Induction of Interference and Interferon Production by Echovirus Type 7

Echovirus type 7 does not multiply in mice, but injection of this virus into mice (intracerebrally or intraperitoneally) increased their resistance to a subsequent infection with Coxsackie B virus, type 5 and to Japanese encephalitis virus by intracerebral route. The effect is evident in the survival rate and the prolongation of life among the mice that did succumb to Coxsackie or Japanese encephalitis virus infection, as well as those that developed paralysis. An adequate dose of active interfering virus and a time interval between the two inoculations were both necessary to obtain a significant interfering effect. Pretreatment of mice with actinomycin D suppressed the interfering effect by Echovirus type 7, and the kinetics of interferon production corresponded to the time of establishment of interference. All these findings suggest that the induction of resistance by Echovirus type 7 is mediated by interferon produced in the early stages of infection.