Prions in Purified Water?
Is There a Risk of Prions Persisting in Purified Water?
I have been asked if there is a risk of prions persisting in pure water.
Disease-Causing Prions are Remarkably Resistent to Inactivation
Prion diseases, or transmissible spongiform encephalopathies (TSEs), are a group of fatal neurodegenerative disorders that includes scrapie and bovine spongiform encephalopathy (BSE) in animals, and Creutzfeldt–Jakob disease (CJD) in humans. The agent responsible for such diseases is a protein molecule called PrPSc, a conformational variant of the normal host protein, PrPC. The key event in the pathogenesis of TSEs is believed to be the conversion of PrPC into the pathogenic isoform, PrPSc , by means of a prion, which is thought to be identical to PrPSc.
Methods to Reduce Prion Infectivity are Not Compatibile
The prion agent has a remarkable resistance to physiochemical inactivation procedures such as heat, ionization, germicidal ultraviolet light, microwaves, and irradiation, and to conventional chemical disinfectants such as detergents, alcohol, glutaraldehyde, and formalin. Methods that reduce TSE infectivity, such as treatment with a strong base, are not compatible with maintaining the purity of water and so the possible presence of prions is a very reasonable concern.
Purification Methods That Can Remove Prions From Water
Fortunately, prions are proteins with a molecular weight of over 35,000 Daltons. This corresponds to a molecular diameter of approximately 3 to 4 nm. Therefore, they can be filtered out of purified water by suitable filtration - nano-filtration, ultrafiltration or reverse osmosis - or removed by distillation. Passage through oxidising 185nm UV and mixed ion exchange resins are also likely to contribute to prion removal.
Purified Lab Water Should Not Be Problem
Transmission of pion diseases of humans has occurred through contaminated surgical instruments and through donations obtained from human tissues (e.g., dura mater, pituitary gland, or cornea) and it is difficult to ensure that prions are absent in many materials but, fortunately, pure water used in the lab, if filtered correctly should not be a problem.
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