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Journal ArticleDOI

The same but different: the biology of Theileria sporozoite entry into bovine cells

01 May 1997-International Journal for Parasitology (Pergamon)-Vol. 27, Iss: 5, pp 457-474
TL;DR: It is suggested that the initial sporozoite binding event triggers the mobilization of intrasporozoite Ca2+ and the activation of both kinase and G-protein associated signalling processes in the parasite, which regulate the invasive capacity of the sporozoites.
About: This article is published in International Journal for Parasitology.The article was published on 1997-05-01. It has received 53 citations till now. The article focuses on the topics: Theileria & Theileria parva.
Citations
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Journal ArticleDOI
TL;DR: The unusual properties of actin and myosin in the Apicomplexa, the highly stereotyped microtubule populations in apicOMplexans, and a network of recently discovered novel intermediate filament-like elements in these parasites are discussed.
Abstract: The Apicomplexa are a phylum of diverse obligate intracellular parasites including Plasmodium spp., the cause of malaria; Toxoplasma gondii and Cryptosporidium parvum, opportunistic pathogens of immunocompromised individuals; and Eimeria spp. and Theileria spp., parasites of considerable agricultural importance. These protozoan parasites share distinctive morphological features, cytoskeletal organization, and modes of replication, motility, and invasion. This review summarizes our current understanding of the cytoskeletal elements, the properties of cytoskeletal proteins, and the role of the cytoskeleton in polarity, motility, invasion, and replication. We discuss the unusual properties of actin and myosin in the Apicomplexa, the highly stereotyped microtubule populations in apicomplexans, and a network of recently discovered novel intermediate filament-like elements in these parasites.

481 citations

Journal ArticleDOI
TL;DR: Key parameters in T. parva population dynamics are the relative importance of asymptomatic carrier cattle and animals undergoing severe disease, in transmission of the parasite to ticks, and the extent of transmission by nymphs as compared to adult ticks.
Abstract: Theileria are economically important, intra-cellular protozoa, transmitted by ixodid ticks, which infect wild and domestic ruminants. In the mammalian host, parasites infect leukocytes and erythrocytes. In the arthropod vector they develop in gut epithelial cells and salivary glands. All four intra-cellular stages of Theileria survive free in the cytoplasm. The schizont stages of certain Theileria species induce a unique, cancer-like, phenotype in infected host leukocytes. Theileria undergoes an obligate sexual cycle, involving fusion of gametes in the tick gut, to produce a transiently diploid zygote. The existence of sexual recombination in T. parva has been confirmed in the laboratory, and is presumed to contribute to the extensive polymorphism observed in field isolates. Key parameters in T. parva population dynamics are the relative importance of asymptomatic carrier cattle and animals undergoing severe disease, in transmission of the parasite to ticks, and the extent of transmission by nymphs as compared to adult ticks. Tick populations differ in vector competence for specific T. parva stocks. Recombinant forms of T. parva and T. annulata sporozoite surface antigens induce protection against parasite challenge in cattle. In future, vaccines might be improved by inclusion of tick peptides in multivalent vaccines.

223 citations


Cites background from "The same but different: the biology..."

  • ...The entry process is probably energy dependent and is likely to involve specific receptors located on the host cells (Shaw, 1997, 2002)....

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  • ...Mobilization of calcium stores within sporozoites, parasite and host cell proteases, and signal transduction via host cell and parasite protein kinases and G proteins have all been demonstrated to play a role in the entry process (Shaw, 1997)....

    [...]

Book ChapterDOI
TL;DR: Structural and biochemical analyses of MIC domains is providing new perspectives on how adhesion is regulated and the potentially distinct roles MICs might play in long or short range interactions during parasite attachment and entry.
Abstract: The invasive stages (zoites) of most apicomplexan parasites are polarised cells that use their actinomyosin-powered gliding motility or “glideosome” system to move over surfaces, migrate through biological barriers and invade and leave host cells. Central to these processes is the timely engagement and disengagement of specific receptors upon the regulated release of apical invasion proteins from parasite secretory organelles (micronemes, rhoptries). In this short review, we summarise recent progress on identification and functional characterisation of apical invasion proteins mobilised to the parasite surface from the microneme organelles. We have restricted our focus to Toxoplasma, Eimeria, Cryptosporidium and the nonerythrocytic stages of Plasmodium because these organisms have been the most intensively studied apicomplexans that invade nucleated cells and because invasion by erythrocytic stages of Plasmodium is covered in the next chapter.

210 citations


Cites result from "The same but different: the biology..."

  • ...This long-standing correlation between micronemes and parasite motility, migration and invasion is well supported by a vari› ety of biochemical and genetic studies which show: ( 1 ) that microneme secretion is rapidly up-regulated when parasites make contact with host cells;^ (2) that some Plasmodium microneme proteins are targets of erythrocytic invasion-inhibitory antibodies; ’ (3) that parasite invasion is blocked when microneme secretion ......

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Journal ArticleDOI
TL;DR: Two families of molecules, which are known for their capacity to interrupt the apoptotic program, are currently discussed in the literature and can directly interfere with molecules of the cellular death machinery.

182 citations

Journal ArticleDOI
TL;DR: The presence of the parasite in the host-cell cytoplasm modulates the state of activation of a number of signal transduction pathways, including nuclear factor-kappa B, which appear to be essential for the survival of Theileria-transformed T cells.
Abstract: Theileria parva and T. annulata provide intriguing models for the study of parasite-host interactions. Both parasites possess the unique property of being able to transform the cells they infect; T. parva transforms T and B cells, whereas T. annulata affects B cells and monocytes/macrophages. Parasitized cells do not require antigenic stimulation or exogenous growth factors and acquire the ability to proliferate continuously. In vivo, parasitized cells undergo clonal expansion and infiltrate both lymphoid and non-lymphoid tissues of the infected host. Theileria-induced transformation is entirely reversible and is accompanied by the expression of a wide range of different lymphokines and cytokines, some of which may contribute to proliferation or may enhance spread and survival of the parasitized cell in the host. The presence of the parasite in the host-cell cytoplasm modulates the state of activation of a number of signal transduction pathways. This, in turn, leads to the activation of transcription factors, including nuclear factor-kappa B, which appear to be essential for the survival of Theileria-transformed T cells.

161 citations

References
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Journal ArticleDOI
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TL;DR: The force required to separate two cells is shown to be greater than the expected electrical forces between cells, and of the same order of magnitude as the forces required to pull gangliosides and perhaps some integral membrane proteins out of the cell membrane.
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Journal ArticleDOI
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Journal ArticleDOI
27 Jan 1995-Cell
TL;DR: This review focuses on the role of dimerization of cell surface receptors in signal transduction, which appears to be a mechanism of general applicability for the regulation of signalTransduction.

1,627 citations