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Antibodies
Specialists from the Institute of Molecular Biology. VA Engelhardt set out to find out what happens to antibodies to the SARS-CoV-2 coronavirus 5-6 months after the onset of the disease.
To do this, they used the blood of people who fell ill with COVID-19 in the spring and who wished to become plasma donors in April-May. The study was conducted on the basis of the clinic of the Federal Medical and Biological Agency shortly before the plasma donation (the blood must be checked for the presence of neutralizing antibodies), and also six months later, at the end of October.
Scientists were only interested in those antibodies that react with a possible reinfection to the coronavirus Spike protein, or rather, its receptor binding domain, the part of the protein responsible for communicating with a human cell.
In the spring, the antibody titer in people who donated blood for analysis was at a high level. When they checked him in October, it was found that he had fallen twice on average.
“It’s impossible to say that the antibodies have completely disappeared,” says Alexander Ivanov, head of the viral infection biochemistry laboratory at IMB RAS. – We really hope that the remaining antibodies neutralize themselves, that is, giving a real rejection to the coronavirus.
T cells
While some are studying the viability of antibodies, other researchers are studying the effect on the virus of our immunity’s reserve “weapon” – T cells, which also infect the virus that has entered the body.
Then, at the National Medical Research Center for Hematology, they decided to study the immunity of T lymphocytes of people who had been sick with COVID-19. The research was conducted with the support of the Russian Science Foundation.
Grigory Efimov, Candidate of Biological Sciences, Head of the Laboratory of Transplant Immunology, revealed the details of the “MK”.
– Do antibodies and T lymphocytes work in the body of people who have been sick at the same time?
– Yes, we see it in most cases. But it happens that we do not find antibodies, only T cells.
– Is it easy to detect T lymphocyte immunity?
– The classic method is that the coronavirus fragments are added to the living T cells, then we estimate how many T cells are activated and go into combat. In principle, for T lymphocytes it is not so important which part of the virus they recognize (since it is important for antibodies). The fact is that T lymphocytes, unlike antibodies, do not recognize the virus itself, but the cell that is affected by it.
– How many percent of those who are cured have T-cell immunity to the coronavirus?
– In our studio, 80-90 percent. But it’s important to note that we’ve looked at how T cells respond to certain fragments of the virus. Meanwhile, the virus is very large and we may simply not see T cells recognizing other SARS-CoV-2 proteins.
– Did they all have antibodies?
In this publication, two out of 34 people whose blood we tested had no antibodies. And they had T cells.
– Antibodies, to fight the virus, must have a special status – “neutralizing”. Do T cells also have some sort of gradation?
– No, T lymphocytes, unlike antibodies, all fight the virus.
– In your work you write that you have found a T-cell response even in people who did not have coronavirus. How can this be explained?
– We divided the “not sick” into two groups. On the one hand, we took blood from the biobank, taken from donors before the coronavirus pandemic began, that is, until the fall of 2019. On the other hand, in the spring of 2020, people without symptoms of a viral infection and a negative PCR test. We understand that among the spring donors there may be potential contact with patients, that is, infected (among them, by the way, there were more people with T-cell immunity to coronavirus). But some of those who donated blood before the pandemic began also had SARS-CoV-2 T cells.
– And how did you answer this question?
– This is called the cross-over immune response. These T lymphocytes were born from contact with other viruses, for example coronaviruses among those that constantly circulate in our country and cause mild seasonal respiratory diseases. A person could get sick with that coronavirus, the T cells that fought with it reacted and then turned into memory cells. Faced with the new coronavirus, they mistook it for the old one and got activated.
– Which group had a more active T-cell response to the new virus?
– Among the spring donors, there was more T cell immunity, and the number of T cells themselves was higher. Furthermore, we have also found this type of immunity in those who easily had coronavirus.
MK Help: “What happens to the T cells after they defeat the virus?”
It is not profitable for the body to constantly keep an army of T cells online, so most of them die and the rest begin to perform only the function of memory cells. When a new threat arises in the form of a familiar virus, the T cells begin to actively multiply again and protect us from infection. “
– How long have you observed the level of T lymphocytes?
– 17 to 60 days after infection. It has been 6 months since then and we are resuming our research.
– Will you summon people again or will you just check the blood you have stored?
– To find out how the level of both the antibodies and T lymphocytes that recognize the coronavirus has changed, let’s call people again.
There is already evidence from Western colleagues that T lymphocytes decline over time, but this is expected. There shouldn’t be many of them, as most of them die after defeating the virus, and a small part turn into memory cells.
– So can you exhale those people who have had the coronavirus? Do they have additional protection in the body in the form of T cells?
– Yes, people who no longer detect antibodies should remember that this is not the only defense mechanism against reinfection. So far, we only measure the response level of T cells in the context of experiments, but we hope to soon create a clinical version of the tests for detecting T cells.
Read the material: “Those who had been sick with antibodies were denied the Russian vaccine against the coronavirus”
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