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Gene-edited pigs show signs of resistance to major viral disease

Published on 24 February 2017

Scientists have used advanced genetic techniques to produce pigs that are potentially resilient to Porcine Reproductive and Respiratory Syndrome (PRRS).

Early tests have revealed that cells from the pigs are completely resistant to infection with two major subtypes of the virus that cause the disease. The animals are otherwise healthy and the change – introduced using gene-editing technology – should not affect their ability to fight off other infections, the researchers say.

PRRS causes severe breathing problems in young pigs and breeding failures in pregnant females. The disease costs the swine industry billions each year.

Previous studies have shown that the PRRS virus targets immune cells called macrophages. A molecule on the surface of these cells called CD163 plays a key role in enabling the PRRS virus to establish an infection.

In collaboration with Genus, scientists at The Roslin Institute used a gene-editing tool called CRISPR/Cas9 to cut out a small section of the CD163 gene in the pigs’ DNA that interacts with the PRRS virus. Studies in cells show that this modification prevents the virus from causing infection.

PRRS is endemic in most pig producing countries. Vaccines have mostly failed to stop the spread of the virus, which continues to evolve rapidly. Consequently, it is one of the greatest challenges facing pig producers today. In Europe alone, the disease is estimated to cost the pig industry more than €1.5 billion each year.

Lead researcher Professor Alan Archibald, of The Roslin Institute, 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. Our results take us closer to realising these benefits and specifically address the most important infectious disease problem for the pig industry worldwide.”

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.  This, and other gene edits, will be evaluated as Genus advances the development of gene editing to confer PRRSv resistance.  Genus is committed to pioneering the responsible application of technology to animal genetic improvement to enhance the well-being of animals, the livelihoods of farmers, and the sustainable approach to producing food for a growing global population.”

Professor Bruce Whitelaw, Interim Director of The Roslin Institute said: "This project which was funded by both the BBSRC and industry is an elegant demonstration of how precise genome editing can be. We have deleted a single exon from the CD163 gene. The opportunity to use this technology to improve animal health and productivity presents an exciting approach to address the food security and one health challenges."

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

Scientists from The Pirbright Institute also contributed to the research.

For further information, please contact:

Jen Middleton, Media & PR Manager, University of Edinburgh
Tel +44 (0)131 650 6514, email Jen.Middleton@ed.ac.uk

Charles Ryland/Vicky Hayns, Public Relations for Genus

Tel +44 (0)207 466 5000