Borna disease virus: immunoelectron microscopic characterization of cell-free virus and further information about the genome.

The etiological agent of Borna disease, a persistent virus infection of the central nervous system with differently expressed symptomatology, was morphologically unknown. Here we provide the first convincing data on its phenotypic architecture. Salt-released virus comprising the biological parameters of Koch's postulates has an unsegmented single-stranded RNA. A dense band (1.22 g/cm3) in CsCl contains 90-nm particles which appear to be enveloped and a fraction of 50- to 60-nm particles. Labeling of the virions with neutralizing antisera and colloidal gold conjugates indicates that the 90-nm particles most likely represent the causative agent.