Ex vivo propagation of infectious sheep scrapie agent in heterologous epithelial cells expressing ovine prion protein

Transmissible spongiform encephalopathies, or prion diseases, are fatal deg enerative disorders of the central nervous system that affect humans and an imals. Prions are nonconventional infectious agents whose replication depen ds on the host prion protein (PrP). Transmission of prions to cultured cell s has proved to be a particularly difficult task, and with a few exceptions , their experimental propagation relies on inoculation to laboratory animal s. Here, we report on the development of a permanent cell line supporting p ropagation of natural sheep scrapie, This model was obtained by stable expr ession of a tetracycline-regulatable ovine PrP gene in a rabbit epithelial cell line. After exposure to scrapie agent, cultures were repeatedly found to accumulate high revels of abnormal PrP (PrPres), Cell extracts induced a scrapie-like disease in transgenic mice overexpressing ovine PrP. These cu ltures remained healthy and stably infected upon subpassaging. Such data sh ow that (i) cultivated cells from a nonneuronal origin can efficiently repl icate prions; and (ii) species barrier can be crossed ex vivo through the e xpression of a relevant PrP gene. This approach led to the ex vivo propagat ion of a natural transmissible spongiform encephalopathy agent (i.e., witho ut previous experimental adaptation to rodents) and might be applied to hum an or bovine prions.