SEA-scFv as a bifunctional antibody: Construction of a bacterial expression system and its functional analysis

A SEA-antibody single chain Fv (SEA-scFv) fusion protein was produced by ba cterial expression system in this study. SEA-scFv has both staphylococcal e nterotoxin A (SEA) effects and antibody activity directed at the epithelial mucin core protein MUC1, a cancer associated antigen. It was expressed mos tly in the cytoplasm as an insoluble form. The gene product was solubilized by guanidine hydrochloride, refolded by conventional dilution method, and purified using metal-chelating chromatography. The resulting SEA-scFv fusio n protein preparation was found to react with MUC1 and MHC class II antigen s and had the ability to enhance cytotoxicity of lymphokine activated kille r cells with a T cell phenotype against a human bile duct carcinoma cell li ne, TFK-1, expressing MUC1. This genetically engineered SEA-scFv fusion pro tein promises to be an important reagent for cancer immunotherapy. (C) 1999 Academic Press.