Citation: Cassmann, E.D.; Frese, A.J.; Moore, S.J.; Greenlee, J.J. Transmission of Raccoon-Passaged Chronic Wasting Disease Agent to White-Tailed Deer. Viruses 2022, 14, 1578. https://doi.org/10.3390/ v14071578 Academic Editors: Holger Wille and Debbie McKenzie Received: 4 May 2022 Accepted: 15 July 2022 Published: 20 July 2022 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). viruses Article Transmission of Raccoon-Passaged Chronic Wasting Disease Agent to White-Tailed Deer Eric D. Cassmann 1 , Alexis J. Frese 1,2 , S. Jo Moore 1,2 and Justin J. Greenlee 1, * 1 Virus and Prion Research Unit, National Animal Disease Center, Agricultural Research Service, United States Department of Agriculture, Ames, IA 50010, USA; eric.cassmann@usda.gov (E.D.C.); alexis.frese@usda.gov (A.J.F.); jo.moore@moredun.ac.uk (S.J.M.) 2 Oak Ridge Institute for Science and Education, 1299 Bethel Valley Rd., Oak Ridge, TN 37830, USA * Correspondence: justin.greenlee@usda.gov; Tel.: +1-515-337-7191 Abstract: The transmission characteristics of prion diseases are influenced by host prion protein sequence and, therefore, the host species. Chronic wasting disease (CWD), a prion disease of cervids, has widespread geographical distribution throughout North America and occurs in both wild and farmed populations. CWD prions contaminate the environment through scattered excrement and de- composing carcasses. Fresh carcasses with CWD prions are accessible by free-ranging mesopredators such as raccoons and may provide a route of exposure. Previous studies demonstrated the suscepti- bility of raccoons to CWD from white-tailed deer. In this study, we demonstrate that white-tailed deer replicate raccoon-passaged CWD prions which results in clinical disease similar to intraspecies CWD transmission. Six white-tailed deer were oronasally inoculated with brain homogenate from a raccoon with CWD. All six deer developed clinical disease, had widespread lymphoid distribution of misfolded CWD prions (PrP Sc ), and had neuropathologic lesions with PrP Sc accumulation in the brain. The presence of PrP Sc was confirmed by immunohistochemistry, enzyme-linked immunoassay, and western blot. The western blot migration pattern of raccoon-passaged CWD was different from white-tailed deer CWD. Transmission of raccoon CWD back to white-tailed deer resulted in an interposed molecular phenotype that was measurably different from white-tailed deer CWD. Keywords: chronic wasting disease; interspecies transmission; prion; transmissible spongiform encephalopathy; white-tailed deer 1. Introduction Transmissible spongiform encephalopathies (TSEs) are a group of neurodegenerative diseases also known as prion diseases [1]. TSEs are caused by a misfolded form (PrP Sc ) of the normal cellular prion protein [2]. Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy that occurs in cervids. Affected animals succumb to a fatal neurodegenerative process that impairs proprioception, fear responses, and motor function deficits that manifest clinically as emaciation, polyuria, polydipsia, bruxism, excessive salivation, regurgitation of rumen contents, esophageal dilation, and ataxia [3]. Since CWD was recognized in mule deer in Colorado in 1967, it has been identified in free-ranging and commercially farmed cervids spanning 30 US states and 4 Canadian provinces in North America [4]. Infectious CWD prions are spread through direct contact of cervids via exposure to bodily fluids and interactions with infectious prions that remain stable for long periods of time in the environment [5–8]. The increase in prevalence of CWD has raised concerns about possible transmission to other species [9]. A naturally occurring connection between CWD in cervids and a human prion disease has not been demonstrated to date, and experimental studies that directly inoculated CWD isolates into non-human primates or humanized transgenic mice demonstrate variable results (reviewed by Otero, et al.) [10]. Viruses 2022, 14, 1578. https://doi.org/10.3390/v14071578 https://www.mdpi.com/journal/viruses