RECOMBINANT CHICKEN INTERFERON FROM ESCHERICHIA-COLI AND TRANSFECTED COS CELLS IS BIOLOGICALLY-ACTIVE

We have expressed a cDNA for virus-induced chick interferon in Escheri chia coli. The product, a 19-kDa protein lacking the signal peptide, w as purified to homogeneity from the bacterial inclusion bodies. Protei ns in the insoluble fraction of bacterial lysates were dissolved in gu anidine hydrochloride and subjected to chromatography on Q-Sepharose a nd MonoS columns. Purified recombinant chick interferon has a specific antiviral activity of approximately 10(8) IU/mg and is a powerful ind ucer of the interferon-responsive promoter of the chicken Mr gene. Cul ture medium of transfected COS cells expressing full-length chick inte rferon cDNA contained up to 5X10(4) IU antiviral activity/ml that coul d be neutralized by antibodies to purified recombinant chick interfero n. The antibodies precipitated proteins of 23-28 kDa from the supernat ants of transfected COS cells. Treatment with endoglycosidase F reduce d the size of the immunoprecipitated proteins to approximately 20 kDa, demonstrating that chick interferon is a glycoprotein.