Localization of LCMV in the brain of clone 13 infected mice. The brains of C57BL/6 mice infected intravenously with LCMV clone 13 were harvested at time points spanning 10 to 200 days post infection. The distribution of LCMV (green) is shown on representative sagittal brain sections, and cell nuclei are shown in blue. On day 10 post-infection clone 13 is detected in the meninges, choroid plexus, ependyma as well as throughout the parenchyma in areas around blood vessels (note the punctuate pattern observed in the parenchyma). From days 20–60 post-infection, the virus inundates the brain parenchyma, spreading almost exclusively through the astrocytic network. Concurrent with reanimation of the peripheral T cell response clone 13 is purged from parenchymal astrocytes, and by day 150 the virus is found in its last refuge - olfactory bulb neurons as well as the meninges, ependyma and choroid plexus. Clone 13 is finally cleared from the brain by day 200 post infection.