Major surface protein of Toxoplasma gondii (p30) contains an immunodominant region with repetitive epitopes

Abstract

Four monoclonal antibodies (mAb) against surface antigens of tachyzoites of Toxoplasma gondii were produced. Immunoprecipitation of extracts of 125I-labeled tachyzoites identified the same polypeptide with apparent molecular weight of 30 000 (p30). A competition binding assay indicated that a single region of p30 was recognized by all 4 of the mAb. Furthermore, we found that single mAb inhibited 25-50% of the specific binding of antibodies of patients with toxoplasmosis to the antigenic extract of tachyzoites. It appears, therefore, that p30 is the most immunogenic constituent of tachyzoites, and that a single region of this molecule contains most of the immunogenic activity. Finally, a two-site/one-antibody immunoradiometric assay with the same mAb indicated that the p30 molecule is multivalent with respect to the expression of a single epitope.

Crystal Structure of the Complex between the Monomeric Form of Toxoplasma gondii Surface Antigen 1 (SAG1) and a Monoclonal Antibody that Mimics the Human Immune Response

“…16,38 Hence, the characterization of SAG1 immunodominant epitopes and their relations with the ligand-binding site has been a longstanding issue addressed through different approaches. [24][25][26][27][31][32][33]38 The monoclonal antibody used in this study recognizes, in the nanomolar range, the native and recombinant SAG1, and efficiently inhibits SAG1 binding to most of the sera from infected patients that we have tested, suggesting that the mAb 4F11E12 is highly representative of the human anti-Toxoplasma response. Consequently, it is likely that mAb 4F11E12 and human sera recognize overlapping areas on SAG1, a region that is considered to be part of an immunodominant B-cell epitope.…”

“…[18][19][20][21][22][23] Several studies, based mainly on chemical or recombinant approaches, have been carried out to identify the different T and B-cell epitopes displayed by SAG1, [24][25][26][27] and to establish the nature of the different immunological responses induced by recombinant SAG1, 28,29 or by SAG1-derived peptides. [30][31][32][33] Although these studies clearly establish that SAG1 is an important target for the induction of specific anti-T. gondii tachyzoite immune responses, the protective value of this response evaluated in vivo in animal models or in vitro using cell lines remains partial.…”

Contribution of the Residual Body in the Spatial Organization of Toxoplasma gondii Tachyzoites within the Parasitophorous Vacuole

“…MDCK cells infected for 24 h were fixed in 3.7% paraformaldehyde for 20 min, permeabilized for 10 min in 0.1% Triton X-100, blocked in 0.5% BSA, and incubated for 2 h with the following primary antibodies diluted in PBS: monoclonal antibody (mAb) TG05.54 anti-SAG1 [21], mAb TG17.43 anti-GRA1, mAb TG17.179 anti-GRA2 [22], and rabbit serum anti-GRA6 [11], each at the dilution of 1 : 500, or mAb T5.2A3 anti-ROP1, mAb T34A5 anti-ROP2, each at the dilution of 1 : 25 [23] (the mAbs anti-ROP proteins were provided by J. F. Dubremetz, CNRS UMR 5539, Université Montpellier II, France, and the rabbit serum anti-GRA6 was obtained from L. D. Sibley, Department of Molecular Microbiology, Washington School of Medicine, Saint-Louis, MO). Cells were rinsed in PBS, incubated for 1 h with goat anti-mouse IgG (H+L) or with goat anti-rabbit IgG (H+L), both coupled to Alexa Fluor 488 (Molecular Probes, USA).…”

Comparing the effect of IL-12 genetic adjuvant and alum non-genetic adjuvant on the efficiency of the cocktail DNA vaccine containing plasmids encoding SAG-1 and ROP-2 of Toxoplasma gondii

“…SAG-1 is the most immunogenic tachyzoite structure of T. gondii (Burg et al 1988;Hunter et al 1999;Kimbita et al 2001;Zinecker et al 2001;Bonenfant et al 2001;Wichroski et al 2002;Haumont et al 2000;Couper et al 2003;Rodriguez et al 1985), which is present only in the tachyzoite stage and is not found in the sporozoite and bradyzoite stages (Burg et al 1988;Hunter et al 1999;Kimbita et al 2001).…”