A recent study has uncovered a connection between severe COVID-19 cases and an overabundance of certain gut fungi that could lead to long-lasting changes in the immune system. This breakthrough could pave the way for future development of antifungal treatments, offering relief to those critically ill with COVID-19.

The study led by researchers at Weill Cornell Medicine and New York-Presbyterian identified that an abundance of fungi, particularly strains of Candida albicans yeast, in the gut could trigger an increase in immune cells, which could worsen lung damage.

Notably, those patients retained an elevated immune response and immune memory against these fungi even a year after the COVID-19 infection, according to the study published in the journal Nature Immunology.

The study findings were based on three clinical cohorts of COVID-19 patients and a mouse model.

The researchers first identified the link between the fungi and severe infection from SARS-CoV-2 infection after analyzing the blood samples from patients diagnosed with severe COVID-19 infection at New York-Presbyterian/Weill Cornell Medical Center.

The researchers noted that in those cases, a particular species of fungi, Candida albicans, increased in the intestines, and the patients developed antibodies specific to attack them. While examining their immune systems, the patients showed a parallel increase in neutrophils or immune cells. The excessive numbers of neutrophils in the lungs further worsened the inflammatory response that already damaged the organs.

The blood analysis also indicated lasting changes in the immune system related to long COVID-19 even a year after the infection.

"Severe and long COVID-19 were not thought to involve fungal blooms in the intestines that, in addition to the virus, can impact patient's immunity," Dr. Iliyan Iliev, a senior author from Weill Cornell Medicine, said in a news release.

When researchers conducted a mice study, they found that mice exposed to fungi from severe COVID-19 patients produced more neutrophils in their blood and lungs. When they were then infected with SARS-CoV-2, they showed signs of heightened inflammation, the effects of which could be mitigated by antifungal drugs.

The researchers hope their findings about the lasting presence of antibodies could help identify people at heightened risk for long COVID-19. Although the results may not have immediate implications for treating severe or long COVID-19, they suggest new opportunities to tailor therapy, according to Dr. Iliev.

The study has certain limitations, as it only involved a limited number of human participants, with 91 patients with severe COVID-19 and 36 in the control group. Given that the study was conducted in 2020, during the initial wave of COVID-19, there may have been changes since then in the virus and immunity, particularly due to vaccination.