Although the genetically modified chickens were resistant to a small amount of the virus, they were still unable to withstand a high dose.
Bird flu is a persistent disease that affects the entire world – from Asia to Europe, Africa and the Americas. It poses a danger to both poultry and wild bird species. And it also poses risks to people’s health. So far, vaccination of poultry has not proven successful, mainly due to the rapidly changing characteristics of the virus. Despite these challenges, vaccination is likely to be an important tool in the fight against bird flu. And so researchers are joining in a new study once again do everything we can to eradicate this worrying viral disease.
More about bird flu
Bird flu is a contagious disease that affects poultry (such as chickens or turkeys) and other wild bird species (such as ducks, pigeons and swans). Bird flu can be caused by many different flu viruses (virus types). In extremely rare cases, some virus types can jump from animals to humans. This only happens with direct and intensive contact between infected birds and people. People who become ill with bird flu experience the same symptoms as with normal winter flu: fever, headache, muscle pain, cough or eye inflammation (conjunctivitis). The disease is usually mild. However, in Asia there are also different types of bird flu viruses that can cause serious complaints. There is therefore an urgent need to take measures to control the spread of the disease.
In the study, the researchers modified a small part of the DNA of chickens to make them resistant in this way. The researchers hope this can reduce the spread of bird flu on poultry farms and at the same time protect people against the virus.
ANP32A-gen
Specifically, the scientists modified the part of the DNA responsible for the production of the protein ANP32A. During an infection, flu viruses use this protein to replicate themselves. The researchers have modified the ANP32A gene in the precursors of reproductive cells to reduce the effect of the flu virus.
Resistant
The results are promising. When the genetically modified chickens were exposed to a regular dose of the H9N2 strain of bird flu, nine out of ten chickens remained healthy and no other chickens became infected. In addition, the genetic adjustments had no negative effects on the health of the chickens, which also laid eggs as usual during the two-year study period. In short, the birds showed no signs that the change in their DNA had any impact on their health or well-being.
Footnote
Despite these encouraging findings, the researchers have a major caveat. The team also exposed the genetically modified chickens to a very high dose of the bird flu virus to see how well they could cope. Unfortunately, that did not go as hoped. For example, the genetically modified chickens turned out to be unable to withstand a dose that was 1,000 times higher. In this case, five out of ten chickens still became infected. The genetic modification did offer some protection, as the gene-edited infected chickens had less virus in their bodies than is normally the case with ‘normal’ chickens. But it is not yet a complete success story. Although the researchers were successful in limiting the virus, they were unable to block it completely.
Statement
Why does the bird flu virus still appear to outsmart the researchers? The team found that in the chickens with the modified ANP32A genes, the virus had changed and now worked with two other similar proteins, ANP32B and ANP32E, to replicate. The next step is to try to create chickens with genetic adjustments to all three genes.
Not enough
With the study, researchers are taking an important step in the fight against bird flu. But we’re not there yet. “The research is encouraging,” said Raina MacIntyre, an expert on influenza and emerging infectious diseases who was not involved in the study. “But editing just the ANP32A gene proved insufficient, as the virus was still able to enter host cells with the help of other members of the ANP32 protein family. However, if we can make chickens genetically resistant to bird flu viruses, this could help reduce the risk of a dangerous virus developing from bird flu. But we must remember that bird flu is not only spread by the chicken trade, but also by wild waterfowl such as ducks and geese. These birds can spread bird flu as they move between countries and continents, without coming into contact with domestic chickens. That is why simply genetically modifying chickens is not enough.”
Mutations
Another concern is that flu viruses are extremely changeable and constantly adapt their characteristics. “This means the virus will likely evolve to avoid the genetic changes in the chickens,” MacIntyre said. Furthermore, for any genetic modification, it is critical to ensure that no unintended changes to DNA occur elsewhere. “Genes usually play a role in more than one function in the body,” explains professor Dimitri Perrin, affiliated with the Queensland University of Technology, out. “A genetic modification can have the desired effect on one specific function, but have undesirable effects on other aspects. In this study it is positive that no differences were found in growth, appearance, behavior or response to vaccination, but further research is needed.”
Despite this, the study shows that it is possible to make chickens at least partially resistant to bird flu. It means that genetic editing may be an effective way to protect chickens from bird flu. The results therefore offer a possible approach to reduce the spread of this nasty disease from wild birds to domestic poultry. Further changes to the DNA could potentially make the chickens completely immune, although the team emphasizes that more thorough research is needed to ensure that this does not have negative consequences for the health of the animals. “Unfortunately, we don’t yet have the right mix of genetic adaptations,” says co-author Wendy Barclay. “But the results have taught us a lot about how the flu virus behaves in infected cells and how we can slow down its replication.”
2023-10-11 09:02:40
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