Fig. 1

Injection of cytokine expressing vectors into the subarachnoid space of rats leads to meningeal inflammation. Lentiviral vectors (LV) expressing TNF and IFNγ were injected into the subarachnoid space where the dye monastral blue was used to identify the correct positioning and location of the injection site (a). Use of a LV expressing eGFP showed significant transduction of meningeal cells lining the cortex down the midline (b), spreading to at least 500 μm anterior to the injection site (b) and along the cortical surface (c). Immunostaining for human TNF showed that expression of the human TNF transgene occurred in cells along the length of the midline (d). Significant levels of human transgene derived TNF and IFNγ were detectable in CSF from cytokine LV but not from GFP LV injected animals at both 28 and 56 days post-injection (e). Low magnification brightfield images of MOG immunised animals showed that injection of vectors for TNF and IFNγ led to the formation of large dense infiltrates of cells within the sagittal sulcus and across the surface of the cortex at 28 days post-injection, which were still present at 56 days (f), whereas the control GFP vector did not induce inflammation. Immunofluorescent staining showed the extensive infiltration of CD4+ and CD8+ T cells in the meninges within the sagittal sulcus and overlying the cortex of cytokine vector injected MOG animals (g,h). CD79a + B-cell aggregates in serial sections of the same area appeared to form more discrete clusters (i,j). The maximal infiltration of T- and B-cells into the sagittal sulcus was seen 28 days after injection for both IFA and MOG immunised animals and decreased by approximately 50% by 56 days (k), with no significant difference between animals immunised with MOG or IFA (1-way analysis of variance with Tukey correction, *** P < 0.001 compared to GFP). CD4+ and CD8+ T cell numbers were approximately equal and twice that of B-cells. Data represents mean ± SEM from n = 5–6 per group. Scale bars = 20 μm