Relationship between host age and persistence of Theiler's virus in the central nervous system of mice.

This study has demonstrated that the ability of BeAn 8386 virus to persist in the central nervous system of mice declines with the increasing age of the host at the time of inoculation. Although persistent infection was established in 1-, 3-, 9-, and 40-week-old mice, there was a significant reduction in both the frequency of virus isolations and the mean virus titers in mice inoculated after 3 weeks of age. The incidence of clinical demyelinating disease (late disease) also decreased in animals infected after 3 weeks of age in parallel with the decline in virus persistence.