Human cytomegalovirus infection of the developing central nervous system (CNS) is a major cause of neurological damage in newborn infants and children. To investigate the pathogenesis of this human infection, we developed a mouse model of infection in the developing CNS. Intraperitoneal inoculation of newborn animals with murine cytomegalovirus resulted in virus replication in the liver followed by virus spread to the brain. Virus infection of the CNS was associated with the induction of inflammatory responses, including the induction of a large number of interferon-stimulated genes and histological evidence of focal encephalitis with recruitment of mononuclear cells to foci containing virus-infected cells. The morphogenesis of the cerebellum was delayed in infected animals. The defects in cerebellar development in infected animals were generalized and, although correlated temporally with virus replication and CNS inflammation, spatially unrelated to foci of virus-infected cells. Specific defects included decreased granular neuron proliferation and migration, expression of differentiation markers, and activation of neurotrophin receptors. These findings suggested that in the developing CNS, focal virus infection and induction of inflammatory responses in resident and infiltrating mononuclear cells resulted in delayed cerebellar morphogenesis.

Human cytomegalovirus (HCMV) infection of the neonatal CNS results in long-term neurologic sequelae. To define the pathogenesis of fetal HCMV CNS infections, we investigated mechanisms of virus clearance from the CNS of neonatal Balb/c mice infected with murine CMV (MCMV). Virus titers peaked in the CNS between post-natal (PN) days 10–14 and infectious virus was undetectable by PN day 21. Congruent with virus clearance was the recruitment of CD8+ T-cells into the CNS. Depletion of CD8+ T cells resulted in death by postnatal day 15 in MCMV infected animals and increased viral loads in the liver, spleen and the CNS suggesting an important role for these cells in the control of MCMV replication in the newborn brain. Examination of brain mononuclear cells revealed that CD8+ T-cell infiltrates expressed high levels of CD69, CD44 and CD49d. IE1168 specific CD8+ T-cells accumulated in the CNS and produced IFN-γ and TNF-α but not IL-2 following peptide stimulation. Moreover, adoptive transfer of brain mononuclear cells resulted in decreased virus burden in immunodepleted MCMV infected syngeneic mice. Depletion of the CD8+ cell population following transfer eliminated control of virus replication. In summary, these results show that functionally mature virus specific CD8+ T-cells are recruited to the CNS in mice infected with MCMV as neonates.