More Worrisome News of Prion Transmission

[jedishrfu]

In a recent Scientific American blog article, it was revealed that prions can be transmitted via optical testing equipment and via sterilized surgical equipment:

https://blogs.scientificamerican.com/artful-amoeba/the-case-for-transmissible-alzheimers-grows/

The unsettling evidence that Alzheimer’s Disease may be transmissible under limited -- but definitely nonzero -- circumstances keeps growing.

Last December I wrote about research that revealed that infectious, lethal proteins called prions have the potential to be transmitted on optical medical equipment because they are present throughout the eyes of victims.

This was all the more disturbing in light of a study I had also recently written about that suggested that peptide aggregates – essentially sticky, self-propagating clumps of misfolded protein bits collectively referred to as amyloid -- found in the brains of Alzheimer’s patients may be transmissible in the same ways that prions are.

 

[jackwhirl]

Prions stick to steel like glue, are stable for decades at room temperature, and survive a bombardment of chemical and physical cleaning assaults that are more than sufficient to obliterate other pathogens. Prions are survivors.

Are they more difficult to denature than properly folded proteins?

 

[jedishrfu]

It would seem that they are much more difficult to denature than their normally folded counterpart.

https://www.worldofmolecules.com/disease/prion.htm

Sterilization

Infectious particles possessing nucleic acid are dependent upon it to direct their continued replication. Prions however, are infectious by their effect on normal versions of the protein. Therefore, sterilizing prions involves the denaturation of the protein to a state where the molecule is no longer able to induce the abnormal folding of normal proteins. However, prions are generally quite resistant to denaturation by proteases, heat, radiation, and formalin treatments,[34] although their infectivity can be reduced by such treatments.

Prions can be denatured by subjecting them to a temperatures of 134 degrees Celsius (274 degrees Fahrenheit) for 18 minutes in a pressurised steam autoclave.[35] Ozone sterilization is currently being studied as a potential method for prion deactivation.[36] Renaturation of a completely denatured prion to infectious status has not yet been achieved, however partially denatured prions can be renatured to an infective status under certain artificial conditions.[37]

The World Health Organisation recommends the following procedure for the sterilisation of heat resistant surgical instruments which are potentially contaminated with prions:

(1) Immerse in a pan containing 1N NaOH and heat in a gravity-displacement autoclave at 121°C for 30 min; clean; rinse in water; and subject to routine sterilization

(2) Immerse in 1N NaOH or sodium hypochlorite (20,000 parts per million available chlorine) for 1 h; transfer instruments to water; heat in a gravity-displacement autoclave at 121°C for 1 h; clean; and subject to routine sterilization

(3) Immerse in 1N NaOH or sodium hypochlorite (20,000 parts per million available chlorine) for 1 h; remove and rinse in water, then transfer to an open pan and heat in a gravity-displacement (121°C) or in a porous-load (134°C) autoclave for 1 h; clean; and subject to routine sterilization [38]

 

[BillTre]

While up in Portland at the eyebank I work for today, I found out that a big reason the eyebank uses dissecting tools (like forceps, scissors, etc.) only once on recoveries (getting corneas for the recently dead) was that it takes much more that mere autoclaving to eradicate any prions that might have contaminated them.
Besides being more expensive and involving a lot of labor, there does not yet seem to be lot of confidence which alternative procedures would be fully effective.

 

[jackwhirl]

It would seem that they are much more difficult to denature than their normally folded counterpart.

It looks like that article is comparing prions to bacterial and viral pathogens, not healthy proteins.

Infectious particles possessing nucleic acid are dependent upon it to direct their continued replication. Prions however, are infectious by their effect on normal versions of the protein.

Maybe they aren't any more difficult to denature, and it just doesn't matter with healthy proteins.

 

[Ygggdrasil]

It looks like that article is comparing prions to bacterial and viral pathogens, not healthy proteins.

Maybe they aren't any more difficult to denature, and it just doesn't matter with healthy proteins.

Most healthy human proteins will denature under fairly mild temperature stress (typical human protein Tm values will probably be around 40-70°C). Prions, are proteins that have already denatured from their native state, but found a more thermodynamically favorable state by agreggating with other denatured proteins. These denatured aggregates are typically much more stable than a native protein.

 

[jackwhirl]

Prions, are proteins that have already denatured from their native state, but found a more thermodynamically favorable state by agreggating with other denatured proteins. These denatured aggregates are typically much more stable than a native protein.

That makes a lot more sense to me now. Thank you.

 

[JamesPhD]

In a recent Scientific American blog article, it was revealed that prions can be transmitted via optical testing equipment and via sterilized surgical equipment:

https://blogs.scientificamerican.com/artful-amoeba/the-case-for-transmissible-alzheimers-grows/

I wouldn't worry about it. The amyloid beta hypothesis of alzheimers disease is no longer convincing. All clinical trials to clear it from the brain resulted in clinical failure. There have been cases where patients have amyloid buildup with no clinical symptoms of alzheimers. The build-up of amyloid occurs in the entorhinal cortex and spreads out because that area of the brain is vulnerable for some reason. There have never been recorded cases of Alzheimer infection. I personally believe the build-up of these prion proteins is a side-effect of metabolic dysfunction. Alzheimers is known as type 3 diabetes.
It is possible that no one was looking for it and maybe infection could occur, there have been no studies. What is more likely is things like your diet influencing the onset of this disease.