What distinguishes the covid-19 BA.2 subvariant from the omicron?
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(CNN Spanish)
- This remains one of the greatest mysteries in science: why are there people who do not get infected with the new coronavirus?
Scientists seek to answer this question and three studies could bring some clarity to this question.
Dr. Elmer Huerta reviews the findings in this episode.
You can listen to this episode on Spotify or your favorite podcast
platform
, or read the transcript below.
Hi, I'm Dr. Elmer Huerta and this is your dose of information about the new coronavirus.
Information that we hope will be useful to take care of his health and that of his family.
The coronavirus infection: what is still a mystery to science
According to data from the United States Centers for Disease Control and Prevention (CDC), 43.3% of Americans have antibodies against SARS-CoV-2, which would imply that little more than half of the population has not had the infection.
Aside from taking good care of themselves during the pandemic, it's not exactly clear why more than half of Americans didn't become infected.
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Similarly, one of the mysteries of this pandemic is to explain why some people, for example the husband or wife of an infected person, did not get the new coronavirus despite living in the same house and sleeping in the same bed. .
Another example is the one we described in the April 8 episode.
Of 36 people who were intentionally infected with SARS-CoV-2 in a challenge study, only 18 became infected.
What was the mechanism by which, despite being infected with the same amount of virus, the other 18 people did not develop the infection, and did not even produce neutralizing antibodies?
Today we will see some possible explanations for this phenomenon.
How does our body respond to an infection?
First of all, let us remember that, when the virus enters a person's body, it triggers the immune response, which broadly comprises two important stages:
the development of T lymphocytes, or memory cells,
and the production of neutralizing antibodies by B lymphocytes.
Memory T cells screen for the invading virus.
Not recognizing it, they take a few days to order the B lymphocytes to make specific neutralizing antibodies against the invading virus.
If the virus is already known, these T lymphocytes, in addition to ordering the production of specific neutralizing antibodies, can directly attack and destroy it.
Recent studies postulate two theories to explain the phenomenon by which some human beings could be resistant to infection with the new coronavirus.
Theories about resistance to infection of the new coronavirus
The first theory says that certain people are able to eliminate the new coronavirus.
This thanks to the neutralizing antibodies and memory T cells that they have in their body, the product of having suffered from old colds.
There are four types of coronaviruses that cause 30 percent of colds in humans.
The second theory says that certain human beings are capable of producing substances within their cells.
These are substances that not only destroy the invading virus, but also destroy the infected cell.
Three studies support the first theory, the one that says that having suffered multiple colds during life, neutralizing antibodies and memory cells directed against those viruses can cross-protect against the new coronavirus.
Studies to find why some people don't get coronavirus
In the first study, British researchers repeatedly tested the blood of a group of healthcare workers highly exposed to the virus during the first wave of the pandemic, when vaccines were not yet available.
What they found was something very surprising.
Those health workers exposed to the virus who did not develop the disease—and were not even capable of producing neutralizing antibodies—formed special memory cells, which have been dubbed cross-reactive T cells.
It is thought that having had colds caused by the four ancient coronaviruses, they stimulated the formation of memory T cells that were able to cross-neutralize the new coronavirus.
What is interesting is that these cross-memory T cells did not attack the spike, but internal structures of the virus.
This opens the possibility of developing new types of vaccines, not directed at the spike, but at internal structures of the virus.
The second study showed that children produce twice as many cross-reactive T cells as adults, suggesting that this is the explanation why children do not have as many symptoms as adults when infected.
In the third study, it was shown that people who lived in the same household and were not infected were also people who produced a greater number of cross-reactive T cells.
Genetics, a key factor
Those three studies then postulate the theory that certain human beings – with the right genetics – are capable of not being infected with the new coronavirus.
The reason is that they have stored memory cells produced by past infections with other coronaviruses.
Those memory cells cross-destroy the new coronavirus.
Specialists estimate that between 10 to 15% of human beings are capable of producing these cross-reactive lymphocytes.
The second theory is also very interesting and says that some human beings (especially children) have a higher amount of natural substances called pattern recognition receptors (PRR) inside their cells.
These PRRs are part of the body's defense system and their mission is to destroy any microorganism that manages to penetrate inside the cell.
A variety of these receptors, called RIG-I, is very active in destroying various types of viruses, including the influenza A virus that enter cells.
And a recent European study finds that the number of RIG-I receptors is higher in children than in adults, which explains why children do not develop severe forms of the disease.
The conclusions of the studies
In short, it seems that certain people, through genetically determined mechanisms, are capable of not being infected by the new coronavirus.
Either because they are cross-protected by old infections by other coronaviruses or because they produce substances within their cells that destroy the virus.
Knowing this type of detail is important for the development of new vaccines or drugs that can give protection to most humans who are sensitive to infection.
Do you have questions about covid-19?
Send me your questions on Twitter, we'll try to answer them in our next episodes.
You can find me at @DrHuerta.
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Thanks for your attention.
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