Susceptibility of corneas from various animal species to in vitro binding and invasion by Acanthamoeba castellanii [corrected]

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Abstract

A crucial requirement for establishing corneal infection by the extracellular protozoal parasite, Acanthamoeba, is the ability of the parasite to bind to the corneal surface. In a series of in vitro studies, we examined the ability of Acanthamoeba castellanii [corrected] to adhere, invade, and damage normal, intact corneas of 11 mammalian and one avian species. A. castellanii [corrected] (80-90% trophozoites and 10-20% cysts) were incubated with corneas for 24 hours in vitro and examined by scanning electron microscopy (SEM). Results of several independent SEM experiments revealed that parasites not only failed to produce cytopathic effects but did not even bind to the corneal epithelium of mice, rats, cotton rats, horses, guinea pigs, cows, chickens, dogs, and rabbits. However, parasites adhered, invaded, and produced severe damage to human, pig, and Chinese hamster corneas during the 24-hour in vitro incubation period. Additional in vitro experiments quantified the binding of A. castellanii [corrected] to the corneas of selected susceptible and nonsusceptible species. In vitro binding assays revealed scant binding of parasites to mouse, rat, and rabbit (range = 5-20 parasites/7.07 mm2 corneal button). In contrast, extensive binding was observed on Chinese hamster, pig, and human corneas (range = 100-200 parasites/7.07 mm2 button). The results indicate that A. castellanii [corrected] exercises rigid host specificity at the host cell surface.