Identification of B cell epitopes of severe acute respiratory syndrome (SARS) and development of diagnostic reagents

• Main Authors: I-Ju Liu, 劉怡如
• Other Authors: Han-Chang Wu
• Format: Others
• Language: en_US
• Published: 2004
• Online Access: http://ndltd.ncl.edu.tw/handle/33856823444483325017

碩士 === 國立臺灣大學 === 口腔生物科學研究所 === 92 === In November 2002, an outbreak of a life-threatening atypical pneumonia for which no etiological agent could be identified occurred in Guangdong Province, in southern China. The disease is unusual in its high morbidity and mortality rates and SARS seems to transmit through direct contact that lead to fast transmission all over the world. Cases of similar respiratory illness were subsequently reported globally including China, Taiwan, Singapore, Vietnam, Canada and USA. In late February 2003, the new disorder was designed “Severe acute respiratory syndrome (SARS)”. A growing body of evidence has convincingly shown that SARS is caused a novel coronavirus, called SARS-associated coronavirus (SARS-CoV). In past, we studied infectious diseases and set up the phage display technology to identify disease-specific epitopes from complex serum samples. To find SARS disease-specific B-cell epitopes, phage-displayed random peptide libraries were panned on serum IgG antibodies from SARS patients. From SP1 patient, forty-nine immunopositive phage clones that bound specifically to SARS patient serum samples were selected. These phage-borne peptides had four consensus motifs, two corresponding to amino acid sequences reported for SARS-CoV. Synthetic peptide binding and competition assay further confirmed that SARS patients generated antibodies against SARS-CoV. Immunopositive phage clones and epitope-based peptide antigens demonstrated clinical diagnostic potential by reacting with serum samples from SARS patients. Antibody response kinetics were evaluated in four SARS patients, and production of IgM, IgG and IgA were documented as part of the immune response. Furthermore, from SP3 and SP4 patients, twenty-four and sixty-five immunopositive phage clones that bound specifically to SARS patient serum samples were selected. These phage-borne peptides had four consensus motifs from SP3 and no corresponding to amino acid sequences reported for SARS-CoV. However, there were five consensus motifs from SP4 and two corresponding to amino acid sequences reported for Spike protein of SARS-CoV. In conclusion, B-cell epitopes of SARS corresponded to novel coronavirus. This suggests that novel coronavirus might be involved in the pathogenesis of SARS. Our epitope-based serologic test may be useful in laboratory detection of the virus and in further study of the pathogenesis of SARS. Identification of viral B-cell epitopes is important in understanding virus-antibody interactions at a molecular level and provides information for development of virus-specific serologic diagnostic reagents and subunit vaccines.