First prion-free cows reported

Hematech and Kirin Brewery Company have announced the production of healthy prion protein-knockout cows.

Prion protein is a natural cellular protein that can become misfolded into infectious particles and cause bovine spongiform encephalopathy (BSE, or mad cow disease) and a lethal variant of Creutzfeldt-Jakob disease (vCJD) in humans.

Hematech is developing a bovine system for production of human polyclonal antibodies. As part of this effort a novel gene targeting system was developed and published in Nature Genetics in June 2004. This gene targeting system was used to produce the prion protein knockout calves reported in the current study.

"By knocking out the prion protein gene and producing healthy calves, our team has successfully demonstrated that normal cellular prion protein is not necessary for the normal development and survival of cattle. The cows are now nearly two years old and are completely healthy," said James M Robl, PhD, president and chief scientific officer of Hematech.

"Hematech has already successfully produced knockout cattle using the sequential gene targeting system. We anticipate that prion protein-free cows will be useful models to study prion disease processes in both animals and humans."

According to the Food and Drug Administration's Center for Food Safety & Nutrition, prions are associated with a group of diseases called Transmissible Spongiform Encephalopathies (TSEs).

In humans, the related illness, which is suspected of being food-borne, is vCJD. The human disease, vCJD, and the cattle disease, BSE both appear to be caused by a mutant form of prion protein.

After an extended incubation period of years, these diseases result in irreversible neurodegeneration.