Intestinal Candida albicans overgrowth in IgA deficiency

Area of Science:

• Immunology
• Microbiology
• Gastroenterology

Background:

• Secretory Immunoglobulin A (IgA) interacts with gut bacteria, but its role in human mycobiota ecology is largely unexplored.
• The association between IgA deficiency and gut fungal dysbiosis remains unknown, necessitating further investigation.

Purpose of the Study:

• To investigate the impact of IgA on the ecology of the gut mycobiota.
• To determine if IgA deficiency is linked to alterations in gut fungal composition and function.

Main Methods:

• Fungi-Flow method used to analyze IgA, IgM, and IgG responses against fungi in healthy donors and IgA-deficient patients.
• Internal transcribed spacer gene sequencing to assess stool mycobiota composition.
• In vitro studies to evaluate the effect of secretory IgA on Candida albicans growth and invasion.

Main Results:

• Homeostatic IgA exhibits selective recognition of commensal fungi.
• Compensatory IgM binding preserves fungal gut ecology in selective IgA deficiency (SIgAd).
• Candida albicans overgrowth occurs in SIgAd patients with decreased TH17/TH22 responses, and secretory IgA inhibits C. albicans in vitro.

Conclusions:

• Secretory IgA plays a crucial role in maintaining fungal-host mutualism by selectively impacting Candida albicans ecology.
• IgA deficiency can disrupt this balance, potentially leading to dysbiosis and overgrowth of pathobionts like C. albicans.