CD8 T cells mediate polyomavirus-associated CNS demyelination

Abstract

Abstract JC polyomavirus (JCV), a common member of the virome in healthy humans, can cause the frequently fatal brain demyelinating disease Progressive Multifocal Leukoencephalopathy (PML) in immunocompromised individuals. PML, a pre-HAART AIDS-defining disease, has reemerged and is increasing in incidence in patients receiving immunodulatory therapies for autoimmune and inflammatory disorders. Lack of an animal model has hampered understanding of PML pathogenesis. We have developed a novel mouse model using intracerebral (i.c.) inoculation of mouse polyomavirus (MPyV), which mimics JCV-associated demyelination and shows similar histological features to PML. By one month after MPyV inoculation, C57BL/6 mice develop diffuse subcortical white matter demyelination, predominantly in the corpus callosum. Diffusion tensor magnetic resonance imaging in infected mice reveals severe peri-ventricular edema and a loss of structural integrity predominately in the corpus callosum and caudate. Virus-specific CD8 T cells robustly infiltrate the CNS and are stably maintained after CNS entry. Antibody-mediated depletion of CD4 and CD8 T cells prior to infection abrogates demyelination in the corpus callosum, despite resulting in a 50–100 fold increase in virus levels. Additionally, CD8 T cell-depletion alone was sufficient to cause higher virus levels in the brain. MPyV was controlled in the absence of CD4 T cells; however, MPyV-specific CD8 T cells in CD4 T cell-deficient mice expressed lower levels of CD103 (aE integrin), which binds epithelial E-cadherin. These data demonstrate that CD8 T cells infiltrating the CNS of MPyV-infected mice play a major role in this demyelinating leukoencephalitis.