Chinese scientists create gene-edited pigs with immunity to Aids-like virus

Researchers say technique can be used to engineer hogs with other desirable qualities, such as leaner meat and suitability as organ donors for humans
Their method can modify two traits in one generation, saving time and money during the breeding process

Science

Zhang Tongin Beijing

Published: 9:39pm, 19 Oct, 2022

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Researchers in China say they have created a group of gene-edited pigs that are immune to a porcine viral disease that causes Aids-like symptoms.

The technique could be applied to promote other desirable traits in the animals, such as leaner meat and suitability as organ donors for humans, according to the team led by Hua Jinlian at Northwest A&F University and Wei Hongjiang of Yunnan Agricultural University.

The process combines gene editing and embryo engineering and provides a safe and effective strategy for genetic modification in domesticated animals, they wrote in the peer-reviewed journal Zoological Research earlier this month.

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Blue ear disease is caused by the porcine reproductive and respiratory syndrome virus (PRRSV). The disease can suppress the immune system and cause organ damage, leading to reproductive disorders in sows, high mortality among piglets and respiratory diseases in adult pigs.

The disease is widespread and considered one of the most expensive diseases affecting pig farming. According to some estimates, about 75 per cent of herds in the US and 80 per cent in China carry the virus. Once infected, pigs have the virus for life.

Hua and Wei found a new way to prevent infection at the root. Their team found the gene fragment that binds with the virus. Then they used an enzyme to cut out the corresponding spot in the DNA of pig embryos, resulting in piglets with immunity to the virus.

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But finding the right gene fragment to target was no easy task, and the team first started working on the problem in 2015, according to Hua. The scientists have been researching embryo engineering since the 1980s.

“There are about three billion base pairs on the genome. First, we need to know exactly where the site is located on the gene pair, and then we use a specific tool – that is, an enzyme – to modify the gene at a specific point,” Hua said in an interview on Tuesday.

The team also cut out genes that inhibit muscle growth to produce pigs with leaner meat.

To modify a second trait, researchers must typically wait for the first generation of gene-edited pigs to grow up and reproduce, which takes more than a year, then perform a second round of experiments on their offspring.

But Hua’s team developed a synchronous gene-editing method that can make two modifications in one edit, saving time and money.

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The success rate is not 100 per cent. The process is affected by multiple factors, including the quality of the embryos and their ability to survive in surrogate sows. According to the paper, only one of three sows involved in the experiments successfully gave birth, resulting in two piglets.

“This research requires support from upstream gene editing, midstream embryo engineering and the downstream pig-breeding industry,” Hua said. “Currently, this technology is at an advanced level globally in terms of efficiency and cost.”

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China is the world’s largest pork consumer, consuming about 700 million pigs each year. The team’s research could lead to further developments in breeding domesticated pigs with multiple genetic modifications at lower cost.

“The next step is to further evaluate the resistance to the PRRS virus and to see whether this trait can be stably inherited,” Hua said.

“When the technology is fully developed, researchers can implement other modifications, such as improving pig metabolism to eliminate or reduce the smell of faeces, producing smaller pet pigs and creating suitable organ transplant donors,” he added.

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