Expression,Purification And Biological Activity Detection Of Human IL-22

Objective:IL-22 is a cytokine secreted mainly by innate lymphoid cells and CD4+T helper cells.Previous studies have shown that IL-22 elicits multiple functions,including host defense,tissue protection and regeneration.More recently,IL-22 was shown to mitigate endoplasmic stress of pancreatic beta cells when administered into type 2 diabetic mice.Thus,IL-22 is regarded as a potential therapeutic protein drug.The objectives of the present study are:To optimize the conditions for heterologous production of human IL-22 in E.coli and to functionally test its therapeutic value in cultured human hepatic cell line and in a mouse model of liver disease.Methods:An expression plasmid containing the human full-length IL-22 CDNA and full-length IL-22 fused in-frame with the Small Ubiquitin-like Modifier(SUMO)tag was introduced into the E.coli strain BL21(DE3)through heat shock transformation.The transformed BL21(DE3)cells were cultured at 18?22?30 and 37? and IL-22 expression was induced using different concentrations of IPTG.Renatured and soluble-IL-22 was purified by affinity chromatography and functionally tested in cultured human hepatic cell line HepG2 and in a mouse model of spontaneous liver inflammation.Results:the obtained recombinant IL-22 protein,was mainly present in the form of inclusion body(IB)in E coli cells with a molecular mass of approximately 16.7 kDa.Following a 4-step denaturating/renaturing protocol and affinity chromatography,approximately 130 mg/L of soluble IL-22 protein with purity over 90%was obtained.When added to cultured HepG2 cells,recombinant IL-22 at a concentration of 100-800 ng/mL showed detectable mitogenic activity.Interestingly,when injected intraperitoneally into mice with spontaneous hepatitis,IL-22 was found to exacerbate,but not mitigate liver inflammation.Conclusion:Functionally active human IL-22 fusion protein can be efficiently produced in E.coli.The therapeutic value of recombinant IL-22 and economic viability of the production system developed was discussed in detail in the current study.