Detection of toxoplasma antigen in tissues by means of enzyme-linked immunosorbent assay (ELISA).

An enzyme-linked immunosorbent assay (ELISA) for the detection of free toxoplasma antigens in patient sera was applied for demonstration of toxoplasmosis in tissues. Unfixed organs stored at room temperature remain antigen-positive for weeks, even when parasites are no longer demonstrable by means of direct immunofluorescence testing. Chronically infected brains, containing tenths of cysts do not react positive, whereas recently infected brains (proliferative stage) are positive, suggesting that with this ELISA method discrimination can be made between different stages of the infection.