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1.
Growth of isolated amastigotes of Trypanosoma cruzi in cell-free medium   总被引:2,自引:0,他引:2  
Amastigotes of Trypanosoma cruzi were purified from overlays of infected Vero cell cultures by centrifugation over a discontinuous gradient of metrizamide. Pure amastigote preparations were usually recovered from the pellet under the layer of specific gravity 1.086. The isolated amastigotes grew in cell-free ML-15HA medium. Growth rate for the different strains of T. cruzi were in the order Y greater than Tulahuen greater than CL. The generation time of amastigotes in ML-15HA medium was 16.8, 18.0 and 26.4 h for the Y, Tulahuen, and CL strains, respectively, in the presence of 5% CO2, and 16.8, 31.2, and 36.4 h, respectively, in the absence of CO2. Intracellular amastigotes did not differ ultrastructurally from amastigotes from either the density-gradient fractionation or culture in cell-free medium.  相似文献   

2.
SYNOPSIS. The effect of malaria on the chronic phase of Chagas’disease was investigated in mice. The animals were given Plasmodium berghei-infected red blood cells 2 to 12 months after their initial inoculation with trypomastigotes of 3 different strains of Trypanosoma cruzi (Y, CL and Gilmar). In all the experiments carried out with one of the strains (CL), a somewhat variable but always considerable percentage of mice (average 39%) relapsed in to the acute phase of Chagas’disease. This relapse was characterized by a significant increase in the number of circulating trypomastigotes. Recrudescence was observed also with a 2nd strain of T. cruzi (Gilmar), which is similar in many aspects to the CL strain, e.g. the morphology of blood stages, curve of parasitemia and susceptibility to antibodies in vitro. In mice whose chronic phase was induced by trypomastigotes of the Y strain, malaria infections did not induce a typical acute phase with high parasitemia by T. cruzi. Bloodstream forms of Y parasites differ from those of CL and Gilmar strains morphologically as well as immunologically, i.e. only the Y strain is easily agglutinated and partly inactivated by specific immune serum. In light of this and other known characteristics of the strains used in the present work, the author speculates on mechanisms which allow malaria infections selectively to suppress acquired host resistance to certain strains of T. cruzi.  相似文献   

3.
Trypanosoma cruzi genomic database was screened for hypothetical proteins that showed high probability of being secreted or membrane anchored and thus, likely involved in host-cell invasion. A sequence that codes for a 21 kDa protein that showed high probability of being secreted was selected. After cloning this protein sequence, the results showed that it was a ubiquitous protein and secreted by extracellular amastigotes. The recombinant form (P21-His6) adhered to HeLa cells in a dose-dependent manner. Pretreatment of host cells with P21-His6 inhibited cell invasion by extracellular amastigotes from G and CL strains. On the other hand, when the protein was added to host cells at the same time as amastigotes, an increase in cell invasion was observed. Host-cell pretreatment with P21-His6 augmented invasion by metacyclic trypomastigotes. Moreover, polyclonal antibody anti-P21 inhibited invasion only by extracellular amastigotes and metacyclic trypomastigotes from G strain. These results suggested that P21 might be involved in T. cruzi cell invasion. We hypothesize that P21 could be secreted in the juxtaposition parasite-host cell and triggers signaling events yet unknown that lead to parasite internalization.  相似文献   

4.
ABSTRACT. The phorbol ester TPA (phorbol 12-myristate 13-acetate) substitutes for CO2 as an agonist for transforming Trypanosoma cruzi epimastigotes to the metacyclic trypomastigote stage in a starvation medium consisting of phosphate buffered saline + 10 mM proline, 10 mM sodium acetate and 0.035% NaHCO3. Since TPA is thought to stimulate protein kinase C by mimicking the activity of the secondary messenger diacylglycerol, the above result suggested that T. cruzi metacyclogenesis could be activated by a Ca2+-dependent protein kinase C signal induction pathway. Accordingly, cytosolic calcium flux ([Ca2+]i) in epimastigotes, activated with 5% CO2 or TPA (10-7 M), was measured with the Ca2+ molecular probe, fluo-3AM. In addition, [Ca2+]i was measured in cells incubated with putative metacyclogenic agonists (e.g. proline, glutamate, bioamines, ionophores and catecholamines). None of the compounds studied, except for EGTA, affected cytosolic Ca2+ levels. Control assays with 11 μM thapsigargin, which mobilizes noncytoplasmic Ca2+ stores by inhibiting endoplasmic reticulum Ca2+-ATPase. validated our fluorometric assay procedure. Although thapsigargin significantly increases cytoplasmic Ca2+ fluorescence, it has no effect on transformation. The protein kinase C inhibitors staurosporine, H-7 and HA 1004 were tested for their effect on T. cruzi metacyclogenesis. Low concentrations of staurosporine and HA 1004 significantly elevated Pent strain transformation while H-7 had no effect on Peru strain metacyclogenesis. Inhibitor H-7 did significantly depress CL transformation. the results indicate that induction of T. cruzi metacyclic trypomastigote formation by CO2 and TPA is not accompanied by changes in cytosolic Ca2+ and do not provide supporting evidence for participation of a protein kinase C-mediated phosphoinositide cascade in metacyclogenesis.  相似文献   

5.
ABSTRACT. Among the known life cycle stages of Trypanosoma cruzi only the amastigote form bound lactoferrin (LF), a glycoprotein produced by neutrophils. This capacity was readily demonstrable by indirect immunofluorescence in amastigotes derived from mice, a mammalian cell culture, or grown in an axenic medium. No LF binding was detectable on trypomastigotes from blood or mammalian cells, insect-derived metacyclics or epimastigotes, or on epimastigotes grown in Warren's medium. Serum levels of LF were increased in mice acutely infected with T. cruzi, and amastigotes from the spleens of these animals were found to have the glycoprotein on their surface. The amastigote LF receptor may have biological significance in parasite-host interaction since mononuclear phagocytes also express a LF receptor, and treatment of these cells with LF has been shown to increase their capacities to take up and kill T. cruzi amastigotes in vitro. The LF receptor is the first marker for T. cruzi amastigotes for which a naturally occurring ligand has been described.  相似文献   

6.
The structures of the glycoinositolphospholipids (GIPLs) from five strains of the protozoan parasiteTrypanosoma cruzi have been determined. Two series of structures were identified, all but one containing the same Man4(AEP)GlcN-Ins-PO4 core. Series 1 oligosaccharides are substituted at the third mannose distal to inositol (Man 3) by ethanolamine-phosphate or 2-aminoethylphosphonic acid, as are some glycosyl-phosphatidylinositol-protein anchors ofT. cruzi. The core can be further substituted by terminal (1–3)-linked -galactofuranose units. In contrast, Series 2 oligosaccharides do not have additional phosphorus-containing groups attached to Man 3, the latter being substituted instead by a single side chain unit of -galactofuranose. Series 1 oligosaccharides are present in all strains (G, G-645, Tulahuen CL, and Y) whereas Series 2 structures are present mainly in CL and Y strains. The lipid moiety in the GIPLs from the G, G-645 and Tulahuen strains is predominantly ceramide, as reported for the Y strain, whilst that from the CL strain is a mixture of ceramide and alkylacylglycerol species. The lipid moiety of the GIPLs, and probably also the phosphoinositol-oligosaccharide structures may play an important immunomodulatory role in infection byT. cruzi.Abbreviations GIPL glycoinositolphospholipid - LPPG lipopeptidophosphoglycan - GPI glycosylphosphatidylinositol - AEP 2-aminoethylphosphonic acid - PI phosphoinositol - GC gas-liquid chromatography - MS mass spectrometry - FAB fast atom bombardment - NMR nuclear magnetic resonance - DQF-COSY double quantum-filtered correlation spectroscopy - TOCSY total correlation spectroscopy - ROESY rotating frame nuclear Overhauser enhancement spectroscopy - EtNP ethanolaminephosphate - HMQC heteronuclear multiple quantum coherence - Man mannose - Galf galactofuranose - GlcN glucosamine - Ins inositol - InsP inositolphosphate - Man 3 third mannose distal to inositol - NOE nuclear Overhauser effect - [M+H]+ protonated molecule - [M–H] deprotonated molecule - RMM relative molecular mass (monoisotopic)  相似文献   

7.
Chagas disease caused by Trypanosoma cruzi is a major neglected tropical parasitic disease. The pathogenesis of this infection remains disputable. There is no suitable vaccine for the prevention. Attenuated live vaccines can provide strong protection against infection; however, there are the concerns about latent infection or reversion to virulence in such attenuated strains. A method to induce T. cruzi death would provide a critical tool for research into the pathophysiological mechanisms and provide a novel design of safe live attenuated vaccines. We established effective inducible systems for T. cruzi employing the degradation domain based on the Escherichia coli dihydrofolate reductase (ecDHFR). The DHFR degradation domain (DDD) can be stabilized by trimethoprim-lactate and can be used to express detrimental or toxic proteins. T. cruzi lines with Alpha-toxin, Cecropin A and GFP under the control of DDD with a hemagglutinin tag (HA) were developed. Interestingly, amastigotes bearing GFP-DDDHA, Alpha-toxin-DDDHA, Cecropin A-DDDHA and DDDHA all resulted in inducible cell death with these fusions, indicating that DDDHA protein is also detrimental to amastigotes. Furthermore, these strains were attenuated in mouse experiments producing no pathological changes and inoculation with these DDDHA strains in mice provided strong protection against lethal wild type infection.  相似文献   

8.

Background

New safe and effective treatments for Chagas disease (CD) are urgently needed. Current chemotherapy options for CD have significant limitations, including failure to uniformly achieve parasitological cure or prevent the chronic phase of CD, and safety and tolerability concerns. Fexinidazole, a 2-subsituted 5-nitroimidazole drug candidate rediscovered following extensive compound mining by the Drugs for Neglected Diseases initiative and currently in Phase I clinical study for the treatment of human African trypanosomiasis, was evaluated in experimental models of acute and chronic CD caused by different strains of Trypanosoma cruzi.

Methods and Findings

We investigated the in vivo activity of fexinidazole against T. cruzi, using mice as hosts. The T. cruzi strains used in the study were previously characterized in murine models as susceptible (CL strain), partially resistant (Y strain), and resistant (Colombian and VL-10 strains) to the drugs currently in clinical use, benznidazole and nifurtimox. Our results demonstrated that fexinidazole was effective in suppressing parasitemia and preventing death in infected animals for all strains tested. In addition, assessment of definitive parasite clearance (cure) through parasitological, PCR, and serological methods showed cure rates of 80.0% against CL and Y strains, 88.9% against VL-10 strain, and 77.8% against Colombian strain among animals treated during acute phase, and 70% (VL-10 strain) in those treated in chronic phase. Benznidazole had a similar effect against susceptible and partially resistant T. cruzi strains. Fexinidazole treatment was also shown to reduce myocarditis in all animals infected with VL-10 or Colombian resistant T. cruzi strains, although parasite eradication was not achieved in all treated animals at the tested doses.

Conclusions

Fexinidazole is an effective oral treatment of acute and chronic experimental CD caused by benznidazole-susceptible, partially resistant, and resistant T. cruzi. These findings illustrate the potential of fexinidazole as a drug candidate for the treatment of human CD.  相似文献   

9.
Epimastigotes of Trypanosoma cruzi, Peru strain, incubated in Contreras' artificial triatomine urine transformed into metacyclic trypomastigotes when 10 mM L-glutamine, L-asparagine or D-fructose was added to the medium. Metacyclogenesis with these substrates was comparable to the percent metacyclic morphotype formation induced by L-proline and significantly greater than that stimulated by 10 mM D-glucose. Sodium acetate (10 mM) increased transformation induced by L-proline, and L-hydroxyproline (10 mM) increased transformation induced by D-fructose. Phosphoenolpyruvate (10 mM) inhibited L-proline-induced metacyclic trypomastigote stage formation. Three antimetabolites, azetidine 2-carboxylate (5 mM), malonic acid (1 mM), and desthiobiotin (5 mM), completely inhibited D-fructose-induced but not L-proline-induced transformation. The Costa Rica, Y, and CL strains of T. cruzi showed different patterns of percent metacyclogenesis with substrates that induce transformation in the Peru strain.  相似文献   

10.

Background

T. cruzi strains have been divided into six discrete typing units (DTUs) according to their genetic background. These groups are designated T. cruzi I to VI. In this context, amastigotes from G strain (T. cruzi I) are highly infective in vitro and show no parasitemia in vivo. Here we aimed to understand why amastigotes from G strain are highly infective in vitro and do not contribute for a patent in vivo infection.

Methodology/Principal Findings

Our in vitro studies demonstrated the first evidence that IFN-γ would be associated to the low virulence of G strain in vivo. After intraperitoneal amastigotes inoculation in wild-type and knockout mice for TNF-α, Nod2, Myd88, iNOS, IL-12p40, IL-18, CD4, CD8 and IFN-γ we found that the latter is crucial for controlling infection by G strain amastigotes.

Conclusions/Significance

Our results showed that amastigotes from G strain are highly infective in vitro but did not contribute for a patent infection in vivo due to its susceptibility to IFN-γ production by host immune cells. These data are useful to understand the mechanisms underlying the contrasting behavior of different T. cruzi groups for in vitro and in vivo infection.  相似文献   

11.
12.

Background

The factors influencing variation in the clinical forms of Chagas disease have not been elucidated; however, it is likely that the genetics of both the host and the parasite are involved. Several studies have attempted to correlate the T. cruzi strains involved in infection with the clinical forms of the disease by using hemoculture and/or PCR-based genotyping of parasites from infected human tissues. However, both techniques have limitations that hamper the analysis of large numbers of samples. The goal of this work was to identify conserved and polymorphic linear B-cell epitopes of T. cruzi that could be used for serodiagnosis and serotyping of Chagas disease using ELISA.

Methodology

By performing B-cell epitope prediction on proteins derived from pair of alleles of the hybrid CL Brener genome, we have identified conserved and polymorphic epitopes in the two CL Brener haplotypes. The rationale underlying this strategy is that, because CL Brener is a recent hybrid between the TcII and TcIII DTUs (discrete typing units), it is likely that polymorphic epitopes in pairs of alleles could also be polymorphic in the parental genotypes. We excluded sequences that are also present in the Leishmania major, L. infantum, L. braziliensis and T. brucei genomes to minimize the chance of cross-reactivity. A peptide array containing 150 peptides was covalently linked to a cellulose membrane, and the reactivity of the peptides was tested using sera from C57BL/6 mice chronically infected with the Colombiana (TcI) and CL Brener (TcVI) clones and Y (TcII) strain.

Findings and Conclusions

A total of 36 peptides were considered reactive, and the cross-reactivity among the strains is in agreement with the evolutionary origin of the different T. cruzi DTUs. Four peptides were tested against a panel of chagasic patients using ELISA. A conserved peptide showed 95.8% sensitivity, 88.5% specificity, and 92.7% accuracy for the identification of T. cruzi in patients infected with different strains of the parasite. Therefore, this peptide, in association with other T. cruzi antigens, may improve Chagas disease serodiagnosis. Together, three polymorphic epitopes were able to discriminate between the three parasite strains used in this study and are thus potential targets for Chagas disease serotyping.  相似文献   

13.
Although imaging the live Trypanosoma cruzi parasite is a routine technique in most laboratories, identification of the parasite in infected tissues and organs has been hindered by their intrinsic opaque nature. We describe a simple method for in vivo observation of live single‐cell Trypanosoma cruzi parasites inside mammalian host tissues. BALB/c or C57BL/6 mice infected with DsRed‐CL or GFP‐G trypomastigotes had their organs removed and sectioned with surgical blades. Ex vivo organ sections were observed under confocal microscopy. For the first time, this procedure enabled imaging of individual amastigotes, intermediate forms and motile trypomastigotes within infected tissues of mammalian hosts.  相似文献   

14.
Trypanosoma cruzi epimastigote forms concentrate their major protease, cruzipain, in the same compartment where these parasites store macromolecules obtained from medium and for this ability these organelles were named as reservosomes. Intracellular digestion occurs mainly inside reservosomes and seems to be modulated by cruzipain and its natural inhibitor chagasin that also concentrates in reservosomes. T. cruzi mammalian forms, trypomastigotes and amastigotes, are unable to capture macromolecules by endocytosis, but also express cruzipain and chagasin, whose role in infectivity has been described. In this paper, we demonstrate that trypomastigotes and amastigotes also concentrate cruzipain, chagasin as well as serine carboxypeptidase in hydrolase-rich compartments of acidic nature. The presence of P-type proton ATPase indicates that this compartment is acidified by the same enzyme as epimastigote endocytic compartments. Electron microscopy analyzes showed that these organelles are placed at the posterior region of the parasite body, are single membrane bound and possess an electron-dense matrix with electronlucent inclusions. Three-dimensional reconstruction showed that these compartments have different size and shape in trypomastigotes and amastigotes. Based on these evidences, we suggest that all T. cruzi developmental stages present lysosome-related organelles that in epimastigotes have the additional and unique ability of storing cargo.  相似文献   

15.
16.
Sulfonamide carbonic anhydrase (CA, EC 4.2.1.1) inhibitors targeting the α-class enzyme from the protozoan pathogen Trypanosoma cruzi, responsible of Chagas disease, were recently reported. Although many such derivatives showed low nanomolar activity in vitro, they were inefficient anti-T. cruzi agents in vivo. Here, we show that by formulating such sulfonamides as nanoemulsions in clove (Eugenia caryophyllus) oil, highly efficient anti-protozoan effects are observed against two different strains of T. cruzi. These effects are probably due to an enhanced permeation of the enzyme inhibitor through the nanoemulsion formulation, interfering in this way with the life cycle of the pathogen either by inhibiting pH regulation or carboxylating reactions in which bicarbonate/CO2 are involved. This type of formulation of sulfonamides with T. cruzi CA inhibitory effects may lead to novel therapeutic approaches against this orphan disease.  相似文献   

17.

Background

Trypanosoma cruzi is a parasitic protist that causes Chagas disease, which is prevalent in Latin America. Because of the unavailability of an effective drug or vaccine, and because about 8 million people are infected with the parasite worldwide, the development of novel drugs demands urgent attention. T. cruzi infects a wide variety of mammalian nucleated cells, with a preference for myocardial cells. Non-dividing trypomastigotes in the bloodstream infect host cells where they are transformed into replication-capable amastigotes. The amastigotes revert to trypomastigotes (trypomastigogenesis) before being shed out of the host cells. Although trypomastigote transformation is an essential process for the parasite, the molecular mechanisms underlying this process have not yet been clarified, mainly because of the lack of an assay system to induce trypomastigogenesis in vitro.

Methodology/Principal Findings

Cultivation of amastigotes in a transformation medium composed of 80% RPMI-1640 and 20% Grace’s Insect Medium mediated their transformation into trypomastigotes. Grace’s Insect Medium alone also induced trypomastigogenesis. Furthermore, trypomastigogenesis was induced more efficiently in the presence of fetal bovine serum. Trypomastigotes derived from in vitro trypomastigogenesis were able to infect mammalian host cells as efficiently as tissue-culture-derived trypomastigotes (TCT) and expressed a marker protein for TCT. Using this assay system, we demonstrated that T. cruzi inositol 1,4,5-trisphosphate receptor (TcIP3R)—an intracellular Ca2+ channel and a key molecule involved in Ca2+ signaling in the parasite—is important for the transformation process.

Conclusion/Significance

Our findings provide a new tool to identify the molecular mechanisms of the amastigote-to-trypomastigote transformation, leading to a new strategy for drug development against Chagas disease.  相似文献   

18.
Chagas disease is a neglected pathology responsible for about 12,000 deaths every year across Latin America. Although six million people are infected by the Trypanosoma cruzi, current therapeutic options are limited, highlighting the need for new drugs. Here we report the preliminary structure activity relationships of a small library of 17 novel pyridyl sulfonamide derivatives. Analogues 4 and 15 displayed significant potency against intracellular amastigotes with EC50 of 5.4?µM and 8.6?µM. In cytotoxicity assays using mice fibroblast L929 cell lines, both compounds indicated low toxicity with decent selectivity indices (SI) >36 and?>23 respectively. Hence these compounds represent good starting points for further lead optimization.  相似文献   

19.
The relationship between progesterone (P4) synthesis by luteal tissue and prostaglandin F (PGF) synthesis by endometrium and luteal tissue from two stages of the cycle, Days 7 to 8 and 15 to 16, was determined. Luteal and endometrial tissues were collected from pigs in three experimental groups at two stages of the cycle: (A) 6 pigs on Days 7 to 8 with spontaneous, 5 to 6 day old corpora lutea (CL); (B) 5 pigs on Days 15 to 16 with spontaneous, 13 to 14 day old CL; and (C) 6 pigs on Days 15 to 16 with spontaneous, 13 to 14 day old CL and 5 to 6 day old CL induced by pregnant mares serum gonadotropin (PMSG) and human chorionic gonadotropin (HCG) injections. Pigs with spontaneous, 13 to 14 day old CL of the cycle and PMSG-HCG induced accessory, 5 to 6 day old CL were used so that P4 and PGF synthesis in tissue from old and new CL could be compared in the same pig on Day 15 to 16 of the cycle. Tissues (100 mg minces) were incubated in 5 ml of Krebs Ringer solution in an atmosphere of 95% 02:5% CO2 for 2 hours at 0° C, 37° C, or 37° C with 1.3 x 10−4M indomethacin (IND). An aliquot of the incubation medium and an aliquot of the supernatant after homogenization of the tissue in the remaining medium of each flask was quantified for P4 and PGF by radioimmunoassay. P4 and PGF release into the medium and total accumulation of P4 and PGF in the flasks indicated that synthesis had occured at 37° C. Compared to tissue from 13 to 14 day old CL, tissue from 5 to 6 day old CL synthesized more P4 per flask (53.9 25.0 ng/mg tissue, P<.001) and released more P4 into the medium (20.8 8.8 ng/mg, P<.001). P4 synthesis by luteal tissue from 5 to 6 day old and 13 to 14 day old CL from pigs in group C was similar to P4 synthesis by luteal tissue from pigs in group A and group B, respectively. Luteul PGF synthesis was not affected significantly by either the age of the CL or by PMSG-HCG treatment. For endometrial samples, the synthesis of PGF was not significantly different among pigs in groups A, B and C. If uterine PGF is involved in luteal regression in the pig, the sensitivity of the CL to PGF may be more important than an increase in PGF secretion during the late luteal phase of the estrous cycle.  相似文献   

20.
Hyaluronic acid (HA) is a high‐value biopolymer used in the biomedical, pharmaceutical, cosmetic, and food industries. Current methods of HA production, including extraction from animal sources and streptococcal cultivations, are associated with high costs and health risks. Accordingly, the development of bioprocesses for HA production centered on robust “Generally Recognized as Safe (GRAS)” organisms such as Bacillus subtilis is highly attractive. Here, we report the development of novel strains of B. subtilis in which the membrane cardiolipin (CL) content and distribution has been engineered to enhance the functional expression of heterologously expressed hyaluronan synthase (HAS) of Streptococcus equisimilis (SeHAS), in turn, improving the culture performance for HA production. Elevation of membrane CL levels via overexpressing components involved in the CL biosynthesis pathway, and redistribution of CL along the lateral membrane via repression of the cell division initiator protein FtsZ resulted in increases to the HA titer of up to 204% and peak molecular weight of up to 2.2 MDa. Moreover, removal of phosphatidylethanolamine and neutral glycolipids from the membrane of HA‐producing B. subtilis via inactivation of pssA and ugtP, respectively, has suggested the lipid dependence for functional expression of SeHAS. Our study demonstrates successful application of membrane engineering strategies to develop an effective platform for biomanufacturing of HA with B. subtilis strains expressing Class I streptococcal HAS.  相似文献   

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