Construction, Expression and Preliminary Pharmacokinetics of IL-1ra Mutants

Interleukin-1 receptor antagonist (IL-1ra), a member of the interleukin-1 (IL-1) family, and a naturally occurring IL-1 inhibitor as 'receptor antagonist' blocked IL-1-mediated biological responses. The recombinant human IL-1ra (rhIL-1ra, Kineret) was introduced in the clinical trials, which involved patients with rheumatoid arthritis. However, a drawback to the therapy is that the dosage of 100-150 mg/day is so big that it greatly influences the patients' physical, psychological, and economical situation. In this study, IL-1ra mutants were established by site-specific mutagenesis to improve its stability. The sites of mutagenesis include R6K7-AA, R93K94-AA, and K97R98-AA. IL-1ra and its mutants were expressed in E. coli BL21 (DE3) using pTIG-Trx expressing system with the induction of IPTG. The recombinant proteins were purified by Ni2+ chelate chromatography and SephadexG75 gel filtration chromatography. The result of bioactivity assay showed that the activity of mutants was as high as that of IL-1ra. The pharmacokinetic profile of IL-1ra and its mutants were characterized and the third mutant's half-life is 2.26 times as long as that of wt IL-1ra. The study provided some approaches and experience for further research to improve the metabolism stability of IL-1ra.