British researchers analyzed samples from the gastrointestinal tract of patients who died after being diagnosed with COVID-19 during the first wave of the pandemic. They see the full impact of the infection on the gut’s lymphoid tissues, which normally maintain healthy gut microbial communities essential for good health. The observed disturbance appears independent of whether or not there is evidence of the presence of virus in the gut. Lead author Prof Jo Spencer, King’s College London, comments: “Our study shows that in severe cases of COVID-19, this key component of the immune system is disrupted, whether the gut itself becomes infected by SARS-CoV-2 or not. This likely contributes to the disruptions of gut microbial communities reported in COVID-19 by previous research.”
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Compromised intestinal immunity
So although severe COVID-19 mainly causes respiratory problems and high fever, some patients also experience gastrointestinal symptoms like diarrhea, nausea, and vomiting, suggesting involvement of the gastrointestinal tract.
The study: observation of the samples reveals that the structure and cellularity of Peyer’s patches – a group of lymphoid follicles that line the small intestine – are altered independently of virus levels. Germinal centers, which normally propagate antibody-producing cells, are found to be depleted in these patients who died from COVID-19. This weak local intestinal immunity may lead to (and explain) the reduction in bacterial diversity, or dysbiosis, observed in these deceased patients.
The team is continuing to research the factors behind such dysregulation of intestinal lymphoid tissues in severe inflammatory responses.
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