[Serological parameters for the diagnosis and follow-up of toxoplasmosis. Experimental models].

BACKGROUND: Toxoplasmosis is a disease of increasing incidence. Its laboratory diagnosis is difficult, specially in acute toxoplasmosis. The data obtained in experimental models attempting to distinguish between acute and chronic toxoplasmosis by the simultaneous study of four serological tests: IgM and IgG antibodies, circulating antigens (CA) and antigens present in immune complexes (IC) are reported. METHODS: The evolution of IgM and IgG antibodies, CA and IC was followed in 3 murine models in acute, subacute and chronic toxoplasmosis, compared with the use of the ELISA technique. RESULTS: Acute toxoplasmosis is characterized by the presence of CA and IC in 100% of the individuals at high concentrations with IgM and IgG only being detectable at low concentrations. In subacute and chronic toxoplasmosis the response to IgG antibodies (100% in animals) is prominent, with detection of IgM being variable and the detection of CA and IC being reduced to the phase considered as acute. CONCLUSIONS: The detection of IgM and IgG antibodies, circulating antigens and immune complexes may be of great usefulness in the differentiation of acute, recently acquired or chronic toxoplasmosis.