Interleukin 18 High Level Expression in E.coli Purification and Renaturation of the Recombinant Protein

Using the total RNA extracted from mitogen-stimulated human peripheral blood mononuclear cells (PBMC) as template, the cDNA of interleukin 18 was amplified by RT-PCR. The cDNA was subsequently cloned into the expression vector pJW2 and sequenced. The recombinant human IL-18 (rhIL-18) was expressed efficiently in inclusion bodies in E.coli with the yield accounting for 20% total bacteria proteins. The inclusion bodies were washed with 2 mol/L urea and rhIL-18 was further purified using Sephadex G-100 column chromatography in 8 mol/L urea. After purification, the purity of rhIL-18 was greater than 90% as judged by SDS-PAGE. The purified rhIL-18 showed significant and dose-dependent IFN-gamma-inducing activity in human PBMC, in the presence of 0.5 mg/L Con A.