The immune responses of HLA-A*0201 restricted SARS-CoV S peptide-specific CD8⁺ T cells are augmented in varying degrees by CpG ODN, PolyI:C and R848

Abstract

The induction of antigen specific memory CD8(+) T cells in vivo is very important to new vaccines against infectious diseases. In the present study, we aimed to evaluate the immune responses of peptide-specific CD8(+) T cells induced by HLA-A*0201 restricted severe acute respiratory syndrome-associated coronavirus (SARS-CoV) S epitopes plus CpG oligodeoxynucleotide (CpG ODN), PolyI:C and R848 as adjuvants. Furthermore, the generation, distribution and phenotype of long-lasting peptide-specific memory CD8(+) T cells were assessed by ELISA, ELISPOT and flow cytometry. Our results showed that antigen specific CD8(+) T cells were elicited by HLA-A*0201 restricted SARS-CoV S epitopes. Furthermore, the frequency of peptide-specific CD8(+) T cells was dramatically increased after both prime and boost immunization with peptides plus CpG ODN, whereas slight enhancements were induced following boost vaccination with peptides plus PolyI:C or R848. SARS-CoV S peptide-specific IFN-γ(+)CD8(+) T cells were distributed throughout the lymphoid and non-lymphoid tissues. Results also demonstrated that the HLA-A*0201 restricted peptide-specific CD8(+) T cells induced by peptides plus CpG ODN carried a memory cell phenotype with CD45RB(+) and CD62L(-) and possessed long-term survival ability in vivo. Taken together, our results implied that HLA-A*0201 restricted SARS-CoV S epitopes plus CpG ODN might be the superior candidates for SARS vaccine.