Scientists have for the first time eliminated a dangerous type of virus found in live pigs that could make it safe for potential organ transplants into humans. The virus was inactivated thanks to the CRISPR gene editing technique.

The pig genome contains porcine endogenous retroviruses, or PERVs (yeah, I know). These viruses can be passed on to humans during a transplant, which has been the main obstacle in using animals to grow organs for us. Pig cells in the lab had already been freed of PERVs but this is the first time it has been shown in living animals.

The groundbreaking results were reported in Science. Thirty-seven genetically engineered piglets have so far been born, 15 of which are still alive. The oldest is now four months. It is unfortunately too early to tell if the CRISPR piglets have a higher mortality rate as piglets often die very young due to infections.

The possibility of using animals to grow organs for humans could have a dramatic impact on the lives of millions of people worldwide. At the time of writing, 117,000 people in the United States are on a waiting list for an organ, with 22 people dying each day waiting for a transplant.

Pigs have long been thought to be excellent candidates for transplants due to similar sizes between their organs and ours. This process, xenotransplantation, has risks due to viruses. Some could be treated with medicines or vaccines but some like the PERVs are embedded directly into the DNA of pigs. There’s no way around that without gene editing.

The team discovered 25 locations in the pig’s fibroblast cells genome that led to the activation of PERVs. To inactivate these locations, they used CRISPR, a revolutionary gene editing technique that allows researchers to slice bits of DNA with great precision. This approach led to having cells that were 90 percent free of PERVs, and by adding additional substances related to DNA repair they reached the amazing 100 percent free goal.

"This is the first publication to report on PERV-free pig production," said Dr Luhan Yang, co-founder and chief scientific officer at eGenesis, who developed the piglets, in a statement. "This research represents an important advance in addressing safety concerns about cross-species viral transmission. Our team will further engineer the PERV-free pig strain to deliver safe and effective xenotransplantation."

The team is now looking to further alter pig genomes to guarantee that the potential transplant organs are absolutely safe and effective for human transplant.