Antiviral Activity of Double Stranded RNA and Virus-like Particles from Penicillium stoloniferum

THE antiviral activity of a culture filtrate from Penicillium stoloniferum was first described in 1952 1 . Landmarks in the evaluation of this material, termed ‘ Statolon ’, came with its initial chemical characterization as a polysaccharide 2 and the discovery that its mode of action was by the induction of interferon 3 . Later it became apparent that a ribonucleic acid component accompanying the polysaccharide had interferon stimulating ability (personal communication from Professor Sir Ernst Chain). It has subsequently been shown that the antiviral activity resided in virus-like particles present in the mould 4 and in the double-stranded ribonucleic acid (ds-RNA) of these virus-like particles 5,6 . During our screening programme for antiviral substances from microorganisms, antiviral activity of a Stemphylium culture was discovered * which was attributed to the presence of virus-like particles. Coincidental with this, workers at the Merck Institute showed that the antiviral activity of helenine (also an antiviral agent produced by a mould) was attributable to ds-RNA, and that other ds-RNAs (poly I.poly C and the replicative form of MS2 phage) possessed similar antiviral activity 7 . Recently, there have been further publications (for example, refs. 8–10) in which the toxicity of poly I.poly C has been examined. It will be interesting to see if the naturally produced ds-RNA is less toxic than poly I.poly C, as might be postulated because of the unnatural base composition in the latter material.