The expression of nlacZ in the DG was almost completely abolished among infected cells as compared to controls (Fig. 10A,B and E), while nlacZ expression in the cerebellum was unchanged (Fig. 10C,D and F), revealing the anatomical selectivity and efficiency of the viral infection mediated ablation of Shh. As expected, there was a marked reduction of the Shh-protein detected by immunohistochemical staining in the AAV injected mice compared to control mice injected with vehicle in the same hemisphere (Fig. 11B,F and T). This evidence concerns the gene SHH and viral infectious disease.