Toxoplasma - specific IgG antibodies avidity ELISA and its role in the differentiation between recent and chronic toxoplasmosis in goats

Abstract

For serological characterization of recent Toxoplasma infection in goats low avidity IgG specific antibodies were studied. Avidity was evaluated as the decrease of absorbance in ELISA test after treating plates with 3, 6 and 9M urea, as a dissociating solution of low avidity antigen-antibody complexes. A concentration of 9M urea best discriminated between recent and old infections in goats experimentally infected with Toxoplasma gondii. Absorbance after treating plates with 9M urea decreased in relation to the duration of infection, levelling off about the 100^th day after inoculation. In a group of 116 serum samples from naturally infected goats patterns of recent, transitional or chronic toxoplasmosis were demonstrated. Serological patterns were previously determined by immunofluorescent assay. For chronic toxoplasmosis infection, the observed decrease of absorbance was 26.32 ± 10.84. For recent toxoplasmosis it was 77.61 ± 13.89, and for transitional pattern, 46.22 ± 11.94.