|Knowles Jr, Donald|
Submitted to: Journal of Virology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/31/2008
Publication Date: 10/6/2008
Citation: Stanton, J.B., Knowles Jr, D.P., Orourke, K.I., Hoesing, L.M., Mathison, B.A., Baszler, T.V. 2008. Small-Ruminant Lentivirus Enhances PrP-Sc Accumulation in Cultured Sheep Microglial Cells. Journal of Virology. 82(20):9839-9847.
Interpretive Summary: Scrapie, a fatal disorder of sheep and goats, is endemic in the United States but subject to an intensive federal/state/industry eradication program. The disorder is thought to be spread among sheep and goats by exposure to fetal placental tissues. Infected animals have a relatively long incubation period, usually lasting for 2 -6 years, during which they remain clinically normal but can spread the disease to flockmates. The central feature of scrapie is the conversion of a normal cellular protein into an abnormal state through a misfolding event. The abnormal prion protein PrP-Sc is eventually disseminated to the brain, where it accumulates in a number of cell types. The immediate causes of the fatal neurodegenerative changes are not known. Methods for studying the pathogenesis of scrapie are limited and there are very few cell culture systems suitable for investigating scrapie pathogenesis in the natural host. In this study, the investigators established two cell culture system using microglial cells fromthe brain of sheep. Following experimental infection, these cell cultures were shown to accumulate PrP-Sc. Microglial cells co-infected with a commonly occurring small ruminant virus demonstrated a two-fold increase in PrP-Sc accumulation. The results demonstrate the utility of this cell culture system for investigating the biology of natural prion disease and show that small ruminant lentiviruses enhance prion conversion under these conditions. The findings are relevant to pathogenesis studies in sheep scrapie and may be of particular value in understanding the disease in goats, a species with a high prevalence of small ruminant lentirvirus infection.
Technical Abstract: Scrapie is the prototype member of the family of transmissible spongiform encephalopathies, fatal neurodegenerative diseases associated with conversion and accumulation of prion proteins in a number of neural and extraneural cell types. Although scrapie has been the focus of research investigations for decades, very little is known about the pathogenesis in the natural host, in part because of the long preclinical period and the limitations of working with the large animal host. Although a number of rodent cell culture systems have been described, there are no reliable cell culture systems from sheep or goats, the natural hosts for scrapie. In this study, the investigators describe development and characterization of two cell culture systems from fetal ovine brain explants. Both systems are microglial in origin. Both the SV-40 transformed cell line and the primary cell line were shown to accumulate PrP-Sc, characterized by protease resistance, beta sheet conformation, specifically inhibited by anti-PrP antibodies, and transmissible in a dose-dependent manner. Primary microglial cells coinfected with a small ruminant lentivirus demonstrated an approximate two fold increase in PrP-Sc accumulation. This study demonstrates the utility of PrP-Sc accumulating ovine cell lines in investigating the biology of prion disease in the natural host and addressing the role of concurrent infection with commonly occurring small ruminant viruses in prion pathogenesis.