Histopathological features and viral tropism within the brain and spinal cord of C57BL/6 mice 8 days after the intracranial inoculation of NIHE virus. (A to D) HE staining. Severe acute necrotizing polioencephalitis and poliomyelitis characterized by perivascular cuffs (arrows), neuronal necrosis (blue stars), satellitosis and neuronophagia (green triangles), and gliosis (black arrowheads). (A) Hippocampus (original magnification, ×100). (B) Hippocampus (Ammon's horn) (original magnification, ×200). (C) Hippocampus (original magnification, ×400). (D) Spinal cord (ventral horns) (original magnification, ×200). GM, gray matter of the spinal cord; WM, white matter of the spinal cord. (E and F) Immunostaining against Theiler's virus (strain DA). (E) Many viral neuronal bodies and processes are labeled in the Ammon's horn of the hippocampus and in thalamic nuclei. Original magnification, ×20. (F) In the Ammon's horn, many virus-positive neurons are seen and are necrotic in CA1 and CA2; in CA3 only a few neurons are infected and necrotic. Original magnification, ×200. CA, Ammon's horn; DG, dentate gyrus; CC, cerebral cortex; Cca, corpus callosum; Lv, lateral ventricle; St, striatum; Th, thalamus; CA1, CA2, and CA3, fields of the Ammon's horn; 3rdV, third ventricle.