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March 15, 2000 Company Says It Cloned Pig in Effort to Aid Transplants Scottish company, PPL Therapeutics, announced yesterday that its scientists had cloned a pig, creating five identical piglets. The goal, PPL said, is to use the technology to create genetically altered pigs whose organs can be transplanted into humans without being rejected by the human immune system. PPL provided no details of how the cloning was done or even how many efforts were needed to succeed. Instead, the company issued a news release announcing that a pig had been cloned. Dr. David Ayares, the vice president of research and development at PPL, said yesterday that he hoped the announcement would attract investors. The company had been talking with drug companies, venture capitalists and investment bankers, he said. Dr. Ayares, who works at the company's laboratories in Blacksburg, Va., said PPL hoped to publish the details of the pig cloning in a scientific journal, either Science or Nature. It was scientists at PPL, working with others at the Roslin Institute, who first cloned an adult mammal, a sheep in 1996. They delayed announcement about the sheep, named Dolly, until the company had filed for patents, notifying the world with a paper published in Nature in 1997. Since then, scientists have cloned cattle and mice, and even clones of clones of mice. But pigs, Dr. Ayares said, "certainly have been more of a challenge." He said the scientists had to modify every step of the process to get it to work for pigs. Like cloning in sheep and cows, Dr. Ayares said, the process is inefficient -- it can take several hundred efforts before a clone is born. To clone, scientists take a cell from an adult animal and slip it into an egg whose own genetic material has been removed. The genes of the adult cell take over the egg, directing it to divide and form an embryo. The embryo is placed in the uterus of a surrogate mother where it grows into a genetically identical copy, a clone, of the adult whose cell was used. The commercial value of cloning, scientists say, is as an effective way to genetically modify animals. Before the adult cell is used to start cloning, scientists could alter it. Whatever changes they make would be carried into the cloned animal. PPL's goal is to make cloned pigs with genetic modifications that make their organs suitable for transplantation into humans. Since pig organs are the right size for humans, and since pigs are inexpensive and easy to breed, scientists have long considered them as potential donors. The problem is that the immune systems of humans or other primates react violently to pig organs, destroying them almost instantly. Dr. John S. Logan, the vice president for research and development at Nextran, a biotechnology company in Princeton, N.J. that hoped to develop pigs with organs suitable for transplant, explained: "When you transplant a pig organ into a nonhuman primate, it is rejected immediately. It just turns black before your eyes, within 30 minutes." The reason, Dr. Logan said, is that pig cells are studded with a sugar molecule, galactose alpha 1-3 galactose, that the human immune system immediately attacks. At Nextran, scientists have avoided the problem by injecting pig embryos with genes that block the immediate rejection process. Cloning provides another potential solution, scientists could eliminate the sugar molecule before using the pig cells to create clones. Even when the immediate rejection is prevented, though, scientists still have to block a long-term rejection process that takes place weeks later. "That really is the limiting factor," Dr. Logan said. By GINA KOLATA Copyright 2000 The New York Times Company http://www.nytimes.com/library/national/science/031500sci-cloning-pig.html janet paterson 53 now / 41 dx / 37 onset a new voice: http://www.geocities.com/janet313/ 613 256 8340 PO Box 171 Almonte Ontario Canada K0A 1A0