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Less lung damage appears to be caused by the new Omicron hypermetastatic mutation compared to previous mutations show research conducted in laboratory animals.
Researchers, in a series of studies, are trying to explain why Omicron causes milder symptoms than previous variants of the coronavirus.
In studies in mice and hamsters, Omicron caused much less devastating infections, often limited to symptoms in the nose, throat and trachea. The variant became less dangerous to the lungs, where problems and breathing difficulties had been identified.
"It would be fair to say that the idea of a disease that manifests itself mainly in the upper respiratory system is emerging," Roland Eils, a biologist at the Berlin Institute of Health, told the New York Times. When the new variant was identified in November, scientists could only guess at its behavior.
Why Omicron is milder
University of Cambridge virologist Ravindra Gupta argued that one cannot predict the behavior of the virus from mutations alone. Last month, more than 12 research groups, including his own, conducted animal studies. At the same time, Omicron was released around the globe, infecting even vaccinated or diseased people. However, at the same time, hospitalizations showed a mild increase, with early studies suggesting that the mutation is less likely to cause serious illness than previous ones, especially in vaccinated people, though the findings came with caveats.
Most research based on animal experiments and made public in recent days came to the same conclusion, that Omicron is milder than Delta and earlier variants. On Wednesday, a large consortium of scientists from Japan and the US published a report on hamsters and mice infected with either Omicron or earlier variants. Animals infected with Omicron had less lung damage, lost less weight and were less likely to die.
\NScientists speculate that Omicron's lower morbidity may be a matter of anatomy. However, scientists say more experiments are needed to reach a more certain conclusion.
The TMPRSS2 protein
Dr. Gupta suspects that his team's research data provides a molecular explanation as to why Omicron does not reach the lungs. Many cells in the lung have a protein, TMPRSS2, on their surface that can inadvertently help passing viruses enter them. This particular protein does not seem to "catch" Omicron very well. Another team from the University of Glasgow came to a similar conclusion.
By an alternative route, coronaviruses can also enter cells that do not make TMPRSS2. Cells in the respiratory tract cells tend not to carry the protein, which may explain why Omicron is found there more often than in the lungs. Scientist Gupta reckons that Omicron does not thrive in the throat and nose, which means it is more likely to be shed in tiny droplets into the surrounding air and meet new hosts.
However, research has not explained why Omicron, although it causes milder disease, is so easily contagious. Scientists explain that more studies are needed to come to a conclusion.
Source: protothema.gr
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