DETECTION OF CIRCULATING ANTIGENS OF TOXOPLASMA-GONDII IN HUMAN INFECTION

Seventy-nine serum specimens from pregnant women and 29 from immunocom promised patients (12 from graft recipients and 17 from patients with acquired immunodeficiency syndrome) were classified into three groups according to their serologic status to Toxoplasma gondii as determined by immunofluorescence and an enzyme-linked immunosorbent assay (ELISA ): no antibodies (group 1), acute acquired infection (group 2), and re activation (group 3). These samples were tested for the presence of ci rculating antigens (CAg) of T. gondii by capture ELISA and immunoblott ing. The presence of CAg was detected by at least one of the two techn iques in six of 31 subjects in group 1, 51 of 68 subjects in group 2, and seven of nine subjects in group 3. Of a total of 108 serum specime ns, 28 were found to be T. gondii-positive by capture ELISA, 57 by imm unoblotting, and 21 by both techniques. Among the nine polypeptides de tected by immunoblotting, 38 recognized p14, 17 recognized p8, and 16 recognized p30. These results demonstrate that the detection of CAg ca n aid in the diagnosis of infection by T. gondii in humans, especially in immunocompromised patients whose serologic response can be impaire d.