A wild-type sequence p53 peptide presented by HLA-A24 induces cytotoxic T lymphocytes that recognize squamous cell...

Evidence has accumulated indicating that HLA-A2-restricted CTLs specific for human wild-type sequence p53 epitopes lyse tumor cells expressing mutant p53. To explore the possibility that wild-type sequence p53 peptides could also be used in vaccines for patients expressing HLA-A24 antigen, another frequent HLA class I allele, we investigated the induction of HLA-A24-restricted p53-specific CTLs from the peripheral blood lymphocytes of normal donors. Of six p53-derived peptides possessing an HLA-A24 binding motif, the p53 peptide 125-134 (p53(125-134)) was found to have a high binding capacity and induced peptide-specific CTLs from peripheral blood mononuclear cells, using peptide-pulsed autologous dendritic cells and subsequent cultivation with cytokines interleukin 2 and interleukin 7. Bulk CTL populations lysed peptide-pulsed HLA-A24+ targets as well as HLA-A24+ squamous cell carcinoma of the head and neck (SCCHN) cell lines. However, IFN-gamma pretreatment of HLA-A24+ SCCHN cell lines was necessary for lysis, suggesting that a ligand density higher than that normally expressed by tumor cells is required for these CTLs to mediate lysis. Moreover, a cloned CTL, designated TH#99, isolated from the bulk population by limiting dilution, lysed HLA-A24+ SCCHN targets more efficiently than the bulk CTL population. Lysis was inhibited by anti-HLA class I monoclonal antibody but not by anti-HLA-DR monoclonal antibody. These results indicate that HLA-A24-restricted CTLs recognizing the wild-type sequence p53(125-134) can be generated using autologous dendritic cells from precursors present in peripheral blood lymphocytes obtained from normal HLA-A24+ donors. This finding suggests that vaccine strategies targeting wild-type sequence p53 epitopes can be extended to a wider range of cancer patients.