American researchers from the Institute of immunology in La JOLLA published a sensational data. The study of samples of donor blood, a fence which was carried out in 2015-2018, found evidence of specific cellular immunity similar to those that appear when a new coronavirus. From this we can conclude that the body of those who had once hurt the other kinds of coronavirus can be resistant to COVID-19.

Today, many are concerned about the question: does the fact of presence of antibodies to the new coronavirus guarantee of immunity? However, the situation with immunity is much more difficult. Its availability depends not only on presence of antibodies (immunoglobulins), but also from the availability of important cells called T-lymphocytes, T-killers (CD8-cells) and T-helper (CD4 cells). T-killers are able to different signs to identify the body cells infected by viruses and, if found, kill them yourself or call other cells to help. And T-helper increase the number and the “devastating” potential of T-killer cells specific against specific virus.

a New study of Americans (until this paper) aims to identify specific antigens of coronavirus, inducing the strongest cellular immune response — this information is very important for the creation of a future vaccine.

But in parallel was an important discovery. Every second sample of donor blood taken in 2015-2018, was found specific CD4+ T-lymphocytes, which is now found in absolutely all ill with novel coronavirus infection. Can we assume that 50% of the population that have not yet met with a new infection, may already be immune to it. In addition, today in the blood of 70% recover from COVID-19 detected specific CD8+ T-lymphocytes. They were found in 20% of samples of donor blood.

the results of the study give reason to assume that a significant portion of the population may have cross-immunity to the virus SARS-CoV-2 due to the previously transferred “seasonal flu”, ie, “normal” coronaviruses. Those who had once hurt the other “crowns” could obtain antibodies, capable of dealing with new virus. Perhaps that is why most of the disease suffer mild or no clinical disease.

“Donors whose blood samples were analyzed, definitely couldn’t hurt COVID-19 in 2015-2018. However, about half of the cases they showed a specific reaction of T cells to the antigens of the virus.

the study’s Authors believe that the case in cross-reactive immunity. They checked the samples of blood that were used in the experiment, antibody to two of the four previously known��x coronaviruses affecting human HcoV-OC43 and HcoV-NL63, and received a positive result of the analysis. That is, these people previously had other coronavirus infections than from COVID-19″ – said a senior researcher CDB Sciences Sergey Kazaap.

“This study is essential for understanding mechanisms of adaptive immunity, – told the “MK” head of the Department of clinical immunology and Allergology First MSMU n. a. I. M. Sechenov, academician of RAS, honored scientist of the Russian Federation Alexander Karaulov. – If the etiology of the disease COVID-19 we learned that the new coronavirus SARS-CoV-2, in respect of the formation of the immune to it are ongoing discussions.

Sometimes this immunity pathogenic (people die from cytokine storm, or excessive immune response), sometimes protective (which is important for vaccines).

the basis of antiviral immunity is not only and not so much the antibody response, many T-cell immune response T cells: CD-4 helper and CD 8 killer cells, and memory cells. These cells are involved in defending the body in response to viral infection, including SARS-CoV-2, and, thanks to them, when acute infection occurs the elimination of the virus, that is the “clearance” of the virus, and the formation of immunity to subsequent infection. And in this sense everything is on the classics.

But the question still is, what determines the severity of infection? We see that elimination of the virus does not occur in some elderly or people with serious diseases such as diabetes or Oncology. They have a link between innate and adaptive immunity violated; adaptive they don’t have enough.

Today, the main hypothesis of the answer to the question of why some get sick easily and others hard, is that sick easily, apparently, have cross-immunity to other coronaviruses. Cross-reactivity occurs with some infections, e.g. the flu.

the fact that the H1N1 flu is easier to hurt those who have been cross-immunity to other influenza strains, that is, they have the T-killer cells active against the virus that allows you to recover faster. Of course, working Americans advanced, the need to conduct additional studies among severe patients in hospitals. All these data prove that the existence of cross-immunity in healthy individuals in response to SARS-CoV-2 possible. And it should be considered in the development of vaccines.

– it Turns out that the owners of T-lymphocytes to the old coronaviruses in meeting the new, likely to have been ill easier?

Yes, through the same cross-reactivity between circulating coronaviruses that cause the common cold. It is approximately 40-60% of healthy individuals with no contact with COVID, which T-memory cells will potentially give an immune response that is Zap��merit active and sufficient T cell cytotoxic (killer) answer, in addition to the antibody response. But these killers are very difficult to identify diagnostically, need special study in the laboratory.

Meanwhile, the journal Nature published another study by biologists from the University of Washington. The patient who suffered severe acute respiratory syndrome (SARS caused by SARS-CoV) in 2003, found antibodies that can block work and SARS-CoV-2.

the causative agent of SARS, SARS-CoV is most similar in its structure and properties to the new SARS-CoV-2. Scientists were able to obtain eight different antibodies using B-memory cells of a patient, which are to varying degrees block the virus. And one of them has demonstrated the ability to bind to S-protein of the novel coronavirus SARS-CoV-2, which is responsible for penetration of the virus into human cells, and therefore is protective, it is protective.

And this is very important, as understanding what pieces of the virus are protective, it is necessary for the development of effective vaccines against coronavirus infection, but also for new methods of treatment COVID-19, according to the scientists. “It is also a way of using a cocktail of antibodies for the prevention and treatment of severe disease,” – said the academician of the guard.