US researchers have developed a new deadly strain of Covid in a lab — following experiments many fear may have started the pandemic.
The mutant variant — a hybrid of Omicron and the original Wuhan virus — killed 80 percent of the mice infected with it at Boston University.
However, when a similar group of rodents were exposed to the standard Omicron strain, they all survived and experienced only “mild” symptoms.
The scientists also infected human cells with the hybrid variant and found that it was five times more infectious than Omicron.
This suggests that the man-made virus may be the most contagious form yet.
In the new research, a team of scientists from Boston and Florida extracted Omicron’s spike protein — the unique structure that binds to and penetrates human cells.
They confirmed the peak of Omicron to the original wild-type strain that first showed up in Wuhan at the start of the pandemic.
In the paper, they wrote, “In… mice, Omicron causes a mild, non-fatal infection, while the Omicron S-carrying virus causes severe disease with an 80 percent mortality rate.”
The researchers said it indicated that while the spike protein is responsible for infectivity, changes in other parts of the structure determine its lethality.
The scientists also looked at the effect of the different strains on human lung cells grown in the lab.
Covid clings to human cells with its spike protein, instructing healthy cells to make copies of themselves.
Scientists measured how many copies each variant caused the health cells to produce.
They found that the hybrid strain produced five times more viral particles than the original Omicron.
The scientists admit that the hybrid virus is unlikely to be as deadly in real humans as it is in mice.
They noted that one limitation of their research was the specific breed of mice used, as other types of mice are more similar to humans.
Mice and humans also do not have identical immune responses, as there are variations in DNA and genes between species.
For example, the genes that regulate the immune system behave differently and the response to stress in mice and humans is different.
The type of mice used in the study were specifically designed to look at severe Covid infection, but currently no mouse model replicates all aspects of Covid in humans.
The Boston University National Emerging Infectious Diseases Laboratories lab is one of 13 biosafety level 4 labs in the US.
These are laboratories authorized to treat the most dangerous pathogens. There are also facilities in Texas, Atlanta and Manhattan, Kansas.
Experiments in these labs often tinker with animal viruses to advance treatments and vaccines that can be used in a future outbreak.
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