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Cloned transgenic farm animals produce a bispecific antibody for T cell-mediated tumor cell killing.

ABSTRACT: Complex recombinant antibody fragments for modulation of immune function such as tumor cell destruction have emerged at a rapid pace and diverse anticancer strategies are being developed to benefit patients. Despite improvements in molecule design and expression systems, the quantity and stability, e.g., of single-chain antibodies produced in cell culture, is often insufficient for treatment of human disease, and the costs of scale-up, labor, and fermentation facilities are prohibitive. The ability to yield mg/ml levels of recombinant antibodies and the scale-up flexibility make transgenic production in plants and livestock an attractive alternative to mammalian cell culture as a source of large quantities of biotherapeutics. Here, we report on the efficient production of a bispecific single-chain antibody in the serum of transgenic rabbits and a herd of nine cloned, transgenic cattle. The bispecific protein, designated r28M, is directed to a melanoma-associated proteoglycan and the human CD28 molecule on T cells. Purified from the serum of transgenic animals, the protein is stable and fully active in mediating target cell-restricted T cell stimulation and tumor cell killing.

SUBMITTER: Grosse-Hovest L

PROVIDER: S-EPMC406432 | biostudies-literature | 2004 May

REPOSITORIES: biostudies-literature

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Project description:Although T cell-recruiting CD3-binding bispecific antibodies (BiMAb) have been proven to be clinically effective for hematologic malignancies, the success of BiMAb targeting solid tumor-associated antigens (TAA) in carcinomas so far remains poor. We reasoned that provision of co-stimulatory BiMAb in combination with αTAA-αCD3 BiMAb would boost T cell activation and proliferative capacity, and thereby facilitate the targeting of weakly or heterogeneously expressed tumor antigens. Various αTAA-αCD3 and αTAA-αCD28 BiMAb in a tetravalent IgG1-Fc based format have been analyzed, targeting multiple breast cancer antigens including HER2, EGFR, CEA, and EpCAM. Moreover, bifunctional fusion proteins of αTAA-tumor necrosis factor ligand (TNFL) superfamily members including 4-1BBL, OX40L, CD70 and TL1A have been tested. The functional activity of BiMAb was assessed using co-cultures of tumor cell lines and purified T cells in monolayer and tumor spheroid models. Only in the presence of tumor cells, αTAA-αCD3 BiMAb activated T cells and induced cytotoxicity in vitro, indicating a strict dependence on cross-linking. Combination treatment of αTAA-αCD3 BiMAb and co-stimulatory αTAA-αCD28 or αTAA-TNFL fusion proteins drastically enhanced T cell activation in terms of proliferation, activation marker expression, cytokine secretion and tumor cytotoxicity. Furthermore, BiMAb providing co-stimulation were shown to reduce the minimally required dose to achieve T cell activation by at least tenfold. Immuno-suppressive effects of TGF-β and IL-10 on T cell activation and memory cell formation could be overcome by co-stimulation. BiMAb-mediated co-stimulation was further augmented by immune checkpoint-inhibiting antibodies. Effective co-stimulation could be achieved by targeting a second breast cancer antigen, or by targeting fibroblast activation protein (FAP) expressed on another target cell. In tumor spheroids derived from pleural effusions of breast cancer patients, co-stimulatory BiMAb were essential for the activation tumor-infiltrating lymphocytes and cytotoxic anti-tumor responses against breast cancer cells. Taken together we showed that co-stimulation significantly potentiated the tumoricidal activity of T cell-activating BiMAb while preserving the dependence on TAA recognition. This approach could provide for a more localized activation of the immune system with higher efficacy and reduced peripheral toxicities.

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Cloned transgenic farm animals produce a bispecific antibody for T cell-mediated tumor cell killing.

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