American researchers from the Institute of Immunology in La Hoya discovered the acquired immune response of T-lymphocytes to SARS-CoV-2 virus antigens in donor blood samples, collected in 2015-2018.
In general, the main goal of the study was to identify specific coronavirus antigens that cause the strongest cellular immune response – this information is very important for creating a future vaccine.
And scientists successfully coped with this task. They, for example, found that a strong immune response of T-helpers is caused not only by the spike-like protein of the virus, but also by its M- and N-proteins. And in the case of T-killers, the spike protein accounts for less than 50% of the immune response. All this means that the use of other antigens of the virus in addition to the spike protein in the vaccine can significantly increase its effectiveness.
But at the same time, scientists made another discovery. During the study, they studied the response to SARS-CoV-2 antigens of T cells contained in donated blood donated between 2015 and 2018. That is, donors whose blood samples were analyzed definitely could not get COVID-19. However, in about half of the cases, they showed a specific T-cell response to virus antigens.
The authors of the study believe that it is all about cross-reactive immunity. They tested donor blood samples that were used in the experiment for antibodies to two of the four previously known coronaviruses that cause seasonal SARS in humans, HcoV-OC43 and HcoV-NL63, and received a positive test result. That is, these people previously had other coronavirus infections other than COVID-19.
Scientists research results published in Cell magazine, and they say that the results provide very “seductive” food for thought about cross-reactive immunity to coronaviruses. But nevertheless, they note that their assumptions on this score can only be confirmed by studying T cells in patients with other coronaviruses before they become infected with COVID-19, and after the illness.
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