New research on intestinal samples from people who have died from COVID-19 has shown the effect of viruses on the intestinal immune system.
The study is published today in Limits in immunology by researchers from King’s College London with funding from the Medica Research Council through the UK Coronavirus Immunology Consortium and support from NIHR Guy’s and St Thomas’ BRC. It 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 intestine usually maintains healthy intestinal microbial populations, which are essential for good health. Researchers observed that the system that would normally regulate the composition of the microbial communities – otherwise known as Peyer’s Patches – was severely disrupted during severe COVID-19. This was regardless of whether there were signs of virus present in the gut or not.
While severe COVID-19 can lead to breathing problems and high fever, some patients may experience diarrhea, nausea, and vomiting, suggesting involvement of the gastrointestinal tract.
Professor Jo Spencer of King’s College London said: “This study shows that in severe COVID-19, this key component of the immune system is disrupted, whether the gut itself is infected with SARS-CoV-2 or not. This is likely to contribute to intestinal microbial disruption. populations in COVID-19 reported by others. “
Observations of the samples found that the structure and cellularity of Peyer’s Patches – a group of lymphoid follicles lining the small intestine – had been altered independently of the local levels of the virus. This included depletion of the germinal centers, which normally proliferate antibody-producing cells, in patients who died with COVID-19.
This resulting poor local immunity can lead to a reduction in microbial diversity, known as dysbiosis. Researchers also noted that the results suggest that oral vaccination may not be effective if the patient is already ill, as the intestinal immune system has already been compromised.
Professor Spencer added: “In the future, it will be important to understand factors that drive such lymphoid tissue dysregulation in severe inflammatory reactions.”