Human Corneal Epithelial Cells Internalize Aspergillus flavus Spores by Actin-Mediated Endocytosis

Area of Science:

• Immunology
• Cell Biology
• Ophthalmology

Background:

• Human corneal epithelial (HCE) cells are crucial for innate immunity against fungal pathogens.
• The precise mechanisms of HCE cell interaction with fungal conidia remain unclear.

Purpose of the Study:

• To elucidate the cellular and molecular mechanisms underlying the phagocytosis of *Aspergillus flavus* conidia by HCE cells.
• To investigate the role of actin polymerization and endosomal trafficking in this process.

Main Methods:

• Confocal microscopy to visualize fungal conidia engulfment.
• Phalloidin staining to assess actin polymerization.
• Treatment with Cytochalasin D to inhibit actin-mediated endocytosis.
• Immunolabeling of early and late endosomal markers (CD71, EEA1, LAMP1, Rab7, cathepsin G).
• Lysotracker red staining to monitor phagosome acidification.
• Proteomic analysis of conidium-containing phagosomes.

Main Results:

• HCE cells actively phagocytose *Aspergillus flavus* conidia.
• Engulfment involves actin polymerization forming a ring around conidia.
• Endosomal maturation, including acidification, occurs within conidium-containing phagosomes.
• Proteomic analysis confirms the recruitment of phagosomal and endosomal proteins.

Conclusions:

• HCE cells employ phagocytosis, a well-defined cellular process, to internalize fungal conidia.
• This active engulfment mechanism contributes significantly to the ocular surface's antifungal defense.
• The findings provide detailed insights into the innate immune response at the ocular surface.