Recruitment of CTL activity by tumor-specific antibody-mediated targeting of single-chain class I MHC-peptide complexes.
The MHC class I-restricted CD8 CTL effector arm of the adaptive immune response is uniquely equipped to recognize tumor cells as foreign and consequently initiates the cascade of events resulting in their destruction. However, tumors have developed sophisticated strategies to escape immune effector mechanisms; their most well-known strategy is down-regulation of MHC class I molecules. To overcome this and develop new approaches for immunotherapy, we have constructed a recombinant molecule in which a single-chain MHC is specifically targeted to tumor cells through its fusion to cancer-specific recombinant Ab fragments. As a model we used a single-chain HLA-A2 molecule genetically fused to the variable domains of an anti-IL-2Ralpha subunit-specific humanized Ab, anti-Tac. The construct, termed B2M-aTac(dsFv), was expressed in Escherichia coli, and functional molecules were produced by in vitro refolding in the presence of HLA-A2-restricted antigenic peptides. Flow cytometry studies revealed the ability to decorate Ag-positive, HLA-A2-negative human tumor cells with HLA-A2-peptide complexes in a manner that was entirely dependent upon the specificity of the targeting Ab fragment. Most importantly, the B2M-aTac(dsFv)-mediated coating of the target tumor cells made them susceptible for efficient and specific HLA-A2-restricted, melanoma gp100 peptide-specific CTL-mediated lysis. These results demonstrate the concept that Ab-guided, Ag-specific targeting of MHC-peptide complexes on tumor cells can render them susceptible and more receptive and thus potentiate CTL killing. This type of approach may open the way for the development of new immunotherapeutic strategies based on Ab targeting of natural cognate MHC ligands and CTL-based cytotoxic mechanisms.
Lev
Avital
A
Faculty of Biology, Technion-Israel Institute of Technology, Haifa, Israel.
Novak
Hila
H
Segal
Dina
D
Reiter
Yoram
Y
D000818:Animals; D000911:Antibodies, Monoclonal / Q000235:genetics / Q000378:metabolism; D000920:Antibody-Dependent Cell Cytotoxicity / Q000235:genetics; D000951:Antigens, Neoplasm / Q000235:genetics; D000970:Antineoplastic Agents / Q000008:administration & dosage / Q000138:chemical synthesis / Q000302:isolation & purification / Q000378:metabolism; D001666:Binding Sites, Antibody / Q000235:genetics / Q000276:immunology; D002294:Carcinoma, Squamous Cell / Q000276:immunology / Q000378:metabolism; D003601:Cytotoxicity Tests, Immunologic / Q000379:methods; D005822:Genetic Vectors / Q000138:chemical synthesis / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D015789:HLA-A2 Antigen / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D006801:Humans; D007128:Immunoglobulin Fragments / Q000235:genetics; D007279:Injections, Subcutaneous; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D008819:Mice, Nude; D010446:Peptide Fragments / Q000235:genetics; D015375:Receptors, Interleukin-2 / Q000235:genetics / Q000276:immunology; D011993:Recombinant Fusion Proteins / Q000138:chemical synthesis / Q000302:isolation & purification / Q000378:metabolism / Q000494:pharmacology*; D013602:T-Lymphocytes, Cytotoxic / Q000276:immunology* / Q000378:metabolism; D014407:Tumor Cells, Cultured; D001613:beta 2-Microglobulin / Q000235:genetics / Q000276:immunology* / Q000378:metabolism; D058951:gp100 Melanoma Antigen
D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D000970:Antineoplastic Agents; D015789:HLA-A2 Antigen; D007128:Immunoglobulin Fragments; D008562:Membrane Glycoproteins; C548637:PMEL protein, human; D010446:Peptide Fragments; C548642:Pmel protein, mouse; D015375:Receptors, Interleukin-2; D011993:Recombinant Fusion Proteins; D001613:beta 2-Microglobulin; D058951:gp100 Melanoma Antigen; C055966:immunoglobulin Fv