Targeting of T lymphocytes to melanoma cells through chimeric anti-GD3 immunoglobulin T-cell receptors

Immunoglobulin T-cell receptors (IgTCRs) combine the specificity of antibod ies with the potency of cellular killing by grafting antibody recognition d omains onto TCR signaling chains. IgTCR-modified T cells are thus redirecte d to kill tumor cells based on their expression of intact antigen on cell s urfaces, bypassing the normal mechanism of activation through TCR-peptide-m ajor histocompatibility complex (MHC) recognition. Melanoma is one of the m ost immunoresponsive of human cancers and has served as a prototype for the development of a number of immunotherapies. The target antigen for this st udy is the ganglioside GD,, which is highly expressed on metastatic melanom a with only minor immunologic cross-reaction with normal tissues. To determ ine an optimal configuration for therapy, four combinations of IgTCRs were prepared and studied: sFv-epsilon, SFV-zeta, Fab-epsilon, Fab-zeta. These w ere expressed on the surface of human T cells by retroviral transduction. I gTCR successfully redirected T-cell effecters in an MHC-unrestricted manner , in this case against a nonT-dependent antigen, with specific binding, act ivation, and cytotoxicity against GD(3+) melanoma cells. Soluble GD, in con centrations up to 100 mug/ml did not interfere with recognition and binding of membrane-bound antigen. Based on the outcomes of these structural and f unctional tests, the sFv-zeta construct was selected for clinical developme nt. These results demonstrate key features that emphasize the potential of anti-GD(3) IgTCR-modified autologous T cells for melanoma therapies.