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Eric C. Ledbetter, Longying Dong, Sung G. Kim; Susceptibility Of The Intact And Traumatized Feline Cornea To In Vitro Binding And Invasion By Acanthamoeba castellanii. Invest. Ophthalmol. Vis. Sci. 2011;52(14):5804.
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Acanthamoeba must bind, and subsequently invade, the host corneal surface to establish infection. Acanthamoeba castellanii displays host specificity at the ocular surface level and is only capable of adhering to the intact cornea of select species. Naturally-acquired Acanthamoeba keratitis is described in the domestic cat (Felis catus); however, the ability of Acanthamoeba to bind to the feline cornea in vitro is unknown. We determined the susceptibility of the intact and traumatized feline cornea to Acanthamoeba castellanii binding relative to a host species with established susceptibility to Acanthamoeba binding (pig) and a host species with established resistance to Acanthamoeba binding (dog).
Feline, porcine, and canine fresh corneas were collected and cut into 6.0 mm diameter full-thickness sections. Corneal epithelium was confirmed intact by fluorescein staining or lightly scarified with a 25 gauge needle in a grid pattern to simulate corneal trauma. Acanthamoeba castellanii (ATCC #30868) was cultivated axenically to a concentration of 3 x 106 amoebae/mL (90% trophozoites and 10% cysts). Corneal sections were incubated with the parasite suspension or parasite-free medium for 18 hours at 35 °C. Corneal sections were rinsed, fixed, and processed for histopathology, immunohistochemistry, and scanning electron microscopy.
Numerous amoebae were bound to feline and porcine corneas incubated with the parasite. In both intact and traumatized corneas, amoebae were detected at all levels of the corneal epithelium and within the anterior stroma. In traumatized corneal sections, clumps of numerous organisms were frequently present in regions of epithelial damage. Corneal architecture was well-preserved in sections incubated with parasite-free medium; however, epithelial cell sloughing and epithelial detachment from the stroma were observed in corneas incubated with amoebae. Intact and traumatized canine corneas were free of adherent amoebae and corneal architecture was indistinguishable between sections incubated with the parasite suspension and parasite-free medium.
The feline cornea is highly susceptible to in vitro binding and invasion by Acanthamoeba castellanii. Acanthamoeba binding to the feline cornea does not require a prior epithelial defect. This characteristic likely contributes to the domestic cat’s vulnerability to naturally-acquired Acanthamoeba keratitis.
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