Sodium hydroxide treatment effectively inhibits PrPCWD replication in farm soil

Detection of chronic wasting disease prions in the farm soil of the Republic of Korea

Chronic wasting disease (CWD) is a highly contagious prion disease occurring in free-ranging and farmed cervids. CWD continues to spread uncontrolled across North America, and cases continue to be detected almost every year in the Republic of Korea. CWD-infected animals contaminate the soil by releasing infectious prions through their excreta, and shed prions accumulate and remain infectious in the soil for years. Given that the upper soil levels can become contaminated with prions and serve as infectivity reservoirs facilitating horizontal transmission of CWD, the ability to detect prions in the soil is needed for monitoring and managing CWD spread. Using the protein misfolding cyclic amplification (PMCA) technique, we investigated whether prions could be amplified and detected in farm soil experimentally exposed to CWD-infected brain homogenate as well as in the soil of CWD-affected farms. From each soil sample, we performed 10 serial extractions and used these 10 extracts as PMCA templates. Here, we show that prion seeding activity was detected in extracts from farm soil following 4 years of incubation with CWD-infected brain homogenate. More importantly, 13 of 38 soil samples collected from six CWD-affected farms displayed prion seeding activity, with at least one soil sample in each farm being PMCA positive. Mouse bioassays confirmed the presence of prion infectivity in the soil extracts in which PMCA seeding activity was detected. This is the first report describing the successful detection of prions in soil collected from CWD-affected farms, suggesting that PMCA conducted on serial soil extracts is a sensitive means for prion detection in CWD-contaminated soil.IMPORTANCEChronic wasting disease (CWD) is a highly contagious prion disease affecting free-ranging and farmed cervids. CWD continues to spread uncontrollably across North America, and multiple cases are detected annually in the Republic of Korea. Prions shed from CWD-infected animals remain infectious in the soil for years, serving as infectivity reservoirs that facilitate horizontal transmission of the disease. Therefore, the ability to detect CWD prions in soil is crucial for monitoring and managing the spread of the disease. In this study, we have demonstrated for the first time that prions in the soil of CWD-affected farms can be reliably detected using a combination of serial soil extraction and a prion amplification technique. Our data, in which at least one soil sample tested positive for CWD in each of the six CWD-affected farms analyzed, suggest that the approach employed in this study is a sensitive method for prion detection in CWD-contaminated soil.

A review of chronic wasting disease (CWD) spread, surveillance, and control in the United States captive cervid industry

Chronic wasting disease (CWD) is a fatal prion disease of the family Cervidae that circulates in both wild and captive cervid populations. This disease threatens the health and economic viability of the captive cervid industry, which raises cervids in contained spaces for purposes such as hunting and breeding. Given the high transmissibility and long incubation period of CWD, the introduction and propagation of the infectious prion protein within and between captive cervid farms could be devastating to individual facilities and to the industry as a whole. Despite this risk, there does not yet exist a literature review that summarizes the scientific knowledge, to date, about CWD spread, surveillance, or control measures. Our review, which focused on peer reviewed, primary research conducted in the United States, sought to address this need by searching Google Scholar, Scopus, and Web of Science with a five-term keyword string containing terms related to the (1) location, (2) species affected, (3) disease, (4) captive cervid industry, and (5) topic of focus. Between the three databases, there were 190 articles that were selected for further examination. Those articles were then read to determine if they were about CWD spread, surveillance, and/or control in captive cervid facilities. The 22 articles that met these inclusion criteria were evaluated in detail and discussed, with recommendations for future collaborative work between captive cervid owners, government agencies, and researchers. This work will help to address, inform, and mitigate the rising problem of CWD spread and establishment.

Chronic Wasting Disease: State of the Science

Chronic wasting disease (CWD) is a prion disease affecting cervid species, both free-ranging and captive populations. As the geographic range continues to expand and disease prevalence continues to increase, CWD will have an impact on cervid populations, local economies, and ecosystem health. Mitigation of this "wicked" disease will require input from many different stakeholders including hunters, landowners, research biologists, wildlife managers, and others, working together. The NC1209 (North American interdisciplinary chronic wasting disease research consortium) is composed of scientists from different disciplines involved with investigating and managing CWD. Leveraging this broad breadth of expertise, the Consortium has created a state-of-the-science review of five key aspects of CWD, including current diagnostic capabilities for detecting prions, requirements for validating these diagnostics, the role of environmental transmission in CWD dynamics, and potential zoonotic risks associated with CWD. The goal of this review is to increase stakeholders', managers', and decision-makers' understanding of this disease informed by current scientific knowledge.

The first report of a strong association between genetic polymorphisms of the prion protein gene (PRNP) and susceptibility to chronic wasting disease (CWD) in sika deer (Cervus nippon)

Prion diseases are incurable neurodegenerative disorders caused by proteinase K-resistant prion protein (PrP^Sc ) derived from normal prion protein (PrP^C ) encoded by the prion protein gene (PRNP). Although the cervid PRNP gene plays a pivotal role in the pathological mechanism of chronic wasting disease (CWD), there is no existing association analysis between susceptibility to CWD and genetic polymorphisms of the PRNP gene in sika deer. We investigated genetic polymorphisms of the PRNP gene using amplicon sequencing in sika deer. In addition, to identify a genetic susceptibility factor, we compared genotype, allele and haplotype frequencies of the PRNP gene between CWD-positive and CWD-negative sika deer. Furthermore, to assess the effect of the genetic polymorphisms on sika deer prion protein (PrP), we performed in silico analysis using PolyPhen-2, PROVEAN and AMYCO. Finally, we analyzed the tertiary structure and electrostatic potential of sika deer PrP based on single nucleotide polymorphisms (SNPs) using the SWISS-MODEL and Swiss-PdbViewer programs. We found a total of 24 SNPs of the PRNP gene including 22 novel SNPs (10 synonymous SNPs and 12 non-synonymous SNPs) in sika deer. Among the non-synonymous SNPs, we found a strong association of the susceptibility to CWD with c.56G>A (Ser19Asn). In addition, we found that c.56G>A (Ser19Asn), c.296A>T (His99Leu) and c.560T>A (Val187Asp) were predicted to have damaging effects on sika deer PrP. Furthermore, we observed significant alterations in the electrostatic potential of sika deer PrP by genetic polymorphisms of the 187Asp allele. To the best of our knowledge, this was the first association study between genetic polymorphisms of the PRNP gene and susceptibility to CWD in sika deer. This article is protected by copyright. All rights reserved.

Prion Dissemination through the Environment and Medical Practices: Facts and Risks for Human Health

Prion diseases are a group of fatal, infectious neurodegenerative disorders affecting various species of mammals, including humans. The infectious agent in these diseases, termed prion, is composed exclusively of a misfolded protein that can spread and multiply in the absence of genetic materials. In this article, we provide an overview of the mechanisms of prion replication, interindividual transmission, and dissemination in communities. In particular, we review the potential role of the natural environment in prion transmission, including the mechanisms and pathways for prion entry and accumulation in the environment as well as its roles in prion mutation, adaptation, evolution, and transmission. We also discuss the transmission of prion diseases through medical practices, scientific research, and use of biological products. Detailed knowledge of these aspects is crucial to limit the spreading of existing prion diseases as well as to prevent the emergence of new diseases with possible catastrophic consequences for public health.

Polymorphisms of the prion-related protein gene are strongly associated with cervids' susceptibility to chronic wasting disease

BACKGROUND

Chronic wasting disease (CWD) is a cervid prion disease that is caused by abnormal prion protein (PrP^Sc ). Recent studies have reported that prion family genes showed a strong association with the susceptibility of several types of prion diseases. To date, an association study of the prion-related protein gene (PRNT) has not been performed in any type of cervid prion disease.

METHODS

In the present study, we investigated PRNT polymorphisms in large deer, including 235 elk, 257 red deer and 150 sika deer. We compared genotype, allele and haplotype frequencies of PRNT polymorphisms between CWD-negative animals and CWD-positive animals to find an association of PRNT polymorphisms with the susceptibility of CWD.

RESULTS

We found a total of five novel single nucleotide polymorphisms (SNPs) in the cervid PRNT gene. Interestingly, we observed significantly different distributions of genotypes and allele frequencies of three PRNT SNPs, including c.108C>T, c.159+30C>T and c.159+32A>C, between CWD-negative and CWD-positive red deer. In addition, significant differences of two haplotype frequencies in red deer were found between the CWD-negative and CWD-positive groups. However, the association identified in the red deer was not found in elk and sika deer.

CONCLUSION

To the best of our knowledge, this report is the first to describe the strong association of PRNT SNPs with the susceptibility of CWD.

In-depth examination of PrPSc in Holstein cattle carrying the E211K somatic mutation of the bovine prion protein gene (PRNP)

Prion diseases are transmissible spongiform encephalopathies caused by deleterious prion protein (PrP^Sc ) derived from normal prion protein (PrP^C ), which is encoded by the prion protein gene (PRNP). We performed an in-depth examination to detect PrP^Sc by using enzyme immunoassay (EIA), real-time quaking-induced conversion reactions (RT-QuIC) and protein misfolding cyclic amplification (PMCA) in nine brain tissues derived from three Holstein cattle carrying the E211K somatic mutation of the bovine PRNP gene. The EIA, RT-QuIC and PMCA analyses were not able to detect the PrP^Sc band in any tested samples. To the best of our knowledge, this report is the first to describe an in-depth examination of PrP^Sc in cattle carrying the E211K somatic mutation of the bovine PRNP gene.

Evaluation of proteinase K-resistant prion protein (PrPres) in Korean native black goats carrying a potential scrapie-susceptible haplotype of the prion protein gene (PRNP)

Prion disease is a fatal neurodegenerative disease with a broad host range in humans and animals. It is caused by proteinase K-resistant prion protein (PrPres). In previous studies, a heterogeneous infection in Cervidae and Caprinae was reported. Chronic wasting disease (CWD) has been frequently reported as the only prion disease in Korea that occurs in livestock. Thus, there is a possibility of transmission of CWD to Korean native black goats. However, PrPres has not been investigated thus far in Korean native black goats. We found strong linkage disequilibrium between c.126G>A and c.414T>C (r2 = 1) and between c.718C>T and c.126G>A (r2 = 0.638). In addition, the haplotype GTGTAAAC (representing codons 42, 102, 127, 138, 143, 146, 218 and 240) showed the highest frequency with 45.1%. Among 41 Korean native black goats, 20 animals (48.78%) were homozygous for the susceptible haplotypes (histidine at codon 143, asparagine at codon 146 and arginine at codon 154). Interestingly, we did not detect PrPres bands in any of the tested animals, including the 20 animals carrying potential scrapie susceptible haplotypes.

A Novel, Reliable and Highly Versatile Method to Evaluate Different Prion Decontamination Procedures

Transmissible spongiform encephalopathies (TSEs) are a group of invariably fatal neurodegenerative disorders. The causal agent is an aberrantly folded isoform (PrP^Sc or prion) of the endogenous prion protein (PrP^C) which is neurotoxic and amyloidogenic and induces misfolding of its physiological counterpart. The intrinsic physical characteristics of these infectious proteinaceous pathogens makes them highly resistant to the vast majority of physicochemical decontamination procedures used typically for standard disinfection. This means prions are highly persistent in contaminated tissues, the environment (surfaces) and, of great concern, on medical and surgical instruments. Traditionally, decontamination procedures for prions are tested on natural isolates coming from the brain of infected individuals with an associated high heterogeneity resulting in highly variable results. Using our novel ability to produce highly infectious recombinant prions in vitro we adapted the system to enable recovery of infectious prions from contaminated materials. This method is easy to perform and, importantly, results in highly reproducible propagation in vitro. It exploits the adherence of infectious prion protein to beads of different materials allowing accurate and repeatable assessment of the efficacy of disinfectants of differing physicochemical natures to eliminate infectious prions. This method is technically easy, requires only a small shaker and a standard biochemical technique and could be performed in any laboratory.