Use of monoclonal antibodies to detect antigens of Toxoplasma gondii in serum and other body fluids

Monoclonal antibodies to Toxoplasma gondii were used in an enzyme-linked immunosorbent assay to detect antigens of the parasite in toxoplasma lysate, in peritoneal fluid of mice, and in sera from humans acutely infected with T. gondii. Four of the six monoclonal antibodies were able to detect antigens of toxoplasma in these specimens. Control sera from individuals not infected with T. gondii and from individuals chronically infected with the parasite were negative in the enzyme-linked immunosorbent assay. Sera from individuals not infected with T. gondii but with positive titers from rheumatoid factor were also negative; 2 or 10 sera from individuals not infected with T. gondii but with positive titers for antinuclear antibodies reacted with the monoclonal antibodies. When the results of the enzyme-linked immunosorbent assay with monoclonal antibodies and with the F(ab)2 fraction of an immunoglobulin G from a rabbit infected with T. gondii were compared, it was noted that the F(ab)2 was more active in detecting parasite antigens than were the monoclonal antibodies. Thus, although monoclonal antibodies can be used to detect antigens of T. gondii in sera and other body fluids, polyvalent antibody (such as the F(ab)2 fraction) appears to be more satisfactory for this purpose.