Development of an artificial antibody specific for HLA/peptide complex derived from cancer stem-like cell/cancer-initiating cell antigen DNAJB8

Background Peptide-vaccination therapy targeting tumour-associated antigens can elicit immune responses, but cannot be used to eliminate large tumour burden. In this study, we developed a therapeutic single-chain variable-fragment (scFv) antibody that recognises the cancer stem-like cell/cancer-initiating cell (CSC/CIC) antigen, DNAJB8. Methods We screened scFv clones reacting with HLA-A24:20/DNAJB8-derived peptide (DNAJB8_143) complex using naive scFv phage-display libraries. Reactivity and affinity of scFv clones against the cognate antigen were quantified using FACS and surface plasmon resonance. Candidate scFv clones were engineered to human IgG1 (hIgG1) and T-cell-engaging bispecific antibody (CD3xJB8). Complement-dependent cytotoxicity (CDC) and bispecific antibody-dependent cellular cytotoxicity (BADCC) were assessed. Results scFv clones A10 and B10 were isolated after bio-panning. Both A10-hIgG1 and B10-hIgG1 reacted with DNAJB8-143 peptide-pulsed antigen-presenting cells and HLA-A24(+)/DNAJB8(+) renal cell carcinoma and osteosarcoma cell lines. A10-hIgG1 and B10-hIgG1 showed strong affinity with the cognate HLA/peptide complex (K-D = 2.96 x 10(-9) M and 5.04 x 10(-9) M, respectively). A10-hIgG1 and B10-hIgG1 showed CDC against HLA-A24(+)/DNAJB8(+) cell lines. B10-(CD3xJB8) showed superior BADCC to A10-(CD3xJB8). Conclusion We isolated artificial scFv antibodies reactive to CSC/CIC antigen DNAJB8-derived peptide naturally present on renal cell carcinoma and sarcoma. Immunotherapy using these engineered antibodies could be promising.