Detection of Toxoplasma gondii IgG antibodies in Thai patients by enzyme-linked immunosorbent and immunoblot assays

Abstract

An in-house ELISA was developed for detection of IgG Toxoplasma antibody using either pellets and/ or supernatant from sonicated Toxoplasma tachyzoites as crude antigen. This method was compared with a commercial p-30 ELISA which uses the membrane protein p-30 protein as the predominant antigen. A total of 259 sera from 3 groups of patients were tested. The in-house ELISA using either parasite pellets or supernatant antigen showed equal sensitivity (87.0%) in detection of IgG antibodies to Toxoplasma. The specificities of pellet and supernatant-based assays were 97.9% and 95.3% respectively. By Kappa analysis, highly significant correlation coefficient was obtained between the in-house ELISA and the commercial test kit (Kappa correlation between the in-house ELISA using pellet as antigen and Platelia = 0.869, p < 0.001; chat using the supernatant as antigen and Platelia=0.822, p < 0.001 ). There was a good concordance between in-house ELISA and p-30 ELISA results. In addition, the usefulness of the immunoblot assay for the detection of IgG antibodies to Toxoplasma was evaluated. Both antigens show generally similar polypeptide bands. The protein component with a molecular weight of 31 kDa reacted strongly with lgG antibodies in the majority of Toxoplasma seropositive sera (75.3%). It may represent a specific marker for diagnosis of Toxoplasma infection in Thai patients.