High expression and purification of recombinant human IL-18 and bioassay of IFN-#gamma# secreted with KG-1 cells under induction of expressed product

Abstract: Objective To highly express rhIL - 18 in E. coli and establish the methods for purification and bioassay. Methods hIL-18 cDNA was amplified from normal human embryo liver tissue by RT-PCR, cloned into pThiohis A vector, transformed to E. coli BL-21, and expressed under the induction of 1mol/L IPTG. The expressed product existing in the form of inclusion body was washed with 2% Triton-X-100, dissolved in 8mol/L urea and purified by denatured anion exchange chromatography. After being renaturalized by dialysis, the expressed product was further purified by Superdex-75 size exclusion chromatography. The biological activity of purified product was evaluated by detecting the INF-γlevel secreted with human myelomonocyte KG-1 under the induction of it.Results rhIL-18 was stably and highly expressed in E. coli. The expressed product contained about 25% of total somatic protein and reached a purity of above 95% after being purified. It induced the secretion of IFN-γsignificantly. Conclusion A method for preparing rhIL-18 with biological activity and high purity is established and can be scaled up. The method laid a foundation of the basic research and clinical application of rhIL-18.