Detection of toxic viral-associated double-stranded RNA (dsRNA) in influenza-infected lung.

While many of the molecular events in viral replication are well studied, the molecular mechanisms by which viral infections trigger such constitutional symptoms as fever and 'malaise' are unknown. The hypothesis that these viral constitutional symptoms can be triggered by the toxic action of dsRNA associated with viral replication was investigated. Total lung RNA from mice acutely infected with PR8 influenza virus, but not from sham-infected mice, was shown to induce fever and altered sleep (excess slow-wave sleep, enhanced amplitudes of electroencephalographic slow waves, and reduced rapid eye movement sleep) when injected into the rabbit brain. Viral-associated dsRNA was shown to be responsible for the rabbit responses by differential nuclease digestion. Influenza viral dsRNA was directly demonstrated in the active lung RNA preparations by reverse transcriptase-polymerase chain reaction techniques. The time course of the responses paralleled those seen in the same model inoculated with nanogram quantities of the synthetic dsRNA polyriboinosinic-polyribocytidylic acid and suggested that they were mediated by induced cytokines. A model for the role of viral-associated dsRNA in eliciting both local cytotoxicity and viral constitutional symptoms is presented.