Cannibalism: A Perfectly Natural History(77)
Victoria Rimmer died in November 1997. After an inquest into her death, coroner John Hughes concluded that she died of natural causes.
In 1994, a 16-year-old schoolgirl and an 18-year-old boy were diagnosed with CJD, which had hardly ever been reported in people less than 30 years of age. By the following year, seven people were already dead or dying.
On March 8, 1996, the hammer fell on the government’s “British Beef is Safe to Eat” stance in the form of a memo written by Dr. Eileen Rubery, a policy maker and longtime government adviser. Rubery confirmed what others had feared for 11 years—the emergence of a new form of spongiform encephalopathy, this one transmitted to humans via the consumption of contaminated beef. She also used the dreaded “e” word: epidemic. The new disease was initially referred to as sporadic CJD or atypical CJD, but scientists eventually settled on Variant Creutzfeldt-Jakob disease (vCJD).
By October 2013, the number of definite and probable deaths from vCJD in the United Kingdom stood at 177. Some researchers see the epidemic as over, pointing to the fact that after peaking in 2000, when 28 people in the UK died of vCJD, deaths from the disease have fallen off dramatically (i.e., three deaths in 2009, three in 2010, and one in 2013). Others believe that these 177 deaths are only the tip of the iceberg. They rationalize that, because thousands of Fore died as adults, sometimes 50 years after being exposed to kuru via ritual cannibalism, many Europeans (and others) who had consumed contaminated beef in the 1970s and 1980s would not have been stricken yet, and might not start dying en masse until decades after exposure.
In a 2013 study published online by the British Medical Journal, researchers tested 32,000 “anonymous appendix samples from people of all ages who had their appendix removed between 2000 and 2012.” Sixteen of the samples, which came from 41 hospitals across England, tested positive for the abnormal prion protein. This translates into one carrier for every 2,000 people in the United Kingdom, a scary number that gets even scarier if you project that out to 493 people per 1 million inhabitants. There are approximately 63.5 million people in the United Kingdom.
On a related but more upbeat note, scientists like Simon Mead and John Collinge, both of whom are experts in the field of kuru research, think there’s another reason why everyone exposed to prion-contaminated meat may not come down with a lethal neurodegenerative disease. As evidence they point to a common human gene (the prion protein gene, or PRNP) with a worldwide distribution. The researchers and their colleagues discovered a mutated form of this gene (i.e., a variant) in descendants of the Fore who survived the famous kuru outbreak. Initially, they hypothesized that this variant might have provided protection from kuru to the individuals who possessed it. These kuru-resistant survivors would have passed down their genes (and their resistance) to their descendants. In 2015, Collinge and his research team published a follow-up study in Nature in which they presented experimental evidence that when the genetic variant of PRNP was transferred to mice, it provided complete resistance to both kuru and classical CJD.
In a best-case scenario, thanks to what may have been their ancient ancestors’ brush with cannibalism (and kuru), at least some of the individuals consuming prion-contaminated meat in the 1980s were already resistant to the disease.52 If this is true, then the gloom-and-gloomers may be waiting for an epidemic that never arrives. From a therapeutic viewpoint, if these genetic variants can somehow be transmitted to humans, we may one day be able to confer resistance to the pathogens that cause spongiform encephalopathies—whether they turn out to be prions or viruses.
On the other hand, if Laura Manuelidis is correct and spongiform encephalopathies are the results of viruses, it would be wise to remember one of their key characteristics: Viruses mutate.
Back in Chelsea, Manuelidis and I were seated in the back of a 9th Avenue bar. As she explained why viruses and not prions were the real culprits in the transmissible spongiform encephalopathy story, we sipped a pair of melon-based something-or-others. In retrospect, given the fact that my understanding of biochemistry was already more than a bit wobbly, a weak drink was probably a good thing.
“What do you make of the fact that researchers in the 1960s never saw an immune response during their experiments with kuru extracts?”
“There is an immune response,” she replied. “They just didn’t see it because it was transient or diminished. Like with HIV, there are many mechanisms that can make something not apparent as an immune response.”
Manuelidis explained that with diseases like kuru, CJD, and BSE, “what we found is that there are innate immune responses, very early in the disease.”
I shifted easily into Insistent Mode. “All right, but why couldn’t prions be the TSE pathogens?”
“Because that stuff [anything composed of protein] gets digested in the gastrointestinal tract, while viruses can go through gastric and intestinal juices unscathed. Viruses are built to be protected from the body’s defense mechanisms—and proteins are not.”
“But what about the reports, by Prusiner and others, indicating that prions couldn’t be destroyed by digestive enzymes like proteases?”
Manuelidis shook her head. She was wearing a look that suggested the question was one she’d heard plenty of times before. “Bill, everyone knows that PrP [prion protein] is relatively resistant to limited exposure to PK [a protein-dissolving enzyme found in our digestive tracts], but it breaks down if given a longer time to digest. In fact, it disappears.”