First aired on Quirks & Quarks (18/6/12)
In the late 1980s, a new disease emerged in British cattle, a strange syndrome called Mad Cow Disease. To control the epidemic, millions of cows were slaughtered. But even more terrifyingly, it became clear in the 1990s that this new disease could be communicated to humans as well. To date, it has claimed more than 170 lives. But what makes Mad Cow Disease, scientifically known as bovine spongiform encephalopathy or BSE, so scary is the cause. The vector for BSE is not a virus or bacteria but a misfolded, infectious protein called a prion. This came as a huge surprise to many scientists. Ten years later, we're still struggling to understand how prions function. In a new book, Fatal Flaws: How a Misfolded Protein Baffled Scientists and Changed the Way We Look at the Brain, Jay Ingram -- science writer, broadcaster and former host of Quirks & Quarks -- recounts the story of the prion and the diseases it causes, and discusses how understanding it might lead to preventing a number of diseases, not only those linked to prions.
BSE is the best known prion-driven disease, but scientists were studying this phenomenon long before the 1980s British breakout. Scrapie, a classic sheep disease, had been affecting sheep populations for centuries. "They knew that was a brain disease," Ingram told Quirks & Quarks host Bob McDonald, adding that "they thought it was a virus because it was quite tiny, smaller than any bacteria." However, further research demonstrated that the transmitting agent had no genetic material whatsoever. It was a protein. "These two ideas -- that you can have just a protein and it can cause disease, it can multiply and kill animals -- that seemed impossible. Proteins just weren't able to do that," Ingram said. "That's when the mystery really started."
Without proteins, we would not exist. They mediate every single chemical reaction in our bodies, and are able to do this by folding into a series of complex formations, a process like "molecular origami," in order to do the many different jobs our bodies require. But when this folding process goes awry, a prion can form. "Prions are proteins that have this tendency to fold incorrectly or to snap out of this regular folding into this weird, misfolded form," Ingram explained.
This process is still a mystery to scientists. But what makes prions so mysterious is not how they misfold, it's how they spread. "They can induce normal ones to misfold as well," Ingram said. "They can recruit normal proteins and turn them into misfolded proteins. That's how they reproduce." Exactly how they do that is what scientists are currently trying to figure out.
Resistance to prions is another big mystery that science is trying to solve. Not only are certain species immune to certain prions -- for example, dogs are resistant to BSE, but cats are susceptible -- but individuals within species can have greater resistance to the same prion-transmitted disease. For example, the 170 people who died from BSE in the U.K. were part of the one-third of the British population who were more susceptible to the disease. According to Ingram, the rest of the population was exposed but they "are more resistant because of their genetics." He went on to point out that "we don't know how resistant they are." The prions could be incubating in their system right now, and they would suffer from BSE in five, 10, 20 or 60 years. Or perhaps it will never incubate. We simply don't know.
The research into how prions work is helping us understand other diseases as well. Research into Alzheimer's, Parkinson's, ALS, juvenile diabetes and chronic traumatic encephalopathy (a disease related to concussions) is benefiting from research into prions. And even though these diseases aren't caused by prions, the similarities are astounding. "The more you understand about how prions flip folded ones into misfolded ones, surely the closer you are to beginning to understand why every one of these major neurological diseases has a similar reaction going on," Ingram said. "And maybe the closer you are to being able to interrupt that process."