Successful transmission of the chronic wasting disease (CWD) agent to white-tailed deer by intravenous blood transfusion

Scrapie versus Chronic Wasting Disease in White-Tailed Deer

White-tailed deer are susceptible to scrapie (WTD scrapie) after oronasal inoculation with the classical scrapie agent from sheep. Deer affected by WTD scrapie are difficult to differentiate from deer infected with chronic wasting disease (CWD). To assess the transmissibility of the WTD scrapie agent and tissue phenotypes when further passaged in white-tailed deer, we oronasally inoculated wild-type white-tailed deer with WTD scrapie agent. We found that WTD scrapie and CWD agents were generally similar, although some differences were noted. The greatest differences were seen in bioassays of cervidized mice that exhibited significantly longer survival periods when inoculated with WTD scrapie agent than those inoculated with CWD agent. Our findings establish that white-tailed deer are susceptible to WTD scrapie and that the presence of WTD scrapie agent in the lymphoreticular system suggests the handling of suspected cases should be consistent with current CWD guidelines because environmental shedding may occur.

Norwegian moose CWD induces clinical disease and neuroinvasion in gene-targeted mice expressing cervid S138N prion protein

Chronic wasting disease (CWD) is a prion disease affecting deer, elk and moose in North America and reindeer, moose and red deer in Northern Europe. Pathogenesis is driven by the accumulation of PrPSc, a pathological form of the host's cellular prion protein (PrPC), in the brain. CWD is contagious among North American cervids and Norwegian reindeer, with prions commonly found in lymphatic tissue. In Nordic moose and red deer CWD appears exclusively in older animals, and prions are confined to the CNS and undetectable in lymphatic tissues, indicating a sporadic origin. We aimed to determine transmissibility, neuroinvasion and lymphotropism of Nordic CWD isolates using gene-targeted mice expressing either wild-type (138SS/226QQ) or S138N (138NN/226QQ) deer PrP. When challenged with North American CWD strains, mice expressing S138N PrP did not develop clinical disease but harbored prion seeding activity in brain and spleen. Here, we infected these models intracerebrally or intraperitoneally with Norwegian moose, red deer and reindeer CWD isolates. The moose isolate was the first CWD type to cause full-blown disease in the 138NN/226QQ model in the first passage, with 100% attack rate and shortened survival times upon second passage. Furthermore, we detected prion seeding activity or PrPSc in brains and spinal cords, but not spleens, of 138NN/226QQ mice inoculated intraperitoneally with the moose isolate, providing evidence of prion neuroinvasion. We also demonstrate, for the first time, that transmissibility of the red deer CWD isolate was restricted to transgenic mice overexpressing elk PrPC (138SS/226EE), identical to the PrP primary structure of the inoculum. Our findings highlight that susceptibility to clinical disease is determined by the conformational compatibility between prion inoculum and host PrP primary structure. Our study indicates that neuroinvasion of Norwegian moose prions can occur without, or only very limited, replication in the spleen, an unprecedented finding for CWD.

Expression of the cellular prion protein by mast cells in the human carotid body

Prion diseases are fatal neurologic disorders that can be transmitted by blood transfusion. The route for neuroinvasion following exposure to infected blood is not known. Carotid bodies (CBs) are specialized chemosensitive structures that detect the concentration of blood gasses and provide feedback for the neural control of respiration. Sensory cells of the CB are highly perfused and densely innervated by nerves that are synaptically connected to the brainstem and thoracic spinal cord, known to be areas of early prion deposition following oral infection. Given their direct exposure to blood and neural connections to central nervous system (CNS) areas involved in prion neuroinvasion, we sought to determine if there were cells in the human CB that express the cellular prion protein (PrPC), a characteristic that would support CBs serving as a route for prion neuroinvasion. We collected CBs from cadaver donor bodies and determined that mast cells located in the carotid bodies express PrPC and that these cells are in close proximity to blood vessels, nerves, and nerve terminals that are synaptically connected to the brainstem and spinal cord.

Dynamics of CWD prion detection in feces and blood from naturally infected white-tailed deer

Chronic wasting disease (CWD) is a prion disease affecting cervids. Confirmatory testing of CWD is currently performed postmortem in obex and lymphoid tissues. Extensive evidence demonstrates the presence of infectious prions in feces of CWD-infected deer using in vitro prion-amplification techniques and bioassays. In experimental conditions, this has been achieved as soon as 6-month post-inoculation, suggesting this sample type is a candidate for antemortem diagnosis. In the present study, we optimized the detection of CWD-prions in fecal samples from naturally infected, pre-clinical white-tailed deer by comparing protocols aiming to concentrate CWD-prions with direct spiking of the sample into the PMCA reactions. Results of this screening were compared with similar analyses made in blood. Our data shows that CWD-prion detection in feces using PMCA is best in the absence of sample pre-treatments. We performed a screening of 169 fecal samples, detecting CWD-prions with diagnostic sensitivity and specificity of 54.81% and 98.46%, respectively. In addition, the PMCA seeding activity of 76 fecal samples was compared with that on blood of matched deer. Our findings, demonstrate that CWD-prions in feces and blood are increased at late pre-clinical stages, exhibiting similar detection in both sample types (> 90% sensitivity) when PrP96GG animals are tested. Our findings contribute to understand prion distribution across different biological samples and polymorphic variants in white-tailed deer. This information is also relevant for the current efforts to identify platforms to diagnose CWD.

Can the administration of platelet lysates to the brain help treat neurological disorders?

Neurodegenerative disorders of the central nervous system (CNS) and brain traumatic insults are characterized by complex overlapping pathophysiological alterations encompassing neuroinflammation, alterations of synaptic functions, oxidative stress, and progressive neurodegeneration that eventually lead to irreversible motor and cognitive dysfunctions. A single pharmacological approach is unlikely to provide a complementary set of molecular therapeutic actions suitable to resolve these complex pathologies. Recent preclinical data are providing evidence-based scientific rationales to support biotherapies based on administering neurotrophic factors and extracellular vesicles present in the lysates of human platelets collected from healthy donors to the brain. Here, we present the most recent findings on the composition of the platelet proteome that can activate complementary signaling pathways in vivo to trigger neuroprotection, synapse protection, anti-inflammation, antioxidation, and neurorestoration. We also report experimental data where the administration of human platelet lysates (HPL) was safe and resulted in beneficial neuroprotective effects in established rodent models of neurodegenerative diseases such as Parkinson's disease, Alzheimer's disease, traumatic brain injury, and stroke. Platelet-based biotherapies, prepared from collected platelet concentrates (PC), are emerging as a novel pragmatic and accessible translational therapeutic strategy for treating neurological diseases. Based on this assumption, we further elaborated on various clinical, manufacturing, and regulatory issues that need to be addressed to ensure the ethical supply, quality, and safety of HPL preparations for treating neurodegenerative and traumatic pathologies of the CNS. HPL made from PC may become a unique approach for scientifically based treatments of neurological disorders readily accessible in low-, middle-, and high-income countries.

Chronic Wasting Disease (CWD) in Cervids and the Consequences of a Mutable Protein Conformation

Chronic wasting disease (CWD) is a prion disease of cervids (deer, elk, moose, etc.). It spreads readily from CWD-contaminated environments and among wild cervids. As of 2022, North American CWD has been found in 29 states, four Canadian provinces and South Korea. The Scandinavian form of CWD originated independently. Prions propagate their pathology by inducing a natively expressed prion protein (PrPC) to adopt the prion conformation (PrPSc). PrPC and PrPSc differ solely in their conformation. Like other prion diseases, transmissible CWD prions can arise spontaneously. The CWD prions can respond to selection pressures resulting in the emergence of new strain phenotypes. Annually, 11.5 million Americans hunt and harvest nearly 6 million deer, indicating that CWD is a potential threat to an important American food source. No tested CWD strain has been shown to be zoonotic. However, this may not be true for emerging strains. Should a zoonotic CWD strain emerge, it could adversely impact the hunting economy and game meat consumers.

Differential Accumulation of Misfolded Prion Strains in Natural Hosts of Prion Diseases

Prion diseases, also known as transmissible spongiform encephalopathies (TSEs), are a group of neurodegenerative protein misfolding diseases that invariably cause death. TSEs occur when the endogenous cellular prion protein (PrP^C) misfolds to form the pathological prion protein (PrP^Sc), which templates further conversion of PrP^C to PrP^Sc, accumulates, and initiates a cascade of pathologic processes in cells and tissues. Different strains of prion disease within a species are thought to arise from the differential misfolding of the prion protein and have different clinical phenotypes. Different strains of prion disease may also result in differential accumulation of PrP^Sc in brain regions and tissues of natural hosts. Here, we review differential accumulation that occurs in the retinal ganglion cells, cerebellar cortex and white matter, and plexuses of the enteric nervous system in cattle with bovine spongiform encephalopathy, sheep and goats with scrapie, cervids with chronic wasting disease, and humans with prion diseases. By characterizing TSEs in their natural host, we can better understand the pathogenesis of different prion strains. This information is valuable in the pursuit of evaluating and discovering potential biomarkers and therapeutics for prion diseases.

Review on PRNP genetics and susceptibility to chronic wasting disease of Cervidae

To date, chronic wasting disease (CWD) is the most infectious form of prion disease affecting several captive, free ranging and wild cervid species. Responsible for marked population declines in North America, its geographical spread is now becoming a major concern in Europe. Polymorphisms in the prion protein gene (PRNP) are an important factor influencing the susceptibility to prions and their rate of propagation. All reported cervid PRNP genotypes are affected by CWD. However, in each species, some polymorphisms are associated with lower attack rates and slower progression of the disease. This has potential consequences in terms of genetic selection, CWD diffusion and strain evolution. CWD also presents a zoonotic risk due to prions capacity to cross species barriers. This review summarizes our current understanding of CWD control, focusing on PRNP genetic, strain diversity and capacity to infect other animal species, including humans.

Decrease in Skin Prion-Seeding Activity of Prion-Infected Mice Treated with a Compound Against Human and Animal Prions: a First Possible Biomarker for Prion Therapeutics

Previous studies have revealed that the infectious scrapie isoform of prion protein (PrP^Sc) harbored in the skin tissue of patients or animals with prion diseases can be amplified and detected through the serial protein misfolding cyclic amplification (sPMCA) or real-time quaking-induced conversion (RT-QuIC) assays. These findings suggest that skin PrP^Sc-seeding activity may serve as a biomarker for the diagnosis of prion diseases; however, its utility as a biomarker for prion therapeutics remains largely unknown. Cellulose ethers (CEs, such as TC-5RW), widely used as food and pharmaceutical additives, have recently been shown to prolong the lifespan of prion-infected mice and hamsters. Here we report that in transgenic (Tg) mice expressing hamster cellular prion protein (PrP^C) infected with the 263K prion, the prion-seeding activity becomes undetectable in the skin tissues of TC-5RW-treated Tg mice by both sPMCA and RT-QuIC assays, whereas such prion-seeding activity is readily detectable in the skin of untreated mice. Notably, TC-5RW exhibits an inhibitory effect on the in vitro amplification of PrP^Sc in both skin and brain tissues by sPMCA and RT-QuIC. Moreover, we reveal that TC-5RW is able to directly decrease protease-resistant PrP^Sc and inhibit the seeding activity of PrP^Sc from chronic wasting disease and various human prion diseases. Our results suggest that the level of prion-seeding activity in the skin may serve as a useful biomarker for assessing the therapeutic efficacy of compounds in a clinical trial of prion diseases and that TC-5RW may have the potential for the prevention/treatment of human prion diseases.

Cervid Prion Protein Polymorphisms: Role in Chronic Wasting Disease Pathogenesis

Chronic wasting disease (CWD) is a prion disease found in both free-ranging and farmed cervids. Susceptibility of these animals to CWD is governed by various exogenous and endogenous factors. Past studies have demonstrated that polymorphisms within the prion protein (PrP) sequence itself affect an animal's susceptibility to CWD. PrP polymorphisms can modulate CWD pathogenesis in two ways: the ability of the endogenous prion protein (PrP^C) to convert into infectious prions (PrP^Sc) or it can give rise to novel prion strains. In vivo studies in susceptible cervids, complemented by studies in transgenic mice expressing the corresponding cervid PrP sequence, show that each polymorphism has distinct effects on both PrP^C and PrP^Sc. It is not entirely clear how these polymorphisms are responsible for these effects, but in vitro studies suggest they play a role in modifying PrP epitopes crucial for PrP^C to PrP^Sc conversion and determining PrP^C stability. PrP polymorphisms are unique to one or two cervid species and most confer a certain degree of reduced susceptibility to CWD. However, to date, there are no reports of polymorphic cervid PrP alleles providing absolute resistance to CWD. Studies on polymorphisms have focused on those found in CWD-endemic areas, with the hope that understanding the role of an animal's genetics in CWD can help to predict, contain, or prevent transmission of CWD.