A group of immunologists from the Pasteur Research Institute of Epidemiology and Microbiology has developed a drug for mass testing of the population for the presence of cellular immunity to coronavirus. According to the procedure, the skin test "CoronaDerm PS" resembles the Mantoux reaction or the Diaskin test. The analysis will distinguish those who have recovered from COVID-19 from those who have not. He will also give the opportunity to make a conclusion about the need for vaccination or revaccination. According to the developers, a skin test will be more objective than an antibody test. The development has passed preclinical tests and submitted for registration to the Ministry of Health of the Russian Federation.

Mechanism and purpose

The presence or absence of antibodies to coronavirus is not a determining indicator in order to accurately understand whether a person is protected from COVID-19. Sometimes, in the presence of antibodies, a second disease occurs, or vice versa - the disease does not occur, despite the fact that there are no antibodies to coronavirus in the body.

In this case, experts talk about the absence or presence of T-cell immunity. These are memory cells that remain in the human body when they encounter an infection - and at the next meeting, the start of the "production" of antibodies that neutralize the coronavirus begins much faster, which makes it possible not to get sick.

In order to assess the presence or absence of T-cell immunity, a new test "CoronaDerm PS" was created at the Pasteur Research Institute of Epidemiology and Microbiology of Rospotrebnadzor.

The drug "CoronaDerm PS" belongs to the group of diagnostic tests. The test subject is given a skin test, which is outwardly similar to the Mantoux reaction. Both are injectable forms, only they contain different antigens. The composition of the "KoronaDerm PS" preparation includes an antigen specially prepared for the test for cellular immunity to SARS-CoV-2.

After 72 hours, when the peak in the development of cellular reactions occurs, the result is assessed by the diameter of the papule: positive or negative. A positive test shows that the subject has cellular immunity, a negative test indicates that there is no cellular immunity to the virus.

“The testing procedure should become routine, give medicine a real objective tool with which it will be possible to make a conclusion about the need for vaccination or revaccination,” says Academician Areg Totolyan, director of the Pasteur Research Institute of Epidemiology and Microbiology, Rospotrebnadzor.

According to him, the idea of ​​creating an easy-to-use and cheap skin test came to a group of immunologists led by Andrey Simbirtsev in the process of research on population immunity, which is being conducted for the second year in 26 regions of Russia and in some neighboring countries.

The test will distinguish between those who have recovered from COVID-19 and those who have not been sick from each other. He will also be able to give an answer about the effectiveness of vaccination, and it will be more objective than an analysis for antibodies, Totolyan said.

Cellular immunity plays an important role in the development of coronavirus infection. T-cell immunity and antibodies to SARS-CoV-2 protect a person in different ways when they encounter an infection. The main difference is speed. Antibodies neutralize the virus immediately, and the cellular memory, when it encounters an infection, prompts the body to produce antibodies. Therefore, the infection will be rebuffed with some delay.

However, as you know, antibodies cannot be at the same high level, their number decreases over time. In some cases, it falls below the sensitivity level of the test - and it shows that there are no antibodies to coronavirus. At the same time, there is protection. A T-cell skin test will show: whether the body remembers the infection, whether the production of antibodies to it will be triggered.

The methods currently used to determine cellular immunity to the causative agent of COVID-19 are very expensive and not generally available, and testing is carried out only in special laboratories of scientific institutions. The new test system is designed for mass use.

Testing and implementation

Scientists received the formula of the drug in the spring. The developers of the test first tested it on themselves, were convinced that the proposed principle works, and also received information about the sensitivity, specificity, and informativeness of the test in case of a previous illness or, if necessary, the selection of persons for whom vaccination is indicated.

“We completed the preclinical tests of the KoronaDerm PS test and submitted the development for registration to the Ministry of Health,” Areg Totolyan clarifies. - Further clinical trials will be required. The protocol has three phases. For the first and second phases of clinical trials, the total number of subjects should be several hundred, the first two phases should keep within one and a half to two months. The third phase of clinical trials requires several thousand volunteers. "

The academician also told how the development is planned to be introduced into everyday medical practice.“With a skin test, the situation is the same as with vaccines. First, the tests will be carried out on adults and it will be applied on adults, and then, after the appropriate clinical trials, we will reach the children, if everything goes according to plan, ”he stressed.

In order to draw a conclusion about the effectiveness of this test, you need to compare it with existing tests for T-cell immunity, as well as the presence of antibodies, says Pavel Volchkov, head of the MIPT genomic engineering laboratory.

"The developments of Rospotrebnadzor are often subjected to systemic criticism due to the lack of presentation of scientific results in peer-reviewed high-ranking journals," says the scientist. "It is too early to talk about the accuracy of the new test, since the necessary comparative information is missing."

He emphasizes that the scientific article should provide specific figures for demonstrating the effectiveness of the test on a large sample of people, information on the time of vaccination of which or past COVID-19 disease is available from Rospotrebnadzor specialists.

“To have such a skin test in the arsenal of means is, of course, tempting,” explains in a conversation with the head of the Department of Virology of the Biological Faculty of Moscow State University. M.V. Lomonosova Olga Karpova. - However, even to the Mantoux reaction, which has been worked out for decades, there is a different reaction, it gives a lot of false positive results. Therefore, it will be extremely difficult to work out the standard of the new test, assessing the skin reaction is extremely difficult. "

Olga Karpova emphasized that it will be possible to draw conclusions about the new test only if, in addition to a scientific article, an analysis of statistical data on a very large sample is in hand.

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