Scientists develop prion-free cows

Scientists in the US have genetically modified cattle that do not produce prions - the proteins which, in mutated form, cause mad cow disease.

Cattle lacking natural prions suffer no ill-health effects

The cattle - developed by pharmaceutical company Hematech - were evaluated by the US Agricultural Research Service (ARS) and found to have no adverse effects on their health.

Juergen Richt of ARS said, “The cattle were monitored for growth and general health status from birth up to 19 months of age. Mean birth and daily gain were both within the normal range for the cattle. General physical examinations, done at monthly intervals by licensed veterinarians, revealed no unusual health problems.”

Prions are proteins that are naturally produced in animals. An abnormal form of prion is believed to cause devastating illnesses known as transmissible spongiform encephalopathies (TSEs), the best known of which is BSE. It is thought that the abnormal disease causing form can transform the normal prion protein simply by coming into contact with it. The cattle are now being injected directly with BSE causing prions to make certain the cattle are immune to it.

“These cattle can help in the exploration and improved understanding of how prions function and cause disease, especially with relation to bovine spongiform encephalopathy,” said Edward B. Knipling, administrator of the ARS.

James Robl, Hematech’s chief scientist, scraped skin cells from cows and ‘turned off’ the gene that makes prions and used these cells to clone 12 calves.

The research goes some way to explaining one mystery of the prion, that of its natural function.

Robl said: “No one knows the function of normal prions and our research suggests the proteins have little value.”