Some cells in the immune system are able to ‘remember’ the coronavirus SARS-CoV-2 and prevent re-infection for at least eight to nine months. This is evidenced by the latest research by scientists.
Already at the beginning of the Covid-19 pandemic was foundthat the levels of antibodies in the blood of those who get sick fall over several months. Concerns about re-infection have proved well-founded, with Hong Kong officially announced in August Confirmed the first such case, but soon a few dozen more cases appeared.
This is partly due to the fact that common colds caused by human coronaviruses (SARS-CoV-2 “relatives”) do not develop long-term immunity and can re-infect them after a year, says a professor of infectious diseases at Griffith University in Australia. Nigel McMillan.
In the article, published in the academic portal The Conversation, the scientist looks at the promising results of recent studies on the immune response to Covid-19.
Just like in war
When an enemy invades a country, it gathers all its forces, engages in war and repels the invaders. After the enemy retreats, the country’s wise leaders send patrols to look for signs of a possible new invasion. These observers know what the enemies look like, what form they have, and how they move by analogy, the professor explains.
Our immune system works exactly the same way, he writes. Every time the human body fights a bacterial or viral infection, there are cells left to heal that remember exactly what an “invader” looks like. These are memory cells, and their job is to report them to the immune system at an early stage in the event of a new invasion, so that an adequate response can be provided.
This means that we do not have to fight again from the beginning, because re-infection will either “go out” immediately, or the time it takes to recover will be significantly shorter.
For some viruses, this memory can be very long. For example, in the case of measles, it will last a lifetime.
B cells in reserve
B cells, or B lymphocytes, which play an important role in the immune response to infection, produce antibodies that capture and kill disease-causing pathogens such as viruses and bacteria.
A group of researchers from Monash University in the Australian city of Melbourne has published preliminary the results of the study on the formation of memory B cells in the body that are specifically targeted to SARS-CoV-2.
Two months after the first infection, a reduction in circulating coronavirus antibodies was observed in 25 patients. However, memory B cells have been discovered that recognize important parts of the virus: the prickly protein (the ‘key’ that allows SARS-CoV-2 to open the cell) and the nucleocapsid (the viral genome and its protein coat).
The study showed that these B cells circulated in the blood for at least eight months, but perhaps longer.
“A decrease in the level of antibodies in the blood serum after one month does not indicate a decrease in immunity, but a decrease in the immune response,” the authors point out. And if a person is re-infected with the coronavirus, the B cells will be able to quickly produce antibodies to fight the infection.
If the author’s “military” analogy continues, then in peacetime it is irrelevant to keep the entire army ready for battle, but in case of an invasion, the troops will quickly mobilize and counter the enemy.
In another study, performed by scientists in the United States, memory B cells were detected at least six months after the first infection.
T killers come to the rescue
Infected cells push fragments of the invading pathogen onto their surface. It is a kind of SOS signal that allows T cells – another type of lymphocyte – to find the hidden enemy, contact the infected cell and destroy it along with the pathogen.
Oxford University scientist study, which shows the response of T memory cells to SARS-CoV-2, concludes that there are T lymphocytes that can remember how to respond to coronavirus-affected cells long after the initial infection has been prevented.
The time during which this memory operates, specified by Chinese and German scientists study.
It targeted patients from Wuhan, a Chinese city where the Covid-19 pandemic began. Therefore, it was possible to test whether and in what way immunity to coronavirus was maintained in those who were among the first to develop Covid-19.
The study showed that the T cell response to the coronavirus was maintained nine months after infection.
Will there be recurrences?
Currently laboratories There are only 24 cases of reinfection with Covid-19 in the world. According to many scientists, this is only a small part of the real cases. However, given that since the beginning of the pandemic in the world have been infected more than 62 million people, re-infection now appears to be very rare.
According to the new data, the human immune system is able to remember and respond to SARS-CoV-2. For at least eight or nine months after the first infection, most patients are protected from re-infection. And if re-infection does occur, the disease is likely to be mild, according to an Australian professor.
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