How Covid-19 differs from other infectious lung diseases at cell-level decoded

The findings confirmed that cells called alveolar epithelial cells are the main targets of infection by the novel coronavirus

Using advanced analysis tools, scientists have revealed at single-cell resolution, how the novel coronavirus infection affects lung tissue in severe cases, compared to other diseases which affect the organ, an advance that may lead to the development of new therapeutics against Covid-19.

In the study, published in the journal Nature, scientists analysed over 6,50,000 cells from patients who had died of severe Covid-19, acute bacterial pneumonia, or bacterial or influenza-related acute respiratory distress syndrome, and from those who had had no lung disease.

The findings confirmed that cells called alveolar epithelial cells, which mediate gas-exchange function in the lungs, are the main targets of infection by the novel coronavirus SARS-CoV-2 that causes Covid-19.

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"Covid-19 is a complex disease, and we still don't understand exactly what it does to a lot of organs, but with this study we were able to develop a much clearer understanding of its effects on the lungs," said study co-author Olivier Elemento from Weill Cornell Medicine in the US.

Based on the analysis, the scientists said infected cells are not solely singled out for attack by lung-infiltrating immune cells, which could explain why inflammation often keeps worsening in severe Covid-19 and ends up causing such extensive and relatively indiscriminate damage.

According to the researchers, white blood cells called macrophages are much more abundant in the lungs of severe Covid-19 patients compared to other lung diseases, whereas white blood cells called neutrophils are most prevalent in bacterial pneumonia.

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"The application of technology like what we've demonstrated here is going to provide a huge boost to the utility of autopsy-based studies of disease," said study co-senior author Alain Borczuk, professor of pathology and laboratory medicine at Weill Cornell Medicine.

The scientists believe the distinction between different infection pathologies revealed by the study may help in the development of future treatments for these diseases.

"Traditionally for lung, liver, and other organ diseases we have these broad diagnoses that in fact cover multiple distinct diseases -- now we have a tool that that will enable us routinely to distinguish among these different diseases, and hopefully make use of those distinctions in treating patients more effectively," said Robert Schwartz, another co-author of the study from Weill Cornell Medicine