| The severe acute respiratory syndrome (SARS), also named infectious atypical pneumonia, is a newly described and highly contagious respiratory disease that first occurred in mid-November of 2002 in Guangdong Province, China, and spread to 33 countries around the world. The mortality of the disease is about 11% (range 7 to 27%) for the most severely affected regions as reported by WHO. SARS has been a growing threat to public health. The disease is characterized by high fever, rigor, headache, lymphopenia, nonproductive cough or dyspnea and may progress to generalized, interstitial infiltrates in the lung, requiring intubation and mechanical ventilation. Some cases progress and deteriorate rapidly to acute respiratory distress syndrome (ARDS), multiorgan failure within 2~3 weeks or even in a much shorter time and easily leading to death. To control the spread of SARS, the World Health Organization (WHO) coordinated extraordinary collaborations among laboratories around the world to identify the causative agent of SARS and completely sequence the virus genome. In April 2003, WHO announced that SARS-coronavirus (SARS-CoV), a new member of the coronavirus family was the aetiological agent of SARS.The SARS-CoV, a positive-stranded RNA virus, has four structural proteins, spike (S), envelope (E), membrane (M) and nucleocapsid (N). The S protein, with its size of 1,255 amino acids and 23 glycosylation sites, is the largest structural protein in the SARS-CoV. Its amino acid sequence is significantly different from that of the other known coronaviruses, with only 24% pairwise amino acid identity, while the topology of this protein is similar to that of the other known coronaviruses. The S protein usually has a' huge amount of ectodomains and short transmembrane spans. The majority of amino acids of the SARS-CoV S protein at the N-terminus (residues 14 to1,195) were found on the outside of the viral particle, while only 13 amino acids at the C-terminus were embedded in the viral membrane. The S protein is responsible for viral attachment to cell receptors and entry into susceptible cells, eliciting neutralizing antibodies and inducing cytotoxic T lymphocyte (CTL) response.A common observation in patients with SARS is pronounced lymphonenia and a notable drop in CD4+ and CD8+ T lymphocyte counts occurring early in the course of the disease is associated with adverse outcomes. Evidence suggests that CD8+ cytotoxic T lymphocytes (CTLs) play a pivotal role in both virus elimination and immunopathology induction in acute respiratory virus infections, following recognition of epitopes presented on target cells in the context of MHC class I. But the molecular mechanisms underlying these CD8+ CTL-mediated effects remain poorly defined. HLA-A2 is the most common HLA-A allele in Asian populations, particularly in Chinese, with an estimated frequency of more than 50%. As SARS has affected many parts of Asia and a reservoir of infection may persist in these regions, the identification of HLA-A*0201 -restricted CTL epitopes of SARS-CoV can contribute greatly to the studies concerning the role of CTLs in SARS-CoV pathogenesis and the protection in at-risk populations.In this study, twenty peptides with binding motifs for HLA-A*0201 were predicted using computer algorithm and verified via MHC-peptide binding assay. Then the capacities of high-affinity candidate peptides to induce CTL in vivo and in vitro were further investigated. We have identified a novel HLA-A* 0201-restricted, immunogenic CD8+T-cell epitope of the SARS-CoV S protein, SSp-1 (RLNEVAK NL). SSp-1 is not only able to induce specific CTL response in HLA-A2.1/Kb transgenic mice but can also mobilize a specific CTL repertoire in PBLs from healthy HLA-A2.1"1" human donors. Moreover, SSp-1 is a naturally processed immunogenic peptide and is recognized by CTLs in an antigen-specific and HLA-A* 0201-restricted manner. Furthermore, we have established a sensitive and specific assay for peptide-specific CTL based on SSp-l/HLA-A*0201 tetramers. To the best of our knowledge,... |
PDF Full Text Request