SNU professor Hwang Woo-sok announced the medical milestone Wednesday, saying that cloned cows possess antibodies specifically targeting prions, the primary cause of mad cow disease. The research team has also filed for a patent application.

With the breakthrough, humans will be protected from mad cow disease, which was first discovered in Britain in 1987. Beef contaminated with mad cow disease that is consumed by a person can cause a variant of Creutzfeldt-Jakob disease, which has claimed 139 lives around the world so far.

Hwang said researchers injected a mutant prion protein into a cow’s eggs and then placed the eggs into surrogate cows, to develop cloned calves. The team found that the calves still had the BSE-resistant gene.

Researchers also plan to send cloned calves from 15 cows to research facilities in Tsukuba, Japan, to verify the research results.

Hwang’s team also developed sterilized miniature pigs, whose organs can be transplanted into humans.

The pigs were cloned from the cells of sterilized pigs, provided by a Chicago medical school, and were embedded with a human decay accelerating factor (hDAF), or a human immunity gene, to avoid rejection when transplanted to a human body. From last September until November, six piglets have been born, but the animals died just few days after birth.

“Breeding mad cow disease-resistant cows will help raise our level of biotechnological sophistication," Hwang said. (Pack Seong-jae, whitesj@chosun.com )