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The research, published in the journal Frontiers in Immunology, looked at samples of the gastrointestinal tract from patients who died after being diagnosed with COVID-19 during the first wave of the pandemic.
Lymphoid tissue in the gut normally maintains healthy intestinal microbial populations which are essential for good health.
Researchers from King’s College London in the UK observed that the system that would normally regulate the composition of the microbial communities — otherwise known as Peyer’s Patches — were severely disrupted in severe COVID-19.
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The researchers noted that while severe COVID-19 can lead to breathing problems and high fever, some patients can experience diarrhea, nausea, and vomiting, which suggests the involvement of the gastrointestinal tract.
”This study shows that in severe COVID-19, this key component of the immune system is disrupted, whether the intestine itself is infected with SARS-CoV-2 or not,” said Professor Jo Spencer, from King’s College London.
”This would likely contribute to the disturbances in intestinal microbial populations in COVID-19 reported by others,” Spencer said. Observations of the samples found the structure and cellularity in Peyer’s Patches — a grouping of lymphoid follicles that lines the small intestines — had been altered independently of the local levels of the virus.
This included depletion of the germinal centers, which normally propagate antibody-producing cells, in patients who died with COVID-19.
This resulting poor local immunity could lead to a reduction in microbial diversity, known as dysbiosis.
Researchers said the findings suggest that oral vaccination may not be effective if the patient is already ill, as the gut immune system is already compromised.
”In the future, it will be important to understand factors driving such lymphoid tissue dysregulation in severe inflammatory responses,” Spencer added.