Serodiagnosis of toxoplasma infection using a purified parasite protein (P30)

The major surface protein (P30) of Toxoplasma gondii has been purified by immunoabsorption with anti-P30 monoclonal antibodies linked to a glutardialdehyde activated affinity absorbant. SDS-PAGE analysis of the eluted material followed by silver staining showed only a single band of 30,000 mol wt. Western blotting using antibodies from a rabbit immunized with purified P30 against the total Toxoplasma extract separated by SDS-PAGE again revealed an unique antigen of 30,000 daltons. The presence of repeated epitopes within P30 was confirmed by a two-site/one-antibody radiometric assay with the purified protein. Sandwich ELISA procedures with purified P30 clearly demonstrated that all 37 tested patients with acute toxoplasmosis presented significantly high levels of IgM anti-P30 antibodies. In addition, all 40 tested patients with chronic toxoplasma infection also showed high IgG anti-P30 antibody levels. These findings represent an essential step for the development of new reagents for the diagnosis of toxoplasmosis.