Long Covid under the magnifying glass of Polish researchers

Even those patients who have had COVID-19 asymptomatically or very mildly are at risk of serious, long-term effects, as researchers point out. The post-COVID post-infection syndrome affects virtually all systems and organs of our body. It can include respiratory and circulatory problems, chronic fatigue not associated with exercise, neurological symptoms including changes in taste, smell, concentration and memory, headaches and dizziness, blood clotting disorders and thromboembolic complications, and even anxiety and depressive.

Scientists believe that pocovid syndrome is caused by not one mechanism, but many biological consequences of viral infection. Importantly, recent studies show that they can affect a huge percentage of all infected.

- The pocovid syndrome affects 43% of of all people who have had an infection, and among those who have suffered from severe disease, this percentage exceeds 60%. - says prof. dr hab. Katarzyna Piwocka. -

The long-term consequences of COVID-19 will therefore affect hundreds of millions of people around the world. The team of prof. Piwocka examines the effects of the transition of COVID-19 in its various forms on the long-term "remodeling" of patients' immune systems and the functioning of their bodies. Scientists asked whether people who were even six months after suffering from Sars-CoV-2 infection, i.e. convalescents are "immunologically healthy", what their immune status looks like according to the severity of the disease, and how these changes correlate with symptoms of long Covid. For this purpose, they use advanced flow cytometry, i.e. a technique that allows very precise determination of the properties of marked cells by simultaneous measurement of several dozen parameters labeled with fluorescent dyes.

Used by the team of prof. Piwocka, the first in Poland 5-laser spectral cytometer allows for the simultaneous assessment of 30 or more parameters of each blood cell. Such multi-parameter analyzes of protein markers at the single cell level allow the investigation of the dynamic state and function of cells of the immune system.

- This provided possibilities incomparable to those of classical cytometry and was of great importance for our research. The obtained data were then subjected to advanced bioinformatics analysis, which allowed us to identify new subpopulations of immune system cells, even those unique and rare, occurring specifically in various groups of convalescents under study. Importantly, our research was conducted for six months, so we were able to see how the polarization of the state and function of the immune system cells changed over time, the researcher explains.

The team found that in patients who contracted COVID-19, very high activity of the immune system persists over the next months, eventually leading to the appearance of markers accompanying aging and the so-called it represents exhaustion, along with elements of chronic inflammation. This is a very serious and unfavorable disorder of the body's functions. This is especially true for patients whose infection was moderate to severe. But long-term symptoms can affect all convalescents.

- Some parameters related to the functioning of the immune system were changed even six months after infection, which means that for a very long time the body is not able to return to the pre-infection baseline if such a recovery is possible at all. Interestingly, we've also seen long-lasting changes in people who have had COVID-19 very mildly, and our advanced, continued research shows the presence of an immune signature specific to this group. This clearly indicates that research, diagnosis and potential treatment should cover all people with symptoms of post-COVID syndrome, not only those who have had a severe form of the disease, the researcher explains.

The key task now is to develop methods to quickly identify people suffering from long COVID/pocovid syndrome and to identify the mechanisms leading to specific symptoms, especially the neurological and thromboembolic ones, which remain the most mysterious so far. This direction is already visible in many countries.

Research by prof. Katarzyna Piwocka are co-financed from EU funds.