PURIFICATION OF HUMAN-LEUKOCYTE INTERFERON-A DERIVED FROM ESCHERICHIA-COLI - AN AGING PROCESS TO PREVENT THE FORMATION OF ITS OLIGOMERS

Recombinant human leukocyte interferon A (rIFN-.alpha.A) was purified from Escherichia coli cells by monoclonal antibody affinity chromatography (Ab) and CM-cellulose column chromatography (CM). By sodium dodecyl sulfate-polyacrylamide gel electrophoresis, the CM eluate was found to contain a large amount of rIFN-.alpha.A oligomers, in addition to the monomer, linked by intermolecular disulfide bonds. In contrast, the Ab eluate was found to contain a large amount of rIFN-.alpha.A monomers. These results show that the oligomers were formed at the CM step. Free SH groups were detected at a significant level in the Ab eluate, but were detected barely in the CM eluate, indicating that the Ab eluate contained some amount of the unstable monomer with free SH groups. To prevent the formation of the oligomers we established a simple and easily scaled-up process, called an aging process, during with the Ab eluate was incubated at pH 3.3 at 37.degree. C for several days. This process is effective for changing the unstable monomer to the stable monomer and thus preventing the formation of the oligomers.