Reverse IgM enzyme-linked immunosorbent assay (Reverse IgM-ELISA) for toxoplasmosis serodiagnosis

A Reverse IgM enzyme — linked immunosorbent assay (Reverse-IgM ELISA) was described in which polyvinyl microplates were sensitized with anti-immunoglobulin M (IgM) antibodies and then sequentially allowed to react with patient's serum, Toxoplasma gondii soluble antigen, peroxidase — labeled specific F(ab')2 fragment and substrat. Measurement of activity of the solid phase bound enzyme conjugate was done by spectrofotometric reading of the final developed color. In a group of 69 sera samples from individuals with recently acquired toxoplasmosis, Reverse-IgM ELISA was positive in every case, showing higher geometric mean titer than others conventional serological tests. Furthermore false-negative IgM samples presented positive Reverse-IgM ELISA results even without adsorption with Staphylococcus aureus protein A . In a group of 104 sera samples from individuals with others pathologies, no interference was observed, even in the false-positive IgM samples due to the presence of IgM rheumatoid factor.