title: Pathways of Prion Spread during Early Chronic Wasting Disease in Deer.
abstract: Among prion infections, two scenarios of prion spread are generally observed: (i) early lymphoid tissue replication or (ii) direct neuroinvasion without substantial antecedent lymphoid amplification. In nature, cervids are infected with chronic wasting disease (CWD) prions by oral and nasal mucosal exposure, and studies of early CWD pathogenesis have implicated pharyngeal lymphoid tissue as the earliest sites of prion accumulation. However, knowledge of chronological events in prion spread during early infection remains incomplete. To investigate this knowledge gap in early CWD pathogenesis, we exposed white-tailed deer to CWD prions by mucosal routes and performed serial necropsies to assess PrPCWDtissue distribution by real-time quaking-induced conversion (RT-QuIC) and tyramide signal amplification immunohistochemistry (TSA-IHC). Although PrPCWDwas not detected by either method in the initial days (1 and 3) postexposure, we observed PrPCWDseeding activity and follicular immunoreactivity in oropharyngeal lymphoid tissues at 1 and 2 months postexposure (MPE). At 3 MPE, PrPCWDreplication had expanded to all systemic lymphoid tissues. By 4 MPE, the PrPCWDburden in all lymphoid tissues had increased and approached levels observed in terminal disease, yet there was no evidence of nervous system invasion. These results indicate the first site of CWD prion entry is in the oropharynx, and the initial phase of prion amplification occurs in the oropharyngeal lymphoid tissues followed by rapid dissemination to systemic lymphoid tissues. This lymphoid replication phase appears to precede neuroinvasion.IMPORTANCEChronic wasting disease (CWD) is a universally fatal transmissible spongiform encephalopathy affecting cervids, and natural infection occurs through oral and nasal mucosal exposure to infectious prions. Terminal disease is characterized by PrPCWDaccumulation in the brain and lymphoid tissues of affected animals. However, the initial sites of prion accumulation and pathways of prion spread during early CWD infection remain unknown. To investigate the chronological events of early prion pathogenesis, we exposed deer to CWD prions and monitored the tissue distribution of PrPCWDover the first 4 months of infection. We show CWD uptake occurs in the oropharynx with initial prion replication in the draining oropharyngeal lymphoid tissues, rapidly followed by dissemination to systemic lymphoid tissues without evidence of neuroinvasion. These data highlight the two phases of CWD infection: a robust prion amplification in systemic lymphoid tissues prior to neuroinvasion and establishment of a carrier state.
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Clare E
authors.initials: CE
authors.lastname: Hoover
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Kristen A
authors.initials: KA
authors.lastname: Davenport
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Davin M
authors.initials: DM
authors.lastname: Henderson
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Nathaniel D
authors.initials: ND
authors.lastname: Denkers
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Candace K
authors.initials: CK
authors.lastname: Mathiason
authors.affiliation: Mitchell Center for Alzheimer's Disease and Related Brain Disorders, Department of Neurology, The University of Texas Medical School, Houston, Texas, USA.
authors.forename: Claudio
authors.initials: C
authors.lastname: Soto
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA.
authors.forename: Mark D
authors.initials: MD
authors.lastname: Zabel
authors.affiliation: Prion Research Center, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins, Colorado, USA edward.hoover@colostate.edu.
authors.forename: Edward A
authors.initials: EA
authors.lastname: Hoover
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000473:pathology; D003670:Deer; D007150:Immunohistochemistry; D008221:Lymphoid Tissue / Q000473:pathology; D000072002:Prion Proteins / Q000276:immunology / Q000302:isolation & purification; D011328:Prions / Q000472:pathogenicity* / Q000502:physiology; D034081:Wasting Disease, Chronic / Q000473:pathology / Q000503:physiopathology*
chemical_list: D000072002:Prion Proteins; D011328:Prions
keywords: chronic wasting disease; prions