Sensitization of tumour cells to lysis by virus-specific CTL using antibody-targeted MHC class I/peptide complexes

A number of cell surface molecules with specificity to tumour cells have be en identified and monoclonal antibodies (mAb) to some of these antigens hav e been used for targeting tumour cells in vivo. We have sought to link the powerful effector mechanisms of cytotoxic T-cells with the specificity of m Ab. by targeting recombinant HLA class I molecules to tumour cells using an antibody delivery system. Soluble recombinant MHC class I/peptide complexe s including HLA-A2.1 refolded around an immunodominant peptide from the HIV gag protein (HLA-A2/gag) were synthesized. and the stability of these comp lexes at 37 degrees C was confirmed by enzyme-linked immunosorbent assay us ing a conformation-specific antibody. MHC class I-negative lymphoma cells ( Daudi) were labelled with a biotinylated mAb specific for a cell surface pr otein (anti-CD20) then linked to soluble biotinylated HL4-A2/gag complexes using an avidin bridge. Flow cytometry revealed strong labelling of lymphom a cells with HLA-A2/gag complexes (80-fold increase in mean channel fluores cence). CTL specific for HLA-A2/gag efficiently lysed complex-targeted cell s, while control CTL (specific for an HLA-A2.1-restricted epitope of melan- A) did not. Similarly, SK-mel-29 melanoma cells were also efficiently lysed by HLA-A2/gag-specific CTL when HLA-A2/gag complexes were linked to their surface via the HMW-MAA specific anti-melanoma antibody 225.28s. With furth er consideration to the in vivo stability of the MHC class I/peptide comple xes, this system could prove a new strategy for the immunological therapy o f cancer. (C) 2000 Cancer Research Campaign.