Lymphocytic choriomeningitis infection of mice as a model for the study of latent virus infection

Lymphocytic choriomeningitis virus has been used to set up a model of a latent virus infection in mice. It has been shown to be possible to induce reproducible virus infections in mice which remain completely symptom-free in spite of levels of viral growth equal to those found in the sick animal, by the inoculation of mice within a few hours of birth. This is a convenient method of producing a latent infection in the mice. The effect of the age of the mice at the time of intracerebral inoculation was studied with respect to the pattern of disease produced. Several methods were tried without success in order to induce overt disease in the latently infected animals. The virus did not cause any demonstrable cytopathogenic effect on mouse tissue and several other types of animal tissue. A slight cytopathogenic effect was observed in a strain of human cells in vitro. Virus persisted for weeks in some of the tissue cultures, without damaging the tissue but with the production of active virus. The bearing of the results obtained is discussed in relationship to current concepts of latent virus infection and particularly immunological tolerance. A concept of a special variety of latency is introduced and the name "vital" infection suggested for this.