Specific status of Echinococcus canadensis (Cestoda: Taeniidae) inferred from nuclear and mitochondrial gene sequences

The specific status of Echinococcus canadensis has long been controversial, mainly because it consists of the mitochondrial lineages G6, G7, G8 and G10 with different host affinity: G6 (camel strain) and G7 (pig strain) with domestic cycles and G8 (cervid strain) and G10 (Fennoscandian cervid strain) with sylvatic or semi-domestic cycles. There is an argument whether the mitochondrial lineages should be recognised as separate species which correspond to the biological or epidemiological aggregation. In the present study, the specific status of E. canadensis was investigated using mitochondrial DNA and single copy nuclear DNA markers. Nucleotide sequences of complete mitochondrial cytochrome c oxidase subunit 1 (cox1) and partial nuclear phosphoenolpyruvate carboxykinase (pepck) and DNA polymerase delta (pold) were determined for 48 isolates of E. canadensis collected from different hosts in a wide range of regions. The mitochondrial phylogeny of cox1 showed that all the isolates were clearly divided into three clades corresponding to G6/G7, G8 and G10. Five and three alleles were confirmed at pepck and pold loci, respectively. These alleles were generally divided into two groups corresponding to G6/G7 or G8 and G10. However, allele sharing was confirmed among individuals belonging to different lineages. The allele sharing occurred primarily in regions where different mitochondrial DNA lineages were found in sympatry. The resultant nuclear mitochondrial discordance suggests the genetic exchangeability among E. canadensis isolates belonging to different lineages. An apparently mosaic parasite fauna that reflects faunal mixing due to natural and anthropogenic disturbance, including introductions and invasion, precludes us from designating each of G6/G7, G8 and G10 into a different species.

Characterization of excretory-secretory products from protoscoleces of Echinococcus granulosus and evaluation of their potential for immunodiagnosis of human cystic echinococcosis

This study describes, for the first time, the characterization of excretory-secretory antigens (ES-Ag) from Echinococcus granulosus protoscoleces, evaluating their usefulness in the immunodiagnosis of human cystic echinococcosis. ES-Ag were obtained from the first 50 h maintenance of protoscoleces in vitro. This preparation contained over 20 major protein components which could be distinguished by 1-dimensional SDS-PAGE with apparent masses between 9 and 300 kDa. The culture of of protoscoleces from liver produced a greater variety of excretory-secretory protein components than those from lung. Determination of enzymatic activities of secreted proteins revealed the presence of phosphatases, lipases and glucosidases, but no proteases. These findings were compared to those obtained from somatic extracts of protoscoleces and hydatid cyst fluid products. Immunochemical characterization was performed by immunoblotting with sera from individuals infected by cystic echinococcosis (n = 15), non-hydatidic parasitoses (n = 19), various liver diseases (n = 24), lung neoplasia (n = 16), and healthy donors (n = 18). Antigens with apparent masses of 89, 74, 47/50, 32, and 20 kDa showed specificity for immunodiagnosis of human hydatidosis. The 89 and 74 kDa components corresponded to antigens not yet described in E. granulosus, whereas proteins of 41-43 kDa and 91-95 kDa were recognized by the majority of the non-hydatid sera studied.

Cystic echinococcosis in Argentina: evolution of metacestode and clinical expression in various Echinococcus granulosus strains

Echinococcus granulosus hydatid cysts were examined in 41 patients from Neuquén and Tucumán provinces in Argentina. Sequencing of the mitochondrial cytochrome c oxidase subunit 1 (CO1) revealed in 19 patients common sheep strain (G1), in 6 patients Tasmania sheep strain (G2), in 1 patient cattle strain (G5), and in 15 patients camel strain (G6). In Argentina the only known is the domestic cycle that affects dogs and herbivorous, including ovine, swine, cattle and goats. These strains produced a total of 58.6% of primary liver infections, 29.2% primary in lung, 2.4% primary in spleen and 9.8% were multiorgan abdominal infections. The metacestode was classified using the evolutive stages proposed by WHO-IWGE (from CE1 to CE5). We estimated that CE1 cyst has a duration of about 22 years, CE2 of 14 years, CE3 of 10 years, CE4 of 19 years and CE5 was not determined. The active types CE1 and CE2 reached 75% of all cases from all strains. In 36 patients with cysts from G1, G5 and G6 strain, there were only two asymptomatic cases. The strains of the E. granulosus complex do not present important clinical differences; only G6 seems to have higher growth rate.

Echinococcus granulosusstrain differentiation based on sequence heterogeneity in mitochondrial genes of cytochromecoxidase-1 and NADH dehydrogenase-1

Genetic analyses ofEchinococcus granulosusisolates from different intermediate host species have demonstrated substantial levels of variation for some genotype (strain) clusters. To determine the range of genetic variability within and between genotypes we amplified and cloned partialcox1andnadh1genes from 16 isolates ofE. granulosusfrom 4 continents. Furthermore, we sequenced different clones from a PCR product to analyse the intra-individual genetic variance. The findings showed a moderate degree of variance within single isolates and a significant degree of variance between the cluster of genotypes G1–G3 (sheep, Tasmanian sheep and buffalo strain), genotypes G4 (horse strain) and G5 (cattle strain) and the cluster of the genotypes G6 (camel strain) and G7 (pig strain). The variance of up to 2·2% within genotypes was relatively low compared with that of 4·3–15·7% among genotypes. The present results indicate that a re-examination of the classification of 5 genotypes ofEchinococcusis warranted. Hence, our data highly support a re-evaluation of the taxonomy of the clades G1–G3, G4, G5, G6/7 and G8 (cervid strain) within the genusEchinococcus.

Genetic relationships between sheep, cattle and human Echinococcus infection in Tunisia

Allozyme variation at seven polymorphic loci (GPI, EST, MDH, MPI, DIA, PEP, PGM) was studied to examine genetic variation within and between sheep, cattle and human populations of Echinococcus granulosus in Tunisia. A high degree of genetic similarity was shown between the cysts of the three host origins. Nevertheless, whereas, the ovine and human samples were highly similar, the cattle samples were slightly different genetically. We conclude that humans are mostly infected by parasites originating from sheep liver. The intense deficiency in heterozygotes was partly artefactual (Wahlund effect) and partly due to self-fertilisation.

Livestock trade history, geography, and parasite strains: the mitochondrial genetic structure of Echinococcus granulosus in Argentina

A sample of 114 isolates of Echinococcus granulosus (Cestoda: Taeniidae) collected from different host species and sites in Argentina has been sequenced for 391 bp from the mitochondrial cytochrome c oxidase subunit I gene to analyze genetic variability and population structure. Nine different haplotypes were identified, 5 of which correspond to already characterized strains. Analysis of molecular variance and nested clade analysis of the distribution of haplotypes among localities within 3 main geographic regions indicate that geographic differentiation accounts for the overall pattern of genetic variability in E. granulosus populations. Significant geographic differentiation is also present when the sheep strain alone is considered. Our results suggest that geographic patterns are not due to actual restricted gene flow between regions but are rather a consequence of past history, probably related to the time and origin of livestock introduction in Argentina.

Functional expression and characterization of Echinococcus granulosus thioredoxin peroxidase suggests a role in protection against oxidative damage

A full-length cDNA sequence coding for Echinococcus granulosus thioredoxin peroxidase (EgTPx) was isolated from a sheep strain protoscolex cDNA library by immunoscreening using a pool of sera from mice infected with oncospheres. EgTPx expressed as a fusion protein with glutathione S-transferase (GST) exhibited significant thiol-dependent peroxidase activity that protected plasmid DNA from damage by metal-catalyzed oxidation (MCO) in vitro. Furthermore, the suggested antioxidant role for EgTPx was reinforced in an in vivo assay, whereby its expression in BL21 bacterial cells markedly increased the tolerance and survival of the cells to high concentrations of H2O2 compared with controls. Immunolocalization studies revealed that EgTPx was specifically expressed in all tissues of the protoscolex and brood capsules. Higher intensity of labelling was detected in many, but not all, calcareous corpuscle cells in protoscoleces. The purified recombinant EgTPx protein was used to screen sera from heavily infected mice and patients with confirmed hydatid infection. Only a portion of the sera reacted positively with the EgTPx-GST fusion protein in Western blots, suggesting that EgTPx may form antibody-antigen complexes or that responses to the EgTPx antigen may be immunologically regulated. Recombinant EgTPx may prove useful for the screening of specific inhibitors that could serve as new drugs for treatment of hydatid disease. Moreover, given that TPx from different parasitic phyla were phylogenetically distant from host TPx molecules, the development of antiparasite TPx inhibitors that do not react with host TPx might be feasible.

Immunochemical characterization of alkaline phosphatase from the fluid of sterile and fertile Echinococcus granulosus cysts

Alkaline phosphatase (ALP) from hydatid cyst fluid (HCF) was purified and characterized for comparison between fertile and sterile HCF. Samples were obtained from slaughtered sheep and then sterile and fertile cysts were separated. ALP was purified from aspirated cyst fluid and biochemical parameters were determined. Sera from patients with hydatid disease (15 samples) and patients with other parasitic diseases including fascioliasis (2 samples), taeniasis ( Taenia saginata, 5 samples) and also sera from uninfected controls (15 samples), were collected and used in immunoblotting experiments with ALP from sterile and fertile HCF as antigen. Our results showed that ALP activity in fertile HCF [10.75+/-3.78 (SD) U/ml) was significantly more than in sterile HCF (6.25+/-2.43 U/ml). There were also some differences between the kinetic parameters and biochemical characteristics of ALP in fertile and sterile HCF. Immunoreactive bands were clearly observed when sera from hydatid infected patients were tested with ALP from fertile HCF as the antigen. However, this method revealed no cross-reaction between purified ALP from sterile HCF and sheep liver tissue. These findings suggest that there is some variation in the immunochemical characteristics of ALP from fertile and sterile HCF.

Mucin-type O-glycosylation in helminth parasites from major taxonomic groups: evidence for widespread distribution of the Tn antigen (GalNAc-Ser/Thr) and identification of UDP-GalNAc:polypeptide N-acetylgalactosaminyltransferase activity

This article focuses on the initiation pathway of mucin-type O-glycosylation in helminth parasites. The presence of the GalNAc-O-Ser/Thr structure, also known as Tn antigen, a truncated determinant related to aberrant glycosylation in mammal cells, and the activity of the UDP-GalNAc:polypeptide N-acetyl-galactosaminyltransferase (ppGaNTase), the enzyme responsible for its synthesis, were studied in species from major taxonomic groups. Tn reactivity was determined in extracts from Taenia hydatigena, Mesocestoides corti, Fasciola hepatica, Nippostrongylus brasiliensis, and Toxocara canis using the monoclonal antibody 83D4. The Tn determinant was revealed in all preparations, and multiple patterns of Tn-bearing glycoproteins were observed by immunoblotting. Additionally, the first evidence that helminth parasites express ppGaNTase activity was obtained. This enzyme was studied in extracts from Echinococcus granulosus, F. hepatica, and T. canis by measuring the incorporation of UDP-(3H)GalNAc to both deglycosylated ovine syalomucin (dOSM) and synthetic peptide sequences derived from tandem repeats of human mucins. Whereas significant levels of ppGaNTase activity were detected in all the extracts when dOSM was used as a multisite acceptor, it was only observed in F. hepatica and E. granulosus extracts when mucin-derived peptides were used, suggesting that T. canis ppGaNTase enzyme(s) may represent a member of the gene family with a more restricted specificity for worm O-glycosylation motifs. The widespread expression of Tn antigen, capable of evoking both humoral and cellular immunity, strongly suggests that simple mucin-type O-glycosylation does not constitute an aberrant phenomenon in helminth parasites.

Alternative mRNAs arising from trans-splicing code for mitochondrial and cytosolic variants of Echinococcus granulosus thioredoxin Glutathione reductase

Thioredoxin and glutathione systems are the major thiol-dependent redox systems in animal cells. They transfer via the reversible oxidoreduction of thiols the reducing equivalents of NADPH to numerous substrates and substrate reductases and constitute major defenses against oxidative stress. In this study, we cloned from the helminth parasite Echinococcus granulosus two trans-spliced mRNA variants that encode thioredoxin glutathione reductases (TGR). These variants code for mitochondrial and cytosolic selenocysteine-containing isoforms that possess identical glutaredoxin (Grx) and thioredoxin reductase (TR) domains and differ exclusively in their N termini. Western blot analysis of subcellular fractions with specific anti-TGR antibodies showed that TGR is present in both compartments. The biochemical characterization of the native purified TGR suggests that the Grx and TR domains of the enzyme can function either coupled or independently of each other, because the Grx domain can accept electrons from either TR domains or the glutathione system and the TR domains can transfer electrons to either the fused Grx domain or to E. granulosus thioredoxin.

In vitro parasiticidal effect of Nitazoxanide against Echinococcus multilocularis metacestodes

When humans serve as inadvertent intermediate hosts for Echinococcus multilocularis, disease (alveolar echinococcosis [AE]) may result from the expanding parasite metacestode in visceral organs, mostly in the liver. Benzimidazole carbamate derivatives such as mebendazole and albendazole are used for chemotherapeutic treatment of AE. However, these treatments are, in most cases, parasitistatic rather than parasiticidal. As treatment is discontinued, a recurrence of parasite growth has been observed in many AE patients with nonradical resections. The only curative treatment for AE is radical surgical resection of the parasite tissue and support by chemotherapy. As there is a need for new treatment options for AE, the in vitro efficacy of nitazoxanide (NTZ), a broad-spectrum drug used against intestinal parasites and bacteria, was investigated. We showed that in vitro treatment of E. multilocularis metacestodes with NTZ induced high levels of alkaline phosphatase activity in the medium. Concurrently, distinct morphological and ultrastructural alterations were detected. Most significantly, two distinct types of alterations were observed as soon as after 3 h of NTZ treatment. At first, the drug induced a peripheral output of membranous vesicles from the tegumental membrane into the laminated layer. Simultaneously, germinal layer-associated undifferentiated cells produced large vacuoles filled with lipid-like and often electron-dense membranous segments. Other alterations were observed at later time points, including vacuolization of the germinal layer, accumulation of lipid droplets, and lastly, loss of microtriches and separation of the laminated and germinal layers. The pattern of damage induced by NTZ was different from the alterations earlier observed in albendazole sulfoxide-treated vesicles. The nonviability of NTZ-treated metacestodes was confirmed through bioassay, i.e., inoculation of treated and untreated parasites into mice. These experiments demonstrate the in vitro parasiticidal effect of NTZ on E. multilocularis metacestodes.

Further molecular discrimination of Spanish strains of Echinococcus granulosus

We have designed two polymerase chain reaction (PCR) primer sets (PEg9F1-PEg9R1 and PEg16F1-PEg16R1) and two PCR protocols (Eg9-PCR and Eg16-PCR) for discrimination of Echinococcus granulosus genotypes. The oligonucleotide sequences originate from two E. granulosus DNA multiplex-PCR amplification fragments, previously reported, that allows species-specific discrimination between Taenia saginata, Taenia solium, and E. granulosus. The Eg9-PCR, Eg16-PCR, and Eg9-PCR linked restriction fragment length polymorphism (RFLP) analysis was used to characterize 53 E. granulosus isolates from the central region of Spain, highly endemic for echinococcosis. The analysis resulted in: (i) the discrimination of E. granulosus from Echinococcus multilocularis; (ii) the characterisation and discrimination of discrete E. granulosus strains from Spain; and (iii) the identification of two distinct genotypes within E. granulosus Spanish pig isolates. To further characterize the genetic variants in pigs, fragments of the NADH dehydrogenase I (ND1) and the cytochrome c oxidase subunit I (CO1) genes were amplified from parasite DNA and sequenced. The results again revealed the presence of two distinct genotypes: the G1 (sheep-dog strain) and G7 (pig-dog strain) genotypes. This observation could have important consequences for human health in Spain. Furthermore, the Eg9-PCR, Eg16-PCR, and Eg9-PCR-RFLP protocols can be used as additional methods to discriminate various E. granulosus genotypes.

Immunisation with Salmonella typhimurium-delivered glyceraldehyde-3-phosphate dehydrogenase protects mice against challenge infection with Echinococcus multilocularis eggs

Recombinant glyceraldehyde-3-phosphate dehydrogenase of the cestode parasite Echinococcus multilocularis was expressed in Escherichia coli and in Salmonella typhimurium. The potential of different forms of the recombinant antigen to protect BALB/c mice against oral challenge infections with E. multilocularis eggs was evaluated. Oral or intraperitoneal immunisation with live attenuated S. typhimurium as a carrier for recombinant glyceraldehyde-3-phosphate dehydrogenase of the E. multilocularis resulted in significant protection, reducing the number of developing metacestodes up to 79.8%. The sera of protected animals did not contain detectable amounts of antibody against glyceraldehyde-3-phosphate dehydrogenase of E. multilocularis. By contrast, although anti-glyceraldehyde-3-phosphate dehydrogenase of E. multilocularis antibodies were detectable in the sera, immunisation with E. coli-expressed recombinant glutathione-S-transferase-fusion protein or with glyceraldehyde-3-phosphate dehydrogenase of E. multilocularis fused to a 6HIS-tag failed to protect the animals against oral challenge infections. These data emphasise that antigen delivery systems play a critical role in vaccination and the induction of protective immunity against helminth parasites.

Echinococcus multilocularis alkaline phosphatase as a marker for metacestode damage induced by in vitro drug treatment with albendazole sulfoxide and albendazole sulfone

Alveolar echinococcosis (AE) is caused by the metacestode stage of the fox tapeworm Echinococcus multilocularis. The disease affects the human liver and occasionally other organs and is fatal if treatment is unsuccessful. The present chemotherapy of AE is based on the administration of benzimidazole carbamate derivatives, such as mebendazole and albendazole. Albendazole treatment has been found to be ineffective in some cases, parasitostatic rather than parasiticidal, and the recurrence rate is rather high. Therefore, chemotherapy usually involves the lifelong uptake of massive doses of albendazole and new treatment options are urgently needed. In order to avoid costly and time-consuming animal experimentation, a first step in searching for novel parasiticidal compounds could be the in vitro drug screening of novel compounds by employing metacestode cultivation. However, presently used techniques (e.g., transmission electron microscopy) for determination of parasite viability involve costly equipment and time-consuming preparation of rather large amounts of parasite material. We therefore searched for a parasite marker which can be easily traced and the presence or absence of which is indicative of parasite viability. In this study we show that the increase of E. multilocularis alkaline phosphatase activity in culture supernatants during in vitro drug treatment with albendazole derivatives correlates with the progressive degeneration and destruction of the metacestode tissue. The inexpensive and rapid assay presented here will serve as an ideal tool for performing first-round in vitro tests on the efficacy of a large number of antiparasitic compounds.

[Iso-enzyme study of Echinococcus granulosus protoscoleces in Algeria]

The purpose of this study is to identity the strains of Echinococcus granulosus the causative agent of unilocular hydatid in Algeria--a high endemic area. For this, the authors established a simple and reproductible electrophoretic techniques for iso enzyme analysis of protoscoleces. The enzymatic extracts of protoscoleces from various hosts and localisations of hidatic cystic analysed by these electrophoretic techniques showed variable electrophoretic profils witness the existence of various strains.

Presence of cholinesterases in Echinococcus granulosus protoscolices

Cholinesterases were detected in protoscolices of Echinococcus granulosus spectrophotometrically and electrophoretically. To characterize these activities as acetylcholinesterases or pseudocholinesterases, BW284C51 and the organophosphate anthelmintic Neguvón were assayed as specific inhibitors of acetylcholinesterases, while Iso-OMPA was employed as specific inhibitor of pseudocholinesterases. We concluded that these cholinesterase (ChE) activities would be considered as possible targets in chemotherapy.

Secondary alveolar echinococcosis in lymphotoxin-alpha and tumour necrosis factor-alpha deficient mice: exacerbation of Echinococcus multilocularis larval growth is associated with cellular changes in the periparasitic granuloma

The availability of mice carrying a deletion of LT-alpha and tumour necrosis factor (TNF)-alpha genes enabled us to investigate the role of the TNF during alveolar echinococcosis. We compared the growth rate of Echinococcus multilocularis in LT-alphaTNF-alpha +/+ mice to that of mice having either no or only one LT-alphaTNF-alpha functionnal allele. LT-alphaTNF-alpha -/- mice harboured a significantly higher parasite burden than did the other two populations at 5, 10, and 15 weeks of infection, and they did not survive thereafter. Liver metacestodes removed from these mice were alive and the dehydrogenase activities of peritoneal metacestodes were decreased. Liver lesions regressed in most wild-type mice. Indeed, dead parasites were cordoned by granulomas containing numerous macrophages and lymphocytes leading to focal liver fibrosis at an early stage of infection. In contrast, most of LT-alphaTNF-alpha -/- mice harboured metacestodes interspersed with leucocytes, realising purulent abscesses with secondary extensive irregular fibrosis at a late stage of infection. Heterozygous mice had behavioural characteristics intermediate between homozygous mutants and wild-type mice. Levels of E. multilocularis-specific delayed-type hypersensitivity and serum antibodies were slightly decreased in LT-alphaTNF-alpha -/- mice. This study shows that TNF-alpha and/or LT-alpha genes play an essential role in the immune protection mechanisms against E. multilocularis at the site of infection.

Dideoxy fingerprinting: application to the genotyping of Echinococcus

Dideoxy fingerprinting is an efficient method for the detection of sequence variation in PCR-amplified DNA segments. It is a hybrid between single-strand conformation polymorphism and dideoxy sequencing, employing only one dideoxynucleotide in the sequencing reaction. Herein, we report the application of dideoxy fingerprinting to genetically type cestodes of the genus Echinococcus, utilising the mitochondrial cytochrome c oxidase subunit I as the gene sequence for analysis. All of the seven genotypes (G1, G4, G6, G8, O, V and M2) examined could be readily differentiated from one another by their characteristic and reproducible dideoxy fingerprinting profiles. Only subtle variation in profiles was detected among some of the eight isolates representing genotype G1, and no variation was detected between two samples of genotype G4 and of genotype M2. The capacity of dideoxy fingerprinting to detect all nucleotide variations over 150-250bp fragments indicates that it should be possible to distinguish among all of the genotypes of Echinococcus thus far described. Although employed herein to display sequence variation in the cytochrome c oxidase subunit I of Echinococcus, dideoxy fingerprinting could be used for the high-resolution analysis of nucleotide variations in other parasite genes, without the need for DNA sequencing. This has important implications for studying the genetic structure of parasite populations.

Purine metabolism in Echinococcus multilocularis

The activities of the enzymes in Echinococcus multilocularis metacestodes involved in purine salvage were studied by HPLC. As in most parasites, this cestode relies entirely on salvage of preformed bases and nucleosides for its purine requirement. Therefore, these enzymes may be targets for drugs in the chemotherapeutic treatment of diseases caused by this parasite. The animals used in this study were gerbils (Meriones unguiculatus). Enzyme activities from sera and hepatic tissue in control and infected animals were similar with the exception of adenine phosphoribosyltransferase which showed an activity 4-fold greater in the serum from control than in serum from infected animals. In the parasite, adenine and hypoxanthine-guanine phosphoribosyltransferases and adenosine deaminase had the highest activities. Therefore, in E. multilocularis metacestodes, this pathway seems to be important for the parasite's metabolism.

Combining data from morphological traits and genetic markers to determine transmission cycles in the tape worm, Echinococcus granulosus

Species of Echinococcus (Cestoda: Taeniidae) require 2 mammalian hosts to complete their life-cycle; a carnivorous definitive host, and a herbivorous or omnivorous intermediate host. For most species of Echinococcus, the definitive host range is restricted to 1 or a few species, but the intermediate host range is very broad. Programmes to control hydatid disease attempt to break the life-cycle of the parasite and their effectiveness is therefore enhanced by an understanding of local patterns of transmission. Although it is known that the rostellar hooks of protoscoleces may be influenced by the species of intermediate host in which they develop, the application of this knowledge to infer transmission cycles has been limited, because the intermediate host effect has not been isolated from other environmental and genetic components of phenotypic variance. This study presents a method for separating these potentially confounding genetic and environmental effects, by combining quantitative genetic analyses of hook traits with data on population structure from neutral genetic markers. The method was applied to 5 hook traits (hook number, total length of large hooks, blade length of large hooks, total length of small hooks, blade length of small hooks) measured on protoscoleces from 2 intermediate host types (sheep and macropod marsupials) in Australia. Although genetic variance was similar for all traits, they differed markedly in the extent of environmental variance attributed to development in different host types. Total length of small hooks was the trait most affected, with 49-60% of phenotypic variance being explained by environmental differences between intermediate host species. Blade length of small hooks was least affected, with none of the phenotypic variance due to intermediate host origin. These data suggest that hook measurements of adult worms from naturally infected definitive hosts could be used to determine the intermediate host species from which infection was acquired, if the appropriate traits are measured.

Indication of the presence of two distinct strains of Echinococcus granulosus in Iran by mitochondrial DNA markers

Sixteen isolates of Echinococcus granulosus, collected from Iranian patients at surgery, and from domestic animals, including sheep, goats, cattle, and camels at slaughterhouses in Tehran and central and southern Iran were analyzed for DNA nucleotide and predicted amino acid sequence variation within regions of the mitochondrial cytochrome c oxidase I (COI) and NADH dehydrogenase subunit I (NDI) genes. A polymerase chain reaction-restriction fragment length polymorphism method, based on the DNA sequence variation in the NDI gene, was also used to rapidly survey the E. granulosus isolates. The isolates were categorized into two distinct and uniform genotype groupings. The analysis clearly indicated that the camel/dog strain (G6 genotype) of E. granulosus as well as the cosmopolitan, common sheep strain (G1 genotype) occur in Iran. The G1 genotype was found present in all four human isolates examined and it was more prevalent in domestic animals than the camel-restricted G6 genotype. In E. granulosus-endemic areas of Iran it is evident, therefore, that the majority of E. granulosus-infected livestock animals can potentially act as reservoirs of human infection, and this has important implications for hydatid control and public health.

Short report: An imported case of cystic echinococcosis in Japan diagnosed by imaging and serology with confirmation of Echinococcus granulosus-specific DNA sequences

We report one case of cystic echinococcosis (CE) in Japan in a native of Nepal. Ultrasonography and computed tomography scan of the liver revealed unique cystic lesions with or without daughter cysts of Echinococcus granulosus. Immunoblot analysis using crude antigens of E. multilocularis and cyst fluid of E. granulosus, without reference to these image analyses, strongly suggested this was a case of CE. We found protoscoleces in surgically removed hepatic lesions and analyzed the mitochondrial cytochrome c oxidase subunit I (COI) gene by the polymerase chain reaction. Based on the similarity in DNA sequences of the COI gene of this Echinococcus spp. with that of previously reported sheep-dog strain (GI), the parasite was considered to be the so-called common sheep strain of E. granulosus.

Echinococcus multilocularis metacestodes: immunological and immunocytochemical analysis of the relationships between alkaline phosphatase and the Em2 antigen

Echinococcus multilocularis metacestodes possess an alkaline phosphatase (EmAP) which has been extensively characterized at the biochemical level in previous studies. The apparent molecular weight of the enzyme monomer and its isoelectric point matched those originally described for the Em2 antigen, a reference antigen currently used for the immunodiagnosis of E. multilocularis infection. These observations raised questions about the molecular relationship between the two molecules. In order to investigate the relations between EmAP and the Em2 antigen, immunoblotting and ELISA were carried out using polyclonal and monoclonal antibodies directed against EmAP and the Em2 antigen, respectively. In addition, the localization of EmAP and the Em2 antigen was compared by immunofluorescence and immunogold electron microscopy in in vitro-generated E. multilocularis metacestodes. The results show that common epitopes between EmAP and Em2 exist, which are predominantly of a peptidic nature. Both antigens are localized in an acellular parasite structure, the laminated layer, with additional locations for the EmAP on the glycocalyx and in the central region of invaginated protoscoleces. These results suggest a putative functional relationship between the two antigens and that Em2 could originate from EmAP.

Antibodies against Echinococcus multilocularis alkaline phosphatase as markers for the specific diagnosis and the serological monitoring of alveolar echinococcosis

The immunological properties of the purified alkaline phosphatase (pAP) of Echinococcus multilocularis metacestodes have been investigated using alveolar echinococcosis (AE) patient sera in ELISA tests. A comparative study was done with EmC-Ag (crude antigen) and pAP-Ag (purified antigen). When the parasite purified enzyme pAP was used as antigen, the specificity of the ELISA was markedly increased since it reached 100% without any decrease of its sensitivity (100%). The serologic follow-up of AE patients was conducted during several months with these two antigens in three categories of patients: cured, stabilized and aggravated. There was a good correlation between clinical and serologic data when the pAP was used as antigen in ELISA tests. The anti-pAP antibodies titres did change more rapidly than anti-EmC antibodies titres when a recurrence occurred. Modifications of the anti-pAP antibodies levels were also observed during the patient's therapy: mebendazole, albendazole and Isoprinosine. These results suggest that pAP-Ag should be used for the diagnosis and the follow-up of AE patients.

Histochemical observations of alkaline phosphatase activity of Echinococcus multilocularis during in vivo development in golden hamsters, an alternative definitive host

Histochemical observations of alkaline phosphatase activity of Echinococcus multilocularis during the in vivo development in golden hamster, an alternative definitive host. The present work reports on the ability of protoscoleces from a European fox strain of E. multilocularis to differentiate and develop into the adult form in the small intestine of male golden hamsters treated with prednisolone. Detection of alkaline phosphatase activity on various stages of the developing worm was performed by histochemical methods. The enzyme activity was not demonstrable in the early stages of infection but occurred with strobilization. Age-related changes in the distribution of the enzyme activity took place during strobilization. Alkaline phosphatase activity was evident in the excretory ducts of 8 to 11 day old strobila and in the tegument of mature proglottis of 16 day old worms. This in vivo procedure with rodents as definitive hosts provides interesting preliminary results on the biology of the E. multilocularis adult. Further investigations on membrane-bound enzymes involved in physiological and nutritional processes are in progress.

Effect of mebendazole and praziquantel on glucosephosphate isomerase and glyceraldehydephosphate dehydrogenase in Echinococcus granulosus cyst wall harbored in mice

AIM

To study effects of antihydatid drugs on glucosephosphate isomerase (GPI) and glyceraldehydephosphate dehydrogenase (GAPDH) in Echinococcus granulosus cyst wall.

METHODS

Mice infected with the parasite for 8-10 months were treated i.g. with mebendazole (Meb) or praziquantel (Pra). The activities of GPI and GAPDH in the cysts were measured by the formation of NADH or NADPH.

RESULTS

GPI activity in the cyst wall was 197 +/- 103 U, while that of GAPDH was 25 +/- 13 U. When infected mice were treated i.g. with Meb 25-50 mg.kg-1.d-1 for 7-14 d, no apparent effect on the GAPDH activity in the cyst was found. In mice treated i.g. with praziquantel (Pra) 500 mg.kg-1.d-1 for 14 d, the GAPDH activity in the cyst wall was inhibited by 26.5%. As to GPI activity only the group treated i.g. with Meb 25 mg.kg-1.d-1 for 14 d showed 33.2% inhibition of the enzyme in the collapsed cyst wall.

CONCLUSION

GPI and GAPDH are not the major targets attacked by the antihydatid drug.

Echinococcus granulosus: genomic and isoenzymatic study of Spanish strains isolated from different intermediate hosts

The phenomenon on intraspecific variation in Echinococcus granulosus is already documented in Spain, where unilocular hydatidosis is an endemic disease. The first speciation studies, focused at a genomic level, showed the existence of three different strains: ovine-bovine-human, equine and swine-caprine. In the present study, the genomic identification, by random amplified polymorphic DNA technique (RAPD) of a larger number of Spanish E. granulosus isolates, using five different primers, showed the maintenance of these groups. Thus, some of these strains may not be infective for man. These conclusions were supported by a phenotypic characterization of the same isolates by zymodeme technique, showing the five isoenzyme systems used that Spanish E. granulosus strains can also be distinguished at a phenotypic level by isoenzymatic patterns. Both techniques (RAPD and zymodemes) were used for statistical analysis and for the construction of two dendrograms, which were slightly different. In addition, some intrastrain variation was detected with both techniques, a phenomenon that is directly related to the different speciation theories proposed for E. granulosus strains. The epidemiological implications of the results are discussed in the text.

Molecular cloning, expression and characterization of a recombinant glutathione S-transferase from Echinococcus multilocularis

We report the identification and characterization of the first cestode glutathione S-transferase (GST) cDNA sequence. A fragment of an Echinococcus multilocularis glutathione S-transferase cDNA was isolated by the polymerase chain reaction. Subsequently, a Lambda zap cDNA library prepared from mRNA from protoscolices of E. multilocularis was screened with this PCR fragment. A complete cDNA clone was isolated and the nucleotide sequence determined. Analysis of the E. multilocularis GST-deduced amino acid sequence indicates that it is clearly related to the mammalian mu-class GSTs. The E. multilocularis GST cDNA was expressed in Escherichia coli, using a protocol designed to produce the native enzyme rather than a fusion protein. The 25.5-kDa enzyme subunit was purified to homogeneity using glutathione-sepharose chromatography. Gel filtration demonstrated that this GST is enzymatically active as a homodimer. The recombinant enzyme had conjugating activity with organic hydroperoxides and with members of the trans,trans-2,4 alkadienal and trans-2-alkenal series, which are secondary products of lipid peroxidation.

Partial purification and kinetic properties of cytoplasmic malate dehydrogenase from ovine liver Echinococcus granulosus protoscolices

Cytoplasmic malate dehydrogenase from ovine liver Echinococcus granulosus protoscolices was purified 22-fold by QAE- and SP-Sephadex chromatography. The pH optimum of the enzyme was 8.0 in either Tris-HCI or barbital buffer. The Km values of oxaloacetate and NADH were 0.400 +/- 0.018 and 0.410 +/- 0.038 mM, respectively. The enzyme lost about 90% of its activity when heated for 2 min at 65 degrees C. A 61.4% inhibition of the enzyme was noted at 4 mM concentration of diethyl pyrocarbonate. A 3 mM concentration of fructose 1,6-diphosphate inhibited the enzyme by 76.5%. The inhibition was non-competitive with respect to NADH with a Ki value of 0.85 mM. A 75% inhibition of the enzyme was noted at 1 mM concentration of mebendazole that inhibited the enzyme upon competing with NADH with a Ki value of 0.176 mM. A 2-mM concentration of citrate almost doubled the enzyme activity. The enzyme was inhibited at high concentrations of either substrate. The enzyme was not inhibited by p-hydroxymercuribenzoate or fumarate. The enzyme was absolutely specific for NADH as a cofactor. The properties of this enzyme are compared with those of the enzyme from the host liver, the cyst fluid and some other animal sources. The results are discussed in terms of the differences among the properties of the host liver, the cyst fluid and the protoscolices enzymes. The biochemical basis for the use of mebendazole in the treatment of echinococcosis is also elucidated.

Cytochemical study of the germinal membrane of the Echinococcus granulosus cyst

The present cytochemical study was undertaken to provide more information on the localization of enzymatic and glycoconjugates in the germinal membrane of the Echinococcus granulosus cyst. The distinctive distribution of binding sites for two lectins (peanut agglutinin and Dilochos biflorus agglutinin) in the germinal membrane are described. An investigation is made of the distribution and specific activity of adenosine triphosphatase, alkaline phosphatase and acid phosphatase. The results suggest that cells located in the deeper layer of the germinal membrane are intrinsic in the cellular differentiation process. The dissimilarities detected in both the enzymatic activity and the lectin-binding receptors could be associated with metacestode development or degeneration.

Echinococcus granulosus, E. multilocularis and mammalian liver-type alkaline phosphatases: a comparative study

The alkaline phosphatases (EC 3.1.3.1) from Echinococcus granulosus and E. multilocularis (Cestoda) were compared to each other and to a liver-type enzyme. The purified proteins (210 and 220 kDa, respectively) had a tetrameric structure composed of 4, 56/53 kDa subunits. Enzymatic removal of their N-linked sugar moieties abolished the differences in their apparent molecular weight under reducing conditions. After phase separation in Triton X-114, the E. multilocularis enzyme was the most amphiphilic, and treatment with PI-P1C reduced the amount of the parasite alkaline phosphatases that were in a hydrophobic form by about 50%. Both parasite enzymes were highly resistant to heat denaturation and insensitive to the inhibitors L-phenylalanine and L-leucine. In addition, L-homoarginine, levamisole and ZnCl2 can be used to differentiate the parasite and mammalian liver-type enzymes from each other. The Echinococcus alkaline phosphatases have original biochemical properties when compared to the mammalian liver-type enzyme.

Effects of mebendazole, albendazole, and praziquantel on glutathione S-transferase and superoxide dismutase of Echinococcus granulosus cyst wall harbored in mice

AIM

To explore the existence of glutathione S-transferase (GST) and superoxide dismutase (SOD) in Echinococcus granulosus cyst, and the effect of anthydatid drugs on these 2 enzymes, mice infected with E granulosus protoscoleces for 10-12 months were used.

METHODS

The activity of GST was measured by conjugation rate of 1-chloro-2,4-dinitrobenzene with glutathione (reduced form), while the activity of SOD was measured by a modified autoxidation of 1, 2, 3-trihydroxy-benzene method.

RESULTS

Activities of both GST and SOD in the cyst wall were 12.3 +/- 4.3 to 13.5 +/- 4.8 mumol min-1/mg protein and 4.4 +/- 2.9 to 6.1 +/- 1.4 U min-1/mg protein, respectively. When infected mice were treated ig with mebendazole (Meb) 25 mg kg-1 d-1 for 14 d, the GST activity of both collapsed and full cyst walls were inhibited by 30.1% and 26.8%, respectively. Whereas SOD activity of the cyst walls were activated by 105%-163%. Albendazole 300 mg kg-1 d-1 for 14 d and praziquantel 500 mg kg-1 d-1 for 14 d had no apparent effect on both GST and SOD of E granulosus cyst wall.

CONCLUSION

The results suggested that the inhibition of GST activity in the cyst wall induced by Meb might damage the defence system of the parasite.

A molecular phylogeny of the genus Echinococcus

Three nucleotide data sets, two mitochondrial (COI and ND1) and one nuclear (ribosomal ITS1), have been investigated in order to resolve relationships among species and strains of the genus Echinococcus. The data have some unusual properties in that mitochondrial heteroplasmy was detected in one strain of E. granulosus, and more than one class of ITS1 sequence variant can occur in a single isolate. The data failed to support the hypothesis that E. granulosus, as it is currently viewed, is a single valid species. Rather, the strains of E. granulosus seem to comprise at least three evolutionarily diverse groups, the sheep strain group, bovine strain group and horse strain group. Molecular distances between them are comparable to, or greater than, molecular evolutionary distances observed between recognized species. The affinities of the cervid strain of E. granulosus are unclear because of ambiguous data, but this strain does not appear to be ancestral to others. E. multilocularis may not be distinct from E. granulosus. However, the remaining two species. E. vogeli and E. oligarthrus appear distinct and rather distant from the first two. Based on the results presented here, taxonomic revision of the genus is clearly warranted.

In vitro quantitative assessment of Echinococcus multilocularis metacestode viability after in vivo and in vitro maintenance

The aim of this study was to apply the enzymatic MTT (3,5 dimethylthiazol-2yl)-2,5-diphenyl tetrazolium bromide--formazan colorimetry for quantifying the viability of Echinococcus multilocularis whole cysts, after maintenance in vivo or in vitro. The enzymatic activities of young cysts freshly removed from rodents were linearly correlated with the parasite cyst weight. A comparative evaluation of the MTT assay and the in vitro viability assessments showed that the number of animals used for drug-screening purposes would be reduced by 35.8%. In this way, the use of different parasite samples removed from the same host is required, because of their different ages and their subsequent different abilities to reduce MTT. Cysts removed from mice exhibited higher colorimetric values than those removed from jirds. Thus, small entire cysts obtained from mice were maintained in the CMRL 1066 culture medium. Their enzymatic activities were evaluated at different times. The results indicate that, in such conditions, the optimal period of time for testing the effect of drugs against the metacestodes is limited to the 10 days following their transfer from mouse to culture flasks. The MTT assay encourages further studies to improve the viability of the whole cysts in vitro, using other standardizable culture conditions.

Isolation and biochemical characterisation of a glutathione S-transferase from Echinococcus granulosus protoscoleces

A protein fraction migrating as a M(r) 24 kDa band on SDS-PAGE was isolated by affinity chromatography on glutathione-agarose from a soluble extract of E. granulosus proto-scoleces from sheep(UK). This fraction had glutathione S-transferase activity of 0.4 mumol min-1 mg-1 when measured using a standard synthetic substrate and its determined N-terminal amino acid sequence most closely resembled Mu class glutathione S-transferases. In addition, protoscoleces from the distinct sheep and horse E. granulosus strains showed a different pattern of glutathione-binding proteins: the M(r) 24 kDa species was obtained in both cases whereas an additional band of slightly faster electrophoretic mobility was isolated from horse(UK) protoscoleces.

Purification and characterization of the alkaline phosphatase from Echinococcus granulosus cyst membranes

The purification to homogeneity and the characterization of Echinococcus granulosus alkaline phosphatase (AP; EC 3.1.3.1) from hydatid cyst membranes are described. After n-butanol extraction, the parasite enzyme was sequentially purified by affinity chromatography on concanavalin A-sepharose followed by gel filtration. The purified protein (210 kDa) had a tetrameric structure composed of 4 56-kDa subunits. Its isoelectric point (4.8) and its kinetic parameters were determined (Km = 0.24 +/- 0.05 mmol/L; Vm = 173 +/- 21 nmol/min/mg protein for p-nitrophenylphosphate). The parasite enzyme differed from the host liver enzyme in its thermal stability, optimum reaction temperature, optimum pH, and catalytic parameters, but not in its apparent molecular weight. Furthermore, sera from patients infected with E. granulosus recognized the parasite AP on immunoblots, whereas uninfected controls were negative. These results as well as the role of this enzyme in the host-parasite relationship emphasize its potential importance as a diagnostic and prognostic antigen in the monitoring of hydatid infection.

Deoxyribonuclease activity in Echinococcus granulosus protoscoleces and hydatid fluid

Deoxyribonuclease activity was detected in E. granulosus protoscoleces from sheep hydatid cysts by electrophoresis in agarose gels of DNA fragments obtained after incubation of integral DNA with a protoscoleces preparation. Preliminary characterization showed that deoxyribonuclease activity was optimal at neutral-alkaline pH, magnesium ions were required, and it was able to digest different types of DNA, making random cuts. Electrophoresis in DNA-containing sodium dodecylsulfate (SDS)-polyacrylamide gels indicated a relative molecular mass, under non-reducing conditions, of 32 kDa. Deoxyribonuclease activity was also found in sheep hydatid fluid. It shared optimal pH, ionic and substrate requirements with the enzyme from protoscoleces but had a higher relative molecular mass (40 kDa), the same as that of normal sheep serum deoxyribonuclease.

Effects of mebendazole, albendazole, and praziquantel on fumarate hydratase, pyruvate kinase, and phosphoenolpyruvate carboxykinase of Echinococcus granulosus cyst wall harbored in mice

Echinococcus granulosus cyst wall exhibited activities of fumarate hydratase (FH), pyruvate kinase (PK), and phosphoenolpyruvate carboxykinase (PEPCK) with 911-1433, 151-215, and 54-98U, respectively. The ratio of PK/PEPCK was 2.2-2.7, indicating that glycolysis is the main pathway of carbohydrate metabolism in the cyst wall. When infected mice were treated ig with mebendazole, albendazole or praziquantel at the respective daily dose of 25-50, 300, and 500 mg.kg-1 for 7-14 d, no apparent change of FH activity in the cyst wall was found, while PK and PEPCK activities in the cyst wall were markedly inhibited by mebendazole and albendazole. The inhibition rates of PK and PEPCK activities in mebendazole group were 85-88% and 90-92%, respectively, while in albendazole group were 55.3 and 71.6%, respectively. The results suggest that PK or PEPCK in the cyst wall may the important site attacked by effective anti-hydatid drugs.

NADH dehydrogenase 1 gene sequences compared for species and strains of the genus Echinococcus

Nucleotide sequences of a 471 bp region of the mitochondrial NADH dehydrogenase 1 gene were obtained for 59 Echinococcus isolates including representatives of each of the 4 recognised species. Ten distinct genotypes were detected among these isolates, including 6 within E. granulosus. This information complements and extends knowledge of inter- and intraspecific variation within Echinococcus and should prove useful in phylogenetic studies.

Synthesis of propargylic alcohols and biological effects on Echinococcus multilocularis metacestodes

This study describes the synthesis of propargylic alcohols derived from isatin and their biochemical and morphological effects on Echinococcus multilocularis metacestodes in Meriones unguiculatus. Propargylic alcohols decreased the alkaline phosphatase and the lactate dehydrogenase activities of the metacestode selectively. The most effective compound, 1b, decreased the lactate dehydrogenase enzymatic activity, and the glucose concentration in the parasite increased, whereas the glycogen content was partially decreased. Furthermore, the ultrastructure study revealed several damages. The host-parasite relationships are very important in the intrahepatic cestodes as shown by the biochemical side effects observed in the host's liver during the treatment. An in vitro enzymatic study was performed with alcohols 1b and 1c.

Effects of mebendazole, albendazole, and praziquantel on succinate dehydrogenase, fumarate reductase, and malate dehydrogenase in Echinococcus granulosus cysts harbored in mice

Echinococcus granulosus cyst wall possess high biochemical activities of malate dehydrogenase (MD) and fumarate reductase (FR), but low activity of succinate dehydrogenase (SD), suggesting that the cyst wall may utilize a partial reverse tricarboxylic acid cycle. When infected mice were given intragastrically with mebendazole, 25-50 mg.kg-1.d-1, albendazole 300 mg.kg-1.d-1 or praziquantel 500 mg.kg-1.d-1 for 7-14 d, no apparent effects on SD and FR activities of the cyst wall were found, while the MD activity was suppressed by all the 3 drugs, the inhibition rates being 34.6-61.6%, 59.8%, and 50.6%, respectively. The results suggested that MD may not be an important target for the antihydatidosis drugs.

[Effects of mebendazole on glucose, glycogen, lactic acid, and lactate dehydrogenase in Echinococcus granulosus cyst wall]

The glucose, glycogen, and lactic acid contents in Echinococcus granulosus cyst wall were 3570 +/- 623, 1276 +/- 126, and 267 +/- 29 micrograms.g-1, respectively. The lactate dehydrogenase (LDH) activity in the cyst wall was 4307 +/- 297 U/(min.mg protein). When infected mice were treated ig with mebendazole (Meb) 25 or 50 mg.kg-1.d-1 for 7-14 d, the glucose and glycogen contents in the cyst wall decreased markedly. No apparent changes in lactic acid and LDH activity were seen. The results suggested that Meb had no effect on glycolysis of the cyst wall, but it exhibited an inhibitory effect on the transport of exogenous glucose from the host to the cyst wall, which might further promote the decomposition of endogenous glycogen for energy supply and resulted in a decrease of endogenous glycogen content in the cyst wall.

Metalloproteinases in the larvae of Echinococcus granulosus

Proteolytic activity in hydatid cyst fluid, cyst membranes and protoscoleces of E. granulosus was analyzed by electrophoresis in gelatin-containing polyacrylamide gels, including characterization with a set of protease inhibitors. All contained metalloproteinases in the range 60-120 kDa, with neutral/alkaline pH optima. Major activity was observed in hydatid fluid and the membranes (five bands) with both exhibiting similar electrophoretic patterns. The samples prepared from protoscoleces shared only some of these bands.