PURPOSE. To determine whether oral immunization mitigates ongoing Acanthamoeba castellanii corneal infections in pigs. METHODS. Pigs were orally immunized with aqueous Acanthamoeba antigen mixed with cholera toxin (Ac-CT) or with saline, before or after ocular infection with A. castellanii. Mucosal secretions (i.e., tears and enteric wash) were tested for Acanthamoeba-specific IgA by enzyme-linked immunosorbent assay. Enteric washes were used as a source of IgA in assays measuring the binding of trophozoites to Chinese hamster corneal epithelial (CHCE) cells. RESULTS. Pigs immunized with Ac-CT before ocular challenge with A. castellanii had significant anti-Acanthamoeba IgA antibody titers in their tears and enteric washes and were protected against ocular infection. Enteric washes from orally immunized pigs inhibited trophozoite binding to CHCE cells in vitro by more than 75%. By contrast, pigs immunized after corneal infections had been established displayed keratitis of the same severity and duration as that in control pigs. However, 80% of the orally immunized animals were resistant to rechallenge with Acanthamoeba-laden contact lenses, whereas none of the control animals was resistant. CONCLUSIONS. Oral immunization with Ac-CT protects against Acanthamoeba keratitis when administered before corneal challenge. However, delaying oral immunization until after corneal disease is established fails to mitigate keratitis. The appearance of parasite-specific tear IgA correlates with protection and may act by preventing the parasite's binding to the corneal epithelium.
|Original language||English (US)|
|Number of pages||7|
|Journal||Investigative Ophthalmology and Visual Science|
|State||Published - Nov 1 1998|
ASJC Scopus subject areas
- Sensory Systems
- Cellular and Molecular Neuroscience