Identification and molecular modification of cytotoxic T-lymphocyte epitopes from osteosarcoma high-expressing antigen PBF / 中国病理生理杂志

ABSTRACT

AIM:To observe whether modified epitopes from osteosarcoma high-expressing antigen papilloma-virus-binding factor (PBF) have HLA-A2 restricted antitumor ability,and to develop peptide-based immunotherapy for os-teosarcoma. METHODS:RT-PCR and Western blot were used to determine the expression of PBF in the osteosarcoma cell lines U2OS and Saos-2. HLA-A2 epitopes from PBF protein were predicted by NetCTL 1.2, SYFPEITHI and IEDB. The modified peptides from PBF containing HLA-A2 binding anchor motifs were designed by replacing the anchor residues. The peptides were synthesized by standard solid-phase methods,and the binding affinity of the peptides to HLA-A?0201 was evaluated by T2A2 cell binding assay. ELISPOT assay was used to investigate the seretion of interferon-γ(IFN-γ) from the peptide-induced specific cytotoxic T-lymphocytes (CTLs). The ability of inducing T-cell response was analyzed by lactate dehydrogenase (LDH) release assay and carboxyfluorescein succinimidyl ester (CFSE) cytotoxicity assay in vitro. RE-SULTSThe expression of PBF was observed in the U2OS and Saos-2 cells. The candidate peptides P75-1Y2L,P412-1Y, P416-1Y2L9V, P107-1Y and P435-1Y2L showed moderate affinity toward HLA-A2 molecule. The modified peptides showed significantly higher affinity with HLA-A2 than the native peptide. ELISPOT assay showed that P412, P412-1Y, P416,P416-1Y2L9V and P435-1Y2L induced specific CTLs to secrete IFN-γ, and P412-1Y and P416-1Y2L9V induced more secretion of IFN-γ than the native peptide. The CTLs induced by P412, P412-1Y, P416 and P416-1Y2L9V lysed U2OS cells. P412-1Y and P416-1Y2L9V peptide-specific CTLs showed higher cytotoxicity against U2OS cells than the native peptide-specific CTLs. CONCLUSION:Compared with the native peptide,modified epitopes P412-1Y and P416-1Y2L9V have higher binding affinity with HLA-A?0201 and retain immunogenecity. In addition,the anti-tumor immunity effects of modified epitopes P412-1Y and P416-1Y2L9V are stronger than the native peptide. The peptides P412-1Y and P416-1Y2L9V is excellent HLA-A?0201 restricted CTL epitopes from tumor antigen PBF,which could serve as new can-didates towards antitumor peptide vaccines.