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 (Pervs) are permanently embedded in the pig genome but research has shown they can infect human cells, posing a potential hazard.
The existence of Pervs 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 in the US used the precision gene editing tool Crispr-Cas9 combined with gene repair technology to deactivate 100 per cent of Pervs in a line of pig cells.
Piglets cloned from the fibroblast (connective tissue) cells turned out to be Perv-free.
"This is the first publication to report on Perv-free pig production," Dr Luhan Yang, chief scientific officer at biotech company eGenesis, said:
"We generated a protocol to enable multiplex genome editing, eradicated all Perv activity using Crispr technology in cloneable primary porcine fibroblasts and successfully produced Perv-free piglets.
"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."
Tests previously demonstrated that pig cells could infect human cells with Pervs in the laboratory. The viruses could then be transmitted to other cells not exposed to pig tissue.
Whether or not Pervs would actually cause diseases in humans is unknown, but they are considered an unacceptable risk.
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