Injection of VACV into mouse brain tissues with and without implanted gliomas. a C57BL/6 and Foxn1nu/nu mice with (w) and without (w/o) GL261 brain tumors were infected with 5 × 106 pfu LIVP 1.1.1 (i.t). For analysis of viral titers, brains were excised 1, 3 and 7 days after virus injection and analyzed by standard plaque assay [n = 4/5 per group (w) and n = 3 per group (w/o) tumor]. All samples were measured in duplicate (data are mean values ± SD; t test *p < 0.05). b Immunohistochemical staining for astrocytes (anti-GFAP, red) and VACV (anti-VACV, green) 1 dpi in GL261 implanted tumors. Shown are representative examples.