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. 2006 Sep 4;203(9):2095–2107. doi: 10.1084/jem.20060420

Figure 1.

Figure 1.

The systemic immune response clears infected astrocytes and virus genomes from the brain. (A) Virally infected cells are astrocytes. To determine the cellular nature of infected cells, confocal microscopy of triple immunolabeling of TK, a marker of adenovirus infection (green); GFAP, an astrocyte marker (magenta); and NeuN, a neuronal marker (red), was performed in 50-μm thick vibratome sections from the brains of animals studied 30 d after intracranial injection of virus, in the absence or presence, of systemic immunization. The top row illustrates TK, GFAP, and the merging of both images as indicated. The vast majority of the TK-immunoreactive cells were also GFAP+ (i.e., >85%). Some of the cells expressing both markers are indicated by white arrows on all three panels (all the TK-immunoreactive cells illustrated in these panels also expressed GFAP). The bottom row shows the same field, but colocalization was studied between TK and NeuN; no colocalization was detected. This indicates that the virus used expresses its marker gene almost exclusively within astrocytes, but not neurons. Bar, 100 μm. (B) Systemic immunization induces an immune response that clears virally infected expressing astrocytes and viral genomes from the brain. Panels a–e illustrate that after the systemic immunization against adenovirus, the adaptive immune response clears virally infected cells from the striatum. Analysis of brain sections from immunized animals (c, low power, and d, high power) show a reduction in the expression of the virally encoded marker gene, TK, when compared with naive animals (a and b). The decrease in the number of infected cells after immunization was assessed by quantifying adenovirally infected, TK-expressing cells (e), and the decrease in the number of viral genomes was quantified using quantitative real-time TaqMan PCR (f). Decreases in the number of infected cells (e), and adenoviral genomes (f), after the systemic immunization against adenovirus was statistically significant (*, P < 0.05; Student's t test). This indicates that the systemic immune response clears transduced astrocytes and viral genomes from the brain. Bars, 1 mm. (C) Adenovirally infected astrocytes express MHC-I. These panels illustrate a GFAP-immunoreactive astrocyte that has been infected with adenovirus and thus is immunopositive for the marker protein TK, expressing MHC-I. Bar, 40 μm.