Compromised gut health in severe COVID-19

Newswise – New research on gut samples from people who died of COVID-19 has shown the impact of the virus on the gut immune system.

The study is published today in Frontiers in immunology by researchers at 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. He examined gastrointestinal tract samples 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 gut microbial populations that are essential for good health. The researchers observed that the system that would normally regulate the composition of microbial communities – otherwise known as Peyer’s patches – was severely disrupted in severe cases of COVID-19. This is regardless of whether or not there is evidence of virus in the gut.

Although 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 cases of COVID-19 this key component of the immune system is disrupted, whether the gut itself becomes infected with SARS- CoV-2 or not.This would likely contribute to the disruptions of gut microbial populations in COVID-19 reported by others.

Observations of the samples revealed that the structure and cellularity of Peyer’s patches – a group of lymphoid follicles that line the small intestine – had been altered independently of local levels of the virus. This included the depletion of germinal centers, which normally spread antibody-producing cells, in patients who died with COVID-19.

This resulting low local immunity could lead to a reduction in microbial diversity, known as dysbiosis. The researchers also noted that the results suggest that oral vaccination may not be effective if the patient is already sick, because the gut immune system is already compromised.

Professor Spencer added: “In the future, it will be important to understand the factors behind such dysregulation of lymphoid tissues in severe inflammatory responses.

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