PURIFICATION OF RECOMBINANT CHIMERIC-B72.3 FAB' AND F(AB')2 USING STREPTOCOCCAL PROTEIN-G

Streptococcal protein G has been used extensively for the purification of antibodies using the interaction of the Fc region with protein G. Many antibodies also interact with protein G through a low-affinity binding site for the Fab region. The exploitation of this low-affinity interaction for the purification of Fab′ fragments is described here. Chimeric mouse-human B72.3 Fab′ and F(ab′)2 fragments were expressed by CHO cells and purified from CHO cell supernatant using protein G-Sepharose. Since chimeric B72.3 Fab' bound weakly to the protein G-Sepharose it could be separated from F(ab′)2 and eluted with a pH 7 wash whereas B72.3 F(ab′)2 required elution at pH 2. Both Fab′ and F(ab′)2 were recovered with full immunoreactivity and could be further purified using gel-filtration chromatography to greater than 99% purity. This method allows the simple purification of directly expressed Fab′ or F(ab′)2 fragments from CHO cell supernatant. © 1992 Academic Press, Inc.