Detection of specific IgG and IgM antibodies to Toxoplasma gondii with a commercially available enzyme immunoassay kit system

[Usefulness of total dry blood samples on filter paper in the detection of antitoxoplasma antibodies]

Direct Agglutination (DA) techniques, both, using dry blood samples in filter paper and serum samples, were compared with the ELISA test in order to detect antibodies against Toxoplasma gondii. The results show the validity of the dry blood samples in filter paper for detecting antitoxoplasma antibodies with a DA test. Our results would confirm their usefulness in field epidemiological surveys.

Biotin-labelled antigen screening test for toxoplasma IgM antibody

A method for the simple preparation of biotin-labelled toxoplasma antigen was used with avidin peroxidase in an IgM-capture enzyme linked immunosorbent assay (BAM-ELISA). Although the overall predictive value of a positive result was only 38%, its low cost and 100% sensitivity makes it a very suitable screening test. Positive results can be confirmed by an alternative assay, thus providing a more economical and effective diagnostic service than either screening all sera by a commercial test or selecting sera for IgM testing.

Rapid indirect enzyme linked immunosorbent assay (ELISA) for detecting antitoxoplasma IgG: comparison with dye test

A rapid and simple enzyme linked immunosorbent assay (ELISA) for the detection of specific IgG against Toxoplasma gondii was compared with the dye test on 533 serum samples. In general, results were comparable but not with sera that contained high concentrations of toxoplasma specific IgM or that had been heated at 56 degrees C. There were no false positive results with sera containing rheumatoid factor or anti-nuclear factor. It is concluded that if a dye test is not to be performed then the serum should be tested for both toxoplasma specific IgG and IgM to avoid misleading results. Heat inactivated serum should also not be tested in this type of specific IgG assay.

Enzyme-linked immunosorbent assays for the measurement of specific antibodies in experimentally induced ovine toxoplasmosis

Tachyzoites of the RH strain of Toxoplasma gondii were inoculated intravenously into sheep following which serum samples were collected at approximately weekly intervals for 9 months. The sera were examined by the toxoplasma dye test and two enzyme-linked immunosorbent assays (ELISA) specifically developed for investigations of ovine toxoplasmosis. One was an antibody class capture assay for the detection of anti-toxoplasma specific IgM, the other an indirect assay which detected anti-toxoplasma IgG. Some of the sheep had antibodies to toxoplasma prior to inoculation but none had specific IgM. Sera collected 17 days after inoculation showed that all had raised specific antibody levels but the only sheep that produced specific antitoxoplasma IgM were those that were initially without any antibody. Specific IgM could be detected in all these particular sheep for at least 1 month after infection and up to 3 months in some. Specific IgG persisted at high levels for at least 3 months and could still be detected at moderate levels for at least 9 months. The ELISA methods described are simple to perform and could clearly distinguish between previous infection and this experimental infection with Toxoplasma gondii.