Specific Targeting of a Naturally Presented Osteosarcoma Antigen PBF Peptide Using an Artificial Monoclonal Antibody [Cell Biology]

June 24th, 2014 by Tsukahara, T., Emori, M., Murata, K., Hirano, T., Muroi, N., Kyono, M., Toji, S., Watanabe, K., Torigoe, T., Kochin, V., Asanuma, H., Matsumiya, H., Yamashita, K., Himi, T., Ichimiya, S., Wada, T., Yamashita, T., Hasegawa, T., Sato, N.

Osteosarcoma is a rare but highly malignant tumor occurring most frequently in adolescents. The prognosis of non-responders to chemotherapy is still poor and new treatment modalities are needed. To develop peptide-based immunotherapy, we previously identified autologous CTL-defined osteosarcoma antigen papillomavirus binding factor (PBF) in the context of HLA-B55 and the CTL epitope (PBF A2.2) presented by HLA-A2. PBF and HLA class I are expressed in approximately 90% and 70% of various sarcomas, respectively. However, the expression status of peptide PBF A2.2 presented by HLA-A2 on osteosarcoma cells has remained unknown because it is difficult to generate a specific probe reacting with the HLA/peptide complex. For detection and qualification of the HLA-A*02:01/PBF A2.2 peptide complex on osteosarcoma cells, we tried to isolate a single-chain variable fragment (scFv) antibody directed to the HLA-*A0201/PBF A2.2 complex using a naive scFv phage display library. As a result, scFv clone D12 with high affinity (KD=1.53x10-9M) was isolated. D12 could react with PBF A2.2 peptide-pulsed T2 cells and HLA-A2+PBF+ osteosarcoma cell lines and simultaneously demonstrated that the HLA/peptide complex was expressed on osteosarcoma cells. In conclusion, scFv clone D12 might be useful to select candidate patients for PBF A2.2 peptide-based immunotherapy and develop antibody-based immunotherapy.