A slew of new research on lab animals and human tissues are offering the first clues as to why the Omicron form of the coronavirus generates less symptoms than prior variants of the virus.
In experiments on mice and hamsters, Omicron caused less severe infections that were mostly restricted to the upper airway, including the nose, throat, and windpipe, rather than the lower airway. The variation caused far less damage to the lungs than prior forms, which often resulted in scarring and severe breathing difficulties.
When the initial report on the Omicron version came out of South Africa in November, scientists could only speculate about how it may vary from prior strains of the virus. Since then, scientists have learned more about the virus. It possessed a peculiar and frightening mix of more than 50 genetic alterations, which was all they knew about it at the time.
Previous study had shown that certain of these alterations made it possible for coronaviruses to latch on to cells with greater tenacity. Others helped the virus to elude antibodies, which serve as the first line of defence against infection when it first enters the body. However, it remained a question as to how the new version would function after it entered the body.
Since last month, more than a dozen research organisations, including Dr. Gupta’s, have been watching and studying the novel disease in the laboratory, infecting cells in Petri dishes with Omicron and spraying the virus directly into the nostrils of animals.
However, even as the number of cases grew, hospitalizations only climbed little. Early patient investigations revealed that Omicron was less likely than other variations to produce serious disease than other variants, particularly in those who had been vaccinated. But there were a number of limitations to those conclusions.
These discrepancies may be resolved via animal experiments, since scientists can test Omicron on similar animals living in identical settings, hence eliminating the need for human trials. Omicron is a milder strain of the virus than Delta and other previous variants of the virus, according to the results of over half a dozen trials that have been made public in recent weeks.
Omicron was shown to cause far less illness in most animals than prior versions of the virus, but the findings in Syrian hamsters, a species that has been known to suffer from severe illness when infected with previous forms of the virus, were especially striking.
It’s possible that the reason Omicron is gentler is due to the way it’s built. During their research, Dr. Diamond and his colleagues discovered that the amount of Omicron detected in the hamsters’ nostrils was the same as that seen in animals infected with an earlier strain of the coronavirus. However, the amounts of Omicron in the lungs were one-tenth or less of the levels seen in the other types.
A similar discovery was made by researchers at the University of Hong Kong, who investigated tissue samples extracted from human airways after surgery and found that they were related. A study of 12 lung samples revealed that Omicron developed more slowly than other variations such as Delta and other variants.
Affected tissue included tissue from the bronchi, which are air passages that go from the windpipe to the lungs and were infected as part of their study. And, inside those bronchial cells, Omicron multiplied at a greater rate than either Delta or the original coronavirus during the first two days after an infection.
Following up on these discoveries will be necessary via more research, such as tests with monkeys or analysis of the airways of individuals who have been infected with Omicron. People infected with Omicron seem to be less likely to be admitted to the hospital than those infected with Delta, if the findings stand up under investigation.
Immune cells in the lungs have the potential to overreact, destroying not just diseased cells but also healthy ones. They have the potential to cause a flare-up of inflammation, damaging the fragile lung walls. Furthermore, viruses may escape from the injured lungs and enter the circulation, creating blood clots and wreaking havoc on other organs in the body.
Omicron’s contagiousness, according to scientists, is due to its capacity to escape antibodies, which allows it to infiltrate cells of vaccinated persons far more readily than other strains. However, they believe that Omicron may also possess some other biological benefits.
A mutation found in the variation, according to experts, may reduce so-called innate immunity, a molecular alert that swiftly activates our immune system at the first hint of an invasion in the nose. The findings were published last week. However, further trials will be required to determine whether or not this is actually one of Omicron’s keys to success.
According to Dr. Cherry, “it might be as simple as the fact that there is a greater amount of virus in people’s saliva and nasal passages.” However, there might be other causes for its rapid dissemination, such as the fact that it is more stable in the air or more effective at infecting new hosts.