Evaluation of the Possible Transmission of BSE and Scrapie to Gilthead Sea Bream (Sparus aurata ) Evgenia Salta1., Cynthia Panagiotidis2., Konstantinos Teliousis3, Spyros Petrakis1,4, Eleftherios Eleftheriadis5, Fotis Arapoglou 5 , Nikolaos Grigoriadis6, Anna Nicolaou7, Eleni Kaldrymidou 3 , Grigorios Krey5, Theodoros Sklaviadis2* 1 Department of Pharmacology, Aristotle University of Thessaloniki, Thessaloniki, Greece, 2 Centre for Research and Technology-Hellas, Institute of Agrobiotechnology, Thessaloniki, Greece, 3 Laboratory of Pathology, School of Veterinary Medicine, Aristotle University of Thessaloniki, Thessaloniki, Greece, 4 Max Delbruck Center for Molecular Medicine, Department of Neuroproteomics, Berlin-Buch, Germany, 5 National Agricultural Research Foundation, Fisheries Research Institute, Nea Peramos, Greece, 6 B’ Department of Neurology, AHEPA University Hospital, Aristotle University of Thessaloniki, Thessaloniki, Greece, 7 Department of Business Administration, University of Macedonia, Thessaloniki, Greece Abstract In transmissible spongiform encephalopathies (TSEs), a group of fatal neurodegenerative disorders affecting many species, the key event in disease pathogenesis is the accumulation of an abnormal conformational isoform (PrPSc) of the host- encoded cellular prion protein (PrPC). While the precise mechanism of the PrPC to PrPSc conversion is not understood, it is clear that host PrPC expression is a prerequisite for effective infectious prion propagation. Although there have been many studies on TSEs in mammalian species, little is known about TSE pathogenesis in fish. Here we show that while gilthead sea bream (Sparus aurata) orally challenged with brain homogenates prepared either from a BSE infected cow or from scrapie infected sheep developed no clinical prion disease, the brains of TSE-fed fish sampled two years after challenge did show signs of neurodegeneration and accumulation of deposits that reacted positively with antibodies raised against sea bream PrP. The control groups, fed with brains from uninfected animals, showed no such signs. Remarkably, the deposits developed much more rapidly and extensively in fish inoculated with BSE-infected material than in the ones challenged with the scrapie-infected brain homogenate, with numerous deposits being proteinase K-resistant. These plaque-like aggregates exhibited congophilia and birefringence in polarized light, consistent with an amyloid-like component. The neurodegeneration and abnormal deposition in the brains of fish challenged with prion, especially BSE, raises concerns about the potential risk to public health. As fish aquaculture is an economically important industry providing high protein nutrition for humans and other mammalian species, the prospect of farmed fish being contaminated with infectious mammalian PrPSc, or of a prion disease developing in farmed fish is alarming and requires further evaluation. Citation: Salta E, Panagiotidis C, Teliousis K, Petrakis S, Eleftheriadis E, et al. (2009) Evaluation of the Possible Transmission of BSE and Scrapie to Gilthead Sea Bream (Sparus aurata). PLoS ONE 4(7): e6175. doi:10.1371/journal.pone.0006175 Editor: Etienne Joly, Universite´ de Toulouse, France Received March 27, 2009; Accepted May 19, 2009; Published July 28, 2009 Copyright: 2009 Salta et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Funding: This work was funded by the European Commission’s Food Quality and Safety: Prevention, Control, Treatment, Management and Risk analysis of Prion Diseases, Neuroprion (NOE), Grant ID: FOOD-CT-2004-506579, URL: http://www.neuroprion.org/en/np-neuroprion.html and TSE & Fish: Evaluation of the possible transmission of prions (Scrapie and BSE) to different fish species, Grant ID: QLK5-2002-00866, URL: http://ec.europa.eu/research/agriculture/projects/ qlrt_2001_00866_en.htm. Evgenia Salta is a scholar of the Greek States Scholarships Foundation, URL: http://www.iky.gr/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Competing Interests: The authors have declared that no competing interests exist. * E-mail: sklaviad@auth.gr . These authors contributed equally to this work. Introduction Transmissible spongiform encephalopathies or prion diseases are a group of fatal neurodegenerative disorders, including Creutzfeldt-Jakob disease (CJD), Fatal Familial Insomnia (FFI) and Gerstmann-Stra¨ussler-Scheinker disease (GSS) in humans, scrapie in sheep and goats and bovine spongiform encephalopathy (BSE) in cattle [1]. The transmission of clinical prion diseases is limited by the so- called ‘‘species barrier’’ to conversion of endogenous host prion protein (PrPC) to its abnormal, partially proteinase K-resistant conformational isoform, PrPSc. When high enough, this ‘‘barrier’’ can greatly impair or prevent potential interspecies transmissions, even under optimal conditions of dose and infection route. However, evidence of TSE replication without accompanying symptoms of clinical disease has prompted debate on the existence of asymptomatic infected individuals in an exposed population [2,3]. The identification of apparent PrP orthologues in lower vertebrates, including fish [4–16], raises the question of their susceptibility to prion diseases. While fish PrP-like sequences do not share high homology with their mammalian relatives (Table S1), they do contain several strongly conserved prion protein structural motifs [17]. Although mammalian to fish TSE transmission is considered unlikely [18], it is not certain that the species barrier would be high enough to prevent TSE transmission to fish. The BSE epidemic has been linked to TSE-infected cattle feed [19] and the recognition of BSE in domestic cattle inevitably raised concerns about the potential risk to other ruminant and PLoS ONE | www.plosone.org 1 July 2009 | Volume 4 | Issue 7 | e6175