Multiplex Immunoassay Diagnoses Toxoplasmosis and Rubella

Currently, tests such as enzyme immunoassay (EIA), enzyme-linked fluorescent assay (ELFA), chemiluminescent microparticle immunoassay, and electrochemiluminescence immunoassay are widely applied in clinical laboratories to diagnose toxoplasmosis.

Scientists at the Carlos Chagas Institute (Curitiba, Brazil) developed a multiplex assay for simultaneous detection of immunoglobulin G (IgG) antibodies produced during toxoplasmosis and rubella infection. They used a quality control panel of contains 92 anti-Toxoplasma gondii IgG-positive serum samples and 30 negative serum samples. The samples were tested for T. gondii IgG by a Vidas ELFA assay. There is no clinical data associated with these samples. To develop assays for the detection of rubella, 23 serum or plasma samples classified as positive for anti- Rubella virus IgG antibodies and two samples negative for anti-R. virus IgG antibodies were used.

The multiplex assay, based on xMap technology to simultaneously diagnose toxoplasmosis and rubella was designed with the best-performing antigens in singleplex and multiplex assays, which included CTOXH, T. gondii lysate, TOX8131, E-1, and E-2. The multiplex assay showed 100% sensitivity and specificity for anti-T. gondii IgG detection and 95.6% sensitivity and 100% specificity for anti-R. virus IgG detection. Fluorescence and median fluorescence intensity (MFI) were determined using a Luminex 200 reader.

The authors concluded that despite the difficulties related to developing multiplex systems, different types of antigens (extracts and recombinant proteins) can be used to develop high-performance diagnostic tests. The assay developed is suitable to screen for prior T. gondii and R. virus infections, because it is a rapid, high-throughput, low-cost alternative to the current standard diagnostic tools, which require multiple individual tests. The study was published in the June 2017 issue of the journal Memórias do Instituto Oswaldo Cruz.

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Carlos Chagas Institute