Pathogenesis of Chronic Wasting Disease in Cervidized Transgenic Mice

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Ample evidence exists for the presence of infectious agents at the maternal-fetal interface, often with grave outcomes to the developing fetus (i.e., Zika virus, brucella, cytomegalovirus, and toxoplasma). While less studied, pregnancyrelated transmissible spongiform encephalopathies (TSEs) have been implicated in several species, including humans. Our previous work has shown that prions can be transferred from mother to offspring, resulting in the development of clinical TSE disease in offspring born to muntjac dams infected with chronic wasting disease (CWD) (1). We further demonstrated protein misfolding cyclic amplification (PMCA)-competent prions within the female reproductive tract and in fetal tissues harvested from CWD experimentally and naturally exposed cervids (1, 2). To assess whether the PMCA-competent prions residing at the maternal-fetal interface were infectious and to determine if the real-time quaking-induced conversion (RT-QuIC) methodology may enhance our ability to detect amyloid fibrils within the pregnancy microenvironment, we employed a mouse bioassay and RT-QuIC. In this study, we have demonstrated RT-QuIC seeding activity in uterus, placentome, ovary, and amniotic fluid but not in allantoic fluids harvested from CWD-infected Reeves' muntjac dams showing clinical signs of infection (clinically CWD-infected) and in some placentomes from pre-clinically CWD-infected dams. Prion infectivity was confirmed within the uterus, amniotic fluid, and the placentome, the semipermeable interface that sustains the developing fetus, of CWD-infected dams. This is the first report of prion infectivity within the cervid pregnancy microenvironment, revealing a source of fetal CWD exposure prior to the birthing process, maternal grooming, or encounters with contaminated environments.IMPORTANCE The facile dissemination of chronic wasting disease within captive and free-range cervid populations has led to questions regarding the transmission dynamics of this disease. Direct contact with infected animals and indirect contact with infectious prions in bodily fluids and contaminated environments are suspected to explain the majority of this transmission. A third mode of transmission, from mother to offspring, may be underappreciated. The presence of pregnancyrelated prion infectivity within the uterus, amniotic fluid, and the placental structure reveals that the developing fetus is exposed to a source of prions long before exposure to the infectious agent during and after the birthing process or via contact with contaminated environments. These findings have impact on our current concept of CWD disease transmission.KEYWORDS CWD, maternal, pregnancy, prions T ransmissible spongiform encephalopathies (TSEs), or prion diseases, are proteinaceous infectious neurodegenerative diseases affecting animals, including humans (3, 4). The disease is caused by the accumulation of an aberrant misfolded form

Section: Discussionsupporting

confidence: 50%

Infectious Prions in the Pregnancy Microenvironment of Chronic Wasting Disease-Infected Reeves' Muntjac Deer

Nalls

McNulty

Hoover

et al. 2017

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“…Establishment of infection requires a potent inoculum, and inoculated mice have relatively low attack rates (29,37). Here, we show that this substantial resistance is negated by breeches in the lingual epithelium, enhancing CWD infection rates from 0 to 100%.…”

mentioning

confidence: 81%

“…Nevertheless, while entry via a lymphatic or hematogenous route cannot be excluded, the most plausible pathway would seem to be trafficking along lingual and facial nerves-a prion phenomenon demonstrated previously by the work of several investigators (5,15,26). Dose dependency in prion infections has been demonstrated extensively (3,18,21,27,29). While environmental contamination almost surely plays a role in CWD transmission, prion concentrations in excretions, soil, and the environment are very low.…”

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confidence: 99%

Minor Oral Lesions Facilitate Transmission of Chronic Wasting Disease

Denkers

Telling

Hoover

2011

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While chronic wasting disease (CWD) prion transmission, entry, and trafficking remain incompletely elucidated, natural exposure of the oral and/or nasal mucous membranes seems certain. Cervids commonly sustain minor lesions on oral mucous membranes that could have an impact on susceptibility to prion infection. To explore this potential cofactor, we studied cohorts of cervid PrP transgenic mice with or without superficial abrasions on the lingual mucosa to determine whether minor oral mucosa lesions may enhance susceptibility to CWD infections. Results demonstrated that minor lingual abrasions substantially facilitate CWD transmission, revealing a cofactor that may be significant in cervids and perhaps other species.Chronic wasting disease (CWD) is a fatal neurodegenerative prion disease affecting deer, elk, and moose. The efficiency by which CWD spreads suggests that transmission occurs primarily by horizontal means (22)(23)(24)(25). Body fluids and excreta, including blood, saliva, urine, and feces from infected cervids, have been shown to contain infectious CWD prions (13,20,35). While the exact mechanisms of CWD prion transmission, entry, and trafficking remain incompletely elucidated, transmission by contact with the oral and/or nasal mucous membranes seems certain. Whether prion infection occurs after mucous membrane exposure may be influenced by cofactors beyond dose, such as particle association with soil and the status of the mucous membrane barrier (12,16,17,30).Oral inoculation studies with sheep scrapie and CWD have indicated that early amplification of the resistant prion protein (PrP Sc/CWD ) occurs within the tonsils, retropharyngeal lymph nodes, and/or Peyer's patches (6, 10, 32). Prion dissemination can also occur through lymphoreticular system (LRS)-independent pathways (4,7,28). The oral cavity is highly innervated (38), and contact between prions and free nerve endings of the cranial-facial nerves may provide a direct site for prion uptake.Cervids acquire lesions in the oral mucous membranes through foraging and tooth eruption (31, 33) that could impact susceptibility to prion entry by facilitating direct contact with exposed nerves or blood vessels. The present work was prompted by a study by Bartz et al. (5), who demonstrated in the transmissible mink encephalopathy (TME) system that lesions on or injection into the tongue enhanced susceptibility to prion infections. We therefore explored the hypothesis that CWD transmission may be facilitated by small lesions on the oral epithelial surface.Transgenic mice that express the elk prion protein [Tg(CerPrP-E226)5037 ϩ/Ϫ mice; Telling laboratory, University of Kentucky] and are susceptible to CWD infection (1) were used in these studies. Clinical criteria for assessing CWD infection included ataxia, lethargy, tail rigidity, poor coat quality, and weight loss. Mice were euthanized when distinct signs of neurologic disease were evident. CWD agent-and sham-inoculated mice were housed in separate rooms to minimize potential for cross contamination.Th...

“…However, researchers have reported the presence of PrP RES by immunohistochemistry (IHC), paraffin-embedded tissue (PET) blotting, or Western blotting (WB) in the kidneys of scrapie-affected sheep (28,35,46,47) and CWD ϩ deer (19), the lingual tissues of hamsters inoculated with the HY (hyper) strain of transmissible mink encephalopathy (10,34), and the salivary glands of scrapieaffected sheep (55) and CWD-infected cervidized transgenic mice (43). While the identification of protease-resistant prion proteins in cervid excretory tissues using conventional assays has proven difficult (2,13,14,24,49), bioassay studies identifying genuine prion infectivity in excretory tissues, albeit limited, date to the 1960s (16) and implicate both the salivary glands of Creutzfeldt-Jakob disease (CJD)-infected mice (41) and kidneys of scrapie-infected mice (12).…”

mentioning

confidence: 99%

Detection of Chronic Wasting Disease Prions in Salivary, Urinary, and Intestinal Tissues of Deer: Potential Mechanisms of Prion Shedding and Transmission

Haley

Mathiason

Carver

et al. 2011

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125

102

Efficient horizontal transmission is a signature trait of chronic wasting disease (CWD) in cervids.Infectious prions shed into excreta appear to play a key role in this facile transmission, as has been demonstrated by bioassays of cervid and transgenic species and serial protein misfolding cyclic amplification (sPMCA). However, the source(s) of infectious prions in these body fluids has yet to be identified. In the present study, we analyzed tissues proximate to saliva, urine, and fecal production by sPMCA in an attempt to elucidate this unique aspect of CWD pathogenesis. Oropharyngeal, urogenital, and gastrointestinal tissues along with blood and obex from CWD-exposed cervids (comprising 27 animals and >350 individual samples) were analyzed and scored based on the apparent relative CWD burden. PrP CWDgenerating activity was detected in a range of tissues and was highest in the salivary gland, urinary bladder, and distal intestinal tract. In the same assays, blood from the same animals and unseeded normal brain homogenate controls (n ‫؍‬ 116 of 117) remained negative. The PrP-converting activity in peripheral tissues varied from 10 ؊11 -to 10 0 -fold of that found in brain of the same animal. Deer with highest levels of PrP CWD amplification in the brain had higher and more widely disseminated prion amplification in excretory tissues. Interestingly, PrP CWD was not demonstrable in these excretory tissues by conventional Western blotting, suggesting a low prion burden or the presence of protease-sensitive infectious prions destroyed by harsh proteolytic treatments. These findings offer unique insights into the transmission of CWD in particular and prion infection and trafficking overall.