Figure. Microscopic lesions of brain caused by human herpesvirus 1 infection in marmosets. A) Histopathogic sample stained with hematoxylin and eosin showing nonsuppurative meningoencephalitis with perivascular infiltrates (black arrow) and infiltrates in piamater (white arrow). B) Histopathologic sample stained with hematoxylin and eosin showing perivascular and vascular infiltrates of mononuclear cells. C, D) Immunohistochemical examination by using polyclonal antibody directed against human herpesvirus 1 and the avidin–biotin–peroxidase complex method, Harris hematoxylin counterstain. Neural cells strongly marked by immunoperoxidase, indicating a positive finding. Scale bars = 100 μm.