Scientists make gene-edited chickens in bid to halt next pandemic
Scientists who created Dolly the sheep reveal plans for gene-edited ‘superchickens’ resistant to flu in bid to halt human pandemic
- Roslin Institute scientists gained fame in 1996 as creators of ‘Dolly the sheep’
- Now developing gene-edited chickens designed to be totally resistant to flu
- First of the transgenic chicks will be hatched later this year
British scientists are developing gene-edited chickens designed to be totally resistant to flu in a new approach to trying to stop the next deadly human pandemic.
The first of the transgenic chicks will be hatched later this year at the Roslin Institute at the University of Edinburgh in Scotland, said Wendy Barclay, a professor of virology at Imperial College London who is co-leading the project.
The birds’ DNA has been altered using a new gene editing technology known as CRISPR.
The gene-edited chickens are designed to be totally resistant to flu in a new approach to trying to stop the next deadly human pandemic
In this case the ‘edits’ are to remove parts of a protein on which the flu virus normally depends, making the chickens totally flu-resistant.
The idea is to generate poultry that cannot get flu and would form a ‘buffer between wild birds and humans’, Barclay said.
Global health and infectious disease specialists cite the threat of a human flu pandemic as one of their biggest concerns.
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THE 1918 FLU OUTBREAK – THE WORLD THE WORLD HAS EVER SEEN
The deadly flu virus attacked more than one-third of the world’s population, and within months had killed more than 50 million people – three times as many as the World War I – and did it more quickly than any other illness in recorded history.
Most influenza outbreaks disproportionately kill juvenile, elderly, or already weakened patients; in contrast the 1918 pandemic predominantly killed previously healthy young adults.
Red Cross volunteers fighting against the Spanish flu epidemic in United States in 1918
To maintain morale, wartime censors minimized early reports of illness and mortality in Germany, Britain, France, and the United States.
However, newspapers were free to report the epidemic’s effects in Spain, creating a false impression of Spain as being especially hard hit – and leading to the pandemic’s nickname Spanish flu.
The close quarters and massive troop movements of World War I hastened the pandemic and probably both increased transmission and augmented mutation, researchers believe.
The global mortality rate from the 1918/1919 pandemic is not known, but an estimated 10% to 20% of those who were infected died, with estimates of the total number of deaths ranging from 50-100 million people.
The death toll in the last flu pandemic in 2009/10 – caused by the H1N1 strain and considered to be relatively mild – was around half a million people worldwide.
The historic 1918 Spanish flu killed around 50 million people.
The greatest fear now is that a deadly strain could jump from wild birds via poultry into humans, and then mutate into a pandemic airborne form that can pass easily between people.
Recently hatched chicks sit in a crate at the Huayu hatchery in Handan, Hebei province, China. The first of the transgenic chicks will be hatched later this year at the Roslin Institute at the University of Edinburgh in Scotland
‘If we could prevent influenza virus crossing from wild birds into chickens, we would stop the next pandemic at source,’ said Barclay.
In research published in 2016 in the journal Nature, Barclay’s team found that a gene present in chickens called ANP32 encodes a protein that all flu viruses depend on to infect a host.
Laboratory tests of cells engineered to lack the gene showed they cannot be infected with flu.
WHAT IS CRISPR-CAS9?
CRISPR-Cas9 is a tool for making precise edits in DNA, discovered in bacteria.
The acronym stands for ‘Clustered Regularly Inter-Spaced Palindromic Repeats’.
The technique involves a DNA cutting enzyme and a small tag which tells the enzyme where to cut.
The CRISPR/Cas9 technique uses tags which identify the location of the mutation, and an enzyme, which acts as tiny scissors, to cut DNA in a precise place, allowing small portions of a gene to be removed
By editing this tag, scientists are able to target the enzyme to specific regions of DNA and make precise cuts, wherever they like.
It has been used to ‘silence’ genes – effectively switching them off.
When cellular machinery repairs the DNA break, it removes a small snip of DNA.
In this way, researchers can precisely turn off specific genes in the genome.
The approach has been used previously to edit the HBB gene responsible for a condition called β-thalassaemia.
Teaming up scientists at the Roslin, Barclay said the plan is to use CRISPR to edit the chicks’ DNA so that only one part of the key protein is changed, leaving the rest of the bird exactly the same, genetically, as it was before.
‘We have identified the smallest change that will stop the virus in its tracks,’ she said.
Roslin Institute scientists gained fame in 1996 as creators of ‘Dolly the sheep’, the world’s first cloned animal.
They have also created gene-edited pigs to make them resistant to a virus.
Barclay said one of the biggest hurdles to this approach would be poultry producers’ concerns about public acceptance.
‘People eat food from farmed animals that have been altered by decades of traditional breeding,’ she said.
‘But they might be nervous about eating gene edited food.’
HOW WAS DOLLY THE SHEEP CREATED?
Dolly was the only surviving lamb from 277 cloning attempts and was created from a mammary cell taken from a six-year-old Finn Dorset sheep.
She was created in 1996 at a laboratory in Edinburgh using a technique called somatic cell nuclear transfer (SCNT).
The pioneering technique involved transferring the nucleus of an adult cell into an unfertilised egg cell whose own nucleus had been removed.
Dolly the sheep made history 20 years ago after being cloned at the Roslin Institute in Edinburgh. Pictured is Dolly in 2002
An electric shock stimulated the hybrid cell to begin dividing and generate an embryo, which was then implanted into the womb of a surrogate mother.
Dolly was the first successfully produced clone from a cell taken from an adult mammal.
Dolly’s creation showed that genes in the nucleus of a mature cell are still able to revert back to an embryonic totipotent state – meaning the cell can divide to produce all of the difference cells in an animal.
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