Production and purification of refolded recombinant human IL-7 from inclusion bodies

Abstract

A recombinant form of human rhIL-7 was overexpressed in Escherichia coli HMS174 (DE3) pLysS under the control of a T7 promoter. The resulting insoluble inclusion bodies were separated from cellular debris by cross-flow filtration and solubilized by homogenization with 6 M guanidine HCl. Attempts at refolding rhIL-7 from solubilized inclusion bodies without prior purification of monomeric, denatured rhIL-7 were not successful. Denatured, monomeric rhIL-7 was therefore initially purified by size-exclusion chromatography using Prep-Grade Pharmacia Superdex 200. Correctly folded rhIL-7 monomer was generated by statically refolding the denatured protein at a final protein concentration of 80-100 μg/mL in 100 mM Tris, 2 mM EDTA, 500mM L-arginine, pH 9.0, buffer with 0.55 g/L oxidized glutathione at 2-8°C for at least 48h. The refolded rhIL-7 was subsequently purified by low-pressure liquid chromatography, using a combination of hydrophobic interaction, cation-exchange, and size-exclusion chromatography. The purified final product was >95% pure by SDS–PAGE stained with Coomassie brilliant blue, high-pressure size-exclusion chromatography (SEC-HPLC), and reverse-phase HPLC. The endotoxin level was