Induction of tolerance to Toxoplasma gondii in newborn mice by maternal antibody.

To develop an animal model for analysing the suppressed immune response to Toxoplasma gondii in newborn humans with congenital toxoplasmosis, newborn mice from chronically infected mothers were inoculated intraperitoneally with bradyzoites of an avirulent strain. The newborn mice with maternal Toxoplasma antibodies showed a marked delay in the production of Toxoplasma antibodies when infected after birth. Many mice (11/13; 85%) developed a state of tolerance to T. gondii after disappearance of the maternal antibody, demonstrable by the absence of Toxoplasma antibody in their sera despite the fact that they were infected. The duration of tolerance differed between individuals, with two mice showing the longest tolerant state of 8 weeks. This murine model might be suitable for analysing the mechanism of suppressed immune response to T. gondii that has been observed in many human cases of congenital toxoplasmosis.