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Qi Bai - One of the best experts on this subject based on the ideXlab platform.
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Observation on the schizont stage of an unidentified Theileria sp. in experimentally infected sheep.
Parasitology research, 2003Co-Authors: Hong Yin, Guangyuan Liu, Jianxun Luo, Guiquan Guan, Jabbar S. Ahmed, Qi BaiAbstract:The schizont stage of an unidentified Theileria sp. infective for small ruminants was observed. Intact sheep were infected with adult Haemaphysalis qinghaiensis collected from fields where ovine theileriosis was prevalent. When the infested sheep developed theileriosis, tissue and organ smears were prepared. Theileria Schizonts were demonstrated in liver, spleen, lung, kidney, lymph node and peripheral blood. Most of the Schizonts were found outside the host cells, which was probably a smear artifact. This study adds our knowledge that lung and kidney can be parasitized by Schizonts of Theileria sp.
W.i. Morrison - One of the best experts on this subject based on the ideXlab platform.
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Characterization of a polymorphic immunodominant molecule in sporozoites and Schizonts of Theileria parva
Parasite Immunology, 1991Co-Authors: Philip G Toye, K. Iams, Antony Musoke, Bruno Goddeeris, W.i. MorrisonAbstract:Summary This study examines several aspects of a polymorphic, immunodominant molecule (P!M) found in the protozoan parasite. Theileria parva. The antigen is present in all T. p. parva stocks examined, and in the related subspecies, T. p. bovis and T. p. lawrencei. It is the predominant antigen recognized by antisera from immune cattle on Western blot analysis of schizont-infected lymphocytes, and is the only antigen which has been shown to react with anti-schizont monoclonal antibodies (MoAbs) on Western blots or in immunoprecipitations. The antigen shows polymorphism in both size and expression of antibody epitopes among the different stocks of T. parva. The antigen is present in sporozoites as well as Schizonts.
Philip J. Rosenthal - One of the best experts on this subject based on the ideXlab platform.
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Falstatin, a cysteine protease inhibitor of Plasmodium falciparum, facilitates erythrocyte invasion.
PLoS Pathogens, 2006Co-Authors: Kailash C. Pandey, Naresh Singh, Shirin Arastu-kapur, Matthew Bogyo, Philip J. RosenthalAbstract:Erythrocytic malaria parasites utilize proteases for a number of cellular processes, including hydrolysis of hemoglobin, rupture of erythrocytes by mature Schizonts, and subsequent invasion of erythrocytes by free merozoites. However, mechanisms used by malaria parasites to control protease activity have not been established. We report here the identification of an endogenous cysteine protease inhibitor of Plasmodium falciparum, falstatin, based on modest homology with the Trypanosoma cruzi cysteine protease inhibitor chagasin. Falstatin, expressed in Escherichia coli, was a potent reversible inhibitor of the P. falciparum cysteine proteases falcipain-2 and falcipain-3, as well as other parasite- and nonparasite-derived cysteine proteases, but it was a relatively weak inhibitor of the P. falciparum cysteine proteases falcipain-1 and dipeptidyl aminopeptidase 1. Falstatin is present in Schizonts, merozoites, and rings, but not in trophozoites, the stage at which the cysteine protease activity of P. falciparum is maximal. Falstatin localizes to the periphery of rings and early Schizonts, is diffusely expressed in late Schizonts and merozoites, and is released upon the rupture of mature Schizonts. Treatment of late schizionts with antibodies that blocked the inhibitory activity of falstatin against native and recombinant falcipain-2 and falcipain-3 dose-dependently decreased the subsequent invasion of erythrocytes by merozoites. These results suggest that P. falciparum requires expression of falstatin to limit proteolysis by certain host or parasite cysteine proteases during erythrocyte invasion. This mechanism of regulation of proteolysis suggests new strategies for the development of antimalarial agents that specifically disrupt erythrocyte invasion.
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Plasmodial serine repeat antigen homologues with properties of schizont cysteine proteases.
Molecular and biochemical parasitology, 1998Co-Authors: Dennis O. Gor, Mark F. Wiser, Philip J. RosenthalAbstract:Proteases appear to be required for critical events in the erythrocytic life cycle of malaria parasites, including the rupture of erythrocytes by mature Schizonts and the subsequent invasion of erythrocytes by daughter merozoites [1,2]. This conclusion is supported by studies showing that parasite rupture and invasion of erythrocytes are inhibited by serine and cysteine protease inhibitors [1] and that the proteolytic processing of late schizont-stage proteins is required for the completion of the erythrocytic cycle [3,4]. A number of schizont protease activities have been identified biochemically [2], but limitations on available quantities of protein have made it difficult to definitively characterize these proteases or to ascertain their specific biological roles. The Plasmodium falciparum serine repeat antigen (known as SERA, SERA-1, SERP or P126 [5–7]) is being studied as a potential vaccine component [8]. A number of SERA homologues have been described, namely serine repeat protein homologue (SERPH [9] or SERA-2 [10]) and SERA-3 [10] from P. falciparum and five homologues from Plasmodium 6i6ax [11]. SERA and SERPH have been localized to the parasitophorous vacuole of mature Schizonts [9,12], and SERA fragments are released into the bloodstream near the time of erythrocyte rupture [12]. SERA and its homologues all contain a 30 kDa ‘protease domain’ that has similarity in sequence to papain-family cysteine proteases, particularly near highly conserved active site residues [13] (Fig. 1A). Taken together, available data suggest that SERA and SERPH may act as late schizontAbbre6iations: SERA, serine repeat antigen; SERPH, serine repeat antigen homologue. * Corresponding author. Tel.: +1 415 2068845; fax: +1 415 2066015; e-mail: rosnthl@itsa.ucsf.edu 1 Note: Nucleotide sequence data reported in this paper are available in the GenBankTM data base under accession numbers U59860, U59861, U59862 and AF052747.
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Short communication Plasmodial serine repeat antigen homologues with properties of schizont cysteine proteases 1
1998Co-Authors: Dennis O. Gor, Mark F. Wiser, Philip J. RosenthalAbstract:Proteases appear to be required for criticalevents in the erythrocytic life cycle of malariaparasites, including the rupture of erythrocytes bymature Schizonts and the subsequent invasion oferythrocytes by daughter merozoites [1,2]. Thisconclusion is supported by studies showing thatparasite rupture and invasion of erythrocytes areinhibited by serine and cysteine protease in-hibitors [1] and that the proteolytic processing oflate schizont-stage proteins is required for thecompletion of the erythrocytic cycle [3,4]. A num-ber of schizont protease activities have been iden-tiÞed biochemically [2], but limitations onavailable quantities of protein have made itdifÞcult to deÞnitively characterize these proteasesor to ascertain their speciÞc biological roles.The Plasmodium falciparum serine repeat anti-gen (known as SERA, SERA-1, SERP or P126[5 Ð 7]) is being studied as a potential vaccinecomponent [8]. A number of SERA homologueshave been described, namely serine repeat proteinhomologue (SERPH [9] or SERA-2 [10]) andSERA-3 [10] from P . falciparum and Þve homo-logues from Plasmodium !i!ax [11]. SERA andSERPH have been localized to the para-sitophorous vacuole of mature Schizonts [9,12],and SERA fragments are released into the blood-stream near the time of erythrocyte rupture [12].SERA and its homologues all contain a ! 30 kDaOprotease domainO that has similarity in sequenceto papain-family cysteine proteases, particularlynear highly conserved active site residues [13](Fig. 1A). Taken together, available data suggestthat SERA and SERPH may act as late schizont-
G H Mitchell - One of the best experts on this subject based on the ideXlab platform.
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correlation of structural development and differential expression of invasion related molecules in Schizonts of plasmodium falciparum
Parasitology, 2004Co-Authors: Gabriele Margos, L H Bannister, Anton R Dluzewski, John M Hopkins, Ian T Williams, G H MitchellAbstract:During asexual development Plasmodium Schizonts undergo a series of complex biochemical and structural changes. Using tightly synchronized cultures of 2 P. falciparum lines (clone C10 and strain ITO4) for light microscopy and fluorescence imaging we monitored the timing and sequence of expression of proteins associated with invasion-related organelles. Antibodies to rhoptry, micronemal and dense granule proteins (Rhoptry Associated Protein 1, Apical Membrane Antigen 1, Erythrocyte Binding Antigen 175, Ring-infected Erythrocyte Surface Antigen) and to pellicle-associated proteins (Merozoite Surface Protein 1, PfMyosin-A) were used. Clone C10 developed faster than ITO4; this difference was also found in the timing of protein expression seen by immunofluorescence. Light microscopic data were combined with transmission electron microscopic analysis using serial sectioning of ITO4 Schizonts to determine nuclear number and organellar development. Thus a timetable of schizont structural maturation was established. Generally, the timing of organelle-specific antigen expression correlates well with the ultrastructural data. Rhoptries are formed mainly between second and fourth nuclear divisions, micronemes between the end of the fourth nuclear division and merozoite separation from the residual body, while dense granules are generated mainly after the micronemes. PfAMA-1 appears in micronemes before EBA-175, suggesting micronemal heterogeneity.
Kerry Woods - One of the best experts on this subject based on the ideXlab platform.
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cell cycle dependent phosphorylation of theileria annulata schizont surface proteins
PLOS ONE, 2014Co-Authors: Olga Wiens, Conrad Von Schubert, Jonathan M Wastling, Dirk A E Dobbelaere, Volker Heussler, Kerry WoodsAbstract:The invasion of Theileria sporozoites into bovine leukocytes is rapidly followed by the destruction of the surrounding host cell membrane, allowing the parasite to establish its niche within the host cell cytoplasm. Theileria infection induces host cell transformation, characterised by increased host cell proliferation and invasiveness, and the activation of anti-apoptotic genes. This process is strictly dependent on the presence of a viable parasite. Several host cell kinases, including PI3-K, JNK, CK2 and Src-family kinases, are constitutively activated in Theileria-infected cells and contribute to the transformed phenotype. Although a number of host cell molecules, including IkB kinase and polo-like kinase 1 (Plk1), are recruited to the schizont surface, very little is known about the schizont molecules involved in host-parasite interactions. In this study we used immunofluorescence to detect phosphorylated threonine (p-Thr), serine (p-Ser) and threonine-proline (p-Thr-Pro) epitopes on the schizont during host cell cycle progression, revealing extensive schizont phosphorylation during host cell interphase. Furthermore, we established a quick protocol to isolate Schizonts from infected macrophages following synchronisation in S-phase or mitosis, and used mass spectrometry to detect phosphorylated schizont proteins. In total, 65 phosphorylated Theileria proteins were detected, 15 of which are potentially secreted or expressed on the surface of the schizont and thus may be targets for host cell kinases. In particular, we describe the cell cycle-dependent phosphorylation of two T. annulata surface proteins, TaSP and p104, both of which are highly phosphorylated during host cell S-phase. TaSP and p104 are involved in mediating interactions between the parasite and the host cell cytoskeleton, which is crucial for the persistence of the parasite within the dividing host cell and the maintenance of the transformed state.
