A new study has suggested that the responses to the SARS-CoV-2 virus in the nose and throat might help determine who will develop severe disease and who will get through with mild disease or not develop the illness.
SARS-CoV-2, like other respiratory coronaviruses, enters through the mouth or nose and initially replicates within the epithelial cells of the human nasopharynx region, generating an upper respiratory infection over several days, the authors explain. A subset of patients develop symptoms of lower respiratory infection, and a complete understanding of why some people lapse into a serious disease while others don’t is still elusive.
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The study that was published in the journal Cell tries to provide answers to this question. Which cells does SARS-CoV-2 primarily target and how does the infection influence the respiratory epithelium, or the tissue that lines the respiratory tract, it asked, and went on to suggest that “failed nasal epithelial anti-viral immunity may underlie and precede severe COVID-19”.
Teams from the Boston Children’s Hospital and the University of Mississippi Medical Centre collaborated to study the SARS-CoV infection in the nasopharyngeal area from those with COVID-19, ranging from subjects who were mildly symptomatic to those who were critically ill.
José Ordovás-Montañés of the Boston Children’s Hospital, and co-senior investigator of the study, has been quoted: “Why some people get more sick 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.”
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Further, he explained: “Everyone with severe COVID-19 had a blunted interferon response early on in their epithelial cells, and were never able to ramp up a defense,” adding that having the right amount of interferon at the right time could be at the crux of dealing with SARS-CoV-2 and other viruses.
Despite equivalent viral loads, in people with mild or moderate COVID-19, the epithelial cells express anti-viral/interferon-responsive genes, whereas the cells in patients with severe COVID-19 have muted anti-viral responses, the authors wrote.
While this is a post facto study, it is hoped that it might at some point be used to predict disease scenarios even before a person tests positive for the infection. If research on ways to boost immune response in these initial entry points for the virus is successful, it might well turn out to be the strongest weapon in the armamentarium against the COVID-19 disease.
