Effect of antilymphocyte serium on tacaribe virus infection in infant mice

Tacaribe virus, a member of the arenovirus group, was demonstrated to have similarities in pathogenesis to the prototype virus of this group, lymphocytic choriomeningitis (LCM) virus. Treatment with antilymphocyte serum (ALS) doubled the survival time of mice neonatally infected with a lethal dose of Tacaribe virus. Twenty-one per cent of ALS-treated infected animals survived more than 30 days. All animals had recoverable virus in brains and serum for the duration of life, and there was no difference between virus growth curves of ALS-treated and control animals. No neutralizing or complement-fixing antibodies were present in infected animals at time of death, with the exception of one long-surviving ALS-treated animal. Certain differences between infections of mice with LCM and Tacaribe viruses were apparent. Tacaribe virus pathogenicity decreased with increasing mouse age, and earlier infection and a more prolonged course of ALS treatment than was needed for LCM virus were necessary to achieve increased survival. Histopathological changes observed in Tacaribe virus-infected control mice were focal choroiditis and focal cerebellar necrosis; these changes were not seen in asymptomic infected mice during the period of transient protection by ALS.