Analysis of Pseudomonas aeruginosa corneal infection using an oligonucleotide microarray

To compare the early gene expression pattern of normal versus Pseudomonas aeruginosa-infected corneas in resistant (cornea heals) versus susceptible (cornea perforates) mice.

A microarray analysis of normal versus postinfection (PI) day 1 BALB/c and B6 corneas was performed with a murine gene microarray. Real-time RT-PCR was used to confirm the microarray pattern selectively.

The 1257 regulated transcripts detected were organized into nine clusters by a self-organizing map (SOM) algorithm according to their different behavior in each mouse group. At least three groups of genes associated with a CD4(+) T-cell type-1 (Th1) immune response and three clusters linked with a type-2 T-cell (Th2) response were identified. Biological categorization revealed that the cornea of B6 mice showed a dominant type-1-like immune response profile, whereas BALB/c mice showed a dominant type-2-like profile. In addition, expression of several genes that promote apoptosis (e.g., caspase-9) was upregulated in BALB/c mouse cornea, whereas genes with apoptosis-inhibiting activity (e.g., BCL2) were significantly upregulated in B6 mouse cornea. The infected cornea of BALB/c mice also showed increased gene expression of factors associated with matrix remodeling and tissue repair (e.g., tissue inhibitor of matrix metalloproteinase [TIMP-2] and epidermal growth factor [EGF]) and/or bacterial killing (e.g., inducible nitric oxide synthase [iNOS]).

The data provide new insight into biological processes involved in Pseudomonas aeruginosa keratitis and confirm that B6 mice are Th1 and BALB/c mice are Th2 cytokine responsive to bacterial antigen early after challenge with P. aeruginosa.