By Kim Tae-gyu
Staff Reporter

A research team has succeeded in cloning mad cow disease-resistant cows and gnotobiotic (sterilized) miniature pigs, which can provide for human organ transplants.

Each of the exploits in animal cloning technology marks the first of its kind in the world and Korea has already applied for international patents for both.

Seoul National University (SNU) professor Hwang Woo-suk and his research team made public the breakthrough yesterday at a news conference at SNU Hospital in Seoul

``Mad cow disease-resistant cows will raise our biotechnology level several notches,’’ said Hwang, who also cloned a pair of cows for the first time in Korea in 1999. ``Gnotobiotic pigs will provide us with much in royalty revenue and exports of the pigs once they are commercialized.’’

Hwang’s team, launched in 2001, used prion mutant protein, which is believed to shield animals from the attack of abnormal prions, the cause of mad cow disease, or bovine spongiform encephalopathy (BSE).

The researchers inserted the new prions into a cow’s eggs, from which the nuclei were removed earlier and the eggs were cultivated in surrogate cows to develop into cloned calves. The method is known as an overexpression model to counter the abnormal prions.

The four calves will be sent to Tsukuba, Japan along with 15 calves expected from 15 pregnant cows for in vivo challenge tests, which are expected to take three to five years to complete.

Hwang said some of the 15 calves-in-waiting are made from an alternative method, called a knockout model, eliminating prions from cells before combining with eggs.

Both knockout and overexpression methods were successful in the case of mouse experiments, which were conducted under the aegis of Dr. Stanley Prusiner, the 1997 Nobel laureate in medicine and physiology.

BSE is a deadly and contagious disease, affecting animals. Since the animal epidemic was first discovered in Britain in 1985, as many as 200,000 head of cattle from 23 countries have been infected with it and a total of 3.5 million cows have been slaughtered to prevent the disease from spreading.

Also, BSE is believed to trigger the variant Creutzfeldt-Jakob Disease (CJD), a human brain disorder, as the two maladies are connected to prions alike and also have similar track records of occurrences.

CJD, which was first detected in 1995 in Britain, came after the peak of BSE, claiming 139 lives throughout the world.

Hwang’s team also developed six gnotobiotic miniature pigs, whose organs can be transplanted into humans, all of which failed to survive more than two days, though.

The pigs were made of cells, embedded with a human decay accelerating factor (hDAF), or a human immunity gene, to avoid rejection reaction when organs are transplanted to human bodies. The gene was detected in two of the six dead pigs.

The mammal with organs that are most similar to those of a human is, surprisingly, a pig. Its organs have almost the same size as those of humans and so are its body’s metabolic functions, according to Hwang.

voc200@koreatimes.co.kr