Link Between Severe COVID-19 and Immune Responses in Nasopharynx Explored

The body's first encounter with SARS-CoV-2 happens in the nose or throat. The muted antiviral responses in these areas could possibly result in severe Covid infection, found a new study.

COVID-19 shows different outcomes in different people. Researchers from the Boston Children's hospital have now found that immune responses in the nasopharynx could possibly determine the seriousness of this viral infection.

"Why some people get sicker than others has been one of the most puzzling aspects of this virus from the beginning. Many studies looking for risk predictors have looked for signatures in the blood, but blood may not really be the right place to look," said Dr.José Ordovás-Montañés, co-senior investigator of the study.

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‘Epithelial cells that line the nose and throat undergo significant changes due to SARS-CoV-2 infection. An increase in the activation of immunity-related genes could result in mild or moderate COVID-19.’

As the body's first encounter with SARS-CoV-2 happens in the nose or upper part of the throat, the researchers sought to investigate how the immune responses created here can help determine the severity of the disease.

For this, they obtained cell samples from the nasal swabs of 35 adults with COVID-19 from April to September 2020, ranging from mildly symptomatic to critically ill.

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Each patient swab yielded an average of 562 cells. The team sequenced RNA in each cell. The data from this analysis indicated the infection and cells that contained RNA originating from the virus.

Key findings of the study:

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• Epithelial cells lining the nose and throat undergo significant changes in the presence of SARS-CoV-2

• Immature ciliated cells and mucus-producing secretory and goblet cells increased in number, but the levels of mature ciliated cells decreased

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• SARS-CoV-2 RNA was present in immature ciliated cells and specific subtypes of secretory cells, goblet cells, and squamous cells

• Epithelial cells that got increased activation of genes involved with antiviral responses were prominent among people with mild or moderate COVID-19

• People who developed severe covid infection had a muted immune response in their epithelial cells, but macrophages and other immune cells that boost inflammatory responses seemed to be increased in them

"Having the right amount of interferon at the right time could be at the crux of dealing with SARS-CoV-2 and other viruses," said Ordovás-Montañés.

The team further planned to investigate the reason behind this differential immune response among covid patients. The findings of the current study were published in the journal Cell .

Source-Medindia