Chronic wasting disease (CWD) is a relentless epidemic disorder caused by infectious prions that threatens the survival of cervid populations and raises increasing public health concerns in North America. In Europe, CWD was detected for the first time in wild Norwegian reindeer (Rangifer tarandus) and moose (Alces alces) in 2016. In this study, we aimed at comparing the strain properties of CWD prions derived from different cervid species in Norway and North America. Using a classical strain typing approach involving transmission and adaptation to bank voles (Myodes glareolus), we found that prions causing CWD in Norway induced incubation times, neuropathology, regional deposition of misfolded prion protein aggregates in the brain, and size of their protease-resistant core, different from those that characterize North American CWD. These findings show that CWD prion strains affecting Norwegian cervids are distinct from those found in North America, implying that the highly contagious North American CWD prions are not the proximate cause of the newly discovered Norwegian CWD cases. In addition, Norwegian CWD isolates showed an unexpected strain variability, with reindeer and moose being caused by different CWD strains. Our findings shed light on the origin of emergent European CWD, have significant implications for understanding the nature and the ecology of CWD in Europe, and highlight the need to assess the zoonotic potential of the new CWD strains detected in Europe.

In order to assess the susceptibility of bank voles to chronic wasting disease (CWD), we inoculated voles carrying isoleucine or methionine at codon 109 (Bv109I and Bv109M, respectively) with CWD isolates from elk, mule deer and white-tailed deer. Efficient transmission rate (100%) was observed with mean survival times ranging from 156 to 281 days post inoculation. Subsequent passages in Bv109I allowed us to isolate from all CWD sources the same vole-adapted CWD strain (Bv109ICWD), typified by unprecedented short incubation times of 25–28 days and survival times of ∼35 days. Neuropathological and molecular characterisation of Bv109ICWD showed that the classical features of mammalian prion diseases were all recapitulated in less than one month after intracerebral inoculation. Bv109ICWD was characterised by a mild and discrete distribution of spongiosis and relatively low levels of protease-resistant PrPSc (PrPres) in the same brain regions. Despite the low PrPres levels and the short time lapse available for its accumulation, end-point titration revealed that brains from terminally-ill voles contained up to 108,4 i.c. ID50 infectious units per gram. Bv109ICWD was efficiently replicated by protein misfolding cyclic amplification (PMCA) and the infectivity faithfully generated in vitro, as demonstrated by the preservation of the peculiar Bv109ICWD strain features on re-isolation in Bv109I. Overall, we provide evidence that the same CWD strain was isolated in Bv109I from the three-cervid species. Bv109ICWD showed unique characteristics of “virulence”, low PrPres accumulation and high infectivity, thus providing exceptional opportunities to improve basic knowledge of the relationship between PrPSc, neurodegeneration and infectivity.

Prions cause fatal and transmissible neurodegenerative diseases, including Creutzfeldt-Jakob disease in humans, scrapie in small ruminants, and bovine spongiform encephalopathy (BSE). After the BSE epidemic, and the associated human infections, began in 1996 in the United Kingdom, general concerns have been raised about animal prions. We detected a prion disease in dromedary camels (Camelus dromedarius) in Algeria. Symptoms suggesting prion disease occurred in 3.1% of dromedaries brought for slaughter to the Ouargla abattoir in 2015–2016. We confirmed diagnosis by detecting pathognomonic neurodegeneration and disease-specific prion protein (PrPSc) in brain tissues from 3 symptomatic animals. Prion detection in lymphoid tissues is suggestive of the infectious nature of the disease. PrPSc biochemical characterization showed differences with BSE and scrapie. Our identification of this prion disease in a geographically widespread livestock species requires urgent enforcement of surveillance and assessment of the potential risks to human and animal health.

Gerstmann-Sträussler-Scheinker disease (GSS) is an inherited neurodegenerative disorder associated with mutations in the prion protein gene and accumulation of misfolded PrP with protease-resistant fragments (PrPres) of 6–8 kDa. With the exception of a few GSS cases characterized by co-accumulation of PrPres of 21 kDa, efforts to transmit GSS to rodents have been unsuccessful. As a result, GSS subtypes exclusively associated with 6–8 kDa PrPres have often been considered as non-transmissible proteinopathies rather than true prion diseases. We show that GSS with P102L, A117V and F198S mutations transmit efficiently and produce distinct pathological phenotypes in bank voles (M. glareolus), irrespective of the presence of 21 kDa PrPres in the inoculum, demonstrating that GSS is a genuine prion disease characterized by both transmissibility and strain variation.

Prion diseases are rare neurodegenerative conditions associated with the conformational conversion of the cellular prion protein (PrPC) into PrPSc, a self-replicating isoform (prion) that accumulates in the central nervous system of affected individuals. The structure of PrPSc is poorly defined, and likely to be heterogeneous, as suggested by the existence of different prion strains. The latter represents a relevant problem for therapy in prion diseases, as some potent anti-prion compounds have shown strain-specificity. Designing therapeutics that target PrPC may provide an opportunity to overcome these problems. PrPC ligands may theoretically inhibit the replication of multiple prion strains, by acting on the common substrate of any prion replication reaction. Here, we characterized the properties of a cationic tetrapyrrole [Fe(III)-TMPyP], which was previously shown to bind PrPC, and inhibit the replication of a mouse prion strain. We report that the compound is active against multiple prion strains in vitro and in cells. Interestingly, we also find that Fe(III)-TMPyP inhibits several PrPC-related toxic activities, including the channel-forming ability of a PrP mutant, and the PrPC-dependent synaptotoxicity of amyloid-β (Aβ) oligomers, which are associated with Alzheimer’s Disease. These results demonstrate that molecules binding to PrPC may produce a dual effect of blocking prion replication and inhibiting PrPC-mediated toxicity.