Development of T cell receptor-engineered T cells targeting the sarcoma-associated antigen papillomavirus binding factor

We previously identified papillomavirus binding factor (PBF) as an osteosarcoma antigen recognized by an autologous cytotoxic T lymphocyte clone. Vaccination with PBF-derived peptide presented by HLA-A24 (PBF peptide) elicited strong immune responses. In the present study, we generated T cell receptor-engineered T cells (TCR-T cells) directed against the PBF peptide (PBF TCR-T cells). PBF TCR was successfully transduced into T cells and detected using HLA-A*24:02/PBF peptide tetramer. PBF TCR-T cells generated from a healthy donor were highly expanded and recognized T2-A24 cells pulsed with PBF peptide, HLA-A24⁺ 293T cells transfected with PBF cDNA, and sarcoma cell lines. To establish an adoptive cell therapy model, we modified the PBF TCR by replacing both α and β constant regions with those of mice (hybrid PBF TCR). Hybrid PBF TCR-T cells also showed reactivity against T2-A24 cells pulsed with PBF peptide and to HLA-A24⁺ 293T cells transfected with various lengths of PBF cDNA including the PBF peptide sequence. Subsequently, we generated target cell lines highly expressing PBF (MFH03-PBF [short] epitope [+]) containing PBF peptide with in vivo tumorigenicity. Hybrid PBF TCR-T cells exhibited antitumor effects compared with mock T cells in NSG mice xenografted with MFH03-PBF (short) epitope (+) cells. CD45⁺ T cells significantly infiltrated xenografted tumors only in the hybrid PBF TCR T cell group and most of these cells were CD8-positive. CD8⁺ T cells also showed Ki-67 expression and surrounded the CD8-negative tumor cells expressing Ki-67. These findings suggest that PBF TCR-T cell therapy might be a candidate immunotherapy for sarcoma highly expressing PBF.