In borna disease virus infected rabbit neurons 100 nm particle structures accumulate at areas of Joest-Degen inclusion bodies.

Borna disease virus infected rabbits were chosen to search for electronmicroscopic structures. Intensively investigated hippocampal neurons showed intranuclear inclusions; 100 nm particle-like structures surrounded by 20 nm granular forms were prominent. In connection with elsewhere reported in situ hybridization studies of virus-specific RNA to areas of the Joest-Degen inclusions we suggest that these particle structures may represent Borna virus. Jost-Degen (8) found intranuclear inclusion bodies in neurons to be pathognomonic for Borna disease (BD) in the horse. Half a century later these structures were suggested to represent BD virus (BDV)-specific antigen aggregates (15). A century later we characterized the virus to contain a single and negative stranded RNA of 8.5 kb, which transcribes in the nucleus (5) and could show that virus complementary RNA seems to hybridize spot-like to nuclear areas, probably representing the Jost-Degen inclusions (7). Electron microscopic (EM) findings on structures in BDV infected brain cells and about particle-like structures obtained from infected tissue culture cells have been reported by different groups (1, 2, 3, 4, 5, 6, 9, 11, 12, 13). The demonstration of crystalline aggregates and filament bundles in the cytoplasma and karyospheridia (nuclear bodies) were prominent. Such structures were seen in infected rabbits, hamsters, rats mice and naturally infected horses. The phenotypic description of filamentous structures, crystalline aggregates in the cytoplasma and large karyospheridia were prominent. Based on our experience with BDV infections in rabbits we selected this species for ultrastructural studies.(ABSTRACT TRUNCATED AT 250 WORDS)