Congenital LCMV virus: mechanism of brain disease in a rat model of congenital viral infection

Lymphocytic choriomeningitis virus (LCMV) infection during pregnancy severely injures the human fetal brain. Neonatal rats inoculated with LCMV are an excellent model of congenital LCMV infection, as they develop neuropathology, including cerebellar injuries, similar to those seen in humans. The goal of this thesis was to determine what underlies brain injury and the differential immune response and to determine the role of T-cells in LCMV induced pathology. First, I examined whether cytokine and chemokine expression after LCMV infection was higher in the cerebellum and olfactory bulbs, which undergo destruction, compared to the hippocampus and septum, which undergo no acute destruction. Second, I used T-cell deficient and T-cell competent animals to evaluate the role of T-lymphocytes in LCMV-induced cerebellar and hippocampus pathology. Finally, I characterized the migration abnormality that develops in the cerebellum after LCMV infection. My results showed that cytokine and chemokine expression is higher in the cerebellum and olfactory bulb than in the hippocampus and septum. Using astrocyte cultures, I determined that astrocytes isolated from the cerebellum have a more robust cytokine response to infection compared to astrocytes from the hippocampus. Furthermore, inoculation of congenitally athymic (rnu/rnu) rats, which are deficient in T-lymphocytes, demonstrated that cerebellar hypoplasia is T-cell independent while cerebellar destruction and abnormal neuron migration is T-cell dependent. In the hippocampus, T-cells protect against loss of dentate granule cells. A study of the migration abnormality determined that LCMV infection disrupts radial glia fibers and extends proliferation of granule cells in a T-cell dependent manner. The findings reported here support a pivotal role of the immune system in regional brain pathology as well as in the disruption of migration.