[rcxdude]

This is not at all how it works. Prion diseases are not at all to do with synthesising proteins 'backwards'. It's entirely because of one protein found in the brain which has a very stable misfolded form which will induce other copies of it to misfold as well (and this misfolds all stick together into something the body struggles to break down, which is what eventually causes the damage). It's not something that can happen to just any protein (lots of other proteins do misfold or are otherwise not made correctly, all the time. But they don't induce other proteins to misfold and the body can easily break them down or otherwise get rid of them)

(in fact, the misfolded form is so stable it can survive cooking, autoclaving(!), sitting in soil for years, and digestion. The main reason it's not a big threat is that it needs to somehow get from the environment into the brain, generally via the gut, which is not a particularly easy process for an inert clump of amino acids: a significant percentage of UK residents actually have detectable levels of this prion in their gut already, but only a very small fraction will develop the disease)