Highly effective and balanced immune response to avoid COVID-19 symptoms

By analyzing blood samples from individuals with SARS-CoV-2, researchers in Singapore have begun to dispense the various responses with the body’s T cells that determine whether a person is individually develops COVID-19. The study, published today in the Journal of Experimental Medicine (JEM), suggests that clearing the virus without developing symptoms requires T cells to trigger an effective immune response that provides a careful balance of pro- and anti-inflammatory molecules.

Many people with the SARS-CoV-2 virus do not develop any symptoms, and the infection is cleared by both antibodies and T cells that specifically recognize the virus. In some cases, however, this immune-mediated response can induce excessive inflammation that damages nappies and causes many of the symptoms associated with COVID-19.

It is not yet known what will determine if a person with a disease develops symptoms. Some studies have suggested that asymptomatic individuals produce fewer anti-SARS-CoV-2 antibodies than individuals who develop symptoms. But it was not clear whether their T cell responses were also reduced.

“Asymptomatic people make up a variable but often large proportion of people with an infection, and should play a key role in understanding the immune response that is able to control the virus without advancing pathology processes, ”says Antonio Bertoletti, a professor at the Duke-NUS School of Medicine in Singapore.

A group of migrant workers who were exposed to SARS-CoV-2 in their dormitories in April 2020. Over six weeks, the researchers took regular blood samples from 85 workers who were infected but remained asymptomatic and compared their T cells with those of 75 hospitalized patients with moderate to severe COVID-19.

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

However, the T cells of asymptomatic humans increased the size of two proteins called IFN-γ and IL-2. These signaling 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 his colleagues challenged some of the blood samples with fragments of viral proteins and found that asymptomatic individuals’ immune cells produce a balanced mixture, with a good proportion of pro- and anti- inflammatory. In contrast, the immune cells of COVID-19 patients produced an unbalanced amount of proinflammatory molecules.

“Overall, our study suggests that weak antiviral immunity is not characterized by people with asymptomatic SARS-CoV-2 infection; on the other hand, they suppress antiviral cell response which is highly effective and fair that protects the guest without causing any obvious pathology., ”the researchers say.

The molecular detail of this response, and how it safely controls SARS-CoV-2 infections, can now be studied in more detail. However, as the majority of study participants were male and of Indian / Bangladeshi origin, the researchers warn that their results need to be confirmed in women and other populations around the world. world.