A team from the University of North Carolina published a paper in Science Advances on Wednesday detailing how they had synthesised a Mers-like bat virus, and used it to infect human cells and humanised mice.
Mers is one of the deadliest viruses, killing around 35 per cent of people that it infects.
The team includes Professor Ralph Baric and Trevor Scobey who worked with Professor Shi Zhengli, of the Wuhan Institute of Virology, before the pandemic creating chimeric viruses by inserting spike proteins from bat viruses into the original Sars virus.
The new experiment used a ‘reverse genetics’ technique to recreate a Mers-like bat virus called BtCoV-422 which was collected by Shi Zhengli’s team in China in 2019.
The scientists said they had performed the latest study to test whether antivirals would work against an infection, but experts warned the experiments were needlessly risky for little gain.
‘Potentially devastating’ and ‘not justified’
Anton van der Merwe, Professor of Molecular Immunology, at Oxford University told the Telegraph: “Because coronaviruses evolve rapidly, these experiments carry the risk of generating variants which are better able to infect human cells and therefore humans.
“Human and equipment error means that infection of those performing the experiments is a risk, and the infected individual could then spread the infection outside the laboratory and initiate a pandemic.
“While the risk is relatively low, the consequences would be potentially devastating and it is not clear to me what the benefits are.
“There is no prospect of using such work to develop a vaccine or antiviral drug since these can only be tested in humans during an actual pandemic. It seems to me this experiment is simply not justified.”
Prof Baric developed the ‘reverse genetics’ technique which not only enables a virus to be brought to life from its genetic code, but allows scientists to ‘mix and match’ parts from other viruses.
In the new experiments, the team found that the virus ‘replicated efficiently’ in human airway and lung cells and caused infections in mice but that antivirals were somewhat effective.
However, experts said that the same experiments could have been carried out by inserting the spike protein of BtCoV-422 into a harmless pseudovirus.
“Pseudovirus experiments should have been the first things they did, before making this live virus,” one scientist who chose to remain anonymous said.
“They went straight to testing the live virus in human cell culture. And they performed experiments in humanised mice – which presents a higher risk of escape than just cell culture.
“If I had seen these sorts of results for pseudovirus, I would have said that it should stop there: the virus is a potential threat. Don’t proceed to using alive virus.”
Marc Lipsitch, Professor in the Department of Epidemiology at Harvard University, who has campaigned against dangerous laboratory work, also said it was unclear why they team had created a live virus.
“It is worth asking them why they created in the lab a virus that they hypothesised had the capacity to infect humans when they could have done it more safely with pseudoviruses,” he said.
“It is not clear to me why they couldn’t use pseudoviruses to answer the question, though I would be open to learning the answer.”
Experts also warned that the experiments were performed at Biosafety Level (BSL) 3 level rather than the highest BSL-4 safety level.
“Accidental releases from BSL-3 labs are unfortunately quite common,” added Prof Van der Merwe.
“Experiments on potentially pandemic organisms should only be performed if there are clear benefits to humanity and should be performed at the very highest level of containment.”
The Telegraph has approached the study authors for comment.