Luxembourg's study shows immunological response appears to have an impact on COVID-19 symptoms

According to medical research from Luxembourg, individuals with mild Covid-19 symptoms have a distinct immunological response from those who develop severe ones.

A study published in the Cell Reports Medicine journal investigated the functioning of the immune system in people who had been infected with Covid-19 but only experienced mild symptoms. It was led by Professors Feng Hefeng and Markus Ollert of the Luxembourg Institute of Health's Infection & Immunology Department (LIH).

This project was launched in April 2020 and surveyed over 100 persons who had received a positive PCR test result during the first three days after testing, followed by three weeks after. Patients were assigned to one of three categories based on their condition: asymptomatic, moderate, and hospitalized.

According to the research published on March 28, however, this immune response varied widely among the various groups. Patients with minor symptoms will benefit from a very early synchronized activation of the immune system's various levels, which are disrupted in patients with severe illness, according to Ollert. The researchers note that the immune system's branches must all collaborate effectively in order to fight the virus.

Improved understanding of the immune system's functions could result in practical applications, such as improved disease management by determining ahead of time how an illness will progress.

Pierre Pailler: You conducted a study to examine the immune system's activity in patients with mild symptoms or no symptoms at all, allowing them to effectively manage the Covid-19 virus. What did you discover?

Markus Ollert. - The immune reaction of lightly sick people is entirely distinct from that of severely ill individuals. It's likewise distinct from asymptomatic individuals. And, of course, it's distinct from people who don't get Covid despite having an infected family member in their home.

What are the differences between these immune responses?

"You must comprehend that the immune system is made up of two arms, one of which is adaptive immunity (comprising T cells and antibodies). Non-specific or innate immunity is the second component of the immune system. The latter is a more ancient form, which even insects have. This one is quite crucial to enable the entire immunological response to function. Without a strong innate immune reaction, you will never be able to produce an effective adaptive immune reaction.

A highly effective natural immune response emerges within 72 hours in patients with minor symptoms. In contrast, those who have severe symptoms show no such response.”

What were your findings from this study?

"The idea that an infected person can only fight the virus when all layers of the immune system are concurrently activated. This is precisely what we discovered in those with minor symptoms, who benefited from a very early unified activation of the immune system's different levels. The activation appears to be disjointed in the severe patient.

It's only when all of your immune system's branches are in sync that you can fight the virus. If anything goes awry, you'll end up with significant problems or perhaps even death.”

Why do some individuals appear to be healthy, even after having direct contact with a confirmed case, for example, at home?

"According to research conducted in Berlin, juveniles may occasionally be completely symptom-free due to a powerful local mucosal immune response.

In our research, we discovered that some symptom-free adult patients have no systemic immunological reaction. Consequently, some individuals may have such a robust local immune reaction that the virus can't transit any further. We didn't go into detail about this since we had just a few such patients. However, we may infer that there is also a local component to the immune reaction that is critical in combating these viruses.”

What suitable measures may be taken from this research?

"When you look at antibodies, you can't tell whether a person has acute or minor symptoms. The same is true for T cells. However, when you consider the entire picture, including the natural immune cells, mild patients differ from severe patients or healthy individuals in their immunological profile.

We can use our data to try to figure out whether a patient will have severe or minor symptoms after we've taken a blood sample. This may assist us in paying greater attention to a patient, allowing us to make the appropriate judgments sooner, such as either sending them home and keeping them hospitalized.”

This research is entirely in Luxembourg. Is there anything unique about the Grand Duchy that made it possible?

"We wouldn't have had the ability to attract so many people with a positive PCR test and minor or no symptoms if we didn't do large-scale testing. This was a one-of-a-kind chance. The people of Luxembourg were also eager to participate in this research. This would not have been possible without their help as well.

The LIH has also advanced a new approach that places it firmly in the translational medicine realm. "We are continuing to expand our LIH biobank, which is now a major resource for us. We have many collaborations with the University of Luxembourg and other institutions around the world, as well as Luxembourg hospitals, the LNS, and others. Biomedical research today only succeeds in collaboration."