Previous contact with other coronaviruses improves immune response to Sars-CoV-2

Hyperaxion Aug 2, 2020

German researchers found that a third of people have T-helper cells capable of recognizing SARS-CoV-2 because they have had previous contact with other types of coronavirus.

Scientists at the Charité university hospital (Universitätsmedizin Berlin) and the Max Planck Institute for Molecular Genetics (MPIMG), both in Germany, have found that some people’s immune systems have a certain advantage against Sars-CoV-2.

Previous contact with other coronaviruses improves immune response to Sars-CoV-2
(Credit: NIAD/HIH).

The reason for this is because they came into contact with other types of coronaviruses responsible for causing the common cold.

The study, published this week in the journal Nature, was based on an analysis of the blood of 18 patients diagnosed with Covid-19 and 68 others who were never exposed to the microorganism.

The scientists realized that one in three volunteers who had not come into contact with the new coronavirus had T-helper cells capable of recognizing Sars-CoV-2.

When a pathogen infects the body, particles of the immune system known as macrophages and dendritic cells surround the invading microorganism, break it down and present fragments of it (antigens) on its cell surface.

T-helper cells scan these fragments for structures that the immune system is already able to recognize. If identification occurs, T-helper cells send a signal to the immune system, which starts to produce antibodies against the pathogen.

That’s when the memory T cells start to act: they are responsible for “remembering” antigens previously found. This mechanism allows a person to become immune to a certain pathogen (or part of it) for days or even years.

With all this in mind, the scientists responsible for the new study believe that Sars-CoV-2 probably shares structural similarities with other types of coronaviruses that cause milder infections.

This would explain why, even though they had never come into contact with the new virus, so many volunteers had T-helper cells that recognized it.

“One of the characteristics of T-helper cells is that they are not only activated by a pathogen with an ‘exact fit’, but also by pathogens with ‘sufficient similarity,” explained Claudia Giesecke-Thiel, one of the researchers, in a statement.

In tests carried out in vitro, not all T-helper cells from patients infected with Covid-19 went into action. Giesecke-Thiel said this was “probably due to fact that T cells cannot be activated outside the human body during an acute or particularly severe phase of an illness.”

The effects of already having T-helper cells when contracting Covid-19, however, were not addressed in the study. Still, scientists theorize that they could speed up antibody production, helping the immune system fight the infection.

“However, it is also possible that cross-reactive immunity could lead to a misdirected immune response and potentially negative effects on the clinical course of COVID-19,” said Leif Erik Sander, a researcher at the Charité’s Medical Department and co-author of the study. “We know this can occur with dengue fever, for instance.”

The team plans to continue studying whether and how these T-helper cells can affect the development of symptoms in people already infected with Covid-19. The next analysis will be a comprehensive immunological investigation and will include volunteers from the hospital itself.

The researchers also plan to collect blood samples from at least 1,000 patients who have had Covid-19. The idea is to find correlations between immunological factors.

“This is of paramount importance, both in terms of people’s day-to-day lives and the treatment of patients,” said researcher Andreas Thiel, also a member of the Charité’s Medical Department.

Related topics:

Coronavirus Covid-19

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