Chickens that had their genes edited to alter protein-producing DNA received partial protection from avian influenza (bird flu), new research has shown.
Researchers at the University of Edinburgh, Imperial College London, and the Pirbright Institute (an animal disease research Centre in Surry) were able to restrict – though not completely block – the virus from infecting chickens by altering a small section of their DNA.
The birds showed no signs that the change in their DNA had any impact on their health or well-being.
The University of Edinburgh said that the findings – published this week – are “an encouraging step forward”. However, the researchers emphasised that further gene edits would be needed to produce a chicken population which cannot be infected by bird flu.
The scientists bred the chickens using gene-editing techniques to alter the section of DNA responsible for producing the protein ANP32A. During an infection, flu viruses use this protein molecule to replicate.
When the gene-edited chickens were exposed to a normal dose of the H9N2-UDL strain of avian influenza, nine out of 10 birds remained uninfected and there was no spread to other chickens.
The research team then exposed the gene-edited birds to an artificially high dose of the virus. When exposed to the higher dose, five out of 10 birds became infected.
However, even in those gene-infected birds that were infected, the amount of virus found in them was lower than the level typically seen during infection in non-gene-edited chickens.
The gene edit also helped to limit further spread of the virus to just one of four non-gene-edited chickens placed in the same incubator, while there was no transmission to other gene-edited chickens.
The virus was able to receive some level of penetration in the infected birds because it found two other proteins to assist in its replication.
For that reason, the ANP32A gene edit, on its own, does not offer enough protection for use in the production of chickens, according to the research team.
The team also carried out tests on lab-grown chicken cells to edit additional sections of DNA that produced ANP32A as well as the other two proteins the virus was using.
When this was done, growth of the virus in laboratory cell cultures was successfully blocked in cells with the three gene edits.
The next step, according to researchers, will be to try to develop chickens with edits to all three genes.
Commenting on the research, the study’s principal investigator, Prof. Mike McGrew from the University of Edinburgh, said: “Bird flu is a great threat to bird populations. Vaccination against the virus poses a number of challenges, with significant practical and cost issues associated with vaccine deployment.
“Gene-editing offers a promising route towards permanent disease resistance, which could be passed down through generations, protecting poultry and reducing the risks to humans and wild birds.
“Our work shows that stopping the spread of avian influenza in chickens will need several simultaneous genetic changes,” Prof. McGrew added.
Prof. Wendy Barclay, from Imperial College London, commented: “Although we haven’t yet got the perfect combination of gene edits to take this approach into the field, the results have told us a lot about how influenza virus functions inside the infected cell and how to slow its replication.”