Worse COVID Illness, Stronger Immunity After?

By Robert Preidt

HealthDay reporter

WEDNESDAY, Jan. 27, 2021 (HealthDay News) – People who have recovered from severe COVID-19 may have stronger long-term immune protection against reinfection than those with milder illness, researchers report.

They examined blood samples from 39 COVID-19 patients and 10 people who had not been exposed to the virus (their blood samples were donated before the pandemic). In total, they analyzed the expression of individual genes from more than 80,000 CD8 + T cells.

CD8 + T cells are immune cells that destroy host cells infected with the virus, and “memory” CD8 + T cells protect the body from reinfection with many types of viruses.

Of the patients with COVID-19, 17 had milder illness and were not hospitalized, 13 had been hospitalized and nine ended up in intensive care. The researchers were surprised to find that patients with milder COVID-19 had weaker CD8 + T cell responses.

The strongest CD8 + T cell responses were seen in critically ill patients requiring hospitalization or intensive care.

“There is an inverse link between poorly functioning T cells and the severity of the infection,” said study co-author Dr Christian Ottensmeier in a press release from the La Jolla Institute for immunology in California. He is a professor at the University of Liverpool in the United Kingdom and an assistant professor at the La Jolla Institute.

Researchers found that CD8 + T cells in people with mild COVID-19 showed signs of T cell depletion, in which cells receive so much stimulation from the immune system to fight viruses that they become less effective. .

Depletion of T cells in people with mild COVID-19 may reduce their chances of long-term immunity, according to the authors.

“People with serious illness are likely to end up with a good number of memory cells,” said study co-author Pandurangan Vijayanand, professor at the La Jolla Institute. “People with milder disease have memory cells, but they seem exhausted and dysfunctional – so they might not be effective for long enough.”

The results “suggest that people with severe cases of COVID-19 may have stronger long-term immunity,” Vijayanand said.

This study highlights the enormous variability in the way humans respond to a viral challenge, Ottensmeier said.

Continued

Although the study offers important new information about the immune response of COVID-19 patients, it is limited due to its dependence on CD8 + T cells found in blood samples, the researchers explained.

To find out more, they plan to test T cells in tissues most affected by the novel coronavirus, such as the lungs, to see how they respond to the virus. This is crucial because the memory T cells that provide long-term immunity must live in the tissues.

The study was published on January 21 in the journal Scientific immunology.

More information

The United States Centers for Disease Control and Prevention has more on COVID-19.

SOURCE: La Jolla Institute of Immunology, press release, January 21, 2021

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