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Prion diseases are transmissible, fatal neurologic diseases that include Creutzfeldt-Jakob Disease (CJD) in humans, chronic wasting disease (CWD) in cervids, bovine spongiform encephalopathy (BSE) in cattle and scrapie in sheep. Prions are extremely difficult to inactivate and established methods to reduce prion infectivity are often dangerous, caustic, expensive, or impractical. Identifying viable and safe methods for treating prion contaminated materials is important for hospitals, research facilities, biologists, hunters, and meat-processors. For three decades, some prion researchers have used a phenolic product called Environ LpH (eLpH) to inactivate prions. ELpH has been discontinued, but a similar product, Wex-cide 128, containing the similar phenolic chemicals as eLpH is now available. In the current study, we directly compared the anti-prion efficacy of eLpH and Wex-cide 128 against prions from four different species (hamster 263K, cervid CWD, mouse 22L and human CJD). Decontamination was performed on either prion infected brain homogenates or prion contaminated steel wires and mouse bioassay was used to quantify the remaining prion infectivity. Our data show that both eLpH and Wex-cide 128 removed 4.0–5.5 logs of prion infectivity from 22L, CWD and 263K prion homogenates, but only about 1.25–1.50 logs of prion infectivity from human sporadic CJD. Wex-cide 128 is a viable substitute for inactivation of most prions from most species, but the resistance of CJD to phenolic inactivation is a concern and emphasizes the fact that inactivation methods should be confirmed for each target prion strain. [ABSTRACT FROM AUTHOR]

The ability of prions to infect some species and not others is determined by the transmission barrier. This unexplained phenomenon has led to the belief that certain species were not susceptible to transmissible spongiform encephalopathies (TSEs) and therefore represented negligible risk to human health if consumed. Using the protein misfolding cyclic amplification (PMCA) technique, we were able to overcome the species barrier in rabbits, which have been classified as TSE resistant for four decades. Rabbit brain homogenate, either unseeded or seeded in vitro with disease-related prions obtained from different species, was subjected to serial rounds of PMCA. De novo rabbit prions produced in vitro from unseeded material were tested for infectivity in rabbits, with one of three intracerebrally challenged animals succumbing to disease at 766 d and displaying all of the characteristics of a TSE, thereby demonstrating that leporids are not resistant to prion infection. Material from the brain of the clinically affected rabbit containing abnormal prion protein resulted in a 100% attack rate after its inoculation in transgenic mice overexpressing rabbit PrP. Transmissibility to rabbits (>470 d) has been confirmed in 2 of 10 rabbits after intracerebral challenge. Despite rabbits no longer being able to be classified as resistant to TSEs, an outbreak of "mad rabbit disease" is unlikely. [ABSTRACT FROM AUTHOR]

Chronic wasting disease (CWD) is a transmissible spongiform encephalopathy, or prion disease, that affects deer, elk, and moose. Human susceptibility to CWD remains unproven despite likely exposure to CWD-infected cervids. We used 2 nonhuman primate species, cynomolgus macaques and squirrel monkeys, as human models for CWD susceptibility. CWD was inoculated into these 2 species by intracerebral and oral routes. After intracerebral inoculation of squirrel monkeys, 7 of 8 CWD isolates induced a clinical wasting syndrome within 33-53 months. The monkeys' brains showed spongiform encephalopathy and proteaseresistant prion protein (PrPres) diagnostic of prion disease. After oral exposure, 2 squirrel monkeys had PrPres in brain, spleen, and lymph nodes at 69 months postinfection. In contrast, cynomolgus macaques have not shown evidence of clinical disease as of 70 months postinfection. Thus, these 2 species differed in susceptibility to CWD. Because humans are evolutionarily closer to macaques than to squirrel monkeys, they may also be resistant to CWD. [ABSTRACT FROM AUTHOR]

Transmissible spongiform encephalopathy (TSE) diseases are characterized by the accumulation in brain of an abnormal protease-resistant form of the host-encoded prion protein (PrP), PrP-res. PrP-res conformation differs among TSE agents derived from various sources, and these conformational differences are thought to influence the biological characteristics of these agents. In this study, we introduced deletions into the flexible N-terminal region of PrP (residues 34-124) and investigated the effect of this region on the conformation of PrP-res generated in an in vitro cell-free conversion assay. PrP deleted from residues 34 to 99 generated 12-16-kDa protease-resistant bands with intact C termini but variable N termini. The variable N termini were the result of exposure of new protease cleavage sites in PrP-res between residues 130 and 157, suggesting that these new cleavage sites were caused by alterations in the conformation of the PrP-res generated. Similarly truncated 12-16-kDa PrP bands were also identified in brain homogenates from mice infected with mouse-passaged hamster scrapie as well as in the cellfree conversion assay using conditions that mimicked the hamster/mouse species barrier to infection. Thus, by its effects on PrP-res conformation, the flexible N-terminal region of PrP seemed to influence TSE pathogenesis and cross-species TSE transmission. [ABSTRACT FROM AUTHOR]

The risk of contamination of tissue culture cells with transmissible spongiform encephalopathy (TSE) agents as a result of the use of animal products as medium components has been considered to be low, in part, because only a few brain-derived cell lines have been reported to be susceptible to TSE infection. In the present study, we demonstrate that the common laboratory fibroblast cell lines NIH/3T3 and L929, which express low levels of cellular mouse prion protein, are susceptible to infection with mouse-adapted scrapie. Our results show that the susceptibility of a cell line to TSE infection cannot be predicted on the basis of its tissue origin or its level of expression of the cellular prion protein, and they suggest that any cell line expressing normal host prion protein could have the potential to support propagation of TSE agents. Thus, testing of cells for TSE susceptibility might be necessary for all cell lines that are routinely used in vaccine production and in other medical applications. [ABSTRACT FROM AUTHOR]

The transmissible spongiform encephalopathy (TSE) diseases are rare, neurodegenerative diseases that include scrapie in sheep, bovine spongiform encephalopathy, and Creutzfeldt-Jakob disease in humans. There are no effective treatments available for clinical use in humans. We now demonstrate that, in 2 different rodent models of scrapie, multiple pretreatments with the cyclic tetrapyrrole phthalocyanine tetrasulfonate (PcTS) were as effective at delaying disease as multiple treatments starting at the time of infection. At low doses of scrapie infectivity, PcTS also protected some mice from peripheral scrapie infection, even if treatment was initiated several weeks after infection. Furthermore, PcTS completely inactivated low levels of scrapie infectivity when incubated with the infectious inoculum. Thus, PcTS has a broad range of antiscrapie activities. These findings suggest that cyclic tetrapyrroles may be useful both prophylactically and therapeutically against TSE diseases in vivo, as well as for inactivation of TSE infectivity suspended in solution. [ABSTRACT FROM AUTHOR]

A key event in the transmissible spongiform encephalopathies (TSEs) is the formation of aggregated and protease-resistant prion protein, PrP-res, from a normally soluble, protease-sensitive and glycosylated precursor, PrP-sen. While amino acid sequence similarity between PrP-sen and PrP-res influences both PrP-res formation and cross-species transmission of infectivity, the influence of co- or post-translational modifications to PrP-sen is unknown. Here we report that, if PrP-sen and PrP-res are derived from different species, PrP-sen glycosylation can significantly affect PrP-res formation. Glycosylation affected PrP-res formation by influencing the amount of PrP-sen bound to PrP-res, while the amino acid sequence of PrP-sen influenced the amount of PrP-res generated in the post-binding conversion step. Our results show that in addition to amino acid sequence, co- or post-translational modifications to PrP-sen influence PrP-res formation in vitro. In vivo, these modifications might contribute to the resistance to infection associated with transmission of TSE infectivity across species barriers. [ABSTRACT FROM AUTHOR]

Transmissible spongiform encephalopathies are characterized by spongiosis, astrocytosis and accumulation of PrPSc, an isoform of the normal host protein PrPC. The exact cell types responsible for agent propagation and pathogenesis are still uncertain. To determine the possible role of astrocytes, we generated mice devoid of murine PrP but expressing hamster PrP transgenes driven by the astrocyte­specific GFAP promoter. After inoculation with hamster scrapie, these mice accumulated infectivity and PrPSc to high levels, developed severe disease after 227 ± 5 days and died 7 ± 4 days later. Therefore, astrocytes could play an important role in scrapie pathogenesis, possibly by an indirect toxic effect on neurons. Interestingly, mice expressing the same transgenes but also endogenous murine PrP genes propagated infectivity without developing disease. [ABSTRACT FROM AUTHOR]

Transmissible spongiform encephalopathies (TSEs or prion diseases) are a rare group of invariably fatal neurodegenerative disorders that affect humans and other mammals. TSEs are protein misfolding diseases that involve the accumulation of an abnormally aggregated form of the normal host prion protein (PrP). They are unique among protein misfolding disorders in that they are transmissible and have different strains of infectious agents that are associated with unique phenotypes in vivo. A wealth of biological and biophysical evidence now suggests that the molecular basis for prion diseases may be encoded by protein conformation. The purpose of this review is to provide an overview of the existing structural information for PrP within the context of what is known about the biology of prion disease. [Copyright &y& Elsevier]

Abstract: Transmissible spongiform encephalopathies (TSEs) are fatal neurodegenerative diseases that include Creutzfeldt–Jakob disease, bovine spongiform encephalopathy and sheep scrapie. Although one of the earliest events during TSE infection is the cellular uptake of protease resistant prion protein (PrP-res), this process is poorly understood due to the difficulty of clearly distinguishing input PrP-res from either PrP-res or protease-sensitive PrP (PrP-sen) made by the cell. Using PrP-res tagged with a unique antibody epitope, we examined PrP-res uptake in neuronal and fibroblast cells exposed to three different mouse scrapie strains. PrP-res uptake was rapid and independent of scrapie strain, cell type, or cellular PrP expression, but occurred in only a subset of cells and was influenced by PrP-res preparation and aggregate size. Our results suggest that PrP-res aggregate size, the PrP-res microenvironment, and/or host cell-specific factors can all influence whether or not a cell takes up PrP-res following exposure to TSE infectivity. [Copyright &y& Elsevier]

Transmissible spongiform encephalopathies (TSEs) are neurological diseases that are associated with the conversion of the normal host-encoded prion protein (PrP-sen) to an abnormal protease-resistant form, PrP-res. Transmission of the TSE agent from one species to another is usually inefficient and accompanied by a prolonged incubation time. Species barriers to infection by the TSE agent are of particular importance given the apparent transmission of bovine spongiform encephalopathy to humans. Among the few animal species that appear to be resistant to infection by the TSE agent are rabbits. They survive challenge with the human kuru and Creutzfeldt-Jakob agents as well as with scrapie agent isolated from sheep or mice. Species barriers to the TSE agent are strongly influenced by the PrP amino acid sequence of both the donor and recipient animals. Here we show that rabbit PrP-sen does not form PrP-res in murine tissue culture cells persistently infected with the mouse-adapted scrapie agent. Unlike other TSE species barriers that have been studied, critical amino acid residues that inhibit PrP-res formation are located throughout the rabbit PrP sequence. Our results suggest that the resistance of rabbits to infection by the TSE agent is due to multiple rabbit PrP-specific amino acid residues that result in a PrP structure that is unable to refold to the abnormal isoform associated with disease. [ABSTRACT FROM AUTHOR]