COVID-19: 3 distinct immune responses to SARS-CoV-2 identified

The discovery could help predict the trajectory of disease in severe cases and ultimately inform treatment decisions

By DTE Staff
Published: Friday 17 July 2020
Three distinct immune responses to SARS-CoV-2 have been identified in 2 US studies. Photo: Flickr__

Three distinct responses by the human body’s immune system to an infection by SARS-CoV-2 or the novel coronavirus have been identified by scientists from the Penn Institute of Immunology in Philadelphia, US.

The virus triggers different immune responses and symptoms in critically ill patients. However, how they correspond, has not yet been properly understood, making treatment decision difficult.

The discovery of the three immune responses could help predict the trajectory of disease in severe novel coronavirus disease (COVID-19) patients and may ultimately help overcome this problem, the researchers feel.

“For patients who are hospitalised with COVID-19, there isn’t just one way for the immune system to respond. There’s a lot of heterogeneity, which we’ve distilled down into what we’re calling three “immunotypes,” E John Wherry, director of the Penn Institute of Immunology in the Perelman School of Medicine at the University of Pennsylvania, said in a statement by the institute.

Wherry is the senior author of the report that has been published in Science.

The study covered 163 patients including 90 hospitalised patients treated at the Hospital of the University of Pennsylvania, 29 non-hospitalised patients, and 44 healthy donors with no COVID-19 infection.

The researchers applied deep immune profiling to capture the individual responses of the 163 patients during the course of their infections, the statement said.

The first immunotype had robust CD4+ T cell activity, with modest activation of CD8+ T cells and peripheral blood lymphocytes. CD4+ and CD8+ act as the main inflammatory immune cells that work to clear viruses.

The second immunotype was characterised mainly by a subset of CD8+ T cells known as EM and EMRA and a modest activation of CD8+ T cells, memory B cells, and peripheral blood lymphocytes.

The third immunotype showed little to no evidence of an immune response to the infection.

Researchers found that the first immune reaction or immunotype was tied to inflammation, organ failure and acute kidney disease.

The second correlated with pre-existing immunosuppression and mortality. The third type, was not associated with specific symptoms or clinical features.

Another study by Michael R Betts, a professor of microbiology and programme leader in the Penn Institute of Immunology, revealed new details about the innate, or initial, response to SARS-CoV2.

The researchers profiled the blood samples of 42 infected patients (with moderate and severe disease) and 12 healthy donors.

They found robust activation of CD4+ and CD8+ T cells, B cells, along with peripheral blood cells, like neutrophils, monocytes, and “natural killer,” or NK, cells.

The researchers observed a decrease of CD15 and CD16 molecules on neutrophils and CD16 on NK cells, immature granulocytes, and monocytes, in patients with more severe disease.

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