Assessment of Prion Inactivation by Combined Use ofBacillus-Derived Protease and SDS

Abstract

Prions, infectious agents causing transmissible spongiform encephalopathy, retain infectivity even after undergoing routine sterilization processes. We found that MSK103 protease, identified in our previous study, effectively reduces infectivity and the level of misfolded isoform of the prion protein in scrapie-infected brain homogenates in the presence of SDS. The treatment therefore can be applied to the decontamination of thermolabile instruments.

Degradation of the Disease-Associated Prion Protein by a Serine Protease from Lichens

“…In experiments more similar to environmental conditions, we tested one of those lichen species and found that intact lichen tissue or a water extract of the tissue could also degrade PrP. The speculated protein-only nature of the TSE agent has prompted numerous studies of proteases as potential prion decontaminants [40]–[45] and has prompted investigation into their use in soil environments [46]. Typical conditions used for prion inactivation by proteases, however, involve elevated temperatures, the presence of detergents and extreme pH values.…”

Guideline for Disinfection and Sterilization of Prion-Contaminated Medical Instruments

“…[55][56][57][58] While prions have been shown to bind tightly to surfaces and to be difficult to remove by cleaning, 59 there are now numerous studies that have shown the effectiveness of specific formulations of alkaline and enzymatic detergents to eliminate the infectivity of prions. [27][28][29][30][31][32][60][61][62][63][64][65][66][67] Caution must be exercised in the use of enzymatic detergents with prion-contaminated instruments, since some enzymatic detergents have been shown to be prionicidal while others have been shown to increase resistance to subsequent inactivation by steam sterilization. 29,33 Second, the prion studies have been performed with tissue homogenates, and the protective effect of tissue may explain, in part, why the CJD agent is difficult to inactivate.…”

“…Several recent studies have demonstrated that prions are inactivated by cleaners such as alkaline detergents and enzymatic detergents. 17,[27][28][29][30]32,40,48,[60][61][62][63][64][65][66][67] Many of these studies used surgical stainless steel wires that were experimentally contaminated with prions; the contaminated wires efficiently transmitted the prion disease after implantation in the brains of mice or hamsters. 28,29,32,33,36,49,78 Several reports have demonstrated the possibility that available decontamination procedures using alkaline or enzymatic detergents (eg, Klenz- 40,48 could significantly reduce the infectivity of TSE agents (eg, scrapie prion strain 263K) and thus minimize or prevent the risk of iatrogenic transmission of undiagnosed or misdiagnosed CJD.…”

Lichens

“…Both others and we have found PK, even at high concentrations, has limited activity to degrade abnormal PrP. 12,25 Other serine proteases including subtilisins, the bacterial proteinase "prionase", Streptomyces E77 protease and PWD-1 keratinase have all shown great promise in degrading PrP, [19][20][21][22][23][24] even when bound to soil. 26 Typical conditions used for prion inactivation by proteases, however, involve elevated temperatures, the presence of environmental conditions, we exposed PrP-enriched preparations or infected brain homogenate to either a small quantity of intact P. sulcata tissue or an aqueous extract of the lichen.…”

“…Few lichen mycobionts can be cultured in the absence of photobionts and gene expression in each organism is almost PrP. [19][20][21][22][23][24] Serine proteases are characterized by the presence of a serine group at the center of their active site and one of the most common serine proteases, proteinase K (PK), is widely used to test for the presence of abnormal PrP. Both others and we have found PK, even at high concentrations, has limited activity to degrade abnormal PrP.…”