Viral Infection of Transgenic Mice Expressing a Viral Protein in Oligodendrocytes Leads to Chronic Central Nervous System Autoimmune Disease

Evans, Claire F.; Horwitz, Marc S.; Hobbs, Monte V.; Oldstone, Michael B.A.

To determine whether lymphocytic infiltration of the CNS occurred after peripheral infection with LCMV, transgenic positive and negative mice were killed at various times postinfection and sagittal brain sections were stained with antibodies to the T cell surface markers CD4 and CD8. Approximately 1,000 lymphocytes were observed per sagittal section at 1 wk after infection in both transgenic positive and negative mice. The majority of these lymphocytes were CD8 Ï© and were found within the meninges and ventricular linings of the brain. These cells were most likely activated by the viral infection and were trafficking through the CNS as a normal part of immune surveillance after activation in the periphery (32) . By 2 wk after infection, fewer meningeal infiltrating cells were observed in both transgenic positive and negative mice. By 3 wk after infection, in nontransgenic mice less than 30 lymphocytes could be found per sagittal section, and by 5 wk after infection less than 5 lymphocytes were detected per section. In contrast, in transgenic positive mice, at 3 wk after infection about 150-300 CD8 Ï© cells were found per section. These cells were located in the brain parenchyma as well as the brain stem and spinal cord, and perivascular cuffs were often observed. In addition, CD4 Ï© cells were present and comprised 20% of the infiltrating T cells. Brains of transgenic positive mice taken at various times after infection were found to contain this level of CD8 Ï© infiltrates as long as 1 yr after infection. By 1 yr after infection, the numbers of CD4 Ï© staining cells had risen to approximately half the number of CD8 Ï© staining cells per section. At 3 wk after infection, the infiltrating cells did not localize to any particular area or location within the brain. By 3 mo after infection, clusters of CD4 Ï© and CD8 Ï© cells were found predominantly within the white matter regions of the CNS, including the corpus callosum, internal capsule, fimbria hippocampus, brain stem, and spinal cord (Fig. 2, A, B, F, G) . Lymphocytes were isolated from the brains of MBP-NP transgenic positive mice 3 wk after LCMV infection and tested in 51 Cr-release CTL assays after in vitro stimulation with LCMV. These lymphocytes were found to effectively lyse MHC-matched target cells infected with either LCMV or recombinant VV expressing the LCMV NP (data not shown).