Fusion proteins of B7.1 and a carcinoembryonic antigen (CEA)-specific antibody fragment opsonize CEA-expressing tumor cells and coactivate T-cell immunity

Abstract

Genetic engineering can be used to generate antigen‐specific molecules for improved tumor immunotherapy. We have constructed genes coding for fusion proteins consisting of a high‐affinity antibody single‐chain antibody fragment (scFv) specific for the human carcinoembryonic antigen (CEA) and the costimulation domain of the murine B7.1 molecule (mB7.1) linked to the antibody moiety by an IgG3 peptide linker. The hybrid genes were constructed in 2 orientations, one with the scFv located N‐terminal to mB7.1 and one vice versa. Soluble proteins were expressed by CHO cells, purified using anti‐idiotype‐affinity chromatography and characterized by tumor‐cell binding and costimulation activity. When tumor cells expressing CEA on the cell membrane were opsonized with the CEA‐specific costimulators, both fusion proteins specifically stimulated murine T‐cell preparations to proliferate in a similar manner. Our data suggest that “costimulation coating” of tumor cells may be a suitable approach for activation of a sustained cellular antitumor response. It also provides the opportunity to increase tumor immunogenicity using easily generated soluble fusion proteins that advantageously link biological functions of both the humoral and the cellular arm of the specific immune system. © 2001 Wiley‐Liss, Inc.

A Novel Bispecific Tetravalent Antibody Fusion Protein to Target Costimulatory Activity for T-cell Activation to Tumor Cells Overexpressing ErbB2/HER2

“…54 To load tumor cells that do not carry Fc-receptors, but express suitable tumor-associated surface antigens with costimulatory molecules, we and others have previously used B7 fusion proteins containing antibodies or antibody fragments that recognize the EGF receptor, 38 ErbB2, 37,38,40,55 carcinoembryonic antigen (CEA), 41,56 or, following a two-step approach, a variety of additional antigens. 57 Usually, in these proteins the full-length extracellular portions of B7-1 or B7-2 were employed, which each consist of two domains related to Ig variable (V) and Ig constant (C) domain sequences.…”

T Cell Activation by Antibody-Like Immunoreceptors: The Position of the Binding Epitope within the Target Molecule Determines the Efficiency of Activation of Redirected T Cells

“…The CEA-expressing colon carcinoma cell lines LS174T (ATCC CCL 188) and SW948 (ATCC CCL 237) and the CEA-negative cell lines A375 (ATCC CRL-1619) and Colo320 (ATCC CCL 220.1) were obtained from American Type Culture Collection. The mouse tumor cell line C15A3 that expresses human CEA after transfection was described earlier (9). OKT3 (ATCC CRL 8001) is a hybridoma cell line that produces the anti-CD3 mAb OKT3.…”

Monoclonal Anti-idiotype Antibody 6G6.C4 Fused to GM-CSF Is Capable of Breaking Tolerance to Carcinoembryonic Antigen (CEA) in CEA–Transgenic Mice

“…4 Because previous studies had shown that 6G6.C4 effectively functions as a surrogate antigen for CEA in mice, rats, and rabbits (15), we have attributed this failure in humans to an insufficient breaking of tolerance toward CEA. Different immunostimulatory cytokines, growth factors, or co-stimulatory antigens have been used either after fusion or by co-administration with antigens or antibodies to improve immune responses (17,18,21,26,36,37). For example, most recently, Reinartz et al (13) have reported on the superiority of a fusion between IL6 and the anti-idiotype antibody (ACA125) mimicking the CA125 TAA compared with the co-administration of the respective single components.…”