Detection of Disease-associated Prion Protein in the Optic Nerve and the Adrenal Gland of Cattle with Bovine Spongiform Encephalopathy by Using Highly Sensitive Immunolabeling Procedures

Abstract

A sensitive immunohistochemical procedure, the tyramide signal amplification (TSA) system, was applied to detect the localization of immunolabeled disease-associated prion protein (PrPSc) in cattle affected with bovine spongiform encephalopathy (BSE). In this procedure, immunolabeling could be visualized in the optic nerve and the adrenal medulla. In the optic nerve, the dual immunofluorescent technique showed that the granular PrPSc was occasionally detected in the astrocytes, microglia, and myelin sheath adjacent to the axon. Clustered PrPSc was also scattered in association with microglial cells and astrocytes of the optic nerve. In the adrenal gland, PrPSc immunolabeling was confined within the sympathetic nerve fibers and endings. The results suggest that (1) PrPSc might centrifugally spread within and between glial cells and/or the non-axonal (also known as ad-axonal) region of nerve fibers, rather than the axonal and/or extracellular space pathway in the optic nerve, and (2) the sympathetic innervations might be important for the trafficking of BSE agent in the adrenal glands of cattle. This study also suggests that tyramide-based immunochemical analysis should be performed to detect immunolabeled PrPSc in the extracerebral tissues of BSE-affected cattle.