Gene-edited pigs resistant to major viral disease

March 02, 2017

Using advanced genetic techniques, a team of researchers from the University of Edinburgh have produced pigs that are potentially resilient to Porcine Reproductive and Respiratory Syndrome (PRRS) — an infection that costs the swine industry billions of dollars each year.

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

In this study, the research team used the gene-editing tool known as 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.

Recent tests have also revealed that cells from the pigs are completely resistant to both major subtypes of the virus that cause PRRS infection and show that the animals are otherwise healthy. The researchers also believe this change should not affect their ability to fight off other infections.

"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,” lead researcher Alan Archibald said in an article. “Our results take us closer to realizing these benefits and specifically address the most important infectious disease problem for the pig industry worldwide."

Previous studies by another research team have produced pigs that lack the entire CD163 molecule, and do not become ill when exposed to the PRRS virus. In this study, however, only the section of CD163 that interacts with the PRRS virus was removed and the molecule appears to retain its other functions.

PRRS causes severe breathing problems in young pigs and breeding failures in pregnant females. It is an endemic in most pig producing countries worldwide as 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.

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