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H. Alizadeh, S. Neelam, M. Hurt, J.Y. Niederkorn; Role of Contact Lens Wear, Bacterial Flora, and Mannose–Induced Pathogenic Protease in the Pathogenesis of Amoebic Keratitis . Invest. Ophthalmol. Vis. Sci. 2005;46(13):5086.
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Purpose: Acanthamoeba trophozoites express a mannose binding receptor, which facilitates adhesion of the trophozoites to mannosylated proteins on corneal epithelial cells. Upon binding, Acanthamoeba castellanii trophozoites secrete a 133 KDa pathogenic protease (MIP133) that is cytolytic to corneal epithelium. We examined the effect of contact lens wear and exposure to ocular flora on the generation of the mannose–induced protease (MIP133) and the pathogenicity of Acanthamoeba trophozoites. Methods:MIP133 was isolated and purified by size exclusion fast protein liquid chromatography and size exclusion chromatography. The purity of the concentrated MIP133 was confirmed by SDS–PAGE. MIP133 levels were quantified by ELISA and MIP133–induced cytotoxicity for corneal cells was measured spectrophotometrically. Eye cup assays were used to determine if exposure of corneal epithelium to contact lenses would induce MIP 133 production. Trophozoites were exposed to high and low mannose expressing bacteria and the MIP133 production was examined by ELISA. Results:Mannosylated proteins on the ocular surface stimulated the amoebae to elaborate a 133 kDa pathogenic protease. The MIP133 was found to mediate apoptosis of the corneal epithelium, facilitate corneal invasion, and degrade the corneal stroma. Contact lens wear significantly upregulated mannosylated proteins on the corneal epithelium, stimulated MIP133 secretion, and exacerbated corneal disease (P<0.05). Corynebacterium xerosis, a constituent of ocular flora, contains large amounts of mannose and is associated with Acanthamoeba keratitis. Amoebae exposed to C. xerosis elicited 40% increase in MIP133 production, resulting more severe corneal disease. Conclusions: The results indicate that two risk factors associated with Acanthamoeba keratitis, contact lens wear and C. xerosis, stimulate Acanthamoeba trophozoites to produce increased quantities of a pathogenic protease (MIP133) resulting in more severe Acanthamoeba keratitis.
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