Oral Prion Infection Via Cranial Nerves

Non-Technical Summary: Prion diseases such as bovine spongiform encephalopathy in cattle, scrapie in sheep, and chronic wasting disease in deer and elk, are caused by novel infectious agents and results in a fatal degeneration of the central nervous system. The goal of this research is to define the pathway of prion agent infection of skeletal muscle following oral prion infection. Prion ingestion establishes infection of lymphoid and nervous system tissues in the gut prior to spread to the central nervous system. In this study, we will examine the ability of the prion agent to spread from the brain to the tongue and infect skeletal muscle and taste cells as well as the mechanism of prion agent entry into muscle cells and the nervous system. These studies can improve our understanding of how the prion agent spreads within a host in order to infect peripheral tissues such as muscle. The findings from this study will be relevant to U.S. agriculture by identifying 1) potential sites of prion agent infection in muscle and 2) the ability of prions to infect the tongue, which is a food product. <P> Approach: The chronological sequence of prion agent spread from the brainstem to the peripheral nervous system and tongue following oral prion infection will be determined. These studies will investigate the site(s) of prion agent replication after exiting the brainstem and spread to the tongue. Nervous system tissues, lymphoreticular tissues, and tongue will be collected each week and the initial sites of prion agent replication will be determined by PrPSc detection. To determine the route of prion entry into the tongue, prion infection will be established in cranial nerves to the tongue and the sites of prion agent deposition will be determined by PrPSc immunohistochemistry. To determine the role of the neuromuscular junction in prion agent entry into skeletal muscle and nerve fibers, unilateral axotomy of the hypoglossal nerve will be performed prior to prion agent inoculation into the tongue. Prion agent infection will be monitored over time in the tongue, ganglia and brainstem by PrPSc Western blot and immunohistochemistry. Confocal microscopy will be performed to determine the cellular and subcellular location of prion infection in the tongue of rodents and sheep with prion disease. The latter studies will be performed in collaboration with scientists at the National Animal Disease Center.