Pigs have always been eyed as potential vessels for organ cultivation, as the size and structure of their organs makes them the most viable - theoretically - for transplantation to humans. The organs are almost the same size and function similarly enough to human organs that scientists think it could work.
But the prospect also raises thorny questions about animal exploitation and welfare.
The pigs are going to save us. The animals would be would be anesthetized and killed humanely. In theory, this should make transplanted organs less prone to attack by a recipient's immune system.
In 2014 Margaret Mann, a retired carer from West Sussex, became the first patient in the world to have a heart valve made of pig tissue.
Is thought the breakthrough could meet resistance with religious groups as some leaders in Muslim and Jewish communities do not support the use of pig kidneys for transplants in humans. These viruses are able to jump from a pig cell to a human when mixed in the lab. The concern about PERVs has been hard to dismiss, however, especially because studies have shown that the viruses can infect human cells in a dish.
There are several obvious problems scientists must overcome before successfully being able to transplant pig organs into humans.
Ian McConnell from the University of Cambridge said, "This work provides a promising first step in the development of genetic strategies for creating strains of pigs where the risk of transmission of retroviruses has been eliminated".
"The field is inherently sort of risky to begin with, and I think a lot of patients have already processed that", he says.
By using the same technology used to create Dolly the sheep, the new genetic information could be placed into a pig's egg to form embryos. To make PERV-free pigs, they needed to start with genetically normal cells straight from a living pig. Of those, 15 are still alive, and the oldest is four months. None has the retroviruses.
The company also is working on something called "Pig 2.0", an animal with "advanced immune compatibility".