Specific secretion of active single-chain Fv antibodies into the supernatants of Escherichia coli cultures by use of the hemolysin system

A simple method for the nontoxic, specific, and efficient secretion of acti ve single-chain Fv antibodies (scFvs) into the supernatants of Escherichia coli cultures is reported. The method is based on the well-characterized he molysin transport system (Hly) of E. coli that specifically secretes the ta rget protein from the bacterial cytoplasm into the extracellular medium wit hout a periplasmic intermediate. The culture media that accumulate these Hl y-secreted scFv's can be used in a variety of immunoassays without purifica tion. In addition, these culture supernatants are stable over long periods of time and can be handled basically as immune sera.