Academic literature on the topic 'Rhoptrie'
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Journal articles on the topic "Rhoptrie"
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Besteiro, Sébastien, Justine Bertrand-Michel, Maryse Lebrun, Henri Vial, and Jean-François Dubremetz. "Lipidomic analysis of Toxoplasma gondii tachyzoites rhoptries: further insights into the role of cholesterol." Biochemical Journal 415, no. 1 (2008): 87–96. http://dx.doi.org/10.1042/bj20080795.
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Rhoptries are secretory organelles involved in the virulence of the human pathogen Toxoplasma gondii. In the present study we have used HPLC and capillary GLC to isolate and quantify lipids from whole Toxoplasma cells and their purified rhoptries. This comparative lipidomic analysis revealed an enrichment of cholesterol, sphingomyelin and, most of all, saturated fatty acids in the rhoptries. These lipids are known, when present in membranes, to contribute to their rigidity and, interestingly, fluorescence anisotropy measurements confirmed that rhoptry-derived membranes have a lower fluidity than membranes from whole T. gondii cells. Moreover, although rhoptries were initially thought to be highly enriched in cholesterol, we demonstrated that cholesterol is present in lower proportions, and we have provided additional evidence towards a lack of involvement of rhoptry cholesterol in the process of host-cell invasion by the parasite. Indeed, depleting the cholesterol content of the parasites did not prevent the secretion of protein-containing rhoptry-derived vesicles and the parasites could still establish a structure called the moving junction, which is necessary for invasion. Instead, the crucial role of host cholesterol for invasion, which has already been demonstrated [Coppens and Joiner (2003) Mol. Biol. Cell 14, 3804–3820], might be explained by the need of a cholesterol-rich region of the host cell we could visualize at the point of contact with the attached parasite, in conditions where parasite motility was blocked.
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Dlugonska, Henryka. "ToxoplasmaRhoptries: Unique Secretory Organelles and Source of Promising Vaccine Proteins for Immunoprevention of Toxoplasmosis." Journal of Biomedicine and Biotechnology 2008 (2008): 1–7. http://dx.doi.org/10.1155/2008/632424.
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Toxoplasma gondiiis an obligate intracellular protozoan parasite classified in the phylum Apicomplexa, which includes numerous notable human and animal pathogens (Plasmodiumspecies,Cryptosporidiumspecies,Neospora caninum, etc.). The invasive stages of apicomplexans are characterized by the presence of an apical complex composed of specialized cytoskeletal and secretory organelles, including rhoptries. Rhoptries, unique apical secretory organelles shared exclusively by all apicomplexan parasites, are known to be involved in an active parasite's penetration into the host cell associated with the biogenesis of specific intracellular compartment, parasitophorous vacuole in which the parasite multiplies intensively, avoiding intracellular killing. Due to the key biological role of rhoptries, rhoptry proteins have recently become vaccine candidates for the prevention of several parasitoses, toxoplasmosis among them. The article presents current data onT. gondiirhoptries biology and new approaches to the development of effective vaccines against toxoplasmosis using rhoptry antigens.
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Alexander, David L., Shirin Arastu-Kapur, Jean-Francois Dubremetz, and John C. Boothroyd. "Plasmodium falciparum AMA1 Binds a Rhoptry Neck Protein Homologous to TgRON4, a Component of the Moving Junction in Toxoplasma gondii." Eukaryotic Cell 5, no. 7 (2006): 1169–73. http://dx.doi.org/10.1128/ec.00040-06.
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ABSTRACT Plasmodium falciparum apical membrane antigen 1 (PfAMA1) coimmunoprecipitates with the Plasmodium homologue of TgRON4, a secreted rhoptry neck protein of Toxoplasma gondii that migrates at the moving junction in association with TgAMA1 during invasion. PfRON4 also originates in the rhoptry necks, suggesting that this unusual collaboration of micronemes and rhoptries is a conserved feature of Apicomplexa.
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SHAW, M. K., D. S. ROOS, and L. G. TILNEY. "Acidic compartments and rhoptry formation in Toxoplasma gondii." Parasitology 117, no. 5 (1998): 435–43. http://dx.doi.org/10.1017/s0031182098003278.
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DAMP (3-(2,4-dinitroanilino)-3′amino-N-methyldipropylamine), which differentially accumulates in acidic compartments, was used to identify such compartments in Toxoplasma gondii tachyzoites at the electron microscope level. In both free tachyzoites and dividing intracellular parasites the only sites of DAMP accumulation were mature and forming rhoptries. No labelling of other secretory organelles (micronemes and dense granules), the ER, Golgi or any other membrane-bounded organelles or anything resembling a lysosomal system was observed. Labelling of the forming rhoptries was higher and more homogenous than in mature rhoptries in which labelling was confined to the expanded ends of each organelle. The acid pH-dependent accumulation of DAMP in the forming and mature rhoptries was blocked by ammonium chloride and monensin, reagents known to abolish intracellular pH gradients. Estimates of rhoptry pH, based on the level of DAMP accumulation, show that the intralumenal pH of forming rhoptries is more acidic (pH 5·5–3·5) than the mature rhoptries (pH 7·0–5·0).
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Dunn, Joe Dan, Sandeep Ravindran, Seon-Kyeong Kim, and John C. Boothroyd. "The Toxoplasma gondii Dense Granule Protein GRA7 Is Phosphorylated upon Invasion and Forms an Unexpected Association with the Rhoptry Proteins ROP2 and ROP4." Infection and Immunity 76, no. 12 (2008): 5853–61. http://dx.doi.org/10.1128/iai.01667-07.
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ABSTRACT The obligate intracellular parasite Toxoplasma gondii infects warm-blooded animals throughout the world and is an opportunistic pathogen of humans. As it invades a host cell, Toxoplasma forms a novel organelle, the parasitophorous vacuole, in which it resides during its intracellular development. The parasite modifies the parasitophorous vacuole and its host cell with numerous proteins delivered from rhoptries and dense granules, which are secretory organelles unique to the phylum Apicomplexa. For the majority of these proteins, little is known other than their localization. Here we show that the dense granule protein GRA7 is phosphorylated but only in the presence of host cells. Within 10 min of invasion, GRA7 is present in strand-like structures in the host cytosol that contain rhoptry proteins. GRA7 strands also contain GRA1 and GRA3. Independently of its phosphorylation state, GRA7 associates with the rhoptry proteins ROP2 and ROP4 in infected host cells. This is the first report of interactions between proteins secreted from rhoptries and dense granules.
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Topolska, Agnieszka E., Thomas L. Richie, Doan Hanh Nhan, and Ross L. Coppel. "Associations between Responses to the Rhoptry-Associated Membrane Antigen of Plasmodium falciparum and Immunity to Malaria Infection." Infection and Immunity 72, no. 6 (2004): 3325–30. http://dx.doi.org/10.1128/iai.72.6.3325-3330.2004.
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ABSTRACT Rhoptry proteins participate in the invasion of red blood cells by merozoites during the malaria parasite's asexual-stage cycle. Interference with the rhoptry protein function has been shown to prevent invasion, and three rhoptry proteins have been suggested as potential components of a vaccine against malaria. Rhoptry-associated membrane antigen (RAMA) is a 170-kDa protein of Plasmodium falciparum which is processed to a 60-kDa mature form in the rhoptries. p60/RAMA is discharged from rhoptries of free merozoites and binds to the red-cell membrane before being internalized to form part of the parasitophorous vacuole of the newly developing ring. We examined the range of anti-RAMA responses in individuals living in an area of endemicity for malaria and determined its association with clinical immunity. RAMA is immunogenic during infections, and at least three epitopes within RAMA are recognized by hyperimmune sera in immunoblots. Sera from individuals living in a region of Vietnam where malaria is endemic possessed strong antibody responses toward two C-terminal regions of RAMA. Cytophilic antibody isotypes (immunoglobulin G1 [IgG1] and IgG3) predominated in humoral responses to both C-terminal epitopes. Acute episodes of P. falciparum infection result in significant boosting of levels of antibody to an epitope at the extreme C terminus of RAMA that harbors the red-cell-binding domain. Immunity to P. falciparum infection was linked to elevated levels of IgG3 responses to this functional domain of RAMA, suggesting that the region may contain a protective epitope useful for inclusion in a multiepitope vaccine against malaria.
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Beckers, C. J., J. F. Dubremetz, O. Mercereau-Puijalon, and K. A. Joiner. "The Toxoplasma gondii rhoptry protein ROP 2 is inserted into the parasitophorous vacuole membrane, surrounding the intracellular parasite, and is exposed to the host cell cytoplasm." Journal of Cell Biology 127, no. 4 (1994): 947–61. http://dx.doi.org/10.1083/jcb.127.4.947.
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The origin of the vacuole membrane surrounding the intracellular protozoan parasite Toxoplasma gondii is not known. Although unique secretory organelles, the rhoptries, discharge during invasion of the host cell and may contribute to the formation of this parasitophorous vacuole membrane (PVM), no direct evidence for this hypothesis exists. Using a novel approach we have determined that parasite-encoded proteins are present in the PVM, exposed to the host cell cytoplasm. In infected cells incubated with streptolysin-O or low concentrations of digitonin, the host cell plasma membrane was selectively permeabilized without significantly affecting the integrity of the PVM. Antisera prepared against whole parasites or a parasite fraction enriched in rhoptries and dense granules reacted with the PVM in these permeabilized cells, indicating that parasite-encoded antigens were exposed on the cytoplasmic side of the PVM. Parasite antigens responsible for this staining of the PVM were identified by fractionating total parasite proteins by SDS-PAGE and velocity sedimentation, and then affinity purifying "fraction-specific" antibodies from the crude antisera. Proteins responsible for the PVM-staining, identified with fraction-specific antibodies, cofractionated with known rhoptry proteins. The gene encoding one of the rhoptry proteins, ROP 2, was cloned and sequenced, predicting and integral membrane protein. Antibodies specific for ROP 2 reacted with the intact PVM. These results provide the first direct evidence that rhoptry contents participate in the formation of the PVM of T. gondii and suggest a possible role of ROP 2 in parasite-host cell interactions.
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BANNISTER, L. H., J. M. HOPKINS, R. E. FOWLER, S. KRISHNA, and G. H. MITCHELL. "Ultrastructure of rhoptry development in Plasmodium falciparum erythrocytic schizonts." Parasitology 121, no. 3 (2000): 273–87. http://dx.doi.org/10.1017/s0031182099006320.
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Prior to the separation of merozoites from the Plasmodium falciparum schizont, various stage-specific organelles are synthesized and assembled within each merozoite bud. The apical ends of the merozoites are initiated close to the ends of endomitotic spindles. At each of these sites, the nuclear membrane forms coated vesicles, and a single discoidal or cup- like Golgi cisterna appears. Reconstruction from serial sections indicates that this structure receives vesicles from the nuclear envelope and in turn gives off coated vesicles to generate the apical secretory organelles. Rhoptries first form as spheroidal structures and grow by progressive fusion of small vesicles around their margins. As each rhoptry develops, 2 distinctive regions separate within it, an apical reticular zone with electron-lucent areas separated by cords of granular material, and a more homogenously granular basal region. The apical part elongates into the duct, with evidence for further vesicular fusion at the duct apex. The rounded rhoptry base becomes progressively more densely packed to form a spheroidal mass, and compaction also occurs in the duct. Typically, one rhoptry matures before the other. Cryofractured rhoptry membranes show asymmetry in the sizes and numbers of intramembranous particles at the internally- and externally-directed fracture faces.
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Bannister, L. H., G. H. Mitchell, G. A. Butcher, and E. D. Dennis. "Lamellar membranes associated with rhoptries in erythrocytic merozoites of Plasmodium knowlesi: a clue to the mechanism of invasion." Parasitology 92, no. 2 (1986): 291–303. http://dx.doi.org/10.1017/s0031182000064064.
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SUMMARYIn merozoites of Plasmodium knowlesi, rhoptries have a dense substructure of fine (2·5 nm diameter) granules and short rods. These are not altered by lipid extraction, and stain with ethanolic phosphotungstate indicating a proteinaceous composition. Various types of fixation also show multilamellar whorls with a periodicity of 5–7 rim in the tips of rhoptries or extruded at the merozoite apex. In merozoites fixed during invasions of red cells, membrane continuity typically occurs between the rim of the rhoptry canal and the red cell membrane, but where this contact has apparently been lost, extensive membranous whorls and blebs are often found at the apex of the parasite. Similar structures occur at the spices of merozoites within late-stage schizonts. It is suggested that the same mechanism which generates these lamellae forms the parasitophorous vacuole by inserting membranous elements formed by the parasite into the red cell membrane, so causing its invagination. A similar mechanism may be responsible for the release of merozoites from the late-stage schizont.
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Kawazoe, U., F. M. Tomley, and J. A. Frazier. "Fractionation and antigenic characterization of organelles ofEimeria tenellasporozoites." Parasitology 104, no. 1 (1992): 1–9. http://dx.doi.org/10.1017/s003118200006073x.
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SUMMARYSporozoites ofEimeria tenellawere disrupted by sonication and subcellular fractions were separated by sucrose gradient ultracentrifugation. Fractions from gradients were characterized by electron microscopical appearance and their polypeptide and antigenic profiles determined by PAGE and Western blotting with antisera to sporozoites and 1st- and 2nd-generation merozoites. Fractions containing micronemes, rhoptries or membranes showed markedly different polypeptide content and antigenic reactivity. Microneme epitopes were strongly conserved between sporozoites and 2nd-generation merozoites whereas the majority of rhoptry epitopes and many membrane epitopes were sporozoite specific. The only polypeptide of sporozoites which was strongly recognized by antisera raised to 1st generation merozoites was a microneme antigen of molecular weight approximately 100 kDa.
Dissertations / Theses on the topic "Rhoptrie"
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Rashid, Muhammad Imran. "RON4 et ROP18 deux protéines de rhoptries de Toxoplasma gondii candidats vaccins ? : Etude dans un modèle de toxoplasmose chronique chez la souris." Thesis, Tours, 2011. http://www.theses.fr/2011TOUR3804.
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Toxoplasma gondii, protozoaire intracellulaire obligatoire, est l’agent responsable de la toxoplasmose, infection qui revêt un caractère sévère au cours de toxoplasmoses cérébrales ou congénitales en médecines humaine et vétérinaire. Aucun vaccin n’est actuellement disponible ; le développement de stratégies vaccinales efficaces est donc d’actualité. Le potentiel vaccinant de deux protéines de rhoptries de T. gondii, RON4 et ROP18, protéines injectées dans la cellule au site de l’invasion lors de l’étape d’attachement à la cellule, a été évalué dans deux stratégies vaccinales contre la toxoplasmose chronique chez la souris: vaccination ADN par voie intramusculaire et vaccination par voie nasale avec des protéines recombinantes. L’immunisation avec des plasmides optimisés exprimant RON4, la partie N-terminale ou la partie C-terminale de RON4 co-administrés avec un plasmide exprimant l’adjuvant GM-CSF ou l’immunisation par voie nasale avec une protéine recombinante RON4 associée à la toxine cholérique, induit des réponses systémiques humorale et cellulaire (mixte Th1/Th2) mais ne confère pas de protection. Dans nos conditions expérimentales RON4 n’est pas un candidat vaccin potentiel. Des stratégies pour augmenter son immunogénicité par voie nasale et pour orienter la réponse cellulaire vers un profil Th1 pourraient cependant être envisagées. L’immunisation avec des plasmides bicistroniques exprimant à la fois ROP18 sous forme sécrétée et le GM-CSF ou ROP18 cytosolique et le GM-CSF, induit des réponses humorales et cellulaires (Th1) similaires et ne confère pas de protection significative. La co-administration d’un plasmide exprimant l’IL-12 n’augmente pas les réponses immunes avant infection mais a néanmoins contribué à augmenter la réponse cellulaire après infection. L’immunisation par voie nasale avec une protéine recombinante ROP18 associée à la toxine cholérique, induit une réponse systémique humorale (Th1/Th2) et confère une protection significative (réduction de la charge parasitaire de 50%). La co-administration de l’adjuvant poly I:C augmente la réponse cellulaire mais n’a pas d’effet sur la protection. Nos résultats suggèrent que ROP18 est un candidat vaccin potentiel, des stratégies pour améliorer son effet protecteur sont à envisager<br>Toxoplasma gondii, an obligate intracellular protozoan, is the etiologic agent of toxoplasmosis. This infection has severe consequences during cerebral or congenital toxoplasmosis both in human and veterinary medicines. No vaccine is currently available, so the design of efficient vaccine strategies is still a topical question. In this study, RON4 and ROP18, two rhoptry proteins of T. gondii which are discharged into the host cell at the invasion site, immediately following intimate contact with the host cell, were evaluated in two vaccine strategies against chronic infection in mice: DNA vaccination by the intramuscular route and recombinant protein vaccination by the nasal route. DNA immunization with optimized plasmids encoding full length RON4, or only the N-terminal, or the C-terminal part of RON4 plus a plasmid encoding the adjuvant GM-CSF or nasal immunization with a recombinant RON4 protein plus cholera toxin induced systemic humoral and cellular responses (mixed Th1/Th2) but failed to confer protection. Strategies intended to enhance the immunogenicity of RON4 by the nasal route and to enhance the Th1 immune response against RON4 could be more effective.DNA immunization with ROP18 expressed as a secreted or a cytosolic form by bicistronic vectors which encode both the antigen and the adjuvant GM-CSF induced similar humoral and cellular (Th1) responses but did not confer significant protection. Co-administration of a plasmid encoding the adjuvant IL-12 did not enhance the immune responses before challenge but was able to prime a cellular immune response that was boosted by the parasite infection. Nasal immunization with a recombinant ROP18 protein plus cholera toxin induced systemic humoral responses (mixed Th1/Th2) and conferred partial protection (50% brain cysts reduction). Co-administration of the adjuvant poly I:C enhanced the cellular response but did not potentiate the protection. Our data suggest that ROP18 is a potential vaccine candidate against toxoplasmosis. Strategies to improve the protective effect of ROP18 should be investigated
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Carcy, Bernard. "Caractérisation de deux antigènes conservés de babesia divergens et analyse moléculaire d'une nouvelle protéine de rhoptrie de plasmodium falciparum identifiée par réaction immunologique croisée." Poitiers, 1992. http://www.theses.fr/1992POIT2273.
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L'analyse de la reponse humorale des 3 hotes de babesia divergens (bovin, gerbille et homme) montre que les antigenes de 70 et 37 kda pourraient etre des candidats interessants pour un vaccin anti-b divergens de seconde generation. Des anticorps polyclonaux diriges contre l'hsp75 de plasmodium falciparum ou contre l'antigene de 37kda de b. Divergens (anti-bd37) ont permis de montrer que: 1) l'antigene de 70kda est une proteine de stress (hsp70) induite par chocs thermiques; 2) l'antigene bd37 est une glycoproteine membranaire palmitoilee principalement localisee a l'apex des merozoites et qui est secretee dans le surnageant de culture. L'anti-bd37 inhibe l'invasion de p. Falciparum en culture in vitro (ic50=300 ug/ml) et a permis de caracteriser une nouvelle proteine (pf60) de rhoptrie de p. Falciparum exprimee en fin de schizogonie. L'analyse moleculaire de pf60 a l'aide de l'anti-bd37 a permis de caracteriser une nouvelle sonde d'adn genomique de p. Falciparum (pf60. 1) qui hybride avec un arnm de 3kb dont la synthese est ponctuelle en schizogonie. La sonde pf60. 1, bien qu'elle ne contienne aucune repetition interne, detecte du polymorphisme de longueur des fragments de restriction et s'avere interessante pour analyser l'importante diversite antigenique de p. Falciparum
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Lentini, Gaëlle. "Identification de nouvelles protéines régulées différentiellement au cours du cycle cellulaire de Toxoplasma gondii." Thesis, Montpellier, 2015. http://www.theses.fr/2015MONTT049.
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Toxoplasma gondii est un protiste apicomplexe responsable de la toxoplasmose. Ce parasite intracellulaire obligatoire possède des organites sécrétoires apicaux dont les rhoptries qui contiennent des facteurs de virulence essentiels à l'invasion et à la modulation de la cellule hôte qu'il infecte. Au cours de la division cellulaire de T. gondii, les protéines de rhoptries sont synthétisées selon la même cinétique. Dans le but d'identifier de nouvelles protéines dont la fonction est potentiellement liée aux rhoptries, nous avons recherché à partir des bases de données du génome de T. gondii, les protéines présentant ce profil particulier d'expression. La localisation subcellulaire de 12 candidats a été réalisée puis une caractérisation phénotypique de quatre d'entre eux a été entreprise. Nous avons identifié une nouvelle protéase de rhoptries, DegP, essentielle à la virulence du parasite in vivo. Nous montrons que DegP contrôle la phase aigüe de l'infection en modulant la réponse immune de l'hôte contribuant ainsi à la dissémination du parasite in vivo. Nous identifions également deux protéines homologues, Claw1 et Claw2, présentant une localisation atypique à l'extrémité apicale du parasite. Notre incapacité à déléter ces gènes pourrait indiquer un rôle essentiel de ces protéines au niveau du complexe apical de T. gondii. Enfin, bien que n'étant pas reliée aux rhoptries, ce crible a permis d'identifier la première protéine associée aux jonctions des vésicules constituant le complexe membranaire interne de Toxoplasma. La délétion de cette protéine, SIP, affecte la forme du parasite, entrainant un défaut de motilité, d'invasion et de virulence in vivo<br>Toxoplasma gondii is an apicomplexan protist and the causative agent of toxoplasmosis. This obligate intracellular parasite harbors apical secretory organelles such as rhoptries that contain essential virulence factors responsible of the invasion and the modulation of the infected host cell. Along the cell cycle of T. gondii, rhoptry proteins share the same timing of expression. In order to identify new proteins involve in rhoptry content, biogenesis or secretion, we screened the genome database of T. gondii to isolate proteins that present this particular profile. We obtained the subcellular localization of 12 candidates and we investigated the biological functions for 4 of them. We showed that DegP, a rhoptry protease is essential for the in vivo virulence of T. gondii. DegP controls the acute phase during infection and modulate the host immune response leading to better parasite dissemination in vivo. Also, we identified Claw1 and its paralog Claw2 that present an atypical localization at the apical end of the parasite. To date, we were unable to disrupt the genes encoding these proteins suggesting that they may have an essential function related to the apical complex in T. gondii. Finally, we also examined a ‘hit' of this screening that was not related to rhoptries and we identified SIP, the first protein associated with the transversal junctions of the inner membrane complex in T. gondii. The disruption of SIP affects the shape of the parasite leading to an aberrant motility, defect in invasion and impaired parasite virulence in mice
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Leriche, Marie-Anne. "Caractérisation du contenu protéique des rhoptries et des granulés denses du tachyzoi͏̈te de Toxoplasma gondii." Montpellier 2, 1989. http://www.theses.fr/1989MON20207.
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Toxoplasma goondi est un protozoaire parasite intracelulaire responsable de la toxoplasmose. L'invasion de la cellule hote semble impliquer des organites particuliers localises a la partie apicale des organismes infectieux (tachyzoites). Le fractionnement subcellulaire de tachyzoites de toxoplasma gondii et l'ultracentrifugation en gradient de densite ont permis d'obtenir une fraction fortement enrichie en rhoptries et legerement contaminee par les granules denses. Cette fraction d'organites a ete utilisee pour produire un immunserum de lapin et des anticorps monoclonaux de souris. Les principaux composants proteiques des rhoptries et des granules denses du toxoplasme ont ete analyses par electrophorese mono et bidimensionnelle et immunoempreinte. Les immunodetections ultrastructurales suggerent l'existence de deux types distincts de phenomenes: 1#o) secretion du contenu de rhoptries dans la membrane de la vacuole parasitophore, intervenant precocement lors de l'invasion de la cellule hote par le parasite. 2#o) exocytose du contenu des granules denses dans le reseau tubulaire intravacuolaire, se produisant plus tardivement, apres installation du toxoplasme a l'interieur de la cellule hote. Des experiences preliminaires ont ete realisees pour rechercher des activites enzymatiques dans la fraction rhoptries granules denses: des phosphatases acide et alcaline et des proteases ont ainsi ete identifiees
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Green, Judith Louise. "Genes encoding rhoptry proteins of the malaria parasite plasmodium." Thesis, University College London (University of London), 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.300303.
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Guérin, Amandine. "Caractérisation du complexe jonctionnel de RONs et étude de la contribution de la cellule hôte lors de l’invasion du parasite Toxoplasma gondii." Thesis, Montpellier, 2017. http://www.theses.fr/2017MONTT009.
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Toxoplasma gondii est un parasite intracellulaire obligatoire responsable de la toxoplasmose. Il appartient au phylum des Apicomplexes, qui regroupe les espèces de Plasmodium responsables de la malaria. Les Apicomplexes ont un mécanisme d’invasion unique, impliquant la formation d’une interaction étroite entre la membrane plasmique du parasite et celle de la cellule hôte, appelée « jonction mobile » (MJ). Cette jonction est composée de la protéine AMA1 exposée à la surface du parasite qui interagit avec le complexe de protéines parasitaires RON2/RON4/RON5/RON8 injecté dans la cellule hôte. Les objectifs de ma thèse ont été d’étayer la composition moléculaire de la MJ et d’étudier la contribution de la cellule hôte dans l’invasion au travers de la recherche de partenaires de l’hôte pour les RONs. Quatre protéines de l’hôte, ALIX, TSG101, CD2AP et CIN85, ont été identifiées à la MJ. Les sites d’interactions ont été cartographiés sur RON2, RON4 et RON5. Des parasites mutants déficients pour le recrutement de ces partenaires ont été générés, et ont permis de montrer l’importance de l’association d’ALIX, TSG101, CD2AP et CIN85 à la MJ pour l’invasion de T. gondii et sa virulence dans un modèle murin. Le rôle de ces protéines dans le maintien des jonctions intercellulaires mais aussi leur participation à des processus de déformation membranaire, suggère que le parasite les recrute afin de favoriser son attachement et son internalisation. Nous avons également identifié un nouveau membre du complexe de RONs, appelé RON14. RON14 n’est pas essentielle pour la survie du parasite in vitro mais contribue à sa virulence in vivo<br>Toxoplasma gondii is an obligate intracellular parasite responsible for toxoplasmosis. It belongs to the phylum Apicomplexa, which include Plasmodium species responsible for malaria. Apicomplexa has developed a unique invasion mechanism, involving the formation of a tight connection between the parasite and the host cell plasma membranes called moving junction (MJ). This junction is composed of AMA1 exposed at the surface of the parasite which interacts with a complex of parasite proteins RON2/RON4/RON5/RON8 injected into the host cell. The objectives of my thesis were to decipher the molecular composition of the MJ and to study the contribution of the host cell during invasion though the search of hosts partners for RONs. Four host proteins, ALIX, TSG101, CIN85 and CD2AP, have been identified at the MJ. Binding sites has been mapped on RON2, RON4 and RON5. By generating mutant parasites deficient for host partners recruitment, we show the importance of ALIX, TSG101, CIN85 and CD2AP association at the MJ for invasion and virulence in a mouse model. The role of these proteins in maintaining the intercellular junctions and inducing membrane deformation suggest that the parasite recruits them in order to favor its attachment and its internalization. We also identified a new member of the RON complex, called RON14. RON14 is not essential for the parasite survival in vitro but contributes to its virulence in vivo
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Awah, Nancy. "Malarial anaemia : the potential involvement of Plasmodium falciparum rhoptry proteins." Licentiate thesis, Stockholms universitet, Wenner-Grens institut, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-8460.
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Malaria remains a challenging health problem in malaria endemic regions. Infection with malaria invariably leads to anaemia. The groups at risk of developing malarial anaemia include children below the age of five years and pregnant women, especially primigravidae. Several factors have been suggested to be responsible for its aetiology, including increased destruction of infected and normal red blood cells together with bone marrow suppression. However, until recently, the molecular mechanisms involved have remained elusive. The aim of the work presented herein was to investigate the mechanisms responsible for the destruction of normal red blood cells in anaemia, and more specifically to define the role of the ring surface protein (RSP/RAP) -2 and other members of the low molecular weight rhoptry associated protein (RAP) complex, RAP-1 and -3. In the first study we showed that antibodies to the RAP complex could mediate the destruction of RSP-2 tagged erythroid cells by phagocytosis or by complement activation and then lysis. In addition, antibodies to RAP-1 and RAP-2 could induce the death of RSP-2/RAP-2 tagged erythroblasts. We further investigated the frequency and functionality of naturally occurring RSP-2/RAP-2 antibodies in the sera of anaemic and non-anaemic Cameroonian children. We found that all sera investigated contained RSP-2/RAP-2 reactive antibodies by both immunoflorescence and flow cytometry. The anaemic group of children had significantly higher levels of antibodies of the IgG isotype than the non-anaemic individuals, while the levels of IgM were similar in both groups. With respect to IgG subclasses, low levels of IgG1 and -3 antibodies were detected. Higher levels of IgG3 were seen in the non-anaemic individuals as compared to anaemic subjects. With regards to antibody functionality, the non-anaemic individuals recognised a greater proportion of RSP-2/RAP-2 tagged erythrocytes and activated complement to a greater extent than the anaemic individuals. From our findings, we can conclude that antibodies to the RAP complex are potentially involved in erythroid cell destruction during malaria which may result in anaemia, and that high levels of such antibodies may be detrimental to the host.
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Fonjungo, Peter Nkong. "Human antibody responses to Plasmodium falciparum merozoite rhoptry associated protein 1 (RAP1)." Thesis, University of Edinburgh, 1998. http://hdl.handle.net/1842/12022.
Full textAbstract:
My main aim was to investigate human Ab responses to RAP1. For this study, I have developed nine recombinant RAP1 proteins (rRAP1) representing almost the entire sequence of mature RAP1 that have been expressed in <I>Escherichia coli</I> as soluble hexa-histidine or GST fusions. The antigenicity of the rRAP1 proteins was assessed by immunogenicity tests in mice and rabbits, and by <I>P. falciparum </I>RAP1-specific mAbs recognising a defined linear epitope. Antisera to seven of the rRAP1 proteins specifically reacted with parasites in immunofluorescence as well as parasite-derived RAP1 protein (<I>Pf</I>RAP1) in immunoblotting. These results indicate that these rRAP1 proteins bear antigenic similarity to <I>P. falciparum</I> RAP1. Affinity purified Abs produced in rabbits against three rRAP1 proteins block invasion of red blood cells by merozoites, and this suggests that the proteins contain protective epitopes. Analysis of serum Abs of residents of malaria endemic regions by ELISA shows that RAP1 is antigenic during naturally transmitted malaria infection. The recombinant proteins are specifically recognised by IgG Abs, with detectable Abs directed mostly towards fragments containing N-terminal sequences of mature <I>Pf</I>RAP1. By contrast, only few individuals had Abs to the C-terminus. Abs from malaria patients do not complete for a linear epitope recognised by an inhibitory anti-RAP1 mAb. This indicates that Abs from malaria patients bind mostly to epitopes different from that recognised by the inhibitory mAb. In a longitudinal study of individuals conducted over a period of 4 years in a region of seasonal and unstable malaria transmission, I have found that Abs to RAP1 are produced only after a documented clinical malaria.
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Harnyuttanakorn, Pongchai. "Epitope mapping studies on a highly conserved rhoptry antigen from Plasmodium falciparum." Thesis, University of Edinburgh, 1993. http://hdl.handle.net/1842/14995.
Full textAbstract:
Malaria is one of the most widespread parasitic diseases. It is caused by <i>Plasmodium</i> protozoa. <i>Plasmodium falciparum</i> infection leads to the most virulent symptoms in human. Researchers have been devoted to develop a malaria vaccine for malaria eradication, especially against <i>P.falciparum</i>. Rhoptry associated protein-1 (RAP-1) is one of the <i>P.falciparum</i> vaccine candidates because it protected monkeys in an immunization experiment and some monoclonal antibodies raised against this protein can inhibit parasite growth <i>in vitro</i>. This thesis describes work in which the epitopes of the inhibitory monoclonal antibodies were mapped by using a combination of recombinant DNA technology and peptide synthesis. The part of the <i>rap-1</i> gene, which contains epitope of inhibitory monoclonal antibodies, was subcloned and expressed in <i>Escherichia coli</i> in a β-galactosidase fusion form. The use of restriction enzymes and exonuclease III to generate different fragements of <i>rap-1</i> gene suggested that the epitopes of these monoclonal antibodies cluster near a proteolytic cleavage site on the protein (between A_190 and D_191). This was confirmed when the epitope of all the inhibitory monoclonal antibodies were located on a TLTPLEELYP_210 peptide generated as one of a series of overlapping decapeptides. The study of RAP-1 protein immunogenicity in rabbit and humans showed that both species are also able to recognize this 'inhibitory epitope'. The epitope mapping of another set of monoclonal antibodies raised against a recombinant RAP-1 protein lacking its 'native' conformation was carried out. The results suggested that this expressed protein can stimulate immune response against the 'inhibitory epitope' but two additional epitopes are also recognized by these monoclonal antibodies. Sequence analysis of the <i>rap-1</i> gene from a number of isolates and clones demonstrated that the RAP-1 protein is highly conserved in <i>P. falciparum</i> from several parts of the world. This finding verified the potential of the RAP-1 protein as a malaria vaccine candidate.
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Zhang, Yang. "Development of aptamers against Toxoplasma gondii rhoptry protein 18 through site-specific SELEX." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709349.
Full textBook chapters on the topic "Rhoptrie"
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Mehlhorn, Heinz. "Rhoptries." In Encyclopedia of Parasitology. Springer Berlin Heidelberg, 2016. http://dx.doi.org/10.1007/978-3-662-43978-4_2722.
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Mehlhorn, Heinz. "Rhoptries." In Encyclopedia of Parasitology. Springer Berlin Heidelberg, 2015. http://dx.doi.org/10.1007/978-3-642-27769-6_2722-2.
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Sam-Yellowe, Tobili. "Rhoptries and Other Merozoite Organelles Involved in Invasion." In Encyclopedia of Malaria. Springer New York, 2015. http://dx.doi.org/10.1007/978-1-4614-8757-9_52-1.
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Suarez, Catherine, Melissa B. Lodoen, and Maryse Lebrun. "Assessing Rhoptry Secretion in T. gondii." In Methods in Molecular Biology. Springer US, 2019. http://dx.doi.org/10.1007/978-1-4939-9857-9_8.
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Dubremetz, Jean François, Abderrahim Sadak, Zoubida Taghy, and Bernard Fortier. "Characterization of a 42 kDa Rhoptry Antigen of Toxoplasma Gondii." In Host-Parasite Cellular and Molecular Interactions in Protozoal Infections. Springer Berlin Heidelberg, 1987. http://dx.doi.org/10.1007/978-3-642-72840-2_42.
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"Rhoptry (toxoneme)." In Encyclopedia of Genetics, Genomics, Proteomics and Informatics. Springer Netherlands, 2008. http://dx.doi.org/10.1007/978-1-4020-6754-9_14623.
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Boothroyd, John C., and Mohamed-Ali Hakimi. "Effectors produced by rhoptries and dense granules: an intense conversation between parasite and host in many languages." In Toxoplasma gondii. Elsevier, 2020. http://dx.doi.org/10.1016/b978-0-12-815041-2.00017-7.
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