The effects of interferon and double-stranded RNA upon the virus-host interaction: studies with togavirus strains in mice.

Partially purified fibroblast interferon and double-stranded RNA (dsRNA) of fungal origin were administered as single graded doses to A2G and Balb/c mice shortly before intraperitoneal infection by specified virulent or avirulent strains of representative togaviruses (Semliki Forest virus, Venezuelan equine encephalomyelitis virus and yellow fever virus). Changes of efficiency of infection arising from interference at the level of clearance or replication and changes of the expression of virulence or protective immunity, were compared for different initial doses of interferon or dsRNA in relation to different levels of infection by defined virus strains. Interferon and dsRNA, although acting through quantitatively different mechanisms, both reduced effective dose of virus and influenced only the extent of primary replication and host stimulation. Neither agent changed in any way the outcome of infection in terms of expression of virulence (regulatory immunity) or protective immunity. These results are discussed in terms of the control of virus infections at stages before or after immune stimulation can be effective.