Researchers have demonstrated that gene editing could someday be used to make chickens resistant to the avian flu—a contagious virus that led to the deaths of 131 million domestic poultry in 2022, either due to infection or culling to stop the spread.
In a new study, published Tuesday in the journal Nature Communications, researchers used the gene editing technology CRISPR/Cas9 to tweak a protein that avian flu relies on to infect chickens. When exposed to the flu virus, the gene-edited birds became infected at a much lower rate than standard chickens did—and they seemed to be less contagious.
“What this shows is that there’s a proof of concept that we can use to move toward making chickens resistant to the virus. But we’re not there yet,” Wendy Barclay, a co-author of the study and virologist at Imperial College London, said at a press conference, per MIT Technology Review’s Abdullahi Tsanni.
Still, the study is a “breakthrough,” as James Wood, an infectious disease specialist at the University of Cambridge in England who did not contribute to the findings, tells the Financial Times’ Donato Paolo Mancini.
Over the last couple of years, a strain of avian flu has spread across the world, leading to a large number of deaths of both wild birds and poultry, according to the World Health Organization (WHO). Last year, more than 52 million birds in the United States died because of avian flu outbreaks. In Peru, 200,000 wild birds died from infection, including more than 40 percent of the country’s pelicans, as the Guardian’s Phoebe Weston wrote in July. Recently, South Africa culled 7.5 million chickens to stop the spread of the virus.
In another attempt to control the outbreak, some countries, including China, Mexico, France and Ecuador, have vaccinated poultry against bird flu, writes New Scientist’s Carissa Wong. But vaccines are expensive, and the virus can quickly evolve to evade them, as Mike McGrew, a co-author of the new study and a developmental biologist at the University of Edinburgh in Scotland, said at a press conference, per Science News’ Erin Garcia de Jesús.
So, in the new study, researchers turned to gene editing. The avian flu virus replicates using a protein called ANP32A in chicken cells. To stop the protein and virus from interacting, the researchers used CRISPR to edit the genes that code for ANP32A in sperm and egg cells of chickens. The researchers injected these edited cells into chicken embryos, which later hatched, grew up, mated and produced offspring that inherited the edited gene, writes Stat News’ Andrew Joseph.
The researchers exposed ten of these edited chickens to the virus, using a normal-sized dose of a bird flu strain that causes relatively mild illness, per New Scientist. Nine of the ten birds resisted infection, and the one chicken that did get sick did not spread the virus to any others. A control group of unedited chickens all became infected when they were exposed to the same dose, and they also spread the illness to some other chickens, per Science News.
But in a second experiment with a much higher dose of the virus—1,000 times more than the first—half of the gene-edited birds became infected and spread the virus to one of four unedited chickens placed in the same incubator, writes MIT Technology Review. They did not pass it to any of the edited chickens that were exposed to them.
Though the virus was unable to interact with ANP32A, it may have infected the gene-edited chickens by using two similar proteins, per New Scientist. Next, the researchers are experimenting with editing genes for these three proteins at the same time in hopes of creating an even more resilient chicken, per Stat News.
So far, the gene editing did not seem to affect the health of the chickens. But the team will need to figure whether making changes to all three of the proteins would cause problems with chicken development. Researchers think the proteins might be involved in developing chicks’ brains, hearts and bones, writes Science News.
The paper shows that editing ANP32A alone isn’t enough to stop the spread of the virus, Alison Van Eenennaam, an animal geneticist at the University of California, Davis, who did not contribute to the findings, tells MIT Technology Review.
“This is a great piece of work showing there might be ways to do it, but it requires much more research,” Benjamin Schusser, who studies chicken immune systems at the Technical University of Munich and was not involved in the study, tells Stat News.