DEVELOPMENT OF SPECIFIC IMMUNOGLOBULIN-G, IMMUNOGLOBULIN-M, AND IMMUNOGLOBULIN-A FOLLOWING PRIMARY TOXOPLASMA-GONDII INFECTION IN PREGNANT-WOMEN

The development of specific antibodies following primary Toxoplasma go ndii infection during pregnancy was assessed by six different antibody assays: dye test, Platelia Toxo-IgG, Toro-Screen DA IgG, Platelia Tox o-IgM, Toxo-ISAGA IgM, and Platelia Toxo-IgA, A total of 126 sera from 27 pregnant women, for whom the time of acquisition of infection coul d be estimated fairly accurately, were included. All tests showed grea t individual variation in the peak amounts of antibodies detected. The times elapsed after infection until the peak was reached also varied greatly from individual to individual: the ranges were 2 to 21 weeks f or the dye test, 4 to 36 weeks for Platelia Toxo-IgG, 4 to 30 weeks fo r Toxo-Screen DA IgG, 2 to 18 weeks for Platelia Toxo-IgM, I to 6 week s for Toxo-ISAGA IgM, and 2 to 21 weeks for Platelia Toxo-IgA, In the early phase of the infection the dye test and the specific-IgM tests w ere the most sensitive. Toro-Screen DA IgG was more sensitive than Pla telia Toxo-IgG in the acute phase, while Platelia Toxo-IgA was clearly the least sensitive assay. Of the sera collected 21 to 52 weeks after infection, all were positive by the dye test, all except one (which w as negative by Platelia Toxo-IgG) were positive by the specific-IgG te sts, approximately 80% were positive by the IgM tests, and 45% were po sitive by the IgA test. Due to the great individual variation it seems impossible to estimate when the infection occurred based on results o btained from a single serum, and it may even be difficult to assess wh en a titer increase in paired sera is detectable unless the first samp le is only marginally positive. As a diagnostic criterion a dye test t iter of greater than or equal to 300 IU/ml has a low sensitivity for r ecent primary infection.