Gene profiling and signaling pathways of Candida albicans keratitis

To compare the global gene expression patterns in uninfected and fungus-infected mouse corneas at the onset of Candida albicans keratitis.

Fungal keratitis was generated by scarifying the corneal epithelium of BALB/c mice followed by topical inoculation with Candida albicans. Corneal infection was allowed to progress for one day, and total RNA was then extracted from excised corneas. Microarray was performed to detect 45,102 murine genes and processed to identify genetic regulation of signaling pathways. Selected genes encoding interleukins (IL), chemokine ligands, and other cytokines were confirmed by quantitative real-time reverse transcriptase polymerase chain reaction (RT-PCR).

Compared to mock-inoculated control eyes, genetic microarray analysis of Candida albicans keratitis showed that 3,977 genes (8.8%) changed at least twofold and 1,672 genes (3.7%) changed at least fourfold. Hierarchical clustering identified that upregulated genes affected immune and inflammatory responses, intercellular signaling, and cellular proliferation. Pathways having more than 20% of their genes significantly upregulated signaled leukocyte extravasation, increased interleukin production, and affected toll-like receptors. Upregulated transcript levels for IL-1beta and IL-6 were confirmed by real-time RT-PCR.

Host gene expression during the initial stage of Candida albicans keratitis involves pathways contributing to acute inflammation mediated by interleukins and other signals of leukocyte recruitment. This murine study confirms the involvement of innate immunity in the cornea during the initiation of Candida albicans keratitis.