Reduced antiviral response to SARS-CoV-2 in severe Covid-19

Arya Sukumar, College of Agriculture, Vellayani

Researchers gathered a lot of information about SARS-CoV-2 and its etiology in the last 18 months. They understand how the virus enters the body, how it infects the mucus layers of the nasal canal after entering through the nose and mouth. However, many concerns remain unresolved, such as when and where the course of severe COVID-19 will be established. Is it true that severe disease begins only when the body’s ability to handle moderate sickness has collapsed or begins much earlier? Researchers from MGH’s Ragon Institute, MIT’s Broad Institute, Boston Children’s Hospital (BCH), and University of Mississippi Medical Center (UMMC) worked on these issues.                                                        

Background and scope of the study

According to new research, cells collected at the time of diagnosis from patients who later had severe COVID-19 exhibit a suppressed antiviral response. The findings were published in the peer-reviewed journal Cell. They understand that infections that stay in the upper airway are usually mild or asymptomatic. While infections that spread down the airway to the lungs are considerably more serious and can lead to deadly illnesses. To test this, researchers compared nose samples from 68 patients who had moderate COVID-19 to those who advanced to more severe illness and required respiratory assistance.

They used cells obtained from nose swabs taken at the time of their first COVID-19 diagnosis. Thirty-five swabs were collected at the time of diagnosis from COVID-19 patients, covering a range of disease stages from moderate to severe. Sixteen swabs came from patients with respiratory failure owing to various reasons, whereas seventeen came from healthy volunteers. Individual cells were separated and sequenced from each sample, seeking RNA that would show what type of proteins the cells were producing. According to the findings, individuals who went on to develop severe COVID-19 had a much weaker antiviral response in the cells collected from their early swabs. The body’s intrinsic antiviral response to initial infection may dictate the course of severe COVID-19, offering up new paths for early treatments that might avoid severe illness.

Cell-mediated response to viral infections                         

Cells employ RNA to produce proteins, which are the tools, machinery, and building blocks that allow the cell to execute various activities and adapt to its surroundings. Researchers can learn how a cell is responding to external changes like a viral infection by examining its transcriptome (RNA) collected from the cell. Nasal swabs capture the top layer of cells, such as those that line the nasal passages.

The researchers used single-cell transcriptome data to investigate how epithelial and immunological cells responded to early COVID-19 infection. Researchers may even utilize the transcriptome to detect if a virus-like SARS-CoV-2 has infected particular cells. Hundreds of single cells from low-input clinical samples have been sequenced using novel techniques. Single-cell sequencing techniques allow us to examine the body’s response to illness at a precise point in time. This allows us to carefully investigate characteristics that distinguish one disease course from another, as well as infected cells from non-infected cells.

First, the researchers discovered that in individuals who had severe COVID-19, the antiviral response, which is mediated by a class of proteins called interferons, was significantly reduced. Second, individuals with severe COVID-19 had more highly inflammatory macrophages, immune cells that contribute to high levels of inflammation, which are frequently observed in severe or fatal COVID-19. These data suggest that the course of COVID-19 may be influenced by the initial or very early response of the nasal epithelium and immune cells to the virus. Finally, the researchers discovered cells and reactions that were specific to individuals who had a mild illness. If the early phases of infection may predict disease, as the team’s research shows, it opens the door for scientists to create early treatments that can help prevent severe COVID-19 from developing.

Conclusion:

The body’s intrinsic antiviral response dictates the severity of COVID-19. According to new research, cells collected at the time of diagnosis from patients who later had severe COVID-19 exhibit a suppressed antiviral response. Nearly all of the severe COVID-19 samples lacked expression of numerous genes associated with an antiviral response. In such individuals, a class of proteins called interferons was significantly reduced. These individuals also had more highly inflammatory macrophages, immune cells that contribute to high levels of inflammation, which are frequently observed in severe or fatal COVID-19. Researchers may be able to develop novel therapeutic methods for COVID-19 and other respiratory viral infections as a result of these findings.

Also read: Can viruses communicate?

Reference:

1. Ziegler, C. G. K., Miao, V. N., Owings, A. H., Navia, A. W., Tang, Y., Bromley, J. D., Lotfy, P., Sloan, M., Laird, H., Williams, H. B., George, M., Drake, R. S., Christian, T., Parker, A., Sindel, C. B., Burger, M. W., Pride, Y., Hasan, M., Abraham, G. E., … Ordovas-Montanes, J. (2021). Impaired local intrinsic immunity to SARS-CoV-2 infection in severe COVID-19. Cell, S0092867421008825. https://doi.org/10.1016/j.cell.2021.07.023

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