A new study led by Weill Cornell Medicine and New York-Presbyterian has shed light on the role of specific gut-dwelling fungi in severe cases of COVID-19. The research suggests that these fungi can exacerbate the extreme inflammation associated with the disease and lead to long-term changes in the immune system. The findings, published in Nature Immunology, have implications for identifying individuals who may benefit from specialized treatments.
The study, conducted using patient samples and preclinical models, revealed that the proliferation of certain fungi in the intestine, notably Candida albicans yeast strains, is associated with an increase in immune cells. These immune cells can worsen lung injury, a common feature of severe COVID-19.
Notably, the research also indicates that patients retain a heightened immune response and immune memory against these fungi for up to a year after recovering from SARS-CoV-2 infection. This suggests that the immune system’s response to these fungi may contribute to long-term complications, including a condition known as long COVID-19.
Dr. Iliyan Iliev, the senior author of the study, pointed out that this research uncovers a new dimension of the complex pathology involved in severe COVID-19. The findings highlight the role of the body’s own inflammatory immune response in causing harm, similar to what is observed in inflammatory bowel disease.
The research team worked with large clinical cohorts of COVID-19 patients and developed a mouse model to investigate the disease. They found that the presence of antibodies targeting gut fungi in the blood of severe COVID-19 patients led them to investigate the role of fungi in the disease.
In severe cases of COVID-19, populations of yeast, particularly Candida albicans, increased in the intestines of patients. This coincided with an increase in immune cells called neutrophils, which are known to contribute to inflammation, particularly in the lungs.
The study also demonstrated that mice bearing fungi from patients with severe COVID-19 produced more neutrophils and showed signs of heightened inflammation when infected with SARS-CoV-2. However, the administration of an antifungal drug reduced these effects.
The research provides insights into potential treatments and therapeutic approaches that may be beneficial for individuals with severe COVID-19. It also contributes to a better understanding of the long-term immune changes associated with the disease, which may be relevant to addressing long COVID-19.
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