Scientists strike a blow against costly porcine disease

RESEARCH: Results address endemic and costly disease problem for pig industry

A team of Edinburgh-based scientists have produced a new breed of ‘super pig’ that has shown resistance to a highly infectious and endemic respiratory swine disease.

The research group from Edinburgh University’s Roslin Institute has been working to target Porcine Reproductive and Respiratory Syndrome (PRRS), which costs the pig industry across Europe upwards of €1.5 billion every year.

Vaccines have, to date, mostly failed to stop the spread of the disease, which causes fetal mortality in pregnant sows and severe breathing problems in young pigs. So instead, the scientists turned to gene-editing techniques that effectively carve away a small section of DNA from the eggs of female pigs.

This prevents the PRRS virus from being able to establish an infection within piglets’ immune cells.

The animals are otherwise healthy and the change should not affect their ability to fight off other infections, the university said.

“Genome-editing offers opportunities to boost food security by reducing waste and losses from infectious diseases, as well as improving animal welfare by reducing the burden of disease,” said lead researcher Professor Alan Archibald, of the Roslin Institute.

“Our results take us closer to realising these benefits and specifically address the most important infectious disease problem for the pig industry worldwide.”

Seeking to allay consumer fears over GM modifications, he stressed the pigs’ DNA has not been supplemented in any way and instead the project simply aimed to close a doorway to animal disease.

“We haven’t added anything that wasn’t there in the first place, so consumers have nothing to worry about in that sense,” said Professor Archibald.

To breed these animals, the Roslin team used CRISPR/Cas9, a carefully targeted enzyme which cuts strands of DNA, to disable a gene called CD163.

This gene is thought to play a key role in allowing the PRRS virus to target pig immune cells.

The study, published in the journal Plos Pathogens, was funded by the Biotechnology and Biological Sciences Research (BBSRC) Animal Health Research Club and Genus.

Jonathan Lightner, chief scientific officer for Genus, said: “This result furthers the case for the criticality of CD163 in PRRSv infection and demonstrates that a targeted removal of the viral interacting domain can confer resistance while the reminder of the protein is present.”

Responding to the study, Ian Jones, professor of virology at Reading University, said: “The authors have removed part of the virus receptor, the cellular doorway the virus uses to initiate infection.

“If the virus can’t get in then disease is prevented.

“The drawbacks of this approach are that all commercial stock would have to be bred to include this mutation, which takes time and public acceptance, and there is always the worry that the PRRS virus would mutate to use a different receptor and so gain access by a ‘back door’.”

Porcine Reproductive and Respiratory Syndrome costs the pig industry across Europe upwards of €1.5 billion every year.