Abstract
Accumulation of prion protein (PrPSc) in the central nervous system is the hallmark of transmissible spongiform encephalopathies. However, in some of these diseases such as scrapie or chronic wasting disease, the PrPSc can also accumulate in other tissues, particularly in the lymphoreticular system. In recent years, PrPSc in organs other than nervous and lymphoid have been described, suggesting that distribution of this protein in affected individuals may be much larger than previously thought. In the present study, 11 non-nervous/non-lymphoid organs from 16 naturally scrapie infected sheep in advanced stages of the disease were examined for the presence of PrPSc. Fourteen infected sheep were of the ARQ/ARQ PRNP genotype and 2 of the VRQ/VRQ, where the letters A, R, Q, and V represent the codes for amino-acids alanine, arginine, glutamine and valine, respectively. Adrenal gland, pancreas, heart, skin, urinary bladder and mammary gland were positive for PrPSc by immunohistochemistry and IDEXX HerdChek scrapie/BSE Antigen EIA Test in at least one animal. Lung, liver, kidney and skeletal muscle exhibited PrPSc deposits by immunohistochemistry only. To our knowledge, this is the first report regarding the presence of PrPSc in the heart, pancreas and urinary bladder in naturally acquired scrapie infections. In some other organs examined, in which PrPSc had been previously detected, PrPSc immunolabeling was observed to be associated with new structures within those organs. The results of the present study illustrate a wide dissemination of PrPSc in both ARQ/ARQ and VRQ/VRQ infected sheep, even when the involvement of the lymphoreticular system is scarce or absent, thus highlighting the role of the peripheral nervous system in the spread of PrPSc.
Highlights
Transmissible spongiform encephalopathies (TSEs; known as prion diseases) are a group of neurodegenerative diseases that affects humans and animals
In some TSEs, including scrapie in sheep and goats, chronic wasting disease (CWD) in deer and variant Creutzfeldt-Jakob disease in humans, PrPSc has been detected in diverse tissues and organs outside the central nervous system (CNS) [1,2]
Evidence suggests that the main route of entry of the agent is through the gut-associated lymphoid tissues, which spreads to the CNS by centripetal transport along the peripheral nervous system (PNS; [3,4])
Summary
Transmissible spongiform encephalopathies (TSEs; known as prion diseases) are a group of neurodegenerative diseases that affects humans and animals. The main feature of these diseases is the deposition of a misfolded form of the prion protein (hereafter referred to as PrPSc) in the central nervous system (CNS). In some TSEs, including scrapie in sheep and goats, chronic wasting disease (CWD) in deer and variant Creutzfeldt-Jakob disease (vCJD) in humans, PrPSc has been detected in diverse tissues and organs outside the CNS [1,2]. Evidence suggests that the main route of entry of the agent is through the gut-associated lymphoid tissues, which spreads to the CNS by centripetal transport along the peripheral nervous system (PNS; [3,4]). PrPSc has been associated with inflammation foci in different organs such as the lung and mammary glands from scrapie infected sheep [11,12,13]
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