One day these little piggies could give you more than just bacon Luhan Yang/Egenesis

Organ transplants from pigs are a step closer, after the birth of piglets that have had harmful viruses in their DNA inactivated using CRISPR gene editing.

Many people with failing hearts, livers and kidneys are saved by donated organs from people who have died (or even some who are still living, in the case of kidneys), but there are not enough to go round. More than 1000 people die every year for lack of an organ in the UK.

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As pigs are similar to us in size and anatomy, there is hope that we can use their organs instead – an idea known as xenotransplantation. One problem with this idea is that pigs can harbour microbes such as hepatitis E virus – but these could be eliminated with medicines or vaccines. However, pigs also have many viruses embedded in their DNA, passed down the generations in sperm and eggs.


When pig cells are grown in a dish along with human cells, these viruses – known as porcine endogenous retroviruses or PERVs – have crossed into the human cells, suggesting they would do the same if pig organs were put into people. If this happened, it may cause diseases like cancer.

Edited clones

Luhan Yang of Boston biotech firm eGenesis and colleagues have previously shown they could use the highly efficient gene-editing technique CRISPR to disable the PERVs in pig cells grown in a dish. Now they have taken the genetic material from such cells and, using a similar technique to the one used to clone Dolly the sheep, inserted it into pig eggs.

They then implanted these into surrogate mother sows, which went on to give birth to pig clones – the first to be free of PERVs. “This is a great step forward for xenotransplantation,” says Joachim Denner of the Robert Koch Institute in Germany.

So far, 37 such piglets have been born. Of those, 15 are still alive, and the oldest is four months. It’s too early to say if this group has a higher death rate than normal, because piglets often die from infections, says collaborator George Church of Harvard University.

The team plans to make pigs that are altered to a greater extent, to make them more immunologically similar to people. In theory, this should make transplanted organs less prone to attack by a recipient’s immune system. Another team has previously altered pigs so their cells lack a certain sugar molecule on their surface that provokes immune rejection.

Robin Weiss of University College London, who first discovered PERVs, says there are other viruses in the pig genome that could theoretically jump across to people, so although the risk of cancer or other problems has been reduced, it has not been completely eliminated.

Journal reference: Science, DOI: 10.1126/science.aan4187

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