Candida albicans in the Gut Linked to Severe COVID-19

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Candida albicans in the Gut Linked to Severe COVID-19

Candida albicans in the Gut Linked to Severe COVID-19

Over the past few years, a longstanding mystery surrounding SARS-CoV-2 infections is that the severity of COVID-19 appears to be random, varying from person to person.

Apart from known vulnerable groups – the elderly, the immunocompromised, or those with pre-existing health issues – it has remained unclear why this disease can have a severe impact on some healthy individuals while causing only mild cold-like symptoms in others.

A hypothesis put forward in 2022 suggested that an individual’s blood type plays a crucial role in determining the severity of COVID-19. But an earlier study indicated that differences in gut bacteria could affect the severity of the disease and the risk of long-term COVID-19 infection.

Candida albicans in the Gut Linked to Severe COVID-19

Recently, hundreds of studies have explored the relationship between the gut microbiome of bacteria and COVID-19, but few have paid attention to the less-welcome fungal populations inside our bodies. The fungal microbiome, referred to as the “mycobiome,” was only discovered in our gut a decade ago.

Researchers from Weill Cornell Medicine became aware of the connection between this mycobiome and changes in inflammation within the body, leading them to investigate if there is a direct link between the mycobiome and severe chronic obstructive pulmonary disease (COPD).

The first phase of the study involved examining blood samples from 91 COVID patients (25 with mild to moderate symptoms, 66 with severe symptoms). Additionally, 36 blood samples were taken from healthy individuals. The study quickly revealed that severe COVID-19 patients had a high concentration of immune antibodies specifically targeting certain gut fungal populations.

By observing stool samples from a small subset of patients, one fungus appeared to be particularly prominent in the most severely ill participants, and that was Candida albicans. Researchers found that an increase in fungus count was significantly correlated with the severity of the COVID-19 disease.

To further investigate this compelling correlation, researchers colonized a group of healthy mice with the fungus isolated from human patients. They observed that these mice exhibited significantly stronger inflammatory responses to the virus compared to mice not infected with the fungus. What’s even more convincing is that enhanced inflammatory responses to SARS-CoV-2 in mice could be suppressed by administering antifungal drugs.

Infectious disease expert Paul Griffin from the University of Queensland described this new study as both interesting and comprehensive, but not without limitations. Aside from the relatively small sample size, Griffin also noted that the patients in the study were from 2020, when the viral form and vaccine landscape were quite different.

“Nonetheless, this study raises many possibilities, including perhaps studying which people may be at greater risk of severe COVID based on their mycobiome,” Griffin explained in an article for The Conversation. He continued, saying, “It might even be possible to try and alter the mycobiome to reduce the risk of COVID infection. But to achieve these goals, we need more research.”

In a commentary on this new study, Katherine Lagree and Peter Chen from the Mount Sinai Medical Center noted that the study’s findings raise many questions. For example, it is still unclear how gut fungi induce a pro-inflammatory state in the body when infected with SARS-CoV-2. However, Lagree, Chen, and Griffin emphasized that this study confirms the role of our fungal microbiome in overall health and underscores the need for more research into fungal residents.

Lagree and Chen concluded, “These intriguing findings highlight the immunological effects of the fungal microbiome in virus-mediated pathologies and will inspire future research on how dysregulation of the fungal microbiome regulates human health and disease.”

This new study was published in the journal “Nature Immunology.”