Fermentation process for double-stranded ribonucleic acid, an interferon inducer.

Double-stranded ribonucleic acid (ds-RNA) isolated from Escherichia coli infected with bacteriophage MS2 is a potent interferon inducer. High levels of ds-RNA are formed in nonpermissive cells infected with MU9, an amber coat protein mutant of MS2. This mutant has been used to develop a process for large-scale ds-RNA production. Preparation of quantities of MU9 lysate sufficient for ds-RNA production in fermentors is described. Over 300 mug of ds-RNA/ml can be accumulated after MU9 infection of cultures grown to high density in corn steep liquor medium. This is approximately 300 times the amount of ds-RNA made by MS2 infection of cells grown in tryptone medium. Maximum ds-RNA formation requires only 3 hr. The ds-RNA is stable and remains inside nonaerated cells for at least 17 hr.