I recently found out about the so-called prion diseases, which are incurable and fatal diseases that affect (a euphemism, the real word is destroy) the CNS and cause a rapid deterioration of mental and physical abilities.
There are many prion diseases, the two most famous are probably the mad cow disease (non-human mammals), and the Creutzfeldt–Jakob disease (CJD) (for human mammals). Both are 100% fatal, and *no one* is known to have survived longer than 2.5 years after a CJD diagnosis. That’s the kind of stuff you wouldn’t wish on your worst enemy.
Why are these diseases so deadly? I read that it has to do with abnormal proteins but that was way over my head.
EDIT : I have another question, can prion diseases be rightly called the most dangerous diseases known to man ?
Thanks;
In: Biology
In regards to your follow-up question:
I personally wouldn’t call it the most dangerous diseases – but it obviously depends fully on how you define dangerous. If you look solely at the fatality rate, it’s definitely up there though. If you factor in how many people are affected yearly, then it’s quite far down the list.
Pros for the title of most dangerous disease:
– fatality rate
– no cure, and no treatment to slow it down
– can occur sporatic, ie. this type can’t be avoided. You’re just unlucky.
Cons:
– very slow progression compared to other fatal diseases
– very rare
Could these be a rather recent development evolutionarily? Could organisms just not have evolved a way to deal with prions yet?
There are a lot of correct answers about the prion diseases but it’s not the real answer to your question.
The real answer to your question is that we don’t have early diagnosis for prion diseases. We simply don’t know if there’s early stage or weak prion diseases that are somehow contained by the body or even reversed, because we don’t know them happening.
So the answer why people live only short post-diagnosis is that because we have only late diagnosis at the moment. And the reason for that is basically it’s a painless disease (no pain receptors in brain), and a little brain damage is usually shadowed by the brain plasticity (so an early damage is not seen because other brain parts can take over functions). On top of that, there’s no molecular diagnosis, no inflammation no any sign of an early and incomplete prion disease.
And that’s why we only see a prion disease when it’s severe enough to be deadly soon.
I think the best way to understand the ‘misfolded proteins’ is it comes down to entropy. It’s not that they’re just ‘misfolded’ and can be ‘unfolded’, because that misfolded state is the most ‘ordered’ state (at least in the biochemical sense, even if not at the ‘physics’ or ‘chemical’ level).
Proteins have multiple ‘levels’ of organisation, at the first level, it’s the string/chain of amino acids, at the next level we make basic protein structures/shapes (based on that string of amino acids), at the level after that those proteins come together and make bigger complex structures (normally due to interactions between amino acids in those simple shapes), and at the fourth level multiple complex structures come together and make bigger structures. Those final levels of shape and the amino acids that present to the outside or inside of the protein is what allows for specific interactions with other cells/molecules.
Normally, we can denature proteins with heat, enzymes, etc. but with prions their structure is dysfunctionally strong. It’s like a black hole for proteins in a sense, and other proteins that come in contact with it can become amalgamated as well as they ‘pass the event horizon’ and can’t escape.
I’m not sure if black holes are understandable by a 5yo but that’s my best attempt. XD
Imagine you have a folding chair. When you have that chair set up in a form that you can sit on it, then you can’t easily stack another chair on top of it. If you did, that stack of chairs would be unstable.
Now imagine you folded that chair. You can easily stack layers upon layers of chairs against the wall. Or you can put the stacked chairs on a rack that you otherwise couldn’t put an unfolded chair on. All in all, this stack of chairs would become much easier to put in storage than unfolded chairs would.
This is how prion diseases work. Normal prion proteins (known as PrP) aren’t able to stack together because that would result in a chemically unstable formation, just like the unfolded chair. However, if a prion protein is misfolded just right, then they can convert those healthy prions into that misfolded form that would actually result in more stable formations when stacked together, just like the folded chairs.
This accumulation of misfolded proteins prevents your brain from doing its normal function. In the end, your brain becomes nothing more than a jumbled mess.
Just to add: misfolded proteins actually happen more frequently than you think. It’s just that enzymes in your body, known as proteases, are able to take care of these.
Prions are protease-resistant, meaning that either proteases cannot catalyze the prions quick enough to keep up with the cascade, or the proteases can’t do anything altogether.
As to your edit: they are very dangerous because there is no vaccine or treatment. Rabies is dangerous as well, but you can at least get treated with a strict vaccine regiment if you’re exposed.
Because the body possesses no defense mechanism against them, they simply don’t recognize the misfolded proteins as a threat.
The good news is that unless you are consuming brain matter or working on brain research (like that scientist who cut herself accidentally and yes, died from Prions) your chances of getting a prion are practically zero.
I think you’re misunderstanding if you believe they’re 100% fatal. We don’t do a lot of looking for random proteins in people, so when we find a prion it’s most likely because someone died from it. It’s kind of like survivor bias.
It sounds like prions have benefits in the developing brain.
https://medicalxpress.com/news/2013-02-good-side-prion-molecule-dangerous.html#:~:text=But%20now%20research%20is%20showing,in%20the%20Journal%20of%20Neuroscience.
More research is needed.
>EDIT : I have another question, can prion diseases be rightly called the most dangerous diseases known to man ?
No. Because they don’t spread very well.
Things like malaria, tuberculosis and smallpox are way more dangerous.
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