Kinetics of IgM and IgG antibodies in mice experimentally infected with cystogenic strain of Toxoplasma gondii.

Mice were infected with a "cystogenic" strain of T. gondii and sera obtained at different times were tested using DT and IFAT (cell wall antibodies tests) and IHAT (performed with extractive cytoplasmic antigen). We found different kinetics of DT- and IFAT- versus IHAT-titers: IHAT is negative during the early phase of the experimental infection when DT and IgM-IFAT are already positive. Furthermore IgM antibodies were never found against cytoplasmic antigens by the IHAT method. At weekly intervals after the experimental infection a biological test was also performed using samples of different organs. We found that one week after the infection only the brain was constantly positive in the biological test. The antibody pattern was similar in every positive test irrespective of the source and size of the material used for the inoculum. These data suggest that the result of a biological test may be available earlier (already after 7 days) if a test for antibodies against cell wall antigens is performed on the IgM fraction of the mouse serum.