Cloning, Expression and Purification of Recombinant Interleukin 1 Receptor Antagonist (IL-1RA) in Escherichia coli

Background: Interleukin 1 (IL-1) is a cytokine that plays an important role in the immune system. However, the excessive IL-1 secretion is responsible for several diseases such as septic shock, cancer, Alzheimer's, etc. Interleukin 1 Receptor Antagonist (IL-1Ra) has been studied and demonstrated the ability to prevent the effects of IL-1 on rheumatoid arthritis. In this study, E. coli BL21(DE3) strain carrying human IL-1Ragene was structured to produce recombinant IL-1Ra as an initial source for rheumatoid arthritis and some other autoimmune diseases application testing. Methods: The il1ra gene encodes for IL-1Ra was codon optimized, chemically synthesized and cloned into the pET-His vector, creating recombinant plasmid pETHis-il1ra to express IL-1Ra under control of T7 promoter. E. coli BL21(DE3)/ pETHis-il1ra strain was formed by the transformation of pETHis-il1ra into E. coli BL21(DE3), cultured in LB medium containing Ampicillin, supplemented with IPTG for the induction T7 promoter. Results: IL-1Ra was excessively expressed in the cytoplasmic in soluble form. E. coli BL21(DE3)/ pETHis-il1ra strain was fermented in an one-liter bioreactor. IL-1Ra began to be expressed after induction of IPTG and reached a large amount after 8 hours of induction. IL-1Ra was purified by cation exchange chromatography with the amount of IL-1Ra protein obtained 43.11 mg with a purity of 95.8%. Conclusion: We successfully cloned il1ra gene into E. coli BL21(DE3) strain as a source of material for production of IL-1Ra. Furthermore, our one-step purification of recombinant IL-1Ra using cation exchange chromatography with Tris-HCl solution was applicable for large scale production. This result laid the groundwork for the study of applying IL-1Ra in the treatment of IL-1.