A major advance towards producing prion-free cows that would be immune to mad cow disease has been made by researchers at companies in the US and Japan.Their principal aim is to make genetically modified cattle that produce pharmaceuticals in their milk. But the companies hope that also making the animals resistant to BSE (bovine spongiform encephalopathy) will reassure consumers.The researchers have now achieved the considerable feat of creating cell lines which have both copies of the cow’s PrP gene switched off. The PrP protein can be switched to an infectious state by contact with a mutated prion. This switch causes prion diseases such as BSE in cows and variant Creutzfeldt Jakob Disease (vCJD) in humans.
