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Morrison LJ, Steketee PC, Tettey MD, Matthews KR. Pathogenicity and virulence of African trypanosomes: From laboratory models to clinically relevant hosts. Virulence 2023; 14:2150445. [PMID: 36419235 DOI: 10.1080/21505594.2022.2150445] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2022] [Accepted: 11/17/2022] [Indexed: 11/25/2022] Open
Abstract
African trypanosomes are vector-borne protozoa, which cause significant human and animal disease across sub-Saharan Africa, and animal disease across Asia and South America. In humans, infection is caused by variants of Trypanosoma brucei, and is characterized by varying rate of progression to neurological disease, caused by parasites exiting the vasculature and entering the brain. Animal disease is caused by multiple species of trypanosome, primarily T. congolense, T. vivax, and T. brucei. These trypanosomes also infect multiple species of mammalian host, and this complexity of trypanosome and host diversity is reflected in the spectrum of severity of disease in animal trypanosomiasis, ranging from hyperacute infections associated with mortality to long-term chronic infections, and is also a main reason why designing interventions for animal trypanosomiasis is so challenging. In this review, we will provide an overview of the current understanding of trypanosome determinants of infection progression and severity, covering laboratory models of disease, as well as human and livestock disease. We will also highlight gaps in knowledge and capabilities, which represent opportunities to both further our fundamental understanding of how trypanosomes cause disease, as well as facilitating the development of the novel interventions that are so badly needed to reduce the burden of disease caused by these important pathogens.
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Affiliation(s)
- Liam J Morrison
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK
| | - Pieter C Steketee
- Roslin Institute, Royal (Dick) School of Veterinary Studies, University of Edinburgh, Midlothian, UK
| | - Mabel D Tettey
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
| | - Keith R Matthews
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK
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Wen YZ, Tang HT, Cai XL, Wu N, Xu JZ, Su BX, Hide G, Lun ZR, Lai DH. PAG3 promotes the differentiation of bloodstream forms in Trypanosoma brucei and reveals the evolutionary relationship among the Trypanozoon trypanosomes. Front Cell Infect Microbiol 2022. [DOI: 10.3389/fcimb.2022.1021332] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022] Open
Abstract
IntroductionTrypanosoma brucei, T. evansi and T. equiperdum are members of the subgenus Trypanozoon and are highly similar morphologically and genetically. The main differences between these three species are their differentiation patterns in the hosts and the role of vectors in their life cycles. However, the mechanisms causing these differences are still controversial.MethodsPAG3 gene was accessed by PCR amplification in 26 strains of Trypanozoon and sequences were then analyzed by BLAST accompanied with T. evansitype B group. RNA interference and CRISPR/Cas9 were used for revealing possible role of PAG3 in slender to stumpy transformation.ResultsThe procyclin associated gene 3 (PAG3) can be found in the pleomorphicspecies, T.brucei, which undergoes differentiation of slender forms to the stumpy form. This differentiation process is crucial for transmission to the tsetse fly vector. However, a homologue of PAG3 was not detected in either T. evansi or in the majority of T. equiperdum strains which are allmonomorphic. Furthere xperiments in T. brucei demonstrated that, when PAG3 was down-regulated or absent, there was a significant reduction in the differentiation from slender to stumpy forms.ConclusionTherefore, we conclude that PAG3 is a key nuclear gene involved in the slender to stumpy differentiation pathway of T.brucei in the mammalian host. Loss of this gene might also offer a simple evolutionary mechanism explaining why T. evansi and some T. equiperdum have lost the ability to differentiate and have been driven to adapt to transmission cycles that by pass the tsetse vector or mechanical contact.
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Abstract
African trypanosomes are responsible for important diseases of humans and animals in sub-Saharan Africa. The best-studied species is Trypanosoma brucei, which is characterized by development in the mammalian host between morphologically slender and stumpy forms. The latter are adapted for transmission by the parasite's vector, the tsetse fly. The development of stumpy forms is driven by density-dependent quorum-sensing (QS), the molecular basis for which is now coming to light. In this review, I discuss the historical context and biological features of trypanosome QS and how it contributes to the parasite's infection dynamics within its mammalian host. Also, I discuss how QS can be lost in different trypanosome species, such as T. brucei evansi and T. brucei equiperdum, or modulated when parasites find themselves competing with others of different genotypes or of different trypanosome species in the same host. Finally, I consider the potential to exploit trypanosome QS therapeutically. Expected final online publication date for the Annual Review of Microbiology, Volume 75 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.
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Affiliation(s)
- Keith R Matthews
- Institute for Immunology and Infection Research, Ashworth Laboratories, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, United Kingdom;
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Rojas F, Matthews KR. Quorum sensing in African trypanosomes. Curr Opin Microbiol 2019; 52:124-129. [PMID: 31442903 DOI: 10.1016/j.mib.2019.07.001] [Citation(s) in RCA: 25] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2019] [Revised: 06/28/2019] [Accepted: 07/17/2019] [Indexed: 01/17/2023]
Abstract
Many microbial eukaryotes exhibit cell-cell communication to co-ordinate group behaviours as a strategy to exploit a changed environment, adapt to adverse conditions or regulate developmental responses. Although best characterised in bacteria, eukaryotic microbes have also been revealed to cooperate to optimise their survival or dissemination. An excellent model for these processes are African trypanosomes, protozoa responsible for important human and animal disease in sub Saharan Africa. These unicellular parasites use density sensing in their mammalian host to prepare for transmission. Recently, the signal and signal transduction pathway underlying this activity have been elucidated, revealing that the parasite exploits oligopeptide signals generated by released peptidases to monitor cell density and so generate transmission stages. Here we review the evidence for this elegant quorum sensing mechanism and its parallels with similar mechanisms in other microbial systems. We also discuss its implications for disease spread in the context of coinfections involving different trypanosome species.
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Affiliation(s)
- Federico Rojas
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, United Kingdom.
| | - Keith R Matthews
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh EH9 3FL, United Kingdom.
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Silvester E, McWilliam KR, Matthews KR. The Cytological Events and Molecular Control of Life Cycle Development of Trypanosoma brucei in the Mammalian Bloodstream. Pathogens 2017; 6:pathogens6030029. [PMID: 28657594 PMCID: PMC5617986 DOI: 10.3390/pathogens6030029] [Citation(s) in RCA: 43] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2017] [Revised: 06/21/2017] [Accepted: 06/22/2017] [Indexed: 12/21/2022] Open
Abstract
African trypanosomes cause devastating disease in sub-Saharan Africa in humans and livestock. The parasite lives extracellularly within the bloodstream of mammalian hosts and is transmitted by blood-feeding tsetse flies. In the blood, trypanosomes exhibit two developmental forms: the slender form and the stumpy form. The slender form proliferates in the bloodstream, establishes the parasite numbers and avoids host immunity through antigenic variation. The stumpy form, in contrast, is non-proliferative and is adapted for transmission. Here, we overview the features of slender and stumpy form parasites in terms of their cytological and molecular characteristics and discuss how these contribute to their distinct biological functions. Thereafter, we describe the technical developments that have enabled recent discoveries that uncover how the slender to stumpy transition is enacted in molecular terms. Finally, we highlight new understanding of how control of the balance between slender and stumpy form parasites interfaces with other components of the infection dynamic of trypanosomes in their mammalian hosts. This interplay between the host environment and the parasite’s developmental biology may expose new vulnerabilities to therapeutic attack or reveal where drug control may be thwarted by the biological complexity of the parasite’s lifestyle.
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Affiliation(s)
- Eleanor Silvester
- Institute for Immunology and Infection Research, Centre for Immunity, Infection and Evolution, School of Biological Sciences, King's Buildings, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK.
| | - Kirsty R McWilliam
- Institute for Immunology and Infection Research, Centre for Immunity, Infection and Evolution, School of Biological Sciences, King's Buildings, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK.
| | - Keith R Matthews
- Institute for Immunology and Infection Research, Centre for Immunity, Infection and Evolution, School of Biological Sciences, King's Buildings, University of Edinburgh, Charlotte Auerbach Road, Edinburgh EH9 3FL, UK.
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6
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Mony BM, Matthews KR. Assembling the components of the quorum sensing pathway in African trypanosomes. Mol Microbiol 2015; 96:220-32. [PMID: 25630552 PMCID: PMC4403954 DOI: 10.1111/mmi.12949] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/24/2015] [Indexed: 12/14/2022]
Abstract
African trypanosomes, parasites that cause human sleeping sickness, undergo a density-dependent differentiation in the bloodstream of their mammalian hosts. This process is driven by a released parasite-derived factor that causes parasites to accumulate in G1 and become quiescent. This is accompanied by morphological transformation to 'stumpy' forms that are adapted to survival and further development when taken up in the blood meal of tsetse flies, the vector for trypanosomiasis. Although the soluble signal driving differentiation to stumpy forms is unidentified, a recent genome-wide RNAi screen identified many of the intracellular signalling and effector molecules required for the response to this signal. These resemble components of nutritional starvation and quiescence pathways in other eukaryotes, suggesting that parasite development shares similarities with the adaptive quiescence of organisms such as yeasts and Dictyostelium in response to nutritional starvation and stress. Here, the trypanosome signalling pathway is discussed in the context of these conserved pathways and the possible contributions of opposing 'slender retainer' and 'stumpy inducer' arms described. As evolutionarily highly divergent eukaryotes, the organisation and conservation of this developmental pathway can provide insight into the developmental cycle of other protozoan parasites, as well as the adaptive and programmed developmental responses of all eukaryotic cells.
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Affiliation(s)
- Binny M Mony
- Centre for Immunity, Infection and Evolution, Institute for Immunology and Infection Research, School of Biological Sciences, University of EdinburghCharlotte Auerbach Road, Edinburgh, EH9 3FL, UK
| | - Keith R Matthews
- Centre for Immunity, Infection and Evolution, Institute for Immunology and Infection Research, School of Biological Sciences, University of EdinburghCharlotte Auerbach Road, Edinburgh, EH9 3FL, UK
- *For correspondence. E-mail ; Tel. (+44) 131 651 3639; Fax (+44) 131 651 3670
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Allison H, O'Reilly AJ, Sternberg J, Field MC. An extensive endoplasmic reticulum-localised glycoprotein family in trypanosomatids. MICROBIAL CELL 2014; 1:325-345. [PMID: 26167471 PMCID: PMC4497807 DOI: 10.15698/mic2014.10.170] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
African trypanosomes are evolutionarily highly divergent parasitic protozoa, and
as a consequence the vast majority of trypanosome membrane proteins remain
uncharacterised in terms of location, trafficking or function. Here we describe
a novel family of type I membrane proteins which we designate ‘invariant
glycoproteins’ (IGPs). IGPs are trypanosome-restricted, with extensive,
lineage-specific paralogous expansions in related taxa. In T.
brucei three IGP subfamilies, IGP34, IGP40 and IGP48 are
recognised; all possess a putative C-type lectin ectodomain and are
ER-localised, despite lacking a classical ER-retention motif. IGPs exhibit
highest expression in stumpy stage cells, suggesting roles in developmental
progression, but gene silencing in mammalian infective forms suggests that each
IGP subfamily is also required for normal proliferation. Detailed analysis of
the IGP48 subfamily indicates a role in maintaining ER morphology, while the ER
lumenal domain is necessary and sufficient for formation of both oligomeric
complexes and ER retention. IGP48 is detected by antibodies from T. b.
rhodesiense infected humans. We propose that the IGPs represent a
trypanosomatid-specific family of ER-localised glycoproteins, with potential
contributions to life cycle progression and immunity, and utilise
oligomerisation as an ER retention mechanism.
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Affiliation(s)
- Harriet Allison
- Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, Scotland, DD1 5EH
| | - Amanda J O'Reilly
- Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, Scotland, DD1 5EH
| | - Jeremy Sternberg
- School of Biological Sciences, University of Aberdeen, Aberdeen, AB24 2TZ, UK
| | - Mark C Field
- Division of Biological Chemistry and Drug Discovery, University of Dundee, Dundee, Scotland, DD1 5EH
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Harris TH, Mansfield JM, Paulnock DM. CpG oligodeoxynucleotide treatment enhances innate resistance and acquired immunity to African trypanosomes. Infect Immun 2007; 75:2366-73. [PMID: 17339353 PMCID: PMC1865757 DOI: 10.1128/iai.01649-06] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Relative resistance to African trypanosomiasis is based on the development of a type I cytokine response, which is partially dependent on innate immune responses generated through MyD88 and Toll-like receptor 9 (TLR9). Therefore, we asked whether enhancement of the immune response by artificial stimulation with CpG oligodeoxynucleotide (ODN), a TLR9 agonist, would result in enhanced protection against trypanosomes. In susceptible BALB/c mice, relative resistance to infection was significantly enhanced by CpG ODN treatment and was associated with decreased parasite burden, increased cytokine production, and elevated parasite-specific B- and T-cell responses. In relatively resistant C57BL/6 mice, survival was not enhanced but early parasitemia levels were reduced 100-fold and the majority of the parasites were nondividing, short stumpy (SS) forms. CpG ODN treatment of lymphocyte-deficient C57BL/6-scid and BALB/cByJ-scid mice also enhanced survival and reduced parasitemia, indicating that innate resistance to trypanosome infection can be enhanced. In C57BL/6-scid and BALB/cByJ-scid mice, the parasites were also predominantly SS forms during the outgrowth of parasitemia. However, the effect of CpG ODN treatment on parasite morphology was not as marked in gamma interferon (IFN-gamma)-knockout mice, suggesting that downstream effects of IFN-gamma production may play a discrete role in parasite cell differentiation. Overall, these studies provide the first evidence that enhancement of resistance to African trypanosomes can be induced in susceptible animals in a TLR9-dependent manner and that CpG ODN treatment may influence the developmental life cycle of the parasites.
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Affiliation(s)
- Tajie H Harris
- Department of Medical Microbiology and Immunology, University of Wisconsin-Madison School of Medicine and Public Health, Wisconsin 53706, USA
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9
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Savill NJ, Seed JR. Mathematical and statistical analysis of the Trypanosoma brucei slender to stumpy transition. Parasitology 2004; 128:53-67. [PMID: 15002904 DOI: 10.1017/s0031182003004256] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
We propose a new model for the Stumpy Induction Factor-induced slender to stumpy transformation of Trypanosoma brucei gambiense cells in immunosuppressed mice. The model is a set of delay differential equations that describe the time-course of the infection. We fit the model, using a maximum-likelihood method, to previously published data on parasitaemia in four mice. The model is shown to be a good fit and parameter estimates and confidence intervals are derived. Our estimated parameter values are consistent with estimates from previous experimental studies. The model predicts the following. Slender cells can be classified as uncommitted, committed and dividing, and committed and non-dividing. A committed slender cell undergoes about 5 divisions before exiting the cell-cycle. Committed slender cells must produce SIF, and stumpy cells must not produce SIF. There are two mechanisms for differentiation, a background differentiation rate, and a SIF-concentration-dependent differentiation rate, which is proportional to SIF concentration. SIF has a half-life of about 1.4 h in mice. We also show, with suitable changes in the parameter values, that the model reflects behaviours seen in other host species and trypanosome strains.
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Affiliation(s)
- N J Savill
- Department of Zoology, Cambridge University, Downing Street, Cambridge CB2 3EJ, UK.
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10
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Huynh TT, Huynh VT, Harmon MA, Phillips MA. Gene knockdown of gamma-glutamylcysteine synthetase by RNAi in the parasitic protozoa Trypanosoma brucei demonstrates that it is an essential enzyme. J Biol Chem 2003; 278:39794-800. [PMID: 12888552 DOI: 10.1074/jbc.m306306200] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The parasitic protozoa Trypanosoma brucei utilizes a novel cofactor (trypanothione, T(SH)2), which is a conjugate of GSH and spermidine, to maintain cellular redox balance. gamma-Glutamylcysteine synthetase (gamma-GCS) catalyzes the first step in the biosynthesis of GSH. To evaluate the importance of thiol metabolism to the parasite, RNAi methods were used to knock down gene expression of gamma-GCS in procyclic T. brucei cells. Induction of gamma-GCS RNAi with tetracycline led to cell death within 4-6 days post-induction. Cell death was preceded by the depletion of the gamma-GCS protein and RNA and by the loss of the cellular pools of GSH and T(SH)2. The addition of GSH (80 microM) to cell cultures rescued the RNAi cell death phenotype and restored the intracellular thiol pools to wild-type levels. Treatment of cells with buthionine sulfoximine (BSO), an enzyme-activated inhibitor of gamma-GCS, also resulted in cell death. However, the toxicity of the inhibitor was not reversed by GSH, suggesting that BSO has more than one cellular target. BSO depletes intracellular thiols to a similar extent as gamma-GCS RNAi; however, addition of GSH did not restore the pools of GSH and T(SH)2. These data suggest that BSO also acts to inhibit the transport of GSH or its peptide metabolites into the cell. The ability of BSO to inhibit both synthesis and transport of GSH likely makes it a more effective cytotoxic agent than an inhibitor with a single mode of action. Finally the potential for the T(SH)2 biosynthetic enzymes to be regulated in response to reduced thiol levels was studied. The expression levels of ornithine decarboxylase and of S-adenosylmethionine decarboxylase, two essential enzymes in spermidine biosynthesis, remained constant in induced gamma-GCS RNAi cell lines.
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Affiliation(s)
- Tu T Huynh
- Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, Texas 75390-9041, USA
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11
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Tyler KM, Higgs PG, Matthews KR, Gull K. Limitation of Trypanosoma brucei parasitaemia results from density-dependent parasite differentiation and parasite killing by the host immune response. Proc Biol Sci 2001; 268:2235-43. [PMID: 11674871 PMCID: PMC1088871 DOI: 10.1098/rspb.2001.1794] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
In the bloodstream of its mammalian host, the "slender" form of Trypanosoma brucei replicates extracellularly, producing a parasitaemia. At high density, the level of parasitaemia is limited at a sublethal level by differentiation to the non-replicative "stumpy" form and by the host immune response. Here, we derive continuous time equations to model the time-course, cell types and level of trypanosome parasitaemia, and compare the best fits with experimental data. The best fits that were obtained favour a model in which both density-dependent trypanosome differentiation and host immune response have a role in limiting the increase of parasites, much poorer fits being obtained when differentiation and immune response are considered independently of one another. Best fits also favour a model in which the slender-to-stumpy differentiation progresses in a manner that is essentially independent of the cell cycle. Finally, these models also make the prediction that the density-dependent trypanosome differentiation mechanism can give rise to oscillations in parasitaemia level. These oscillations are independent of the immune system and are not due to antigenic variation.
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Affiliation(s)
- K M Tyler
- Department of Pathology, Northwestern University Medical School, 303 E. Chicago Avenue, Chicago, IL 60611, USA.
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12
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Fuxa JE, Fuxa JR, Richter AR, Weidner EH. Prevalence of a trypanosomatid in the southern green stink bug, Nezara viridula. J Eukaryot Microbiol 2000; 47:388-94. [PMID: 11140453 DOI: 10.1111/j.1550-7408.2000.tb00065.x] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
The southern green stink bug, Nezara viridula (L.), and certain of its host plants were examined to determine the prevalence and biological characteristics of an intestinal trypanosomatid. Promastigotes with short (< or = 17.5 microm excluding flagellum) and long forms (> or = 25.0 microm) usually infected < 50% of the bugs before August and > 50% (maximum 95%) during August-October, but prevalence was not host-density dependent. The flagellate was detected in adults and in all nymphal instars, at all sampling sites where at least 10 bugs were captured, and in bugs from all host plants sampled (soybean, red clover, vetch). Of bugs with flagellates, 27% were heavily infected (> 20 flagellates per 160X microscope field). Weights of infected and uninfected adults did not differ. Live flagellates were detected in bug feces and in one stem of red clover. When bugs were fed soybean pods, tomatoes, or snap beans in the laboratory, only once were flagellates detected in plant tissue (snap beans). The flagellate was cultured in modified Medium 199. This flagellate is prevalent in N. viridula populations in Louisiana and apparently does not cause significant pathological effects in N. viridula or its host plants, including soybean.
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Affiliation(s)
- J E Fuxa
- Department of Entomology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803, USA.
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Shiels BR. Should I stay or should I go now? A stochastic model of stage differentiation in Theileria annulata. PARASITOLOGY TODAY (PERSONAL ED.) 1999; 15:241-5. [PMID: 10366832 DOI: 10.1016/s0169-4758(99)01451-9] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
The events that initiate and determine stage differentiation of protozoan parasites are not fully understood. In this article, Brian Shiels suggests that for differentiation to the merozoite in Theileria annulata the process is predetermined by the parasite, but can be initiated and modulated by changes to the extracellular environment. Shiels proposes a mechanism operating on the basis of factors that regulate gene expression reaching a commitment threshold. Similarities across protozoan and higher eukaryotic differentiation systems lead Shiels to speculate that the T. annulata model may be of relevance to other parasites.
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Affiliation(s)
- B R Shiels
- Department of Veterinary Parasitology, University of Glasgow, Bearsden Road, Glasgow, UK.
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14
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Chapter 33 Principles of parasitology and parasitic disorders. Microbiology (Reading) 1998. [DOI: 10.1016/s1569-2582(97)80017-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
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15
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Reuner B, Vassella E, Yutzy B, Boshart M. Cell density triggers slender to stumpy differentiation of Trypanosoma brucei bloodstream forms in culture. Mol Biochem Parasitol 1997; 90:269-80. [PMID: 9497048 DOI: 10.1016/s0166-6851(97)00160-6] [Citation(s) in RCA: 114] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Differentiation from replicating slender forms to non-dividing stumpy bloodstream forms of T. brucei limits the parasite population size in the mammalian host in addition to and independently of the antibody response. Using a culture system for pleomorphic strains of T. brucei we show that slender forms very efficiently differentiate to stumpy forms in vitro and that the induction of differentiation is correlated to cell density. Differentiation in the host and in culture were compared using a battery of markers including cell morphology and volume, cell cycle position, the kinetics of the differentiation, expression of NADH dehydrogenase (diaphorase), expression of several differentially regulated transcripts and the kinetics of transformation to replicating procyclic forms after induction with cis-aconitate. By all available criteria, differentiation in culture reflects the natural process in the mammalian host. Time course experiments reveal a very tight temporal correlation between cell cycle arrest of bloodstream forms, appearance of a stumpy differentiation marker and the competence of a bloodstream form population to initiate transformation to procyclic forms in response to cis-aconitate. Our results show that induction of bloodstream form differentiation can occur independently of host-derived cues. We suggest a density sensing mechanism which induces differentiation to the non-dividing stumpy stage and thereby enables the parasite population to autoregulate its proliferation.
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Affiliation(s)
- B Reuner
- Max-Planck-Institut für Biochemie, Genzentrum, Martinsried, Germany
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Tyler KM, Matthews KR, Gull K. The bloodstream differentiation-division of Trypanosoma brucei studied using mitochondrial markers. Proc Biol Sci 1997; 264:1481-90. [PMID: 9364788 PMCID: PMC1688710 DOI: 10.1098/rspb.1997.0205] [Citation(s) in RCA: 43] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In the bloodstream of its mammalian host, the African trypanosome Trypanosoma brucei undergoes a life cycle stage differentiation from a long, slender form to a short, stumpy form. This involves three known major events: exit from a proliferative cell cycle, morphological change and mitochondrial biogenesis. Previously, models have been proposed accounting for these events (Matthews & Gull 1994a). Refinement of, and discrimination between, these models has been hindered by a lack of stage-regulated antigens useful as markers at the single-cell level. We have now evaluated a variety of cytological markers and applied them to investigate the coordination of phenotypic differentiation and cell cycle arrest. Our studies have focused on the differential expression of the mitochondrial enzyme dihydrolipoamide dehydrogenase relative to the differentiation-division of bloodstream trypanosomes. The results implicate a temporal order of events: commitment, division, phenotypic differentiation.
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Affiliation(s)
- K M Tyler
- School of Biological Sciences, University of Manchester, UK.
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Hesse F, Selzer PM, Mühlstädt K, Duszenko M. A novel cultivation technique for long-term maintenance of bloodstream form trypanosomes in vitro. Mol Biochem Parasitol 1995; 70:157-66. [PMID: 7637696 DOI: 10.1016/0166-6851(95)00027-x] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
We used an axenic cultivation system to grow African trypanosomes in vitro. Long-term cultivation for more than 60 days has been achieved by replacing the culture medium at regular intervals between 6 and 48 h. In contrast to a control culture without medium replacement, increasing amounts of maximum cell concentrations have been obtained, ranging from 5 x 10(6) to 2 x 10(7) trypanosomes ml-1, whereas the generation doubling time remained constant (about 6 h). Higher cell concentrations have only been obtained by total medium replacement; neither addition of fresh medium nor serum led to a higher cell yield, suggesting that a trypanosome-derived factor or metabolite accumulated in the medium rather than medium was depleted of an essential nutrient. Most interestingly, however, successive waves have been obtained which eventually led to a damped oscillation curve with a constant high population density after about 40 days of cultivation. Cultures were started with a homogeneous population of the long-slender form. As judged by light microscopy, cells showed a stumpy morphology during the declining phase and became slender again in the following growth phase. At later time points, when cells remained in a stationary phase at high population density, many different morphological stages have been observed, similar to those described by early authors as intermediate forms [Ormerod, W. E. (1979) In: Biology of the Kinetoplastida, Vol. 2, pp. 340-393], although many dividing forms are still present at that time. In contrast, identically treated procyclic cultures were unable to produce cyclic growth waves. Based on these results, a novel concept considering a possible differentiation mechanism is discussed.
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Affiliation(s)
- F Hesse
- Physiologisch-chemisches Institut der Universität, Tübingen, Germany
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Murphy NB, Pellé R. The use of arbitrary primers and the RADES method for the rapid identification of developmentally regulated genes in trypanosomes. Gene 1994; 141:53-61. [PMID: 8163175 DOI: 10.1016/0378-1119(94)90127-9] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Biological processes, such as the cell-division cycle, differentiation and development, are driven by changes in gene expression. Short oligodeoxyribonucleotide primers (10-mers) of arbitrary sequence are currently used in the polymerase chain reaction (PCR) to generate genomic fingerprints (RAPDs) for the characterisation and differentiation of organisms and for mapping loci of interest. Since the products of such reactions are generally less than 1 kb in size, the use of arbitrary primers on cDNA should generate RAPDs which are characteristic of expressed genes. To assess this possibility, two model systems were employed; one in which actively dividing Trypanosoma brucei brucei bloodstream forms differentiate to non-dividing forms, and the second in which non-dividing metacyclic forms of T. congolense differentiate to actively dividing bloodstream forms. In the technique herein, mRNA from each differentiated form was reverse transcribed into cDNA which was then used as the template in the PCR. The resultant products were examined by agarose-gel electrophoresis. As few as 10(3) trypanosomes were sufficient for the generation of a RAPD print after first amplifying the total cDNA through exploitation of the fixed 3' and 5' ends of trypanosome nuclear mRNAs. Differences in RAPD patterns between the differentiated forms examined were mainly due to differences in gene expression. The technique can rapidly identify genes expressed at very low levels and which are up- or down-regulated in the different forms examined. PCR products of interest are easily purified from the agarose gels for direct cloning and complete sequence determination due to their relatively small size (0.1-1 kb).
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Affiliation(s)
- N B Murphy
- International Laboratory for Research on Animal Diseases (ILRAD), Nairobi, Kenya
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Reduth D, Grootenhuis JG, Olubayo RO, Muranjan M, Otieno-Omondi FP, Morgan GA, Brun R, Williams DJ, Black SJ. African buffalo serum contains novel trypanocidal protein. J Eukaryot Microbiol 1994; 41:95-103. [PMID: 8167620 DOI: 10.1111/j.1550-7408.1994.tb01480.x] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
The high ability of African buffalo, as compared to domestic cattle, to control infections with Trypanosoma brucei brucei ILTat 1.4 organisms did not correlate with the timing or magnitude of parasite surface coat-specific antibody responses and may have resulted from the constitutive presence in buffalo blood of a novel trypanocidal factor. Buffalo plasma and serum contained material that killed bloodstream stage T. b. brucei, T. b. rhodesiense, T. b. gambiense, T. evansi, T. congolense, and T. vivax organisms during four h of incubation at 37 degrees C in vitro. Serum from eland was also trypanocidal whereas serum from oryx, waterbuck, yellow-back duiker, cattle, horse, sheep, goat, mouse, rat, and rabbit was not trypanocidal. The buffalo serum trypanocidal material was not lipoprotein, or IgG, and had the following properties: 1) a density of > 1.24 g/ml determined by flotation ultracentrifugation; 2) insolubility in 50% saturated ammonium sulphate; 3) non-reactivity with anti-bovine IgM, and anti-bovine IgG; 4) non-reactivity with protein G, and protein A; 5) a relative molecular mass of 152 kDa determined by chromatography on Sephacryl S 300, and of 133 kDa determined by chromatography of the 50% SAS cut of IgG-depleted buffalo serum on Superose 12; 6) no associated cholesterol; and 7) inactivation by digestion with proteinase K that was immobilized on agarose.
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Morgan GA, Laufman HB, Otieno-Omondi FP, Black SJ. Control of G1 to S cell cycle progression of Trypanosoma brucei S427cl1 organisms under axenic conditions. Mol Biochem Parasitol 1993; 57:241-52. [PMID: 8433715 DOI: 10.1016/0166-6851(93)90200-h] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Abstract
Trypanosoma brucei S427cl1 organisms made 6 divisions in modified minimal essential medium (BMEM) supplemented with fetal bovine serum (FBS)-low or high density lipoprotein (LDL, HDL) and fatty acid-free bovine serum albumin (FAF-BSA). Omission of lipoproteins or FAF-BSA from the medium caused the parasites to accumulate in G1 of the cell cycle and to lose the ability to replicate at 37 degrees C. Proteinase K-treated LDL or HDL, which did not have detectable apolipoprotein, supported the G1 to S cell cycle transition of T. brucei S427cl1 organisms in BMEM supplemented with FAF-BSA. Addition of C6:0, C7:0 or fatty C8:0 fatty acid (1 mol fatty acid mol-1 FAF-BSA in the incubation mixture) to serum-free medium supplemented with LDL or HDL and FAF-BSA prevented T. brucei S427cl1 organisms from progressing through G1 into S of the cell cycle. T. brucei S427cl1 organisms became stumpy-like forms during plateau phase growth under axenic conditions. Stumpy-like T. brucei S427cl1 organisms were mainly in G1 of the cell cycle, expressed raised levels of NAD diaphorase activity, were unable to replicate at 37 degrees C, but were able to differentiate to replicating procyclic organisms. Medium collected from plateau phase cultures of T. brucei S427cl1 did not support the G1 to S cell cycle transition of exponentially growing T. brucei organisms. The capacity of plateau phase medium to support G1 to S transition of T. brucei S427cl1 organisms was restored by addition of FAF-BSA and its capacity to support 4 cycles of replication of the parasites was restored by addition of FAF-BSA and LDL or HDL.
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Affiliation(s)
- G A Morgan
- Department of Microbiology, Ohio State University, Columbus 43210-1292
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Wheeler-Alm E, Shapiro SZ. Evidence of tyrosine kinase activity in the protozoan parasite Trypanosoma brucei. THE JOURNAL OF PROTOZOOLOGY 1992; 39:413-6. [PMID: 1640387 DOI: 10.1111/j.1550-7408.1992.tb01473.x] [Citation(s) in RCA: 23] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Phosphorylation of proteins at tyrosine is an important mechanism for regulating cell growth and proliferation in metazoan organisms. In this report, we have demonstrated that Trypanosoma brucei, a protozoan parasite, possesses a tyrosine kinase that plays a role in regulation of proliferation of this protozoan. Genistein, a tyrosine kinase inhibitor, prevented multiplication of the parasite. An in vitro kinase assay demonstrated the presence of a kinase capable of phosphorylating an exogenous substrate at tyrosine, and genistein was able to reduce trypanosome-mediated phosphorylation of this substrate. An alkali digestion of 32P-labeled trypanosome proteins separated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis indicated several proteins phosphorylated at tyrosine. These results indicate that T. brucei has a tyrosine kinase that is involved in proliferation or growth regulation of the parasite and provide further evidence for the possibility of growth factor regulation and signal transduction in trypanosomes.
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Affiliation(s)
- E Wheeler-Alm
- Department of Veterinary Pathobiology, University of Illinois, Urbana 61801
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Development of Trypanosomes. Development 1992. [DOI: 10.1007/978-3-642-77043-2_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/14/2022]
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Parsons M, Valentine M, Deans J, Schieven GL, Ledbetter JA. Distinct patterns of tyrosine phosphorylation during the life cycle of Trypanosoma brucei. Mol Biochem Parasitol 1991; 45:241-8. [PMID: 1710035 DOI: 10.1016/0166-6851(91)90091-j] [Citation(s) in RCA: 56] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Regulation of tyrosine phosphorylation is a critical element in controlling growth and differentiation in higher eukaryotes. We have determined that the protozoan Trypanosoma brucei, which diverged early in the eukaryotic lineage, possesses multiple proteins which react with a specific anti-phosphotyrosine antiserum. Anti-phosphotyrosine immunoprecipitates of [32P]orthophosphate-labeled cells were shown to contain phosphotyrosine by two-dimensional electrophoresis. Western analysis of cells from different stages of the life cycle demonstrates the appearance of tyrosine-phosphorylated proteins at 40-42 kDa during the transition from slender to stumpy blood-forms. Growth of procyclic form cells in orthovanadate resulted in increased levels of specific tyrosine-phosphorylated proteins. The demonstration of phosphotyrosine-containing proteins in T. brucei and their differential regulation during the life cycle suggests that tyrosine kinases and phosphatases may play an important role in the biology of primitive protozoa.
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Affiliation(s)
- M Parsons
- Seattle Biomedical Research Institute, WA 98109
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