Intraocular granuloma: a Schistosoma mansoni model of ocular inflammation

An experimental uveitis model was developed in New Zealand rabbits by an intraocular injection of Schistosoma mansoni eggs. An inflammatory response was clinically apparent after 5 days and histologically was characterized by an eosinophilic infiltrate into the vitreous and choroid. The chorioretinitis that developed resulted in the disruption of the photoreceptor layer. After 30 days, eggs were enveloped by a granulomatous host response similar to that observed in animals infected systemically with Schistosoma mansoni. Reduction (immunomodulation) of granuloma size and cellularity compared with controls was observed in paraffin sections of eyes challenged (100 eggs) 4 weeks after a priming injection (500 eggs) in the contralateral eye. The granulomatous response was not evident when heat-killed eggs were injected intraocularly. Extracts made from viable eggs also induced an intense vitreous infiltrate 12 hr after injection. Serum collected from rabbits injected with 500 or more eggs showed antibody (7s) reactivity for 125I-labeled bovine S antigen, as demonstrated by immunoprecipitation with Staphylococcus aureus (Pansorbin). This model is useful for analyzing immunologic parameters involved in ocular granulomatous and parasitic diseases, humoral and cellular responses mediating autosensitization to retinal or other ocular antigens, and possible for screening chemotherapeutic agents for immunomodulation of potentially injurious host inflammatory responses.