Individuals with the long form of COVID-19 and who present neurological symptoms have a different intestinal flora, we heard Wednesday as part of the first Canadian Symposium on Long COVID, which takes place at the hotel Hilton Midtown, in Montreal.
This microbiota can lead to the appearance of neurological symptoms when it is transferred to mice which had been genetically modified to not have intestinal flora and which had never been infected by the COVID-19 virus, specified the DD Emilia Liana Falcone, from the Montreal Clinical Research Institute (IRCM).
A lot of scientific literature has focused on the role of the intestinal microbiota in various health problems, she recalled during her presentation.
“We know that, through its interaction with the immune system, it can have an impact on neurological disorders, heart disease, lung disease, metabolic disorders,” said the DD Falcone. So why wouldn’t this be as involved in the context of long COVID? »
The DD Falcone directs the IRCM post-COVID-19 research clinic (IPCO). She and her colleagues found that the gut microbiota of their long-term COVID patients with neurological symptoms was less diverse, “and diversity is associated with better health,” she recalled.
On the other hand, the intestinal microbiota of patients with the long form of COVID-19, but who do not have neurological symptoms, is comparable to that of patients who have never had COVID.
A distinct microbiota
“The gut microbiota signature of patients who have COVID and neurological symptoms is distinct,” said Dr.D Falcone. Some microbes are more represented, but some are less. »
Some of these underrepresented microbes are more present in patients who have not developed serious symptoms of COVID, or who have never been infected with the virus, she said.
The researchers grafted the microbiota of long-term COVID patients with neurological symptoms and those of long-term COVID patients without neurological symptoms into mice with sterile intestines. The mice in the first group performed less well than those in the second during different tests.
The researchers also measured an association between increased severity of the long form of COVID-19 and an increase in intestinal barrier dysfunction. The more severe the symptoms of long COVID were, the more a protein was found in the patients’ blood that indicates greater permeability of the intestinal barrier — in other words, a leaky gut.
These leaks ― which were still detectable 12 months after the initial infection ― could then disrupt the functioning of the patient’s immune system and predispose them to an autoimmune response.
“We do not think that this intestinal dysbiosis is the only player in this mechanism,” said the DD Falcone. We believe that viral persistence also plays a role. It is likely the combination of the two that contributes to the sustained inflammation. »
This inflammation, she added, could then contribute to the immune system dysregulation and microcoagulation problems that other studies have implicated in explaining long-form COVID-19.
“I think it’s all interrelated,” said Dr.D Falcone.
Some 4.7 million Canadians have been infected with SARS-CoV-2 since the start of the pandemic. It is estimated that around 15% of them will have long-term after-effects of their infection.