Escherichia coli is a robust, economic and rapid expression system for the production of recombinant therapeutic
proteins. However, the expression in bacterial systems of complex molecules such as
antibodies and fusion
proteins is still affected by several drawbacks. We have previously described a procedure based on
uteroglobin (UG) for the engineering of very soluble and stable polyvalent and polyspecific fusion
proteins in mammalian cells (Ventura et al. 2009. J. Biol. Chem. 284∶26646-26654.) Here, we applied the UG platform to achieve the expression in E. coli of a bivalent human recombinant antibody (L19) toward the
oncofetal fibronectin (B-FN), a pan-
tumor target. Purified bacterial L19-UG was highly soluble, stable, and, in all molecules, the L19 moiety maintained its immunoreactivity. About 50-70% of the molecules were covalent homodimer, however after refolding with the redox couple
reduced-glutathione/
oxidized-glutathione (GSH/
GSSG), 100% of molecules were covalent dimers. Mass spectrometry studies showed that the
proteins produced by E. coli and mammalian cells have an identical molecular mass and that both
proteins are not glycosylated. L19-UG from bacteria can be freeze-dried without any loss of
protein and immunoreactivity. In vivo, in
tumor-bearing mice, radio-iodinated L19-UG selectively accumulated in neoplastic tissues showing the same performance of L19-UG from mammalian cells. The UG-platform may represent a general procedure for production of various
biological therapeutics in E. coli.