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The study points to the key to a balanced T-cell response to avoid COVID-19 symptoms

Credit: © 2021 Le Bert et al. Originally published in The Journal of Experimental Medicine. https://doi.org/10.1084/jem.20202617

By analyzing blood samples from individuals infected with SARS-CoV-2, researchers in Singapore are beginning to unpack the different responses of T cells in the body that determine whether or not an individual has COVID-19. The study published today in The Journal of Experimental Medicine (C.), Indicates that eliminating the virus without showing symptoms requires the T cells to make an effective immune response that produces a delicate balance between pro- and anti-inflammatory molecules.

Many people infected with SARS-CoV-2 have no symptoms, and the infection is cleared up by antibodies and T cells that specifically recognize the virus. However, in some cases, this protective immune response can trigger excessive inflammation that damages tissues and causes many of the symptoms associated with COVID-19.

What determines whether an affected individual has symptoms remains unknown. Some studies have suggested that asymptomatic individuals produce fewer antibodies to SARS-CoV-2 than symptomatic individuals. But it’s unclear if their T-cell responses are also low.

“Individuals without symptoms make up a variable but often large proportion of infected individuals, and they should hold the key to understanding the immune response that is able to control the virus without causing pathological processes,” says Antonio Bertoletti, professor at Duke-NUS School of Medicine. Singapore.

Bertoletti and colleagues, including Nina Le Bert, Senior Research Fellow at Duke-NUS School of Medicine, and Clarence C. Tam, Associate Professor at the National University of Singapore, Saw Swee Hock School of Public Health studied a group of migrant workers exposed to SARS-CoV-2 in Their dormitories in April 2020. Over a period of six weeks, the researchers took regular blood samples from 85 workers who had been infected but remained asymptomatic and compared their T cells with the cells of 75 patients hospitalized with mild to moderate COVID-19.

Surprisingly, the researchers found that soon after infection, the frequency of T-cells recognizing SARS-CoV-2 was similar in both asymptomatic individuals and COVID-19 patients. “The total volume of T-cell responses against the different viral proteins was similar in both groups,” says Nina Le Bert.

However, the T cells of asymptomatic individuals produce greater amounts of two proteins called IFN-and IL-2. Signal proteins or cytokines help coordinate the immune system’s response to viruses and other pathogens.

Accordingly, the immune response to SARS-CoV-2 appears to be more coordinated in asymptomatic individuals. Bertoletti and colleagues challenged some blood samples with fragments of viral proteins and found that the immune cells of asymptomatic individuals produced a well-balanced and well-proportioned mixture of pro- and anti-inflammatory molecules. In contrast, the immune cells of COVID-19 patients produced a disproportionate amount of inflammatory-causing molecules.

“In general, our study indicates that individuals infected with SARS-CoV-2 do not have symptoms of impaired antiviral immunity. On the contrary, they perform a highly efficient and balanced antiviral cellular response that protects the host without causing any apparent diseases,” he says. Researchers.

The molecular details of this response, and how to safely control SARS-CoV-2 infection, can now be studied in more detail. However, since most of the study participants were male and of Indian / Bangladeshi descent, the researchers cautioned that their findings would need confirmation in women and other populations around the world.

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Le Burt et al. 2021. J. Exp. Med. https: //rupress.Deer /C /Search for an article /Doi /10.1084 /C.20202617? PR

Around The Journal of Experimental Medicine

Journal of Experimental Medicine (JEM) He publishes peer-reviewed research on immunology, cancer biology, stem cell biology, microbial pathogenesis, vascular biology, and neuroscience. All editorial decisions regarding research manuscripts are made through collaborative consultation between professional scientific editors and the academic editorial board. Founded in 1896, C. It is published by The Rockefeller University Press, a division of The Rockefeller University in New York. For more information, visit jem.org.

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