A monoclonal-based IgM capture ELISA for detection of antibodies to 22 and 41 kDa membrane antigens of Toxoplasma gondii.

A murine monoclonal antibody which reacts to 22 and 41 kDa Toxoplasma gondii surface antigens was employed in an IgM capture enzyme-linked immunosorbent assay (ELISA). A total of 125 patients' sera were tested in the monoclonal-based assay. When compared with a commercial ELISA test (Abbott Toxo-M EIA) which uses polyclonal anti-T. gondii antibodies, good correlation (Pearsons coefficient r = 0.91) was observed. The specificity of the assay was studied by testing a panel of control sera obtained from healthy individuals and blood transfusion donors; all sera gave negative results. Serum samples positive for T. gondii antibodies were treated with 2-mercaptoethanol (2-ME) to demonstrate the specificity of the test for IgM antibodies. Reactivity of these sera was lost after the treatment. The test is not subject to interference by rheumatoid factor as sera positive for rheumatoid factor were negative in the assay. Reproducibility was good with the coefficients of variation for within-day tests below 10% and not exceeding 18% for day-to-day tests. The monoclonal-based assay is simple to perform and appears to be a viable test for diagnosis of T. gondii infection.