What does SARS-CoV-2 do to the body?
Pneumologists, intensive care physicians and lung researchers at the DZL site Munich are gathering knowledge about Covid-19.
The corona virus sneaks into the body via the mouth, nose and throat. But it is in the lungs, where its destructive power unfolds. Lung researchers therefore want to use their previous knowledge to understand what happens in the lungs after a SARS-CoV-2 infection. One aspect must not be forgotten: The lung is a highly complex organ. More than 40 different cell types interact in processes ranging from gaseous exchange to purification. Many of the processes occurring in these lung cells and the approximately 300 million pulmonary alveoli are still being intensively researched.
Immune reaction in the lung - suddenly harmful
Prof. Jürgen Behr, Principal Investigator at the DZL site Munich, sees the effects of Covid-19 in front of his eyes daily. He is Director of Polyclinic V at the University of Munich Hospital as well as Medical Director of the Asklepios Fachkliniken München-Gauting. There, in Gauting, 58 Covid-19 patients were treated, three of whom died, but most fortunately have since been discharged (as of April 22nd 2020). Professor Behr's hypothesis: What the lungs normally do for us in a positive way, seems to be reversed in the case of Covid-19:
"The lung is one of the most immunologically active organs because it is in constant contact with the environment and requires a strong immunological defence to protect itself from external pollutants and infectious agents. Accordingly, the lung is predisposed to immunological reactions. However, this also means that these reactions can lead to organ damage if they become excessive.”
What data reveal - where SARS-CoV-2 docks
Researchers at the German Centre for Lung Research (DZL) now know exactly how the virus gets into lung cells. As part of the Human Cell Atlas (HCA) Lung Biological Network, they carried out a meta-analysis of COVID-19-related genes that was published in Nature Medicine. Co-authors of this work were the DZL-PIs Ali Önder Yildirim, Herbert Schiller (CPC-M) and Fabian Theis (ICB). The result of the analysis: which cells of the lung express ACE2-receptors – the docking site of the SARS-CoV-2 virus. These receptors normally regulate the tension of blood vessels. Probably the largest currently existing data set of lung cells also revealed another clue: The genes of men, smokers and elderly people show higher expression of the receptor.
ACE2-R is therefore at the centre of the destructive process in the lung, explains pneumologist Prof. Jürgen Behr:
"This ACE2-R is particularly strong on lung cells, which is why the lung is the main target organ of the virus. Therefore, the combination of strong ACE2-R expression in the lung on the one hand and its immune response on the other hand probably leads to acute lung failure in covid-19 infections.“
Which cell types in the human body are potential targets for SARS-CoV2 to cause COVID-19? To further investigate this, the global research community can use a website to jointly analyse the data: www.covid19cellatlas.org
Riddle Corona - Multiple disorders in many organs
In the Department of Anaesthesiology at the LMU Clinic in Munich, intensive care physicians, together with colleagues from Internal Medicine and Surgery, treated 63 Covid-19 patients. Eight of them have died, 27 are still in intensive care (as of May 4th 2020). One observation is particularly worrying said the director of the Clinic, Prof. Bernhard Zwißler: Covid-19 triggers many other disorders compared to other bacterial and viral lung infections or influenza:
"Covid-19 affects not only the lungs but also many other organ systems such as the heart, circulation, kidney function, blood coagulation, immune system, etc. In particular, we see a high proportion of patients with kidney failure and thromboembolic events. We also observe more microcirculation disorders, probably due to a complex interaction between blood coagulation, vascular endothelium and immune system. In addition, SARS-CoV-2 often leads to cardiac dysfunction, which can also affect lung function due to the interaction between the heart and lungs.”
And after Corona? Will Covid-19 cause delayed effects?
Vaccines, antibody tests, drugs, treatment options: the entire world is working on measures to combat the Corona pandemic. However, Prof. Behr is already concerned that he will continue to treat patients with Covid-19 after the end of the pandemic:
"Covid-19 could also cause long-term damage to the lungs, as we observe after other lung infections with ARDS (Acute Respiratory Distress Syndrome). This is particularly true for patients with previous lung disease. Whether these changes persist, regress over time or are treatable cannot yet be answered for Covid-19 infection because of the lack of long-term observations. However, doctors and centres specialising in interstitial lung diseases, as well as the CPC, are preparing for an increasing number of such patients with "post-Covid" disease patterns. At the CPC Munich we therefore plan a structured follow-up of as many patients as possible who have survived a Covid-19 infection".