demonstrated that the antibody responses determined by IFA and enzyme-linked immunosorbent assays were similar (4,6). Third, only 29.5% of SARS patients who survived and were treated in our hospital were followed for more than 1 year and enrolled in this study.…”

“…Prior studies pointed out that (i) the specific antibody to SARS-CoV appears as early as 9 days after the disease onset and a high level of the antibody can last for 1 to 2 months (3, 9), (ii) IgM and IgG to SARS-CoV appear at almost the same time (4,6,14), (iii) the peak IgG titer is usually noted 4 to 12 weeks after the disease onset (7,14), and (iv) the IgM to SARS-CoV is usually undetectable 180 days after the disease onset (14). Our present study demonstrated similar results.…”

“…Ten serum samples from healthy volunteers and 10 other serum samples from adult patients with bacteremic pneumonia, collected 17 to 30 days after their disease onsets, were also included in the test for comparison. All of the serum samples were measured for IgMand IgG-specific antibodies to SARS-CoV using a commercially available indirect immunofluorescent assay (IFA) (Euroimmune, Lübeck, Germany) (2,4). This test utilizes slides coated with SARS-CoV-infected cells together with noninfected cells to detect specific antibodies in patient serum samples.…”

Recombinant Protein-Based Assays for Detection of Antibodies to Severe Acute Respiratory Syndrome Coronavirus Spike and Nucleocapsid Proteins

“…Persistent levels of SARS-CoV IgG have been detected in SARS cases for several months and up to 2 years after disease onset (4,11,12,19,21). In this study, serum samples from 48 SARS patients from Vietnam and the United States were collected 221 to 735 days (44 from days 221 to 250; 4 from days 633 to 735) after the onset of illness and tested for the presence of SARS-CoV-and N-and S-protein-specific IgG by ELISA.…”