An experiment by Chinese scientists where a modified coronavirus killed 100% of infected mice made the headlines and stirred discussion over the necessity of such studies. But is there a reason to be concerned?
The experiment is mostly covered in tabloid media for an apparent reason — it mentions keywords like "lethal," "coronavirus," and "China," says Dr. Gytis Dudas, a senior researcher at Vilnius University Life Sciences Center.
He points out that the experiment's findings appeared on a preprint server, which publishes articles before they are accepted in scientific journals. Moreover, the findings have not been independently reviewed.
Dudas explains that the experiment uses a coronavirus isolated from pangolins, which is related to SARS-CoV-2, the virus that caused the COVID-19 pandemic. The virus, GX_P2V, was not specifically modified but propagated in the cell culture.
According to the preprint, the researchers used "humanized" mice.
"Mice were genetically modified to express a human ACE2 receptor used by coronavirus spike protein," Dudas tells Healthnews.
In the infected mice, high viral loads were detected in both lung and brain tissues, according to the preprint. The infection resulted in 100% mortality in mice, potentially attributable to late-stage brain infection.
Dudas says there can be many reasons why the virus has reached the brain. One of the possible explanations could be a specific genetic modification in mice where the coronavirus receptor is expressed by a neuron.
Why are such experiments necessary?
The preprint authors say the findings underscores a spillover risk of the virus into humans and "provides a unique model for understanding the pathogenic mechanisms of SARS-CoV-2-related viruses."
Prof. Francois Balloux, director at the University College London Genetics Institute, called the study "terrible" and "scientifically pointless."
"I can see nothing of vague interest that could be learned from force-infecting a weird breed of humanized mice with a random virus. Conversely, I could see how much stuff might go wrong," he wrote on X.
I had a look at the preprint. It's a terrible study, scientifically totally pointless. I can see nothing of vague interest that could be learned from force-infecting a weird breed of humanised mice with a random virus. Conversely, I could see how such stuff might go wrong ...undefined Prof Francois Balloux (@BallouxFrancois) January 10, 2024
Dudas says that when viruses are propagated in the cell culture, they can gain certain mutations useful for viruses in a certain environment.
"Without experiments like this, we would not know if one or another virus found in the environment could pose a danger. They are necessary if we want to be ready for viruses jumping to humans or animals that are economically beneficial to us," he says.
However, there is always a question of safety. Experiments that require infecting animals involve the risk of transmitting the virus to other animals or jumping to humans.
"Every institution has to make sure that risky experiments are carried out taking all the necessary precautions," Dudas adds.
The study comes as scientists and governments worldwide are still trying to figure out the origin of SARS-CoV-2, a virus that caused the COVID-19 pandemic.
One of the theories is that the virus leaked from the laboratory at the Wuhan Institute of Virology (WIV) in China, which conducted extensive research on coronaviruses before the pandemic.
U.S. intelligence agencies, however, did not find direct evidence that the institute's scientists worked on SARS-CoV-2 or viruses close to it, according to a report declassified in 2023.
Modifying viruses in the lab is a sensitive issue. Last year, Boston University scientists went under fire for creating a synthetic form of the SARS-CoV-2 virus, which killed 80% of lab mice. Meanwhile, the then-dominant Omicron variant caused only non-lethal disease.
The study sparked discussions about regulations of gain-of-function research, which refers to altering organisms to enhance their biological functions, such as making viruses more dangerous or contagious.
The spillover from animals remains the most likely cause of the COVID-19 pandemic. Scientists believe that the SARS-CoV-2 virus made a leap from animals to humans in the Huanan Seafood Wholesale Market in Wuhan.
- bioRxiv. Lethal Infection of Human ACE2-Transgenic Mice Caused by SARS-CoV-2-related Pangolin Coronavirus GX_P2V(short_3UTR).
- Office of the Director of National Intelligence. Potential Links Between the Wuhan Institute of Virology and the Origin of the COVID pandemic.