Bioassays and Inactivation of Prions

Abstract

The experimental study of prions requires a model for their propagation. However, because prions lack nucleic acids, the simple techniques used to replicate the propagation of bacteria and viruses are not applicable. For much of the history of prion research, time-consuming bioassays in animals were the only option for measuring infectivity. Although cell models and other in vitro tools for the propagation of prions have been developed, they all suffer limitations, and animal bioassays remain the gold standard for measuring infectivity. A wealth of recent data suggests that β-amyloid (Aβ) and tau proteins, which aggregate in Alzheimer’s disease, and α-synuclein, which aggregates in Parkinson’s disease, also become prions. Cell and animal models that recapitulate some of the key features of cell-to-cell spreading of these additional prions have been developed. The unusual resistance of prions to inactivation was an early indication that they represented a different class of infectious agents to bacteria or viruses. Incomplete inactivation of prions has led to medically induced, or iatrogenic, Creutzfeldt–Jakob disease (CJD). Worldwide, the number of elderly individuals who undergo surgery has increased, and due to the unusually long asymptomatic phase of CJD, there are a growing number of cases in which surgical instruments are used on an asymptomatic patient and then reused repeatedly before a CJD diagnosis is confirmed. Recent data suggesting the potential for iatrogenic transmission of Aβ amyloidosis has raised renewed interest in the field of prion inactivation.

Evaluation of the Application for new alternative biodiesel production process for rendered fat of Cat 1 (BDI‐RepCat process, AT)

“…Additionally, the results of different experiments are sometimes contradictory. In some cases, prior exposure to high temperatures or ethanol may lead to increased thermostability (Taylor, 1999;Giles et al, 2017), although these data cannot be considered conclusive, as there are contradictory observations and they do not cover all the temperature ranges used in the process under evaluation.…”

“…Additionally, the results of different experiments are sometimes contradictory. In some cases, prior exposure to high temperatures or ethanol may lead to increased thermostability (Taylor, ; Giles et al., ), although these data cannot be considered conclusive, as there are contradictory observations and they do not cover all the temperature ranges used in the process under evaluation. In the proposed process, there is an exposure to methanol in the conversion phase in the absence of alkaline or acidic conditions. The impact of this procedure on the thermostability of TSEs has not been assessed in the literature.…”

“…TSE infectivity is reduced by NaOH and this has been removed from the process. In addition, methanol could have protein‐fixation potential, and this may impact on the level of TSE reduction attained (Giles et al., ). Further experiments showed resistance to inactivation by various chemicals including glutaraldehyde, peracetic acid or ethanol, and to extended heating, including at 160°C for 24 h (Dickinson and Taylor, ). In the available literature, reduction of TSE infectivity has been assessed in spiked tallow which has been treated chemically or physically after addition of aqueous solutions which may also contain methanol.…”

“…TSE infectivity is reduced by NaOH and this has been removed from the process. In addition, methanol could have protein-fixation potential, and this may impact on the level of TSE reduction attained (Giles et al, 2017). Further experiments showed resistance to inactivation by various chemicals including glutaraldehyde, peracetic acid or ethanol, and to extended heating, including at 160°C for 24 h (Dickinson and Taylor, 1978).…”

A role for astroglia in prion diseases

“…Do the iPSC-derived astrocytes indeed replicate prion infectivity, or do they simply store exogenous infectivity without multiplying it? The presence of prions is often equated with the appearance of proteinase Kresistant PrP, yet prion infectivity can exist in the absence of protein resistance (Leske et al, 2017) and vice versa (Giles et al, 2017). The Scottish authors have addressed this issue by testing whether prion-infected astrocytes would transmit the infection to a second generation of naive astrocytes.…”