C. albicans complexed to a human buccal epithelial cell.

In vitro adherence assay showing C. albicans germ tubes complexed to a human buccal epithelial cell. The germ tubes are covalently attached to the epithelial cell.

C. albicans attached to human buccal epithelial cells expressing transglutaminase 1.

Human buccal epithelial cells terminally differentiated and dislodged from buccal surfaces were mixed with C. albicans forming germ tubes expressing GFP under the control of the hypha-specific HWP1 gene upstream region; Epithelial transglutaminase 1 is indicated in red. Epithelial cell nuclei are stained with DAPI.

Cytology of mucosal candidiasis.

Cytology from patient sample showing human oral epithelial cells with yeast and hyphal forms of C. albicans.

Surfaces of hyphal growth forms display antigens not found on yeast growth forms.

Indirect immunofluorescence assay demonstrating the presence of surface proteins specific to the hyphal growth form; Polyclonal antiserum was generated against formalin fixed germ tubes and exhaustively adsorbed with yeast growth forms prior to the assay.

Hwp1 is abundantly expressed on germ tubes and absent or barely detectable on yeast forms.

Indirect immunofluorescence assay demonstrating the presence of Hyphal Wall Protein 1 (Hwp1) on germ tube surfaces of C. albicans. Polyclonal antiserum was generated against the purified N-terminal TGase domain prior to the assay.

Appearance of normal human soft palette, which is non-keratinized.

Low power view of normal, uninfected human soft palette stained with PASH (periodic acid Schiff hematoxylin); Note the absence of hyperkeratinzation on the surface of the epithelium.

Human soft palette infected with C. albicans appears keratinzed.

A. Low power view showing loosely packed keratinized layers at the surface of epithelium (see bracket and black arrows for examples).
B. Enlargement of boxed region in A showing the loose parakeratin at the epithelial surface.
C. Enlargement of boxed region in B. Note the presence of hyphae (black arrows) in both the lightly-stained parakeratin and the more intensely-stained surface layers of epithelial cells.
C and D. Note hyphae (white arrowheads) impinging on epithelial cell layers just superficial to the spinous layer.
Scale bars A. 250 mm B-D. 50 mm. Taken from Cellular Microbiology 1:946-966. 2009

Changes in actin dynamics in epithelial cells at an early stage of differentiation in the presence of C. albicans.

Co-culture of the human oral keratinocyte cell line OKF6/Tert-2 with C. albicans changes actin dynamics. Note formation of stress fibers by 3 h and lamellopodia by 6 h, which are accompanied by motility and a tripling in cell area. Actin fibers retract at 12 h and are tangled by 24 h. Incubation with S. cerevisiae causes minimal effects on actin dynamics. Taken from Cellular Microbiology 1:946-966. 2009.

Formation of cell-cell adhesions in human oral OKF6/Tert-2 keratinocytes in the presence of C. albicans.

Note the co-localization of actin and E-cadherin forming puncta by 3 hours that merge by 6 hours. The keratinocytes appear to be responding to a wound. Taken from Cellular Microbiology 1:946-966. 2009.

Dissolution of cell-cell adhesions in human oral OKF6/Tert-2 keratinocytes in the presence of C. albicans.

The cell-cell adhesions dissolve between 12 and 24 hours. Actin retraction fibers formed at 12 hours are accompanied by the loss of cell-cell adhesions and a complete loss of E-cadherin by 24 hours. Cell perimeters are characterized by tangled actin fibers at 24 hours. Taken from Cellular Microbiology 1:946-966. 2009.

Global changes in keratinocytes occur despite minimal contact with C. albicans endocytosis.

At a yeast:keratinocyte ratio of 0.3:1, only 14% of the OKF6/Tert-2 cells come in contact with C. albicans, yet the changes in actin dynamics and other parameters occur in 100% of the cells. Taken from Cellular Microbiology 1:946-966. 2009.

Changes in expression of differentiation markers in human oral OKF6/Tert-2 keratinocytes in the presence of C. albicans.

Early differentiation markers involucrin and keratin 19 decrease while late markers SPRR3 and keratin 13 increase over 24 hours of co-culture with C. albicans. Taken from Cellular Microbiology 1:946-966. 2009.

Loss of the antifungal protein calprotectin in human oral OKF6/Tert-2 keratinocytes over 24 hours in the presence of C. albicans. Taken from Cellular Microbiology 1:946-966. 2009.

Model of the pathogenesis of mucosal candidiasis.

A. In the presence of impaired immunity, colony forming units of C. albicans in the oral cavity increase. Upon contact with differentiated keratinocytes lining the oral cavity, germ tube formation is induced accompanied by the presence of hypha-specific gene expression. Hyphal growth within the surface of the epithelium leads to the production of aspartyl proteinases 4-6, which trigger a keratinocyte response analogous to that of a response to a chemical wound. Loss of cell-cell adhesions leads to an impairment in the barrier function of the stratified squamous epithelium which leads to increased differentiation, loss of anti-fungal defense proteins such as calprotectin and to hyperkeratinization of the epithelium.