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Adhesion mechanisms of Acanthamoeba
Morton, Laura Dill
Doctoral Committee Chair(s)
Whiteley, Herbert E.
Department of Study
Degree Granting Institution
University of Illinois at Urbana-Champaign
Health Sciences, Ophthalmology
Health Sciences, Pathology
The pathogenesis of Acanthamoeba keratitis, an increasingly reported and often unmanageable protozoal infection occurring primarily in wearers of soft contact lenses, is unknown. Since adherence of a pathogen to the corneal epithelium is an important initial event in the development of microbial keratitis, a description of factors that influence the adherence of Acanthamoeba to corneal epithelium may be useful in understanding the pathogenesis of amebic keratitis. An in vitro coincubation assay was used to measure adhesion of radiolabeled Acanthamoeba trophozoites to monolayers of rabbit corneal epithelium, monolayers of rabbit corneal stromal fibroblasts, and wounded ex vivo rat corneas. Adhesion of amebae to corneal epithelium occurred rapidly, was higher at 25$\sp\circ$C than at 37$\sp\circ$C or 4$\sp\circ$C, did not totally account for the reported in vivo pathogenicity of the strain of Acanthamoeba, and was inhibited by mannose or methyl-a-D-mannopyranoside. More than twice as many amebic trophozoites adhered to corneal stromal fibroblasts as to corneal epithelial cells. Subtle partial epithelial defects did not augment adherence of Acanthamoeba trophozoites to ex vivo rat corneas. These findings suggest that at temperatures of 25$\sp\circ$C or higher Acanthamoeba organisms can quickly adhere to epithelium or contact lens deposits containing epithelial debris, possibly by recognition of mannose moieties. Stromal exposure appears to augment adherence, suggesting a role for penetrating corneal wounds in the pathogenesis of amebic keratitis.