Identification of SARS-COV Spike Protein-Derived and HLA-A2-Restricted Human CTL Epitopes by Using a New Muramyl Dipeptide-Derivative Adjuvant

Severe acute respiratory syndrome (SARS) spread during the winter of 2003, and attempt have been made to develop vaccines against SARS corona virus (SARS-CoV). The present study provides a strategy to rapidly identify SARS-CoV-derived antigenic peptides recognized by HLA-A2-restricted cytotoxic T lymphocytes (CTLs). Forty-three candidate peptides having HLA-A2-binding motifs were selected in silico and HLA-A2/D^b chimeric MHC class I-transgenic mice were immunized with these peptides and a new derivative of muramyl dipeptide that can induce upregulation of HLA-DR, CD80, CD86, and CD40 in human CD14⁺ antigen presenting cells, was administered as an adjuvant. Six HLA-A2-restricted mouse CTL epitopes were identified, including two new epitopes which have never been reported before. One of the novel peptides was naturally processed and successfully induced HLA-A2-restricted specific CTLs in both HLA transgenic mice and healthy donors. The method was useful, convenient and efficient for rapid identification of CTL epitopes derived from SARS-CoV proteins and will be possibly applicable for other pathogens to develop a peptide-based vaccine.