Transmissible Spongiform Encephalopathies in Sheep: Experimental Determination of Genetic Susceptibility and Interspecies Transmission
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Iowa State University Capstones, Theses and Graduate Theses and Dissertations Dissertations 2019 Transmissible spongiform encephalopathies in sheep: Experimental determination of genetic susceptibility and interspecies transmission Eric Cassmann Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/etd Part of the Animal Diseases Commons, Pathology Commons, and the Veterinary Medicine Commons Recommended Citation Cassmann, Eric, "Transmissible spongiform encephalopathies in sheep: Experimental determination of genetic susceptibility and interspecies transmission" (2019). Graduate Theses and Dissertations. 17418. https://lib.dr.iastate.edu/etd/17418 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Graduate Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. Transmissible spongiform encephalopathies in sheep: Experimental determination of genetic susceptibility and interspecies transmission by Eric David Cassmann A dissertation submitted to the graduate faculty in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY Major: Veterinary Pathology Program of Study Committee: Justin Greenlee, Co-major Professor Jodi Smith, Co-major Professor M. Heather West Greenlee Shankumar Mooyottu Joseph Haynes The student author, whose presentation of the scholarship herein was approved by the program of study committee, is solely responsible for the content of this dissertation. The Graduate College will ensure this dissertation is globally accessible and will not permit alterations after a degree is conferred. Iowa State University Ames, Iowa 2019 Copyright © Eric David Cassmann, 2019. All rights reserved. ii DEDICATION This dissertation is dedicated to Samantharae Isaiah Gabriel John iii TABLE OF CONTENTS Page ACKNOWLEDGMENTS .................................................................................................. v ABSTRACT ...................................................................................................................... vii GENERAL INTRODUCTION AND LITERATURE REVIEW ................ 1 Dissertation Organization .............................................................................................. 1 Literature Review .......................................................................................................... 1 Abstract .......................................................................................................................... 1 Background .................................................................................................................... 2 Transmission and Pathogenesis of Scrapie in Sheep ..................................................... 7 Determinants of Susceptibility and Resistance of Sheep to the Scrapie Agent ............. 9 Strains of the Scrapie Agent ........................................................................................ 10 Atypical Scrapie .......................................................................................................... 12 Diagnostic and Research Methods for Studying the Scrapie Agent ............................ 13 Interspecies Transmission of the Scrapie Agent .......................................................... 16 Transmission of Non-Scrapie TSE Agents to Sheep ................................................... 18 Scrapie Eradication in the United States ..................................................................... 20 Summary ...................................................................................................................... 20 References ................................................................................................................... 22 SHEEP WITH THE HOMOZYGOUS LYSINE-171 PRION PROTEIN GENOTYPE ARE RESISTANT TO CLASSICAL SCRAPIE AFTER EXPERIMENTAL ORONASAL INOCULATION...................................................... 37 Abstract ........................................................................................................................ 37 Introduction ................................................................................................................. 38 Materials and Methods ................................................................................................ 40 Results ......................................................................................................................... 43 Discussion .................................................................................................................... 47 References ................................................................................................................... 50 Figures ......................................................................................................................... 54 Tables ........................................................................................................................... 59 SHEEP ARE SUSCEPTIBLE TO THE AGENT OF TME BY INTRACRANIAL INOCULATION AND HAVE EVIDENCE OF INFECTIVITY IN LYMPHOID TISSUES................................................................... 62 Abstract ........................................................................................................................ 62 Introduction ................................................................................................................. 63 Results ......................................................................................................................... 65 Discussion .................................................................................................................... 69 Materials and Methods ................................................................................................ 72 References ................................................................................................................... 79 Figures ......................................................................................................................... 83 Tables ........................................................................................................................... 88 iv GENERAL CONCLUSIONS .................................................................... 90 General Discussion ...................................................................................................... 90 Future Directions ......................................................................................................... 92 v ACKNOWLEDGMENTS I would like to express my deepest appreciation to my committee co-chairs, Drs. Justin Greenlee and Jodi Smith and my committee members, Heather West Greenlee, Shankumar Mooyottu, and Joseph Haynes for their guidance throughout the course of my graduate training. I am especially grateful to Dr. Justin Greenlee and Dr. Heather Greenlee of the Greenlee lab at the National Animal Disease Center. The completion of this dissertation would not have been possible without their support and encouragement as a scientist. Their thoughtful suggestions and experience were critical to my success. I am also grateful to Dr. Jodi Smith for being instrumental in my neuropathology training, giving me unwavering guidance, constructive criticism, and lending her extensive knowledge. Thanks should also go to Drs. Jesse Hostetter, Michael Yaeger, and Mark Ackermann for previously serving on my committee. These individuals and numerous others including Drs. Amanda Fales-Williams, Claire Andreasen, Shannon Hostetter, Heather Flaherty, Austin Viall, Tomislav Jelesijević, and Shannon McClelland also contributed to my training in pathology, and I am grateful for that! I would also like to thank my friends, colleagues, the department faculty and staff for making my time at Iowa State University a wonderful experience. I would like to acknowledge the assistance of the following USDA technicians: Leisa Mandell, Trudy Tatum, Kevin Hassall, Joe Lesan, Robyn Kokemuller, Martha Church, Ginny Montgomery, and Judy Stasko. These individuals were instrumental to the research projects, and their extensive knowledge was helpful for troubleshooting laboratory techniques. vi I also wish to thank Dr. John Melville (Doc) for initially cultivating my interest in research. His support has been firm for nearly 15 years. Also, Dr. Al Jergens provided me with critical exposure to veterinary research early in my veterinary medical education, and his support and encouragement has been very important to me. Last, but certainly not least, I would like to extend my deepest gratitude to my wife, Samantharae, for giving me unconditional support during my graduate training. Her support never wavered, and I could not have done this without it. Thank you! I am also grateful to my parents, David and Lisa, and my brother, Christopher, for believing in me and always being supportive. vii ABSTRACT Transmissible spongiform encephalopathies (TSE) are a group of infectious diseases caused by a misfolded protein. Naturally occurring TSEs are found in numerous species including sheep, cattle, and mink. The naturally occurring TSE of sheep is called scrapie. Scrapie is one of the oldest described TSEs, and it is caused by a misfolded protein (PrPSc) that initiates an autocatalytic