New data on coronavirus immunity gives hope

Antibodies

Specialists of the Institute of Molecular Biology. V.A.Engelhardt set out to find out what is happening with 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 had recovered from COVID-19 in the spring and who wished to become plasma donors in April-May. The study was carried out on the basis of the clinic of the Federal Medical and Biological Agency before the very donation of plasma (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 re-infection to the Spike coronavirus protein, or rather, to its receptor-binding domain – the part of the protein that is responsible for communication with a human cell.

In the spring, the titer of antibodies in people who donated blood for analysis was at a high level. When they checked it in October, it turned out that it fell by an average of two times.

“It’s impossible to say that antibodies have disappeared altogether,” says Alexander Ivanov, head of the laboratory of biochemistry of viral infections at the IMB RAS. – We really hope that the remaining antibodies are neutralizing, that is, giving a real rebuff to the coronavirus.

T cells

While some are studying the vitality of antibodies, other researchers are investigating the effect of the action on the virus of the reserve “weapon” of our immunity – T cells, which also infect the virus that has entered the body.

So, at the National Medical Research Center for Hematology, they decided to study the T-cell immunity of people who have recovered from COVID-19. The research was carried out 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-cells work in the body of people who have been ill at the same time?

– Yes, we see this in most cases. But it happens that we do not find antibodies, only T cells.

– Is it easy to detect T-cell immunity?

– The classical method is that fragments of the coronavirus are added to living T-lymphocytes, and then we estimate how many T-cells are activated and enter into a fight. In principle, for T-lymphocytes it is not so important which part of the virus they recognize (as it is important for antibodies). The fact is that T-lymphocytes, unlike antibodies, recognize not the virus itself, but the cell that is affected by it.

– How many percent of those who have recovered have T-cell immunity to coronavirus?

– In our study, 80-90 percent. But it’s important to note that we looked at how T cells respond to certain fragments of the virus. Meanwhile, the virus is very large, and we may simply not see the T cells that recognize other SARS-CoV-2 proteins.

– Did everyone have antibodies?

-In this publication, two out of 34 people whose blood we analyzed did not have antibodies. And they had T cells.

– Antibodies, in order to fight back the virus, must have a special status – “neutralizing”. Do T cells also have some kind of gradation?

– No, T cells, unlike antibodies, all fight against the virus.

– In your work, you write that you 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 start of the coronavirus pandemic, that is, until the fall of 2019. On the other hand, in the spring of 2020, people with no symptoms of a viral infection and a negative PCR test. We understand that among the spring donors there could be potentially 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 start of the pandemic also had T-lymphocytes to SARS-CoV-2.

– And how did you answer this question?

– This is called a cross-immune response. These T-lymphocytes arose from contact with other viruses, for example, coronaviruses from among those that circulate in our country constantly and cause mild seasonal respiratory diseases. A person could get sick with that coronavirus, the T cells that fought with it reacted, and then transformed into memory cells. Faced with the new coronavirus, they mistook it for the old one and activated.

– Which group had a more active T-cell response to the new virus?

– Among spring donors, there were more with T-cell immunity and the number of T-cells themselves was higher. Moreover, we found this type of immunity even in those who easily had a coronavirus.

MK help: “What happens to T cells after defeating the virus?”

It is unprofitable for the body to constantly keep an army of T cells in line, so most of them die, and the rest begins to perform only the function of memory cells. When a new threat arises in the form of a familiar virus, then T-cells begin to actively multiply again and protect us from infection. “

– How long did you look at the level of T-cells?

– From 17 to 60 days after infection. Now 6 months have passed since then, and we are resuming our research.

– Will you summon people again or just check the blood you have stored?

– In order to find out how the level of both antibodies and T-lymphocytes that recognize the coronavirus has changed, we call people again.

There is already evidence from Western colleagues that T-lymphocytes decrease over time, but this is expected. There should not be many of them, since most of them die after defeating the virus, and a small part turns into memory cells.

– So you can breathe out those people who have had 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 re-infection. So far, we measure the level of T-lymphocyte response only as part of experiments, but we hope that we will soon create a clinical version of tests for the detection of T-lymphocytes.

Read the material: “Those who had been ill with antibodies were denied a Russian vaccine against coronavirus”

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