Development of a highly purified multicomponent leukocyte IFN-alpha product.

A purification process was developed to obtain a human interferon- alpha (IFN-alpha) product that contains all major IFN-alpha subtypes produced by human leukocytes. The purification was accomplished by immunoaffinity chromatography using two monoclonal antibodies (mAb) and gel filtration. The process comprised two effective virus inactivation steps, solvent detergent treatment, 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 the process was about 60% when starting from the culture supernatant of Sendai 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-alpha 1, IFN-alpha 2, IFN-alpha 8, IFN-alpha 10, IFN-alpha 14, IFN-alpha 17, and IFN-alpha 21. The subtypes IFN-alpha 4 and IFN-alpha 7 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 was stable in both solutions for 2 years at 2-8 degrees C. The new method makes it possible to extensively purify all major IFN-alpha subtypes and obtain a virus-safe and stable product with a constant subtype composition.