Redirection of T cell-mediated cytotoxicity by a recombinant single-chain Fv molecule.

We have produced two single-chain Fv (sFv) proteins by bacterial periplasmic secretion, one sFv with specificity for the hapten DNP, and the other for the human transferrin receptor. After solubilization and refolding, we recovered several mg of active sFv per liter of bacterial culture. Each sFv bound to cells bearing the appropriate Ag and could be used to direct targeted cellular cytotoxicity. Targeting relied on a universal bispecific antibody designed to cross-link CD3 on the cytotoxic T cell with a peptide fused to the sFv carboxyl-terminus. The universal bispecific antibody was used in combination with the Ag-specific sFv to redirect human cytotoxic T cells to kill a variety of target cells. Such an approach has a number of advantages that may make it useful for the immunotherapy of cancer and other diseases.