Eating human brains protected isolated tribe

Discovery big step to understanding prion diseases

The Fore people, a once-isolated tribe in eastern Papua New Guinea, had a long-standing tradition of mortuary feasts — eating the dead from their own community at funerals.

Men consumed the flesh of deceased relatives, while women and children ate the brain. It was an expression of respect for the lost loved ones, but the practice wreaked havoc on the communities they left behind.

That’s because a deadly molecule that lives in brains was spreading to the women who ate them, causing a horrible degenerative illness, kuru, that at one point killed two per cent of the population each year.

The practice was outlawed in the 1950s, and the kuru epidemic began to recede. But it left an irreversible mark on the Fore, one that has implications far beyond Papua New Guinea: After years of eating brains, some Fore developed a genetic resistance to the molecule that causes several fatal brain diseases, including kuru, mad cow disease and some cases of dementia.

The single, protective gene is identified in a study published this week in the journal Nature. Researchers say the finding is a huge step toward understanding these diseases and other degenerative brain problems, including Alzheimer’s and Parkinson’s.

The gene works by protecting people against prions, a strange and sometimes deadly kind of protein. Though naturally manufactured in all mammals, prions can be deformed in a way that makes them turn on the body that made them, acting like a virus and attacking tissue. The deformed prion is even capable of infecting the prions that surround it, reshaping them to mimic its structure and its malicious ways.

The prions’ impact on their hosts is invariably fatal. Among the Fore, prions riddled victims’ brains with microscopic holes, giving the muscle a spongy texture. In cattle, prions cause mad cow disease — the U.K. epidemic of the late ’80s required hundreds of thousands of cattle to be destroyed.

They have been linked to a bizarre form of fatal insomnia. And they’re the source of the degenerative neurological disorder Creutzfeldt-Jakob disease (CJD), characterized by rapid dementia, personality changes and eventually an inability to move or speak.

Most prion-diseases are “sporadic,” seemingly appearing without cause. But study author John Collinge of University College London said a portion of cases are inherited from parents, and an even smaller percentage are acquired from consuming infected tissue. Variant CJD, often called the “human mad cow disease,” is caused by eating beef from infected cows.

When researchers looked at the part of the genome that encodes prion-manufacturing proteins, they found only the resistant Fore had an amino acid called valine.

Collinge said the process involved in prion diseases — prions changing molecules’ shape and damaging the brain — is likely responsible for the deadly effects of degenerative brain illnesses: Alzheimer’s, Parkinson’s and dementia chief among them.