C. albicans ergosterol modulates the antifungal response of human neutrophils by masking β-glucan

Introduction Ergosterol-targeting azoles are widely used in the treatment of Candida albicans infection. In addition to direct antifungal activity, azoles are known to enhance neutrophil-mediated killing of C. albicans, but the underlying mechanisms remain unclear, particularly whether ergosterol depletion directly modulates host immune responses. Gap Statement It remains unknown whether reduced ergosterol levels alone, independent of broader disruption to sterol biosynthesis and fungal morphogenesis, influence neutrophil antifungal activity. Aim This study aimed to determine how genetic disruption of late-stage ergosterol biosynthesis affects neutrophil-mediated responses to C. albicans. Methodology Doxycycline-repressible GRACE mutants targeting late-stage ergosterol biosynthesis genes (ERG4, ERG5, ERG3 and ERG28) were co-incubated with primary human neutrophils. Fungal survival, oxidative burst, phagocytosis, neutrophil extracellular trap (NET) formation and cell wall composition were assessed.

All ergosterol-deficient strains induced elevated neutrophil reactive oxygen species (ROS) production; however, only ERG4 depletion was associated with enhanced fungal clearance. This phenotype correlated with increased phagocytosis and reduced NET formation. Cell wall analysis revealed no changes in total chitin or mannan content but demonstrated significantly increased surface exposure of β-1,3-glucan in ERG4-depleted cells.

These findings indicate that disruption of late-stage ergosterol biosynthesis, particularly via ERG4, enhances neutrophil antifungal responses and is associated with increased β-glucan exposure. This study highlights a potential role for ergosterol in immune evasion and suggests that targeting terminal steps of the pathway may improve host-mediated clearance of C. albicans. Competing Interest Statement The authors have declared no competing interest.