Covid and Covid vaccines can have serious effects on the gut microbiome
An imbalance in the fungal flora present in the gut could contribute to excessive inflammation in people with severe COVID-19 or persistent COVID-19. A study, reported in the journal Nature, found that subjects suffering from serious illnesses had high levels of a fungus that can activate the immune system and induce lasting changes.
The work, published October 23 in Nature Immunology1 , raises the possibility that antifungal treatment could provide some relief to people critically ill from COVID-19.
“We know that inflammation is what causes severe disease,” says Martin Hönigl, a clinical mycology researcher at the Medical University of Graz in Austria, who was not involved in the study. This work, he says, provides a potential mechanism of pathogenic inflammation that may have been overlooked.
Digging deeper into the topic, trillions of microorganisms live in our bodies, helping us digest food, protecting us from harmful pathogens, and more. Although much of the microbiome consists of bacteria, previous research has shown that the fungal portion, the mycobiota, also interacts with the immune system2.
Previous studies have shown that many people with COVID-19 have altered microbial composition in the gut and compromised protective barriers, which could allow pathogens to enter the blood. And some individuals seriously ill with COVID-19 have contracted dangerous fungal infections in their lungs.
Immunologist Iliyan Iliev at Weill Cornell Medicine in New York City and his colleagues wanted to further investigate the link between the mycobiota and COVID-19. Researchers examined the blood of 91 people hospitalized for the disease in 2020. Nearly three-quarters of these people had severe COVID-19 and had received more than six liters of supplemental oxygen per minute or invasive mechanical ventilation, while the rest had a disease moderate or mild.
Compared to 36 individuals who had never tested positive for SARS-CoV-2, people with severe COVID-19 produced about four times more antibodies against three common fungal species in the gut, including the yeast Candida albicans. A high presence of antibodies suggests that these people had high amounts of these fungi. Fecal samples collected in early 2021 from 10 people with COVID-19 also showed that they had overall higher levels of intestinal fungi, particularly Candida species, than 10 healthy individuals. For these people, Candida abundance was positively correlated with disease severity. The presence of some fungal species, in particular C. albicans, has been shown to activate the immune system6.
In a subset of people with severe COVID-19, the number of antibodies to C. albicans in their blood correlated with the number of immune cells called neutrophils, which can trigger inflammation.
When the researchers infected mice with C. albicans extracted from people with severe COVID-19 and then infected them with SARS-CoV-2, they observed that more neutrophils invaded the animals' lungs and triggered an inflammatory response compared to mice with only SARS-CoV-2. If these mice were treated with an antifungal drug, the number and activity of neutrophils was reduced.
The study also found that people with severe COVID-19 continued to have elevated levels of antibodies against C. albicans and neutrophil precursors ready to fight off the fungi even a year after recovering from the disease in some cases. These factors suggest that mycobiota changes during a SARS-CoV-2 infection could contribute to persistent COVID-associated inflammation.
“There are several theories about what might trigger persistent symptoms after COVID,” says Aran Singanayagam, a respiratory immunologist at Imperial College London. “Microbial dysbiosis, both of the gut and the lungs, is one of the main proposed theories, so I think this lends weight to that theory.”
Researchers agree that more studies need to be done to delve deeper into the link between gut fungi and COVID-19. It's unclear whether the changes seen in the mycobiota of people with COVID-19 resulted from the disease or preceded it, making people more susceptible, Singanayagam says.
The NIH had previously already detected a link between variations in the severe intestinal microbiome and Covid or Covid vaccination, with the possibility of also developing serious ulcerative pathologies of the colon . Among other things, the microbiome-vaccine interference was considered bidirectional, with also the second that could intervene on the effects of the first.
If future studies reveal more details about the mechanisms involved, existing antifungal treatments could be repurposed to help people with COVID-19. Iliev hopes that this work “will get people to start thinking about those common types of biology that we see in very different diseases and how we can exploit that.”
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The article Covid and Covid vaccines can have serious effects on the intestinal microbiome comes from Economic Scenarios .
This is a machine translation of a post published on Scenari Economici at the URL https://scenarieconomici.it/covid-e-vaccini-covid-possono-avere-effetti-gravi-sul-microbioma-intestinale/ on Wed, 25 Oct 2023 12:00:32 +0000.