Detection of circulating antigen during acute infections with Toxoplasma gondii by enzyme-linked immunosorbent assay.

The serodiagnosis of toxoplasmosis is usually based on demonstration of antibodies by means of different serological methods. However, for confirmation of active toxoplasmosis, examination of paired sera is still needed. In this study a description is given of a sensitive enzyme method (enzyme-linked immunosorbent assay) with which it is possible to detect circulating antigens during the acute stage of mouse and human toxoplasmosis. Preliminary investigations of human sera suggested that circulating antigens are only found during a short period (active phase) of the toxoplasma infection and that they can be found in cases of fresh infections as well as during reinfections. The possible clinical relevance is discussed.