Structural changes and expression of hepatic fibrosis-related proteins in coculture of Echinococcus multilocularis protoscoleces and human hepatic stellate cells.

BACKGROUND: Echinococcus multilocularis is the causative agent of human hepatic alveolar echinococcosis (AE). AE can cause damage to several organs, primarily the liver, and have severe outcomes, such as hepatic failure and encephalopathy. The main purpose of this study was to explore the interactions between hepatic stellate cells (HSCs) and E. multilocularis protoscoleces (PSCs). The results of this study provide an experimental basis for further examination of the pathogenesis of hepatic fibrosis due to AE infection. METHODS: We investigated the role of Echinococcus multilocularis (Echinococcus genus) PSCs in hepatic fibrosis by examining structural changes and measuring hepatic fibrosis-related protein levels in cocultures of PSCs and human HSCs. Structural changes were detected by transmission electron microscopy (TEM), and levels of the hepatic fibrosis-related proteins collagen I (Col-I), alpha-smooth muscle actin (α-SMA) and osteopontin (OPN) were measured by western blotting and enzyme-linked immunosorbent assay (ELISA). RESULTS: Under coculture (1) both PSCs and HSCs exhibited morphological changes, as observed by TEM; (2) Col-I, α-SMA, and OPN expression levels, which were determined by western blotting and ELISA, significantly increased after 3 days of incubation. CONCLUSIONS: The results of this study provide insights into the molecular mechanisms of AE-induced hepatic fibrosis.

Digest the Sugar, Kill the Parasite: A New Experimental Concept in Treating Alveolar Echinococcosis.

INTRODUCTION: The E. multilocularis laminated layer (LL) is a heavily glycosylated parasitic structure that plays an important role in protecting the larval stage (metacestode) of this parasite from physiological and immunological host reactions. We elaborated an experimental design with the idea to modify the (glycan) surface of the LL by a targeted digestion. This should allow the host defense to more easily recognize and attack (or kill) the parasite by immune-mediated effects. METHODS: Experimentally, E. multilocularis (clone H95) metacestodes were cultured in vitro with or without addition of α1-3,4,6-galactosidase or ß1-3-galactosidase in the medium. Morphological changes were subsequently measured by microscopy at different time points. Parasites were then recovered at day 5 and reinjected into mice for assessing their viability and infectious status. For finally recovered parasites, the respective load was assessed ex vivo by wet weight measurement, and host-related PD1 and IL-10 levels were determined as the key immunoregulators by using flow cytometry. RESULTS: Our experiments demonstrated that the parasite vesicular structure can be directly destroyed by adding galactosidases into the in vitro culture system, resulting in the fact that the parasite metacestode vesicles could not anymore infect and develop in mice after this glycan digestion. Moreover, when compared to the mice inoculated with E. multilocularis metacestode without galactosidases, PD1 expression was upregulated in CD4+ Teffs from mice inoculated with E. multilocularis metacestode pretreated with ß1-3-galactosidase, with a lower IL-10 secretion from CD4+ Teffs; there was no difference of PD1 and IL-10 expression levels regarding CD4+ Teff from mice inoculated with E. multilocularis metacestode pretreated with α1-3,4,6-galac-tosidase. DISCUSSION: We raised our hypothesis that this "aborting" effect may be linked to an altered PD1 and IL-10 response fine-tuning between immunopathology and immune protection. These findings justify a continuation of these experiments upon therapeutical in vivo administration of the enzymes.

Echinococcus multilocularis (Cestoda, Cyclophyllidea, Taeniidae): functional ultrastructure of the penetration glands and nerve cells within the oncosphere.

The fine structure of the infective hexacanths of Echinococcus multilocularis was examined with particular emphasis on the functional ultrastructure of penetration glands and nerve cells directly involved in the mechanism of initial host infection. The oncosphere contains two types of penetration glands, PG1 and PG2, that differ slightly in size and form a large U-shaped bi-nucleated syncytial structure. The arms of each gland at each end of the U, directed towards the hook region, exit into the tegument peripheral layer between the median and lateral hook pairs. The lobate nuclei of PG1 and PG2 contain prominent spherical nucleoli surrounded by several large electron-dense islands of heterochromatin. The syncytial cytoplasm of both types of glands is rich in free ribosomes, polysomes, several mitochondria, and heavy accumulations of discoid secretory granules of moderate to high electron density. The secretory granules, sg1 and sg2, differ in their ultrastructure and electron density; the sg2 are much smaller and more flattened in shape. A common characteristic for sg1 and sg2, evident under high magnification, is their high electron density and discoidal shape, with two bi-concave surfaces. Both sg1 and sg2 are frequently grouped in characteristic parallel stacks, the "rouleau"-shaped assemblages with sometimes six to ten granules. Two nerve cells of neurosecretory type are situated in the central part of the hexacanth, each one in a deep U-shaped invagination between the two penetration glands. The nuclei of nerve cells contain several large heterochromatin islands closely adjacent to their nuclear membranes. Their cytoplasm is characterized by having membrane-bound, dense-cored neurosecretory-like granules not only in nerve cell perikarya but also in the elongated nerve processes frequently adjacent to gland arms and to both somatic or body musculature, including the complex system of hook muscles. The results of the present study, when supported with literature data on oncospheres of other cestode species, allow for a better understanding of the important role and coordinated functions of three structural components, i.e., oncospheral hooks, penetration glands, and nerve cells, in the mechanism of intermediate host infection. Presence or absence of nerve cells in oncospheres of various cestodes is reviewed, and perspectives on the value and application of research on functional morphology of oncospheres are discussed.

Echinococcus multilocularis (Cestoda, Cyclophyllidea, Taeniidae): origin, differentiation and functional ultrastructure of the oncospheral tegument and hook region membrane.

Both the oncospheral tegument and the hook region membrane (HRM) of Echinococcus multilocularis hexacanths originate from a syncytial binucleate complex that appears in the early stage of morphogenesis and organogenesis of the hexacanth larva. The primordium of this binucleate complex forms a binucleate syncytial cap or "calotte" situated beneath the inner envelope at one pole of the developing embryo. During oncospheral differentiation, the binucleate perikaryon of the syncytial cap is sunk progressively deeper into the central part of the embryo, but remains always connected with the distal cytoplasm by a tendrillar cytoplasmic connection or bridge. Following migration or sinking of the binucleate perikaryon, numerous cytoplasmic vesicles appear in the distal cytoplasm. These vesicles fuse progressively together and form a single large cavity or lacuna. The walls of this cavity are becoming at this point the walls of two delaminated layers: (1) the distal anucleated cytoplasmic layer is transformed into the oncospheral tegument and (2) the proximal thin cytoplasmic layer is transformed into the "hook region membrane". This delamination of the initially compact layer of distal cytoplasm into two layers seems to be closely associated with differentiation of oncospheral hooks, the elongating blades of which protrude progressively into a newly formed cavity. The pressure of hook blades on the hook region membrane appears to facilitate its further separation from the basal layer of distal cytoplasm which is transformed into the peripheral layer of oncospheral tegument. In the mature oncosphere, the surface of this peripheral layer forms a regular brush border of cytoplasmic processes or microvilli and represents the true body covering of the hexacanth. The very thin cytoplasmic connection between the peripheral layer of tegument and binucleate perikaryon appears only very seldom in the ultrathin sections as a narrow cytoplasmic strand and has a plasma membrane that is reinforced by a single row of cortical microtubules. The HRM covers only one pole of the oncosphere and is attached to the oncosphere surface. The HRM is clearly visible in the mature oncosphere and is draped over the hook blades, the sharp points of which are protected by moderately electron-dense caps. Comparison of the above morphology with that of TEM study of the tegument of adult cestodes shows a great similarity as well as homology in the body covering of both larval and adult cestodes.

Origin, differentiation and functional ultrastructure of egg envelopes in the cestode Echinococcus multilocularis Leuckart, 1863 (Cyclophyllidea: Taeniidae).

The origin, differentiation and functional ultrastructure of oncospheral or egg envelopes in Echinococcus multilocularis Leuckart, 1863 were studied by transmission electron microscopy (TEM) and cytochemistry. The purpose of our study is to describe the formation of the four primary embryonic envelopes, namely vitelline capsule, outer envelope, inner envelope and oncospheral membrane, and their transformation into the oncospheral or egg envelopes surrounding the mature hexacanth. This transformation takes place in the preoncospheral phase of embryonic development. The vitelline capsule and oncospheral membrane are thin membranes, while the outer and inner envelopes are thick cytoplasmic layers formed by two specific types of blastomeres: the outer envelope by cytoplasmic fusion of two macromeres and the inner envelope by cytoplasmic fusion of three mesomeres. Both outer and inner envelopes are therefore cellular in origin and syncytial in nature. During the advanced phase of embryonic development, the outer and inner envelopes undergo great modifications. The outer envelope remains as a metabolically active layer involved in the storage of glycogen and lipids for the final stages of egg development and survival. The inner envelope is the most important protective layer because of its thick layer of embryophoric blocks that assures oncospheral protection and survival. This embryophore is the principal layer of mature eggs, affording physical and physiological protection for the differentiated embryo or oncosphere, since the outer envelope is stripped from the egg before it is liberated. The embryophore is very thick and impermeable, consisting of polygonal blocks of an inert keratin-like protein held together by a cementing substance. The embryophore therefore assures extreme resistance of eggs, enabling them to withstand a wide range of environmental temperatures and physicochemical conditions.

Echinococcus multilocularis (Cestoda, Cyclophyllidea, Taeniidae): oncospheral hook morphogenesis.

Ultrastructural characteristics of the oncospheral hook morphogenesis in the taeniid cestode Echinococcus multilocularis Leuckart, 1863, a parasite of medical and veterinary importance, are described. Oncospheral hook primordia appear at the preoncospheral phase of the embryonic development. Within six specialised cells of the so-called oncoblasts, high concentration of mitochondria, numerous ribosomes and extended Golgi regions are involved in hook development. During hook growth, the blade and base gradually protrude outside the oncoblast plasma membrane. The nucleated oncoblast persists around the handles of fully formed hooks. Simultaneously with the hook primordium elongation and transformation into a blade, handle and base, the hook material differentiates into an electron-dense cortex and a less dense inner core. The exit of the blade of each mature hook, protruding from the oncosphere, is surrounded by a circular, septate desmosome and two rigid, dense rings on either side. The pattern of oncospheral hook morphogenesis in E. multilocularis is compared with that of other previously examined cyclophyllidean cestodes. Though oncoblasts have never been observed around the mature hooks, their remnants are often still visible in the fully developed infective oncospheres in particular in some taeniid species so far examined in this respect. The origin and formation of oncospheral hooks in E. multilocularis, evidently differs from that of the rostellar hooks. Thus, although the hooks may have slight similarity at the gross level, they are neither analogous nor homologous structures.

Comparative analysis of Wnt expression identifies a highly conserved developmental transition in flatworms.

BACKGROUND: Early developmental patterns of flatworms are extremely diverse and difficult to compare between distant groups. In parasitic flatworms, such as tapeworms, this is confounded by highly derived life cycles involving indirect development, and even the true orientation of the tapeworm antero-posterior (AP) axis has been a matter of controversy. In planarians, and metazoans generally, the AP axis is specified by the canonical Wnt pathway, and we hypothesized that it could also underpin axial formation during larval metamorphosis in tapeworms. RESULTS: By comparative gene expression analysis of Wnt components and conserved AP markers in the tapeworms Echinococcus multilocularis and Hymenolepis microstoma, we found remarkable similarities between the early stages of larval metamorphosis in tapeworms and late embryonic and adult development in planarians. We demonstrate posterior expression of specific Wnt factors during larval metamorphosis and show that scolex formation is preceded by localized expression of Wnt inhibitors. In the highly derived larval form of E. multilocularis, which proliferates asexually within the mammalian host, we found ubiquitous expression of posterior Wnt factors combined with localized expression of Wnt inhibitors that correlates with the asexual budding of scoleces. As in planarians, muscle cells are shown to be a source of secreted Wnt ligands, providing an explanation for the retention of a muscle layer in the immotile E. multilocularis larva. CONCLUSIONS: The strong conservation of gene expression between larval metamorphosis in tapeworms and late embryonic development in planarians suggests, for the first time, a homologous developmental period across this diverse phylum. We postulate these to represent the phylotypic stages of these flatworm groups. Our results support the classical notion that the scolex is the true anterior end of tapeworms. Furthermore, the up-regulation of Wnt inhibitors during the specification of multiple anterior poles suggests a mechanism for the unique asexual reproduction of E. multilocularis larvae.

Fertilization in the cestode Echinococcus multilocularis (Cyclophyllidea, Taeniidae).

Fertilization in the taeniid cestode Echinococcus multilocularis with uniflagellate spermatozoa was examined by means of transmission electron microscopy (TEM). Fertilization in this species occurs in the oviduct lumen or in the fertilization canal proximal to the ootype, where the formation of the embryonic capsule precludes sperm contact with the oocytes. Cortical granules are not present in the cytoplasm of the oocytes of this species, however, several large bodies containing granular material where frequently observed. Spermatozoa coil spirally around the oocytes and syngamy occurs by lateral fusion of oocyte and sperm plasma membranes. In the ootype, one vitellocyte associates with fertilized oocyte, forming a membranous capsule which encloses both cell types. In this stage, the spirally coiled sperm body adheres partly to the external oocyte surface, and partially enters into the perinuclear cytoplasm. The electron-dense sperm nucleus becomes progressively electron-lucent within the oocyte cytoplasm after penetration. Simultaneously with chromatin decondensation, the elongated sperm pronucleus changes shape, forming a spherical male pronucleus, which attains the size of the female pronucleus. Cleavage begins immediately after pronuclear fusion.

In vivo activity of albendazole in combination with thymol against Echinococcus multilocularis.

Human alveolar echinococcosis (AE) is caused by the fox tapeworm Echinococcus multilocularis and is usually lethal if left untreated. The current strategy for treating human AE is surgical resection of the parasite mass complemented by chemotherapy with benzimidazole compounds. However, reliable chemotherapeutic alternatives have not yet been developed stimulating the research of new treatment strategies such as the use of medicinal plants. The aim of the current study was to investigate the efficacy of the combination albendazole (ABZ)+thymol on mice infected with E. multilocularis metacestodes. For this purpose, mice infected with parasite material were treated daily for 20 days with ABZ (5 mg/kg), thymol (40 mg/kg) or ABZ (5 mg/kg)+thymol (40 mg/kg) or left untreated as controls. After mice were euthanized, cysts were removed from the peritoneal cavity and the treatment efficacy was evaluated by the mean cysts weight, viability of protoscoleces and ultrastructural changes of cysts and protoscoleces. The application of thymol or the combination of ABZ+thymol resulted in a significant reduction of the cysts weight compared to untreated mice. We also found that although ABZ and thymol had a scolicidal effect, the combination of the two compounds had a considerably stronger effect showing a reduction in the protoscoleces viability of 62%. These results were also corroborated by optical microscopy, SEM and TEM. Protoscoleces recovered from ABZ or thymol treated mice showed alterations as contraction of the soma region, rostellar disorganization and presence of blebs in the tegument. However both drugs when combined lead to a total loss of the typical morphology of protoscoleces. All cysts removed from control mice appeared intact and no change in ultrastructure was detected. In contrast, cysts developed in mice treated with ABZ revealed changes in the germinal layer as reduction in cell number, while the treatment with thymol or the ABZ+thymol combination predominantly showed presence of cell debris. On the other hand, no differences were found in alkaline phosphatase (AP), glutamate oxaloacetate transaminase (GOT) and glutamate pyruvate transaminase (GPT) activities between control and treated mice, indicating the lack of toxicity of the different drug treatments during the experiment. Because combined ABZ+thymol treatment exhibited higher treatment efficiency compared with the drugs applied separately against murine experimental alveolar echinococcosis, we propose it would be a useful option for the treatment of human AE.

Treatment of echinococcosis: albendazole and mebendazole--what else?

The search for novel therapeutic options to cure alveolar echinococcosis (AE), due to the metacestode of Echinococcus multilocularis, is ongoing, and these developments could also have a profound impact on the treatment of cystic echinococcosis (CE), caused by the closely related Echinococcus granulosus s.l. Several options are being explored. A viable strategy for the identification of novel chemotherapeutically valuable compounds includes whole-organism drug screening, employing large-scale in vitro metacestode cultures and, upon identification of promising compounds, verification of drug efficacy in small laboratory animals. Clearly, the current focus is targeted towards broad-spectrum anti-parasitic or anti-cancer drugs and compound classes that are already marketed, or that are in development for other applications. The availability of comprehensive Echinococcus genome information and gene expression data, as well as significant progress on the molecular level, has now opened the door for a more targeted drug discovery approach, which allows exploitation of defined pathways and enzymes that are essential for the parasite. In addition, current in vitro and in vivo models that are used to assess drug efficacy should be optimized and complemented by methods that give more detailed information on the host-parasite interactions that occur during drug treatments. The key to success is to identify, target and exploit those parasite molecules that orchestrate activities essential to parasite survival.

Amino ozonides exhibit in vitro activity against Echinococcus multilocularis metacestodes.

Artemisinin is an antimalarial sesquiterpene lactone that contains a 1,2,4-trioxane heterocycle. Dihydroartemisinin and artesunate demonstrated activity against Echinococcus multilocularis metacestodes in vitro but were not effective in a mouse model. In this study, the in vitro effects of a small library of synthetic ozonides (1,2,4-trioxolanes) were investigated. Initial compound screening against E. multilocularis metacestodes was performed at 20µM, and selected ozonides were further assessed in dose-response studies in metacestode cultures and mammalian cells. Transmission electron microscopy (TEM) was employed to characterise compound-induced structural alterations. At 20µM, the most potent ozonides (OZ401, OZ455, OZ491 and OZ494) led to death of ca. 60-100% of the parasites. Subsequent dose-response experiments demonstrated that OZ401, OZ455 and OZ491, which contain an aminopropylether substructure, were the most potent, with 50% inhibitory concentrations ranging from 11µM to 14µM. Cytotoxicity for these three ozonides, assessed in human foreskin fibroblasts, rat hepatoma cells and green monkey epithelial kidney (Vero) cells, was evident only at high concentrations. TEM demonstrated that OZ401 and OZ491 treatment induced considerable metabolic impairment in metacestodes at 1 day post exposure. At Day 3 post exposure, the germinal layer was severely distorted, although some intact cells were still visible, demonstrating that not all cell types in the parasite tissue were equally affected. Complete destruction of the germinal layer was noted at 5 days post exposure. Synthetic ozonides could represent interesting leads that will be further investigated in a suitable in vivo model of E. multilocularis infection.

In vitro efficacy of dicationic compounds and mefloquine enantiomers against Echinococcus multilocularis metacestodes.

The current chemotherapy of alveolar echinococcosis (AE) is based on benzimidazoles such as albendazole and has been shown to be parasitostatic rather than parasiticidal, requiring lifelong duration. Thus, new and more efficient treatment options are urgently needed. By employing a recently validated assay based on the release of functional phosphoglucose isomerase (PGI) from dying parasites, the activities of 26 dicationic compounds and of the (+)- and (-)-erythro-enantiomers of mefloquine were investigated. Initial screening of compounds was performed at 40 µM, and those compounds exhibiting considerable antiparasitic activities were also assessed at lower concentrations. Of the dicationic drugs, DB1127 (a diguanidino compound) with activities comparable to nitazoxanide was further studied. The activity of DB1127 was dose dependent and led to severe structural alterations, as visualized by electron microscopy. The (+)- and (-)-erythro-enantiomers of mefloquine showed similar dose-dependent effects, although higher concentrations of these compounds than of DB1127 were required for metacestode damage. In conclusion, of the drugs investigated here, the diguanidino compound DB1127 represents the most promising compound for further study in appropriate in vivo models for Echinococcus multilocularis infection.

In vitro and in vivo efficacies of mefloquine-based treatment against alveolar echinococcosis.

Alveolar echinococcosis (AE) is caused by the metacestode stage of the fox tapeworm Echinococcus multilocularis and causes severe disease in the human liver, and occasionally in other organs, that is fatal when treatment is unsuccessful. The present chemotherapy against AE is based on mebendazole and albendazole. Albendazole treatment has been found to be ineffective in some instances, is parasitostatic rather than parasiticidal, and usually involves the lifelong uptake of large doses of drugs. Thus, new treatment options are urgently needed. In this study we investigated the in vitro and in vivo efficacy of mefloquine against E. multilocularis metacestodes. Treatment using mefloquine (20 µM) against in vitro cultures of metacestodes resulted in rapid and complete detachment of large parts of the germinal layer from the inner surface of the laminated layer within a few hours. The in vitro activity of mefloquine was dependent on the dosage. In vitro culture of metacestodes in the presence of 24 µM mefloquine for a period of 10 days was parasiticidal, as determined by murine bioassays, while treatment with 12 µM was not. Oral application of mefloquine (25 mg/kg of body weight administered twice a week for a period of 8 weeks) in E. multilocularis-infected mice was ineffective in achieving any reduction of parasite weight, whereas treatment with albendazole (200 mg/kg/day) was highly effective. However, when the same mefloquine dosage was applied intraperitoneally, the reduction in parasite weight was similar to the reduction seen with oral albendazole application. Combined application of both drugs did not increase the treatment efficacy. In conclusion, mefloquine represents an interesting drug candidate for the treatment of AE, and these results should be followed up in appropriate in vivo studies.

Echinococcus multilocularis: the impact of ionizing radiation on metacestodes.

Alveolar echinococcosis is caused by the metacestode stage of the fox tapeworm Echinococcus multilocularis. Current chemotherapeutical options for the treatment of echinococcosis are not satisfactory, and novel drugs and/or other potential means of therapy are needed. E. multilocularis metacestodes are characterized by almost potentially unlimited growth, and also display other features of cancerous tumours. In this study, we exposed metacestodes that were generated in vitro to 50-100 Gy ionizing irradiation, and subsequently investigated the short-term (10-12 days post-treatment) and long-term (14 weeks post-treatment) effects. We found, that in the short-term, no release of alkaline phosphatase (EmAP) activity as a measure for potentially induced damage and loss of viability could be detected, and that the protein expression pattern and protease activities in vesicle fluids and medium supernatants did not alter dramatically following irradiation. However, irradiation was associated with distinct morphological and ultrastructural alterations in the tissue of metacestodes, affecting most notably cell-cell contacts, mitochondrial shape, glycogen-storage cells and lipid droplet formation. These could be detected already at 10 days following treatment and remained as such also in the long-term. In addition, as determined after 14 weeks of culture, irradiation affected the proliferation and the growth of E. multilocularis metacestodes. Thus, we demonstrate that radiotherapy does not have a clear-cut parasitocidal effect, but can lead to metabolic impairment of E. multilocularis metacestodes, as reflected by the distinct morphological and structural alterations induced by irradiation treatment.

Gene silencing in Echinococcus multilocularis protoscoleces using RNA interference.

We investigated the potential of gene silencing in Echinococcus multilocularis protoscoleces using RNA interference (RNAi). For the introduction of siRNA, soaking and electroporation were first examined for their effects on the viability of protoscoleces and their efficacy for siRNA introduction. Consequently, electroporation using 100 V and 800 µF showed the optimal results. This electroporation procedure was then evaluated for its ability to induce RNAi in protoscoleces using siRNAs targeting the 14-3-3 and elp genes. It was found that the levels of 14-3-3 and elp mRNA in 14-3-3 siRNA- and elp siRNA-treated protoscoleces were reduced to 21.8 ± 2.6 and 35.5 ± 0.4% of those of the untreated control by day 3, respectively. Moreover, the target proteins significantly decreased in the siRNA-treated samples by day 15. In the analysis of viability, the untreated control, electroporation control, 14-3-3 siRNA-treated, and elp siRNA-treated samples displayed 98.4 ± 1.4, 83.0 ± 2.5, 58.0 ± 23.0, and 55.1 ± 14.6% viability, respectively, on day 15. In conclusion, we successfully demonstrated that RNAi mediated the knock-down of target gene expression in E. multilocularis protoscoleces at both the transcriptional and translational levels.

Echinococcus multilocularis: the parasite-host interplay.

Alveolar echinococcosis (AE) is a severe chronic helminthic disease caused by the intrahepatic tumor-like growth of the metacestode of Echinococcus multilocularis. Metacestodes are fluid-filled, asexually proliferating vesicles, which are entirely covered by the laminated layer, an acellular carbohydrate-rich surface structure that protects the parasite from immunological and physiological reactions on part of the host. The E. multilocularis metacestode has acquired specific means of manipulating and using the immunological host response to its own advantage. These include the expression of distinct immunoregulatory parasite molecules that manipulate and interfere in the functional activity of macrophages and T cells. Recent research findings have led to a better understanding of the protein- and glycoprotein composition of the laminated layer and the E/S fraction of the metacestode, including Em2- and Em492-antigens, two metacestode antigen fractions that exhibit immunosuppressive or -modulatory properties. Understanding of the events taking place at the host-parasite interface is the key for development of novel immuno-therapeutical and/or chemotherapeutical tools.

In vitro and in vivo effects of 2-methoxyestradiol, either alone or combined with albendazole, against Echinococcus metacestodes.

The metacestode (larval) stage of the tapeworm Echinococcus multilocularis causes alveolar echinococcosis (AE), a mainly hepatic disease characterized by continuous asexual proliferation of metacestodes by exogenous budding, resulting in the tumor-like, infiltrative growth of the parasite lesion. Current chemotherapeutical treatment of AE relies on the use of benzimidazoles (albendazole, mebendazole), but these drugs act parasitostatic rather than parasitocidal, and in case of side effects such as liver toxicity, patients are left without valuable alternatives. 2-ME2 is a natural metabolite of estradiol, with a documented anti-angiogenic and broad spectrum anti-tumour activity. Treatments of in vitro cultured E. multilocularis metacestodes with 2-ME2 (2-10 microM) showed that the drug has an adverse effect on parasite viability. First, 2-ME in vitro treatment downscaled the transcription of the 14-3-3-pro-tumorogenic zeta-isoform in E. multilocularis metacestodes. Second, scanning and transmission electron microscopy showed that the germinal layer of E. multilocularis metacestodes was dramatically damaged following 2-ME2-treatment, and the effect was dose-dependent. Similar results were obtained with E. granulosus metacestodes. Bioassays were performed in mice injected with 2-ME2-treated and albendazole-treated metacestodes, or parasites-treated with both 2-ME and albendazole in combination. These assays indicated that, despite inducing considerable damage in vitro, neither of the drugs was capable of exerting a true parasiticidal effect, but best results were achieved with a combination of both compounds. In vivo treatment in E. multilocularis-infected mice for a period of 6 weeks showed that a combined 2-ME2/albendazole based treatment lead to a reduction in parasite weight, but the results did not show statistical difference from the application of albendazole alone.

[In vitro cultivation of Echinococcus multilocularis metacestodes and observation of their growth].

OBJECTIVE: To observe the growth and development of Echinococcus multilocularis metacestodes under in vitro cultivation. METHODS: Hepatoma cell line was used for the cultivation. The number and morphology of the cysts were observed under light microscope. The parasite tissue was fixed and observed under electron microscope. RESULTS: During the first 21 days of cultivation, metacestodes in cyst-suspension derived cultures increased dramatically, and from the 22nd day on, the number of cysts remained as 6-7 times more than that of the 3rd-4th day of culture. Budding of new cysts was observed and the diameter of the cysts increased as time went on. On the 22nd day, larger cysts occupied 30%. Cysts were found with morphology between protoscolex and metacestode. CONCLUSION: An in vitro cultivation for the cysts of E. multilocularis has been established and basic feature of growth and development of the larvae observed.

In vitro metacestodicidal activities of genistein and other isoflavones against Echinococcus multilocularis and Echinococcus granulosus.

Echinococcus multilocularis and Echinococcus granulosus metacestode infections in humans cause alveolar echinococcosis and cystic echinococcosis, respectively, in which metacestode development in visceral organs often results in particular organ failure. Further, cystic hydatidosis in farm animals causes severe economic losses. Although benzimidazole derivatives such as mebendazole and albendazole are being used as therapeutic agents, there is often no complete recovery after treatment. Hence, in searching for novel treatment options, we examined the in vitro efficacies of a number of isoflavones against Echinococcus metacestodes and protoscoleces. The most prominent isoflavone, genistein, exhibits significant metacestodicidal activity in vitro. However, genistein binds to the estrogen receptor and can thus induce estrogenic effects, which is a major concern during long-term chemotherapy. We have therefore investigated the activities of a number of synthetic genistein derivatives carrying a modified estrogen receptor binding site. One of these, Rm6423, induced dramatic breakdown of the structural integrity of the metacestode germinal layer of both species within 5 to 7 days of in vitro treatment. Further, examination of the culture medium revealed increased leakage of parasite proteins into the medium during treatment, but zymography demonstrated a decrease in the activity of metalloproteases. Moreover, two of the genistein derivatives, Rm6423 and Rm6426, induced considerable damage in E. granulosus protoscoleces, rendering them nonviable. These findings demonstrate that synthetic isoflavones exhibit distinct in vitro effects on Echinococcus metacestodes and protoscoleces, which could potentially be exploited further for the development of novel chemotherapeutical tools against larval-stage Echinococcus infection.

A new technique to avoid losing the strains of Echinococcus multilocularis during passaging.

OBJECTIVE: To examine the survival of Echinococcus multilocularis (E. multilocularis) and the formation of protoscoleces, under refrigerated conditions over a 43-day observation period. METHODS: We conducted this study in Ege University, School of Medicine, from May-December, 2004. We included 4 healthy females and 2 males, 8-12 week old M. unguiculatus species (approximately 60-70 gr) for the study, as they are known to be susceptible to E. multilocularis. In this experimental study, we aimed to define a technique to keep the strains during these passages. RESULTS: We found preserved viability and virulence of E. multilocularis stored in RPMI 1640 plus 10% fetal calf serum at +4 degrees C. We accomplished the infection of the Meriones unguiculatus after in-vivo passaging from that flask, which we kept at +4 degrees C, and this proves the viability of protoscoleces and membranous structures perfectly at the 43rd day. CONCLUSION: We also found that E. multilocularis metacestodes and the formation of protoscoleces keep their viability up to 60 days and virulence up to 43 days under this condition. We recommend storing an extra flask during each passage as a precaution against losing strains.