Incomplete Growth Cycle of Influenza Virus in Mouse Brain

Abstract

Summary

Mouse brain, previously considered as insusceptible to infection with non-neurotropic strains of influenza virus, has been found to support a single cycle of viral reproduction in which hemagglutinin and complement-fixing antigen increase without concomitant rise in infective titer. Rather, the infective titer decreases progressively in mouse brain. The newly formed, incomplete virus is non-infectious, but is produced only if the intracerebral inoculum contains fully infectious virus. The yield of incomplete virus is proportional to the amount of infectious virus inoculated. In mouse brain, as in the allantoic membrane, the constant period preceding a rise in hemagglutinin titer is longer for the Lee than for the PR8 strain. These findings appear to have significance in relation to the “toxicity” of non-neurotropic influenza viruses and to their ability to interfere with unrelated neurotropic viruses, and to the problem of viral adaptation to experimental hosts.