Prions Are Forever
Prion diseases are most commonly acquired by inheriting a faulty prion protein gene from a parent, consuming prion-contaminated food, or receiving prion-contaminated donor tissues or organs.
But there is a final disturbing transmission possibility, one that stems from prions' mind-boggling powers of endurance.
Those powers are considerable. According to one account, prions resist digestion by protein-cleaving enzymes, may remain infectious for years when fixed by drying or chemicals, can survive 200°C heat for 1-2 hours, and become glued to stainless steel within minutes. Oh, and they’re also resistant to ionizing radiation.
Why are prions so hard to kill (if kill is even the right word for an evil protein meme)?
No one knows for sure. One expert hypothesized that because our decontamination methods have always targeted DNA and RNA – molecules possessed by all actual living creatures – they are by design not as effective on proteins.
The structure of prions themselves may also lend them supernatural survival powers. Just 3% of a prion protein is composed of beta-sheets, a common fold. But 43% of a prion is so folded. Such a substantial percentage makes the protein highly resistant to degradation, the reasoning goes. The herding of prions into chain-linked amyloid fiber may also protect them from assault.
Whatever the cause, prions are, to put it mildly, good survivors. And that may be why neurosurgical equipment can remain infectious even after it undergoes standard sterilization.
At least 2 cases of prion disease were contracted by people whose implanted depth electrodes had been previously used on a patient with Creutzfeldt-Jakob but were “inadequately” cleaned with benzene and disinfected with 70% alcohol and formaldehyde and sat unused for 2 years prior to implantation. And at least nine other cases of spontaneous Creutzfeldt-Jakob seem likely to have been contracted from inadequately sterilized medical equipment.
What is actually required to remove prions from medical equipment could best be described as destructive at best and draconian at worst and usually involves large quantities of sodium hydroxide or bleach (which is very hard on stainless steel), heat, and pressure, but even these measures are not 100% certain to get the job done. The World Health Organization recommends disposing of any suspected contaminated equipment entirely.
Standard sterilization routines have improved since most of the suspected surgical transmission cases occurred. And it should be heartily emphasized that the number of strongly suspected or confirmed cases of surgical prion transmission is tiny.
But because the incubation period of prion diseases can be decades, patients with prion diseases don’t always know they are ill when operated on, and hospitals still don’t routinely use the extreme sterilization protocols recommended for prions, risk remains. Many people have been so exposed over the years, a worrying occurrence Scientific American editor Phil Yam wrote about just a few years ago.
ARE PRIONS MORE COMMON THAN WE REALIZE?
The enduring infectious power of prions is unsettling all on its own, but some scientists are beginning to suspect something far scarier.
Aggregates of prions form amyloids. But amyloids also form from proteins called amyloid-beta, tau, and alpha-synuclein. You may recognize these names. The accumulation of these proteins in amyloids as plaques, tangles, and Lewy bodies are signature indications, and perhaps causes, of Alzheimer’s and Parkinson’s diseases. These amyloids, like prions, stick to surgical instruments “like glue” and survive standard sterilization procedures. They, too, are distressingly hard to "kill".
https://blogs.scientificamerican.com/artful-amoeba/prions-are-forever/