DETECTION OF TOXOPLASMA-GONDII-SPECIFIC IGA IN THE AQUEOUS-HUMOR OF CATS

Toxoplasma gondii-specific IgA, IgM, and IgG were measured by ELISA in the serum and aqueous humor of 29 client-owned cats with endogenous u veitis and 7 specific-pathogen-free cats tested sequentially for 20 we eks after inoculation with T gondii. Local antibody production in aque ous humor was estimated by multiplying the aqueous humor-to-serum T go ndii-specific antibody ratio by the serum-to-aqueous humor total IgG ( C value) or calivirius-specific IgG (CTC value) ratio. Evidence for lo cal produc tion of antibody in aqueous humor was defined as C value gr eater than 8 or CTC value greater than 1. Toxoplasma gondii-specific I gM CTC values, IgG CTC values, or IgA CTC values greater than 1 were d etected in the aqueous humor of 18 of 29 (62.1%) client-owned cats wit h endogenous uveitis; 2 cats had IgA CTC values greater than I without detectable IgM or IgG in aqueous humor. Toxoplasma gondii-specific Ig M was not detected in the aqueous humor of experimentally inoculated c ats before or after inoculation. Immunoglobulin G C values greater tha n 8 were detected in all 7 experimentally inoculated cats and ranged f rom 10.4 to 145.5. Immunoglobulin G C values greater than 8 were first detected 4 to 8 weeks after T gondii inoculation and were undetectabl e by week 16 after inoculation. Immunoglobulin A C values greater than 8 were detected in 4 of 7 cats and ranged from 12.7 to 264.3. Immunog lobulin A C values greater than 8 were first detected 4 to 8 weeks aft er inoculation, and were detected in 2 cats during week 20 after inocu lation. It was concluded that some cats infected with T gondii develop detectable concentrations of T gondii-specific IgA in aqueous humor.