Increased toxicity of double-stranded ribonucleic acid in virus-infected animals.

Virus-infected mice were significantly more susceptible to the toxic effects of double-stranded ribonucleic acid (RNA) than uninfected mice. A dramatic increase in mortality was observed after injection of either synthetic (polyriboinosinic.polyribocytidylic acid) or natural (mycophage) double-stranded RNA in mice infected with Newcastle disease virus (NDV) or vesicular stomatitis virus (VSV). With the exception of endotoxin, interferon inducers other than double-stranded RNA, such as tilorone-hydrochloride and chlorite-oxidized oxyamylose, did not show this increased toxicity in virus-infected animals. The increased susceptibility of virus-infected animals to the toxic effects of double-stranded RNA appears to be related to the levels of interferon induced by the virus infection, either systemically, in the blood stream (after inoculation of NDV), or locally, in the brain (after infection with VSV).