FELINE SERUM ANTIBODY-RESPONSES TO TOXOPLASMA-GONDII AND CHARACTERIZATION OF TARGET ANTIGENS

The Toxoplasma gondii-specific target antigens for feline immunoglobul in M (IgM) and immunoglobulin G (IgG) immune responses were studied lo ngitudinally using western blot immunoassay in 8 cats experimentally i noculated with T. gondii strain ME49. Multiple antigens were recognize d by IgM and IgG during the course of infection. Dense bands were asso ciated with 12 antigens in the IgM western blot immunoassay and 30 ant igens in the IgG western blot immunoassay. Immunoglobulin M responses were maximal on week 4 postinoculation (PI) and were greatly diminishe d by week 20 PI. Immunoglobulin G responses were maximal on week 12 PI . On week 20 PI, the 19-kDa (6/8 samples), 26-kDa (8/8 samples), 28-kD a (8/8 samples), 31-kDa (7/8 samples), 35-kDa (6/8 samples), 51-kDa (6 /8 samples), 55-kDa (7/8 samples), and 65-kDa (7/8 samples) antigens w ere recognized most commonly in the IgG western blot immunoassay. When the western blot immunoassay results were compared to enzyme-linked i mmunosorbent assay (ELISA) results, there was no clear advantage to th e development of IgM-ELISA, IgG-ELISA, IgM western blot immunoassay, o r IgG western blot immunoassay using a single antigen instead of multi ple antigens as the detection system for the diagnosis of recent infec tion.