title: Monoclonal anti-idiotype antibody 6G6.C4 fused to GM-CSF is capable of breaking tolerance to carcinoembryonic antigen (CEA) in CEA-transgenic mice.
abstract: Internal image anti-idiotypic antibodies are capable of mimicking tumor-associated antigens and thus may serve as surrogate for vaccination strategies in cancer patients. The monoclonal antibody (mAb) 6G6.C4 mimics an epitope specific for the human carcinoembryonic antigen (CEA) and generates a CEA-specific response (Ab3) in various experimental animals. In humans, however, 6G6.C4 only yields a very limited humoral anti-CEA reaction presumably due to tolerance against the CEA autoantigen. In this study, we investigated the CEA-specific Ab3 response in mice transgenic for the human CEA and tested whether the antigen tolerance could be overcome by fusing a recombinant single-chain variable fragment of 6G6.C4 (scFv6G6.C4) to the murine granulocyte macrophage colony-stimulating factor (GM-CSF). Like mAb 6G6.C4, the fusion protein (scFv6G6.C4/GM-CSF) retained binding to the CEA-specific idiotype mAb T84.66. Also, scFv6G6.C4/GM-CSF was biologically active as measured by proliferation of the GM-CSF-dependent murine FDC-P1 cells in vitro. After immunization with the scFv6G6.C4/GM-CSF fusion protein, CEA-transgenic animals showed significantly enhanced Ab3 antibody responses to scFv6G6.C4 (P=0.005) and to CEA (P=0.012) compared with the scFV6G6.C4 alone. Sera from mice immunized with the fusion protein specifically recognized CEA in Western blot analyses with no cross-reaction to CEA-related antigens. Finally, the Ab3 antisera detected single CEA-expressing tumor cells in suspension as shown by flow cytometry. Taken together, these data show in a model antigenically related to the human system that vaccination with scFv6G6.C4/GM-CSF improves vaccination against an endogenous tumor-associated antigen resulting in a highly specific humoral Ab3 response in vivo that is capable of bind single circulating CEA-positive tumor cells.
authors.affiliation: Department of Internal Medicine and Clinical Immunology Bad Bramstedt, University of Lübeck, Lübeck, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Schwegler
authors.forename: Alexandra
authors.initials: A
authors.lastname: Dorn-Beineke
authors.forename: Stefanie
authors.initials: S
authors.lastname: Nittka
authors.forename: Carol
authors.initials: C
authors.lastname: Stocking
authors.forename: Michael
authors.initials: M
authors.lastname: Neumaier
mesh_terms: D000818:Animals; D000888:Antibodies, Anti-Idiotypic / Q000276:immunology*; D000911:Antibodies, Monoclonal / Q000276:immunology*; D000918:Antibody Specificity; D000951:Antigens, Neoplasm / Q000276:immunology; D015153:Blotting, Western; D002272:Carcinoembryonic Antigen / Q000276:immunology* / Q000378:metabolism; D049109:Cell Proliferation; D002478:Cells, Cultured; D003106:Colon / Q000276:immunology / Q000378:metabolism; D003110:Colonic Neoplasms / Q000276:immunology / Q000378:metabolism / Q000628:therapy; D000939:Epitopes; D005260:Female; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000276:immunology / Q000378:metabolism; D006801:Humans; D007108:Immune Tolerance; D007114:Immunization; D007128:Immunoglobulin Fragments / Q000276:immunology; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D009360:Neoplastic Cells, Circulating / Q000276:immunology / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000276:immunology / Q000378:metabolism
chemical_list: D000888:Antibodies, Anti-Idiotypic; D000911:Antibodies, Monoclonal; D000951:Antigens, Neoplasm; D002272:Carcinoembryonic Antigen; D000939:Epitopes; D007128:Immunoglobulin Fragments; D011993:Recombinant Fusion Proteins; D016178:Granulocyte-Macrophage Colony-Stimulating Factor