Patent ID: 7968315

Claim:
A method of recovering an IL-29 polypeptide comprising: (a) providing an ompT deficient and fhuA deficient E. coli host cell comprising an expression vector comprising the following operably linked elements: (i) a transcription promoter; (ii) a nucleic acid molecule encoding an IL-29 polypeptide comprising amino acid residues 1-176 of SEQ ID NO:6; and (iii) a transcription terminator; in a suitable growth medium; (b) adding an inducing agent to induce expression of the IL-29 polypeptide; (c) harvesting the host cells; (d) lysing the host cells; (e) centrifuging the lysed host cells; (f) recovering the inclusion body pellet; (g) solubilizing the inclusion body pellet; (h) adding the solubilized IL-29 polypeptide to a refolding buffer pH7.3-8.5 to a final concentration of 0.5-3.0 mg/ml, said refolding buffer comprises 0.05%-0.5% polyethylene glycol, 0.5-1.25 M arginine, and a mixture of reduced and oxidized molecule, wherein the solubilized IL-29 polypeptide is refolded for 1-26 hours at a temperature of 4-30° C.; (i) quenching the refolding reaction by adjusting the pH to 5.5-6.5; (j) diluting the quenched refolding solution 1.5- to 10-fold in water or low ionic strength buffer at pH 5-7; and (k) filtering the quenched, diluted refolding solution through filters to remove precipitate or particulates.