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Pig cells made resistant against PRRS

A team from mostly UK scientists has produced pigs that may be protected from Porcine Reproductive and Respiratory Syndrome (PRRS).

The team, made up of researchers from the University of Edinburgh’s The Roslin Insitute and England-based The Pirbright Institute, was complemented by staff from breeder Genus in the USA. They used advanced genetic techniques to produce pigs that are potentially resilient to PRRS.

Completely resistant to PRRS

A news release shared by the University of Edinburgh explained that early tests have revealed that cells from the pigs are completely resistant to infection with both major subtypes of the virus that causes the disease. The team reported their findings in an article that was published in PLOS Pathogens.

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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.

PRRS virus targets macrophages

The news article explained that PRRSv targets immune cells or macrophages. A molecule on the surface of these cells called CD163 plays a key role in enabling the PRRS virus to establish an infection.

The research team used a gene-editing tool called CRISPR/Cas9 to cut out a small section of the CD163 gene in the pigs’ DNA code. Laboratory tests of cells from the pigs with the modified CD163 gene have confirmed that this change in the pig’s DNA blocks the virus from being able to cause infection.

Next stage: Does it work in pigs?

The next stage in the study will be to test whether the pigs are resistant to infection when exposed to the virus. Previous studies by another team have produced pigs that lack the entire CD163 molecule, and which do not become ill when exposed to the PRRS virus.

A close-up of a DNA strain. Photo: Yang Nan | Dreamstime
A close-up of a DNA strain. Photo: Yang Nan | Dreamstime

In the latest study, only the section of CD163 that interacts with the PRRS virus is removed and the molecule appears to retain its other functions.

Genome-editing offers opportunities

Lead researcher, professor Alan Archibald, The Roslin Institute, was quoted in the news article, saying: “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.”

Targeted removal of viral interacting domain

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.”

The study in PLOS Pathogens was authored by Christine Burkard, Simon G. Lillico, Tahar Ait-Ali, C. Bruce A. Whitelaw and Alan L. Archibald, University of Edinburgh, Scotland, UK; Elizabeth Reid and Ben Jackson, The Pirbright Institute, UK; Alan J. Mileham, Genus, DeForest, WI, USA.

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