Dr. Robert Hawley and scientists at Immerge, in collaboration with Dr. Kenth Gustafsson, first identified the gene that produces GGTA1 and eliminated, or knocked it out, of the DNA of the cells from the miniature swine. This genetic material was then sent to Dr. Prather's lab, where Dr. Liangxue Lai and colleagues implanted it into an egg that had its DNA eliminated. The egg was stimulated to begin dividing and was later implanted into a sow. Prather and Immerge announced in January 2002 in the journal Science that they had successfully cloned the world's first single knock-out miniature swine. The genetic material from these swine was then re-engineered with the aim of knocking out the second copy of this critical gene. These cells were then subjected to another round of nuclear transfer cloning, leading to the birth of the double knock-out piglet on November 18, 2002.
In addition to the modified genetics, the Immerge miniature swine also have other important advantages as potential transplantation candidates.
"The strain of swine we are working with seems to be incapable of transmitting Porcine Endogenous Retrovirus (PERV) to human cells in culture, as we reported in March 2002 in the Journal of Virology," said Julia Greenstein, Ph.D., CEO and President, of Immerge. Unlike other viruses, which can be eliminated either through breeding or raising pigs in a clean lab environment, multiple copies of PERV form part of the normal genomic DNA of pigs and are therefore passed from one generation to the next "Although the risk of any harm posed by PERV to xenotransplant recipients may be purely theoretical, use of this line of miniature swine would help minimize this particular risk of this new technology," said Dr. Greenstein.
Contact: Susan Hayes
S. Hayes Consulting