Quantitative Immunolocalization of a P29 Protein (GRA7), a New Antigen of Toxoplasma Gondii

Abstract

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)

Characterisation of NcGRA7 and NcSAG4 proteins: Immunolocalisation and their role in the host cell invasion by Neospora caninum tachyzoites

“…This labelling pattern suggests that NcGRA7 migrates from intracellular dense granules into the parasitophorous vacuole where it would interact with matrix components by developing oligomeric complexes through its hydrophobic domains. This is similar to the actions of its orthologue, TgGRA7 (Cesbron-Delauw 1994, CesbronDelauw et al 1996, Bonhomme et al 1998, Fischer et al 1998, Braun et al 2008. Our NcGRA7 immunolocalisation studies confirm those previously described by others , Schares et al 1999, Vonlaufen et al 2004.…”

Toxoplasma gondii Recombinant Antigens as Tools for Serodiagnosis of Human Toxoplasmosis: Current Status of Studies

“…In the past 35 years, several dozen genes encoding T. gondii proteins have been cloned into bacterial and eukaryotic expression systems, as follows: the surface antigens SAG1 (P30) (9-12), SAG2 (P22) (12)(13)(14)(15), SAG3 (P43) (16), and P35 (15); the dense granule antigens GRA1 (P24) (11,17), GRA2 (P28) (18)(19)(20)(21)(22), GRA4 (23,24), GRA5 (25), GRA6 (P32) (15,26,27), and GRA7 (P29) (11,(28)(29)(30)(31); the rhoptry antigens ROP1 (P66) (20) and ROP2 (P54) (32)(33)(34); and B10 (P41) (35), MAG1 (36), and MIC1 (37). Many of these recombinant antigens have been used for the detection of T. gondii-specific antibodies in human serum samples (38).…”

GRA Proteins of Toxoplasma gondii: Maintenance of Host-Parasite Interactions across the Parasitophorous Vacuolar Membrane

“…A single mRNA transcript of 1.3 kb was detected by Northern blot [64], and the deduced 236 amino acid protein contains a putative N-terminal signal peptide, 1 site of potential N-linked glycosylation, and, close to the C-terminus, a further hydrophobic, putative transmembrane domain. The p29 accumulates within the PV and PVM in tachyzoite infected cells whereas in bradyzoite-infected cells, p29 is present within the host cell cytoplasm [65]. Properties of GRA7 that are pertinent to its membrane targeting and to GRA7-directed immune resistance were studied in detail [66] that GRA7 is exclusively membrane-associated in both parasites and infected host cells with the hydrophobic stretch from amino acid 181-202 providing a possible membrane anchor.…”