Development of a highly purified multicomponent leukocyte IFN-alpha product

A purification process was developed to obtain a human interferon-alpha (IF N-alpha) product that contains all major IFN-alpha subtypes produced by hum an leukocytes. The purification was accomplished by immunoaffinity chromato graphy using two monoclonal antibodies (mAb) and gel filtration. The proces s comprised two effective virus inactivation steps, solvent detergent treat ment, and incubation at low pH, and the purified product was filtered with a 15-nm pore size virus removal filter. The overall yield of IFN-alpha in t he process was about 60% when starting from the culture supernatant of Send ai virus-induced human leukocytes. The specific activity was about 1.0 x 10 (8) IU/mg. The level of DNA and protein impurities including mouse IgG was very low. The product contained seven main subtypes: IFN-alpha1, IFN-alpha2 , IFN-alpha8, IFN-alpha 10, IFN-alpha 14, IFN-alpha 17, and IFN-alpha 21. T he subtypes IFN-alpha4 and IFN-alpha7 were minor components. Reverse-phase HPLC indicated a constant subtype composition for the product from batch to batch. Stabilization of the pure IFN-alpha solution with albumin and Tween 80 was compared. In virus filtration, a better yield and higher filtration capacity were obtained with Tween. The addition of albumin resulted in the formation of IFN-albumin aggregates. During long-term storage, IFN-alpha w as stable in both solutions for 2 years at 2-8 degreesC. The new method mak es it possible to extensively purify all major IFN-alpha subtypes and obtai n a virus-safe and stable product with a constant subtype composition.