Antiviral effect of interferon on influenza virus infection in mice.

The antiviral effect of highly purified mouse interferon (IFN) was studied on influenza virus infection in mice, by changing the routes of administration. By repeated intravenous (i.v.) administrations of IFN, no antiviral effect was observed. However, IFN was effective when the infected mice received either intraperitoneal (i.p.) or intranasal (i.n.) administrations. While all of the untreated mice died within 10 days after infection, 20% of the i.p. treated mice and 67% of the i.n. treated mice survived more than 30 days. To explain these different effects after administration by different routes, the distribution of given IFN in mouse organs was examined. Fifteen min after i.v. injection, only a low-titered IFN was detected in the serum, lung, spleen and liver of the mice and soon disappeared. However, a relatively high-titered IFN was detected 30 min after i.p. administration in the lung and serum. After i.n. administration, high-titered IFN was detected in the lung within 15 min after administration and continued for 90 min. Thus the findings demonstrated that the maintenance of a detectable amount of IFN in mice organs is dependent on the route of administration, and the higher the titer of IFN in the lung, the higher the protective effect of IFN against influenza virus infection.