scientists transferred prion populations from brain cells to other cells in culture and observed the prions that adapted to the new cellular environment out-competed their brain-adapted counterparts. When returned to the brain cells, the brain-adapted prions again took over the population.

Charles Weissmann, head of Scripps Florida’s department of infectology who led the study, said: “On the face of it, you have exactly the same process of mutation and adaptive change in prions as you see in viruses.

“This means that this pattern of Darwinian evolution appears to be universally active. “In viruses, mutation is linked to changes in nucleic acid sequence that leads to resistance.

“Now, this adaptability has moved one level down- to prions and protein folding – and it’s clear that you do not need nucleic acid (DNA or RNA) for the process of evolution.”
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He said: “The prion protein is not a clone, it is a quasi-species that can create different protein strains even in the same animal. “The abnormal prion proteins multiply by converting normal prion proteins.

“The implication of Charles Weissmann’s work is that it would be better to cut off that supply of normal prion proteins rather than risk the abnormal prion adapting to a drug and evolving into a new more virulent form.