title: Targeting of a B7-1 (CD80) immunoglobulin G fusion protein to acute myeloid leukemia blasts increases their costimulatory activity for autologous remission T cells.
abstract: Transfection of tumor cells with the gene encoding the costimulatory molecule B7-1 (CD80), the ligand for CD28 and cytotoxic T lymphocye antigen-4 on T cells, has been shown to result in potent T-cell-mediated antitumor immunity. As an alternative approach, this study analyzed the costimulatory capacity of a human B7-1 immunoglobulin G (IgG) fusion protein targeted to the cell membrane of human acute myeloid leukemia (AML) blasts. Flow cytometric analysis revealed a low constitutive expression of B7-1 on human AML blasts (on average, 3.0 +/- 4.3%; n = 50). In contrast, the expression of B7-2 (CD86) was highly heterogeneous and higher in AML blasts of French-American-British classification types M4 and M5 (P <.0001). The B7-1 IgG fusion protein used in this study efficiently costimulated the proliferation of resting and preactivated T cells when immobilized on plastic. After preincubation with B7-1 IgG, specific binding of the fusion protein to the high-affinity Fcgammareceptor I (CD64) on leukemic cells was demonstrated and was found to increase the proliferation of both allogeneic and autologous T cells in costimulation experiments. Furthermore, targeting of B7-1 IgG to the tumor membrane resulted in increased proliferation of autologous remission T cells and had the potential to generate an enhanced redirected cytotoxic T-cell response against autologous AML blasts. In summary, the targeting of B7-1 IgG fusion protein described in this study represents a strategy alternative to gene therapy to restore the expression of the costimulatory molecule B7-1 on human AML blasts, thereby enhancing their immunogenicity for autologous T cells. This new approach may have implications for T-cell-mediated immunotherapy in AML.
authors.affiliation: Department of Hematology and Oncology, Freie Universität Berlin, Universitätsklinikum Benjamin Franklin, Berlin, Germany.
authors.forename: M
authors.initials: M
authors.lastname: Notter
authors.forename: T
authors.initials: T
authors.lastname: Willinger
authors.forename: U
authors.initials: U
authors.lastname: Erben
authors.forename: E
authors.initials: E
authors.lastname: Thiel
mesh_terms: D018122:B7-1 Antigen / Q000276:immunology*; D002462:Cell Membrane / Q000276:immunology; D003602:Cytotoxicity, Immunologic; D005434:Flow Cytometry; D015870:Gene Expression; D006801:Humans; D007074:Immunoglobulin G / Q000235:genetics* / Q000276:immunology*; D016219:Immunotherapy, Adoptive; D015470:Leukemia, Myeloid, Acute / Q000276:immunology*; D008213:Lymphocyte Activation; D017452:Receptors, IgG / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000276:immunology / Q000378:metabolism; D013601:T-Lymphocytes / Q000276:immunology*; D014162:Transfection; D014407:Tumor Cells, Cultured
chemical_list: D018122:B7-1 Antigen; D007074:Immunoglobulin G; D017452:Receptors, IgG; D011993:Recombinant Fusion Proteins