[Investigation of the protein composition and immunochemical properties of Toxoplasma gondii excretory and secretory antigen]. / Izuchenie belkovogo sostava i immunokhimicheskikh svoistv ékskretorno-sekretornogo antigena Toxoplasma gondii.

The major proteins of T. gondii excretory and secretory antigens (ESA) obtained during cultivation of tachyzoites by using cultured Vero cells were shown to have molecular weights of 79, 70, 57, 48, 36, and 29 kD. ESA and somatic antigen immunoblotting demonstrated that there were noticeable differences in the immunoactive proteins of these antigens. The antibodies of the sera of patients with toxoplasmosis mainly interacted with ESA proteins having molecular weights of 79, 70, 57, 48, 36, and 29 kD, 57-kD ESA protein antibodies being present on the immunoblots of all the tested sera. When ESA was used as an antigen during enzyme immunoassay, it showed a high sensitivity in the detection of IgM antigens in congenital toxoplasmosis. At the same time, ESA identified the antibodies of this class in the sera of healthy donors much infrequently than somatic antigen (p < 0.05).

[Composition of circulating immune complexes in acute toxoplasmosis]. / Izuchenie sostava tsirkuliruiushchikh immunnykh kompleksov pri ostrom toksoplazmoze.

The circulating immune complexes (CIC) that form in the hot just in early Toxoplasma gondii invasion can be present in the blood bed for a while. At the same time, the data on the antigenic composition of CIC in toxoplasmosis are fragmentary and rather contradictory. The investigation used enzyme immunoassay (EIA) to detect specific CIC that contain antigens to T. gondii tachyzoites in the sera of different populations and studied their antigenic composition by immunoblotting after 2-6% polyethylene glycol 6000-induced deposition. Examining 464 sera from groups of individuals with varying-stage T. gondii invasion indicated CIC in each, but showing their different frequency. CIC were virtually present in all sera from children who had been diagnosed as having congenital toxoplasmosis. In groups of seropositive pregnant women, CIC detection rates were noticeably higher in the samples showing both IgG and IgM antibodies (40.2 and 66.4%, respectively). CIC were also revealed in 9.8% of the seronegative blood donors; however, immunoblotting failed to confirm that they had no components that specifically reacted with T. gondii tachyzoite antigen antibodies. There were some differences in the composition of CIC in the serum yielding positive results in both EIA and immunoblotting. The serum CIC from pregnant women that exhibited only IgG antibodies contained mainly T. gondii antigens having molecular weights of 67 and 30 kD. The serum CIC from children with congenital toxoplasmosis and from pregnant women with serologically detected IgM antibodies to Toxoplasma antigens were found to contain 55-58-, 48-, 44-, 38-, 30-, and 26-kD components. The same molecular weight proteins were detected by electrophoretic studies of Toxoplasma excretory-secretory antigen (ESA). Comparing the findings suggests that in acute toxoplasmosis, the circulating complexes mainly contain ESA of the tachyzoites which appear in human blood just at the onset of invasion. Thus, this study demonstrates that specifically CIC are detectable in the sera of individuals infected with T. gondii and their antigenic composition varies with the stage of disease. In the authors' opinion, the detection of specific CIC and the determination of their antigenic composition may be serve an additional test in diagnosing acute toxoplasmosis.