Antibody Response of Patients with Severe Acute Respiratory Syndrome (SARS) Targets the Viral Nucleocapsid

Abstract

The recent outbreak of severe acute respiratory syndrome (SARS) provided an opportunity to study the antibody response of infected individuals to the causative virus, SARS coronavirus. We examined serum samples obtained from 46 patients with SARS, 40 patients with non-SARS pneumonia, and 38 healthy individuals, by use of Western blotting (WB), enzyme-linked immunoassay (ELISA), and immunofluorescence assay, using both native and bacterially produced antigens of the virus. We found a highly restricted, immunoglobulin G-dominated antibody response in patients with SARS, directed most frequently (89% by ELISA) and predominantly at the nucleocapsid. Almost all of the subjects without SARS had no antinucleocapsid antibodies. The spike protein was the next most frequently targeted, but only 63% of the patients (by ELISA) responded. Other targets of the response identified by use of WB included antigens of 80 and 60 kDa. Several nonstructural proteins cloned were not antigenic, and the culture-derived nucleocapsid appeared to be specifically degraded.

Severe acute respiratory syndrome diagnostics using a coronavirus protein microarray

“…2A Right). These results are consistent with previous studies that identified the N proteins of coronaviruses as the most abundant and reactive antigens (11).…”

“…However, it is not useful once the infection is cleared and can be challenging to implement in clinical application; the collection of samples such as nasopharyngeal or bronchial alveolar aspirates from SARS patients is dangerous and can put healthcare workers at high risk. ELISAs tend not to be highly sensitive and usually require large amounts of sample (8)(9)(10)(11). Moreover, existing ELISAs, such as one manufactured by Euroimmun (Luebeck, Germany), use whole viral extracts, thereby increasing the chance of misdiagnosis due to crossreactivity with proteins from other viruses.…”

Vaccination of mice with recombinant baculovirus expressing spike or nucleocapsid protein of SARS-like coronavirus generates humoral and cellular immune responses

“…Anti-N antibodies were present at high levels in SARS patients and persisted for a long time. In agreement, vectors that expressed full-length or truncated N proteins were highly immunogenic Guan et al, 2004;Huang et al, 2004;Leung et al, 2004;Tan et al, 2004;Woo et al, 2004). Hence, the S and N proteins may be the most promising vaccine candidates against SARS-CoV.…”

Induction of T-cell response by a DNA vaccine encoding a novel HLA-A*0201 severe acute respiratory syndrome coronavirus epitope

“…Subunit vaccines containing HLA-A*0201 restricted peptides is highly effective for the induction of strong cytotoxic T-cell response against infectious virus [6]. Among the four structure proteins of the SARS-CoV, the S and N proteins are the major targets for vaccine research studies due to their potency in triggering immune responses [7][8][9][10][11][12][13][14]. The S protein contains 1256 amino acids and is involved in viral entry through angiotensin-converting enzyme 2 receptor on host cell surface [15,16] and the N protein contains 422 amino acids and is involved in the viral RNA packaging [17,18].…”