Porcine endogenous retroviruses are embedded in the pig genome but research has shown they can infect human cells. Now, US scientists have successfully removed it.
Growing human transplant organs in pigs has become a more realistic prospect after scientists used advanced gene editing to remove threatening viruses from the animals' DNA.

Porcine endogenous retroviruses are permanently embedded in the pig genome but research has shown they can infect human cells, posing a potential hazard.

The existence of the virus has been a major stumbling block preventing the development of genetically engineered pigs to provide kidneys and other organs for transplant into human patients.

That hurdle may now have been cleared away, according to new research reported in the journal Science.

Researchers at Harvard University and a private company used the precision gene editing tool Crispr-Cas9 combined with gene repair technology to deactivate 100 percent of the virus in a line of pig cells.

Piglets cloned from the fibroblast (connective tissue) cells turned out to be virus-free.

Dr Luhan Yang, co-founder and chief scientific officer at the biotech company eGenesis, said: 'This is the first publication to report on virus-free pig production.

'We generated a protocol to enable multiplex genome editing, eradicated all Perv activity using Crispr technology in cloneable primary porcine fibroblasts and successfully produced virus-free piglets.

'This research represents an important advance in addressing safety concerns about cross-species viral transmission.

'Our team will further engineer the virus-free pig strain to deliver safe and effective xenotransplantation.'