Monday, November 30, 2009

Evolution produces immunity to mad-cow disease

Fromm BBC: "Villagers suffering from a major epidemic of Kuru, a fatal CJD-like brain disease, seem to have developed a strong genetic resistance to the condition.

The infection, which is associated with mortuary feasts, where mainly women and children consume the remains of respected relatives, devastated populations in the remote eastern highlands of Papua New Guinea. Things go so bad that in some villages there were no women of child-bearing age left alive and the practice was banned in the late 1950's and quickly died out.

But it seems that natural selection was already developing a response of its own. Scientists working on the new variant of CJD associated with eating meat from cattle infected with BSE have found that people living around the Purosa valley in Papua New Guinea, where Kuru was most rife, have a unique genetic variation that seems to offer high, or even complete, protection against the disease.

The scientists from the MRC's Prion Unit studied over 3,000 people from the area, including 709 who had participated in cannibalistic mortuary feasts, 152 of whom subsequently died. They discovered that many of the survivors, and their children, seemed to have a unique variation in the prion protein gene G127V. …

Professor John Collinge, director of the unit, said it was a fascinating example of Darwinian selection at work. 'This community has developed its own biologically unique response to a truly terrible epidemic. The fact that it has happened in decades is remarkable'.

The discovery is exciting because it could help scientists to understand the genetic mechanisms that underpin the development of CJD in people and even BSE in animals.

But it's also important because many of those same genetic mechanisms play a vital role in the development of other debilitating brain conditions including Alzheimers and Parkinson's disease.

In could be that the cannibalism in Papua New Guinea holds the key to cures for a wide range of degenerative brain disorders.

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