Patients with severe Covid-19 produce Sars-CoV-2-reactive T cells

Hyperaxion June 30, 2020 1:52 am

Research also indicates that people with severe Covid-19 have increased production of immune cells to fight the infection.

Covid-19 patients suffering from severe respiratory symptoms can quickly generate T cells that attack Sars-CoV-2 and may also have an increased production of these cells over time, suggests a study published in the journal Science Immunology last Friday (26).

Patients with severe Covid-19 produce Sars-CoV-2-reactive T cells
Cell infected with the new coronavirus (Sars-CoV-2). (Credit: NIAID).

The research analyzed ten patients in intensive care and the control group was composed of ten healthy individuals, who had never had contact with the new coronavirus. Among the people in the control group, two had T cells reactive to Sars-CoV-2. According the scientists, this may indicate that these immune cells are able to react to the microorganism due to past infections related to other types of coronavirus.

The new findings bring scientists closer to answering two questions that have puzzled them about Sars-CoV-2. First, whether the response of these specific T cells to the new coronavirus varies over time in infected people, depending on the severity of each case; and second, whether patients with severe symptoms can produce T cells that protect them from the virus.

The novelties brought by the study may also help in the development of vaccines and to improve our understanding of exaggerated immune responses, such as the cytokine storm observed in severe cases of Covid-19.

Methodology

Researchers led by Daniela Weiskopf, from the La Jolla Immunology Institute in the United States, extracted blood samples from critically ill patients as soon as they were admitted to an intensive care unit. Then, they exposed the samples to Sars-CoV-2 epitopes, that is, to the smallest part of the antigen capable of generating an immune response. This technique serves to capture a large fraction of the T cells reactive to the virus.

That’s how scientists found “helper” T cells (also called CD4+ cells), important in the adaptive immune system. In addition, they found “killer” T cells (CD8+ T-cell), responsible for killing infected cells, in eight out of 10 patients.

The study also found that Sars-CoV-2-reactive T cells were present relatively early throughout the course of the infection and increased in patients with severe Covid-19. Supporting the results of previous studies, the recently published research reinforces that T cells have strong immune responses against the spike protein, a glycoprotein on the surface of the virus that is an excellent target for drugs and potential vaccines.

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