|Ph.D Student||Haus-Cohen Maya|
|Subject||Potentiation of Anti-tumor and Anti-viral Immunity|
|Department||Department of Biology||Supervisor||Professor Yoram Reiter|
|Full Thesis text|
Cancer immunotherapy employs two distinct approaches: (i) antibody therapy and (ii) cell based therapeutic approaches. Herein, we present a new two strategies for studying and targeting cancer and virus infected cells. First we developed a process to isolate unique antibodies, termed T-Cell Receptor-like antibodies, which recognize and bind tumor/viral-associated MHC-peptide complexes normally recognized by cytotoxic T lymphocytes (CTLs). By using antibody phage display, we isolated a panel of human recombinant Fab TCR-like antibodies directed toward the HIV-1 epitope -SL9 (Gag 77-85) in complex with MHC-I molecule. We characterized one of these antibodies, E5. The E5 antibody was used to visualize, the specific HLA-A2/Gag epitope on antigen presenting cells (APCs) that were pulsed with the Gag peptide, or on cells that have complexes formed by naturally occurring active intracellular processing of the antigen as well as on the surface of virus infected cells.
Moreover, we constructed an immunotoxin molecule by using the E5 Ab. Specific cytotoxicity of this molecule was achieved on APCs that were pulsed with the Gag peptide. Furthermore we transformed the E5 Fab into a IgG1 molecule. The E5 IgG showed more sensitive and specific binding to HLA-A2/Gag complexes, and is planed to be tested for its ability to cause ADCC and CDC. Seconded we constructed a fusion molecule that can bridge between antibody targeting against tumor cells, and recruiting cells with potent killing activities from the immune system. We designed two fusion molecules: (i) chemokine CCL21 was fused to a scFv antibody which targets EGFR (CCL21-scFv225). The CCL21-scFv225 fusion molecule possess two functional domains, the scFv that can specifically target tumor cells, and the CCL21 chemokine that can recruit specific populations from the immune system. (ii) scHLA-A2/scFv225 fused via a flexible linker to the CCL21 chemokine. The scHLA-A2/scFv225-CCL21 fusion molecule possess three functional domains, the scFv that can specifically target tumor cells, the MHC-peptide complex that can recruit specific populations of CTLs depending on the antigenic peptide within the MHC groove, and the CCL21 chemokine which can recruit different subpopulation from the immune system. We show that the fusion molecules can bind the native antigen expressed on the surface of tumor cells. The fusion molecules can chemoattract PBMCs, and can mediate efficient lysis of EGFR positive HLA-A2 negative tumor cells by PBMCs. These results suggest that our new fusion molecules could represent a new approach for cancer immunotherapy, bridging antibody and immune system attacks on cancer cells.