CRISPR genome editing has been used to make chickens immune to a common virus. The approach could boost meat and egg production globally while improving welfare.
The modified chickens exhibited no signs of disease even when exposed to high dosages of the avian leukosis virus (ALV). The virus is a challenge for poultry farmers around the world, says Jiri Hejnar at the Czech Academy of Sciences.
Infected birds become sick, withered and depressed, and frequently develop tumours. The virus gets into cells by attaching to a protein called chicken NHE-1 (chNHE-1). Hejnar’s team has earlier shown that removing three DNA letters from the chNHE-1 gene that makes this protein stops ALV from infecting chicken cells.
The challenge was to make this alteration in entire animals rather than only in a few cells. No breeds of chickens naturally have this mutation, so it can’t be done by breeding only. But genetically altering chickens is more difficult than altering other animals such as pigs.
The traditional method is to extract so-called primordial germ cells, modify them outside the body and then insert the modified cells to embryos inside newly laid eggs. This approach was used to make CRISPR chickens in 2016, but the success rate is very low.
In 2017, Hejnar developed a better technique: using changed germ cells to reinstate semen production in sterilized cockerels. His team then went on to make a cockerel with sperm that have the exact deletion in the chNHE-1 gene.
By crossing its offspring, they have reproduced a flock of white leghorn chickens that have this removal in both copies of the gene.
A company called Biopharm is now in talk with poultry producers in China and Vietnam about bringing this change into commercial breeds. “It’s fairly simple to do,” says Hejnar.
Hejnar also intends to use CRISPR to make chickens immune to other viruses, such as bird flu. This would make us all securer: bird flu viruses sometimes kill people and there are worries a mutant breed could cause a lethal global pandemic.
Though, there is still resistance to GM foods in many countries. It is yet to be seen whether consumers will find CRISPR chickens to their taste.