Quantitative immunolocalization of four immunodominant antigens of Toxoplasma gondii

Quantitative immunolocalization of a P29 protein (GRA7), a new antigen of toxoplasma gondii

Ultrastructural localization of a P29 protein of Toxoplasma gondii was examined on thin sections by an immunogold technique using a P29 antigen-specific monoclonal antibody (5-241-178). Immunolocalization of the P29 protein in extracellular tachyzoites demonstrated that this antigen was present in the dense granules. Thus, we have identified this P29 antigen as the seventh protein (GRA7) to be localized to the dense granules of T. gondii. P29 immunolocalization in intracellular tachyzoites demonstrated association of this antigen with the parasite membrane complex, tubular elements of the intravacuolar network, and with the parasitophorous vacuolar membrane. Our immunolabeling data suggest trafficking of the P29 (GRA7) antigen from the dense granule via the intravacuolar network to the parasitophorous vacuolar membrane on invasion of the tachyzoite into the host cell. (J Histochem Cytochem 46:1411-1421, 1998)

Analysis of Toxoplasma gondii antigens with sera from toxoplasmosis patients

Some proteins of the Toxoplasma gondii are recognized by IgG, IgM and IgA antibodies in patients with acute and chronic toxoplasmosis, depending on the strain and stage of the Toxoplasma. Sixty-nine sera from immunocompetent individuals were studied through the Western-Blot Test: 20 has an acute infection, 29 has a chronic toxoplasmosis infection and 20 were healthy (seronegatives). The protein analysis revealed by IgG and IgM antibodies were performed through the immunoplot method in order to know their recognition frequency (f) and be valued as infection markers. In the acute phase, the IgM antibodies showed a recognition frequency (f = 0.60) for the 60 kDa protein, and in the chronic phase the IgG antibodies showed a recognition frequency (f = 0.68) for the 12 kDa protein. Seronegatives revealed no type of band. The protein of 12 kDa can be a diagnostic marker of the chronic phase while protein 60 kDa of the acute phase of toxoplasmosis.

[Immunological properties of the 30 kDa antigen of toxoplasma gondii]

The molecular weight 30 kDa membrane protein of Toxoplasma gondii (Toxoplasma 30 kDa) apparently conserved in most strains of T. gondii and sera of infected hosts. The present study aimed to elucidate Toxoplasma 30 kDa as a useful diagnostic antigen for serodiagnosis of toxoplasmosis by ELISA and for induction of protective immunity. Murine spleen cells immunized with the membrane antigen of T. gondii were fused with mouse Sp2/O-Ag14 myeloma cells. Out of 8 clones selected, five were IgG2b, the others belonged to IgG1 and IgG2a. The 30 kDa antigen was distributed mainly on the surface membrane of tachyzoites by indirect fluorescence method. Murine peritoneal macrophages which were activated by 30 kDa antigen produced more amounts of NO2 compared with crude antigen-treated group, however there were no significant differences in toxoplamacidal activity between the two groups. Higher specificity of Toxoplasma 30 kDa antigen was recognized for serodiagnosis of toxoplasmosis than the crude antigen. From these results, Toxoplasma 30 kDa antigen enhances the cytotoxic effect of macrophages as well as a more reliable means for the serodiagnosis of toxoplasmosis by ELISA.

Kinetics study of the localization and quantitation of target antigens of immunoglobulin a antibodies in acquired and congenital toxoplasmosis

The cellular distribution (localization and quantitation) of the target parasite's antigens in the tachyzoite along the IgA kinetics was determined in the course of acquired toxoplasmosis and congenital toxoplasmosis. In the case of acquired toxoplasmosis, throughout the IgA kinetics a correlation was noted between the membrane and submembrane immunolabeling and the results of the immunocapture and enzyme-linked immunosorbent assay IgA (ELISA-A) tests. The rhoptries' immunolabeling remained higher. The immunolabeling evolution and the results of the immunology tests were not closely related to the treatment (Rovamycin). From the congenital toxoplasmosis cases it was observed that membrane immunolabeling correlated with the results of the serology tests and with the treatment (Fansidar). The rhoptry antigens were recognized throughout the IgA kinetics; even when the serology tests became negative, immunolabeling persisted. Rhoptries appeared as secretory organelles of antigens recognized during acute, chronic, and congenital stages of Toxoplasma infection.

Subcellular localization and quantitative analysis of Toxoplasma gondii target antigens of specific immunoglobulins G, M, A, and E

The target antigens of specific immunoglobulins G, M, A, and E from patients with acquired acute toxoplasmosis were determined using immunocytochemistry. The relative repartition of these antigens in four cellular compartments of Toxoplasma (membrane complex, apical area, rhoptries, and dense granules) was quantitatively evaluated. Rhoptry antigens mainly react positively with IgA. Membrane, submembrane area (membrane complex), and rhoptry antigens are immunodominant for IgA and IgM. Apical area antigens are recognized by IgM two times more than IgG and IgA. IgE recognized only rhoptry antigens. The localization of pathogenetically antigenic components and their identification by the immune system appeared to be of importance for selection of immunodominant or recombinant antigens. Such localization would improve laboratory diagnosis of serious congenital toxoplasmosis or in immunocompromised patients with toxoplasmic complications after cyst reactivation.

Toxoplasma gondii-structure variations of the antigen P30

The major surface immunodominant antigen (P30) of Toxoplasma gondii was purified by two methods (i) SDS-PAGE and (ii) immunoaffinity chromatography. The secondary elements within this protein were assessed by circular dichroism and spectra obtained were compared to those proposed by Manavalan & Johnson (1983). The results allowed us to determine an all beta protein status for this antigen. This experimental result was in agreement with the predicted secondary structures deduced from the P30 primary sequence. Modifications in conformation according to pH and temperature were recorded without any change in immunoactivity. The epitope, which was always recognized by a monoclonal antibody against P30, could be a linear epitope.