Echinococcus granulosus: first report of microcysts formation from protoscoleces of cattle origin using the in vitro vesicular culture technique

Evaluation of structural changes of Echinococcus granulosus protoscoleces following exposure to different protoscolicidal solutions evaluated by differential interference contrast microscopy

The present study was aimed to assess the structural changes in protoscoleces of Echinococcus granulosus sensu stricto following exposure to different natural and chemical protoscolicidal agents using differential interference contrast (DIC)/Nomarski microscopy. Protoscoleces of sheep's liver cysts were collected aseptically. Individually, about 1000 protoscoleces were exposed to 0.5% silver nitrate, 20% hypertonic saline solution, 0.5% cetrimide solution and two different concentrations of garlic chloroformic extraction as well as phosphate-buffered saline (PBS). The protoscoleces viability was assessed using 0.1% eosin solution, and structural modifications in the protoscoleces were examined by DIC/Nomarski microscopy. The results revealed the degeneration of the tegument, disorganization of the hooks, and reduction of the size of the protoscoleces exposed to cetrimide, hypertonic sodium chloride, and silver nitrate. Furthermore, calcareous corpuscles became blurred and opaque and their numbers decreased in all the exposed samples except, those in PBS. The exposed protoscoleces to cetrimide and hypertonic sodium chloride solution showed extensive degeneration of the tegument and disorganization of the hooks. In the group exposed to 200 mg/ml chloroformic garlic extract, the protoscoleces' width decreased. The length, width, and number of calcareous corpuscles also decreased significantly in the silver nitrate-exposed protoscoleces. The study concludes that protoscoleces exposed to different solutions; cetrimide 0.5% and hypertonic sodium chloride 20% caused more pronounced structural changes in the exposed protoscoleces. These changes were well demonstrated by DIC microscopy and can be used as a supplementary tool to evaluate the effects of protoscolicidal agents.

Supplementary Information

The online version contains supplementary material available at 10.1007/s12639-023-01632-4.

The effects of glucose and ascorbic acid on in vitro development of Echinococcus granulosus metacestodes

Echinococcus granulosus-developed metacestodes in the cultured medium are used for the assessment of its susceptibility to different compounds; however, this procedure is time-consuming and risky. In the present study, aspirated protoscoleces from the infected sheep were used to evaluate the effects of glucose, as an energy source, as well as ascorbic acid, as an antioxidant vitamin, on larval development. Protoscoleces were maintained in RPMI₁₆₄₀ culture media containing 10% fetal calf serum, as well as different concentrations of glucose (4, 6, and 8 mg/ml) and ascorbic acid (25, 50, and 100 µg/ml). A culture medium containing 4 mg/ml of glucose was served as the control. Larger cysts were achieved in a shorter time from the medium enriched with 6 mg/ml of glucose (740 ± 20 µm) compared to the control group (420 ± 40 µm). However, in the groups treated with ascorbic acid, the number of cysts was higher in 100 µg/ml (32.5 ± 0.7) compared to the control group (12.5 ± 0.7). Additionally, the mature cysts were achieved on the 7th day of cultivation with 100 µg/ml of ascorbic acid compared to 18 days in the control group.

In vitro evaluation of albendazole-loaded nanostructured lipid carriers on Echinococcus granulosus microcysts and their prophylactic efficacy on experimental secondary hydatidosis

To enhance the therapeutic effects of albendazole (ABZ) on Echinococcus granulosus protoscoleces and metacestodes, ABZ-loaded nanostructured lipid carriers (ABZ-NLCs) are prepared by the hot high-speed homogenization method. Protoscoleces and microcysts were treated in vitro with free ABZ and ABZ-NLCs (concentrations of 1, 5, and 10 μg/ml), and the corresponding effects were monitored by methylene blue exclusion test and scanning and transmission electron microscopy. Chemoprophylactic treatment was performed on Balb/C mice 1 day before intraperitoneal injection of viable protoscoleces. The drugs were administered daily by intragastric inoculation for a period of 30 days. The prophylactic efficacy was assessed based on the number and weight of cysts developed in treated mice. The ultrastructural alterations in cysts were examined by transmission electron microscopy. After 18 days, all the protoscoleces incubated with 10 μg/ml ABZ-NLCs were killed, while 51.25 ± 4.03% of the protoscoleces incubated with 10 μg/ml free ABZ were still viable. Microcysts treated with ABZ-NLCs underwent degenerative alterations in a shorter time than when free ABZ was applied. The mean weight of the cysts recovered from mice of ABZ-NLCs group was significantly lower than that of the free ABZ group (P < 0.05), yielding prophylactic efficacy of 92.45% and 38.53%, respectively. The cysts treated with ABZ-NLCs showed marked ultrastructural changes in the germinal layer. This study demonstrated that both in vitro and in vivo treatments with ABZ-NLCs are significantly more efficient than treatment with free ABZ against E. granulosus protoscoleces, metacestodes, and prevention of cyst development in mice.

Transcriptomic Features of Echinococcus granulosus Protoscolex during the Encystation Process

Cystic echinococcosis (CE) is a zoonotic infection caused by Echinococcus granulosus larvae. It seriously affects the development of animal husbandry and endangers human health. Due to a poor understanding of the cystic fluid formation pathway, there is currently a lack of innovative methods for the prevention and treatment of CE. In this study, the protoscoleces (PSCs) in the encystation process were analyzed by high-throughput RNA sequencing. A total of 32,401 transcripts and 14,903 cDNAs revealed numbers of new genes and transcripts, stage-specific genes, and differently expressed genes. Genes encoding proteins involved in signaling pathways, such as putative G-protein coupled receptor, tyrosine kinases, and serine/threonine protein kinase, were predominantly up-regulated during the encystation process. Antioxidant enzymes included cytochrome c oxidase, thioredoxin glutathione, and glutathione peroxidase were a high expression level. Intriguingly, KEGG enrichment suggested that differentially up-regulated genes involved in the vasopressin-regulated water reabsorption metabolic pathway may play important roles in the transport of proteins, carbohydrates, and other substances. These results provide valuable information on the mechanism of cystic fluid production during the encystation process, and provide a basis for further studies on the molecular mechanisms of growth and development of PSCs.

Antiparasitic effects of Zataria multiflora essential oil nano-emulsion on larval stages of Echinococcus granulosus

Various protoscolicidal agents are indicated for the prevention of recurrence of cystic echinococcosis caused by the larval stage of Echinococcus granulosus; however, most of these chemicals have adverse side effects. This study evaluated the effects of Zataria multiflora essential oil (ZEO) nano-emulsion and emulsion at the concentrations of 1, 2, 5, 10, 15, and 20 µl/ml on E. granulosus protoscoleces. Albendazole (5 mg/ml), normal saline, and nano-emulsion without ZEO served as control groups. Optimal concentrations of ZEO nano-emulsion and emulsion on the microcysts were also investigated. ZEO emulsion at a concentration of 20 µl/ml for the duration of 15 min and nano-emulsion for the duration of 10 min resulted in the death of 100% of the protoscoleces. Additionally, densely packed aggregates were formed inside the microcysts treated with ZEO nano-emulsion and emulsion at a concentration of 20 µl/ml after 40 min, but the complete destruction of laminated layers did not occur. The results indicate that ZEO nano-emulsions have a higher protoscolicidal effect than its emulsion, but these two compounds had similar effects on microcysts.

Echinococcus granulosus: Insights into the protoscolex F-actin cytoskeleton

Echinococcus granulosus is a cestode parasite whose cytoskeleton plasticity allows it to enter and develop inside its hosts, completing thus its life cycle. We focused our attention on F-actin organization and distribution in E. granulosus protoscoleces (PSC) in order to contribute to the knowledge of the parasite cytoskeleton. In particular, we addressed some aspects of F-actin rearrangements in PSC at different stages of the evagination/invagination process. The use of light microscopy allowed us to identify different PSC structures and phalloidin staining displayed a parasite's highly organized F-actin cytoskeleton. Suckers exhibit an important musculature composed of a set of radial fibers. At the rostellum, the F-actin filaments are arranged in a bulbar shape with perforations that appear to be the attachment places for the hooks. Also, "circular" structures of F-actin were identified, which remind the flame cells. Furthermore, parasite F-actin filaments, unevenly distributed, seem to have remained substantially unchanged during the evagination/invagination process. Finally, we showed that the scolex of an evaginated E. granulosus PSC reinvaginates in vitro without any treatment.

Validation of the methylene blue test for assessment of viability of protoscolices from hydatid cysts

Background:

Methylene blue was used as a vital stain for the assessment of viability of protoscolices from hydatid cysts taking advantage of the chemical nature of the dye as a redox indicator and the kinetically distinct molecular transfer systems of Echinococcus protoscolex for uptake of materials across the tegument.

Aim:

The present study attempts to validate the application of methylene blue staining for assessment of viability of protoscolices.

Methods:

To validate the criteria by which viability is assessed, control tests were performed using normal protoscolices and protoscolices previously treated with distilled water at 60°C for 5 minutes. Performance of methylene blue was further studied at intervals over a period of 50 minutes after protoscolex exposure using 1% dye concentration.

Results:

Normal protoscolices were able to adsorb and reduce the dye and have, therefore, lost the blue color. Protoscolices previously treated with warm water on the other hand, being functionally dead, failed to reduce the adsorbed dye and permanently retained the blue color. Results also indicated that a clear distinction between dead and alive protoscolices can be made within 1 minute. Reading of the test after 10 minutes would be misleading giving a false result.

Conclusion:

These findings suggest that viability of protoscolices can be assessed on the basis of acquisition and loss/retaining of the dye blue color. Increasing the concentration of methylene blue to 1% was noticed to be associated with remarkable enhancement of contractility, sucker movement, and evagination. Such an excitatory action of the dye may be exploited in viability tests which adopt these criteria.

Comparison of different staining methods for determination of viability on Mesocestoides vogae tetrathyridia

Mesocestoides vogae is widely employed as a model for studying the biology, differentiation, and experimental chemotherapy of cestodes. Currently, there are few techniques to measure the viability of M. vogae metacestodes during pharmacological experiments. The aim of the present work was to evaluate and compare different staining techniques to determine objectively the viability of M. vogae tetrathyridia. Eosin (0.05% w/v), methylene blue (0.01% w/v), propidium iodide (PI, 2 μg/ml), and fluorescein diacetate (FDA, 0.5 μg/ml) solutions were tested against live, heat-killed (cultivated at 65 °C for 2 h) and thymol-treated tetrathyridia (50 and 250 μg/ml). Parasites were counted under a dissecting microscope or a fluorescence compound microscope, as appropriate. Studies by scanning electron microscope were performed to compare the ultrastructural damage with the viability of parasites. After comparing the performance of different dyes, we chose the eosin staining technique because its simplicity, rapidity, sensitivity, low cost and fidelity.

Efficiency of flubendazole-loaded mPEG-PCL nanoparticles: A promising formulation against the protoscoleces and cysts of Echinococcus granulosus

None of the existing drugs can effectively treat the human cystic echinococcosis. This study aimed to improve the efficacy of flubendazole (FLBZ) against the protoscoleces and cysts of Echinococcus granulosus by preparing polymeric FLBZ-loaded methoxy polyethylene glycol-polycaprolactone (mPEG-PCL) nanoparticles. The protoscoleces and microcysts were treated with FLBZ-loaded mPEG-PCL nanoparticles (FLBZ-loaded nanoparticles) and free FLBZ at the final concentrations of 1, 5, and 10 μg/mL for 27 and 14 days, respectively. The chemoprophylactic efficacy of the drugs was evaluated in experimentally infected mice. The nanoparticles were stable for 1 month, with an average size of 101.41 ± 5.14 nm and a zeta potential of -19.13 ± 2.56 mV. The drug-loading and entrapment efficiency of the FLBZ-loaded nanoparticles were calculated to be 3.08 ± 0.15% and 89.16 ± 2.93%, respectively. The incubation of the protoscoleces with the 10 μg/mL nano-formulation for 15 days resulted in 100% mortality, while after incubation with the 10 μg/mL free FLBZ, the viability rate of the protoscoleces was only 44.0% ± 5.22%. Destruction of the microcysts was observed after 7 days' exposure to the FLBZ-loaded nanoparticles at a concentration of 10 μg/mL. The in vivo challenge showed a significant reduction in the weight and number of the cysts (P <  0.05) in the mice treated with the FLBZ-loaded nanoparticles, yielding efficacy rates of 94.64% and 70.21%, correspondingly. Transmission electron microscopy revealed extensive ultrastructural damage to the cysts treated with the FLBZ-loaded nanoparticles. The results indicated that the FLBZ-loaded nanoparticles were more effective than the free FLBZ against the protoscoleces and cysts of E. granulosus both in vitro and in vivo.

In vitro and in vivo effects of chitosan-praziquantel and chitosan-albendazole nanoparticles on Echinococcus granulosus Metacestodes

Cystic echinococcosis (CE), which is caused by the metacestode of Echinococcus granulosus, is one of the most important zoonoses affecting humans. Benzimidazoles (in particular albendazole) and praziquantel (PZQ) are effective against CE, but poor water solubility of these agents often leads to inadequate results. Here, we evaluate the effects of chitosan-albendazole (ChABZ) and chitosan-praziquantel (ChPZQ) nanoparticles as a new formulation on hydatid cysts both in vitro and in vivo. Developed microcysts in culture were treated with different concentrations of ChABZ and ChPZQ nanoparticles (either alone or in combination), and ABZ + PZQ suspension. The viability rate of microcysts was used to evaluate the drug efficacies. In addition, the prophylactic and therapeutic effects of the drugs were studied on infected DBA/2 mice. Transmission electron microscopy was used to observe the ultra-structural changes. The viability rate of microcysts and differences in cyst weights were compared by ANOVA, and the cyst numbers were compared using the Kruskal-Wallis test. The combination of ChABZ + ChPZQ nanoparticles was more effective than the ABZ + PZQ suspension in vitro (p < 0.05). In prophylaxy, a significant reduction was observed both in size and in number of the cysts in ChABZ + ChPZQ nanoparticle groups compared with the control group (p < 0.05). In the therapeutic stage, however, this treatment only reduced the cyst numbers. Degeneration of the microcysts treated with the drugs was evident in the ultra-structural imaging. Overall, the nanoparticulate drugs were more effective than their suspension counterparts, but further studies are recommended to evaluate the full potential of these nanoparticles in the treatment of human CE.

Could thymol have effectiveness on scolices and germinal layer of hydatid cysts?

Scolicidal solutions remain indispensable in the treatment of hydatid cyst disease. Properties of an ideal solution would be inexpensiveness and the promotion of a rapid and complete scolicidal effect with an absence of local and systemic side effects. From this point of view, no ideal solution and agents have been described yet. The aim of the present work was to determine the in vitro effect of high concentrations of thymol against protoscoleces, microcyst and cyst of Echinococcus granulosus and to evaluate its possible role as a scolicidal agent during surgery or PAIR. After short exposure times, a rapid effect was observed depending on the parasitic material. After 2 min of exposure to thymol, viability of protoscoleces was approximately 1.3% at a concentration of 250 μg/ml. The protoscolicidal effect is dose and time dependent. The results of the in vitro treatment with thymol were similar in both microcysts and secondary murine cysts. The employment of SEM and TEM allowed us to examine, at an ultrastructural level, the effects induced by thymol on E. granulosus protoscoleces, microcysts and murine cysts. In conclusion, the data obtained clearly demonstrated that thymol caused severe damages to the parasite even after short incubation times. This fact and the lack of toxicity at the evaluated concentrations, allow us to propose it as a possible scolicidal agent during hydatid cysts surgery and/or PAIR.

Echinococcus granulosus tegumental enzymes as in vitro markers of pharmacological damage: a biochemical and molecular approach

Cystic echinococcosis is a chronic, complex, and neglected disease. Novel therapeutical tools are needed to optimize human treatment. A number of compounds have been investigated, either using in vitro cultured parasites and/or applying in vivo rodent models. Although some of these compounds showed promising activities in vitro, and to some extent also in the rodent models, they have not been translated into clinical applications. Membrane enzyme activities in culture supernatants of treated protoscoleces with calcium modulator drugs and anthelmintic drugs were measured and provided an indication of compound efficacy. This work describes for the first time the detection of alkaline phosphatase, gamma-glutamyl-transpeptidase and acetylcholinesterase activities in supernatants of in vitro treated Echinococcus granulosus protoscoleces. Marked differences on the enzymatic activities in supernatants from drug treated cultures were detected. We demonstrated that those genes that show the highest degree of conservation when compared to orthologs, are constitutively and highly expressed in protoscoleces and metacestodes. Due to high sensibility and the lack of activity in supernatants of intact protoscoleces, gamma-glutamyl-transpeptidase is proposed as the ideal viability marker during in vitro pharmacological studies against E. granulosus protoscoleces.

Comparative performances of flubendazole and albendazole in cystic echinococcosis: ex vivo activity, plasma/cyst disposition, and efficacy in infected mice

The need to identify improved therapy against cystic echinococcosis (CE) has motivated pharmacology-based research. The comparative pharmacological performances of the benzimidazole compounds flubendazole (FLBZ) and albendazole (ABZ) were addressed here. The goals of the work were as follows: (i) to evaluate the ex vivo activities of FLBZ, ABZ, and their respective metabolites against Echinococcus granulosus protoscoleces, (ii) to compare the plasma and cyst disposition kinetics for the two drugs in infected mice, and (iii) to compare the clinical efficacies of FLBZ and ABZ against CE in mice. For the ex vivo study, E. granulosus protoscoleces were incubated with FLBZ, reduced FLBZ (R-FLBZ), ABZ, and ABZ-sulfoxide (ABZSO) (10 nmol/ml). Protoscolex viability was monitored by the methylene blue exclusion test and scanning electron microscopy (SEM). For the pharmacokinetic study, BALB/c mice with CE were allocated to two different groups and orally treated with either FLBZ or ABZ (5 mg/kg of body weight), both formulated as a cyclodextrin-based solution. Blood and cyst samples were taken up to 12 h posttreatment and analyzed by high-performance liquid chromatography (HPLC). For the efficacy study, CE-infected BALB/c mice were divided into three groups: the unmedicated control group and the FLBZ- and ABZ-treated groups. Oral treatments were performed twice a day during 25 days. After treatment, all animals were killed and the weight of the cysts was recorded. Loss of protoscolex viability was observed after drug incubation. FLBZ was detected in plasma (area under the concentration-versus-time curve [AUC] = 1.8 μg · h/ml) and cysts (AUC = 0.3 μg · h/g) collected from treated infected animals. Conversely, ABZSO was the only active molecule measured in plasma (AUC = 4.4 μg·h/ml) and cysts (AUC = 1.5 μg·h/g) after ABZ treatment. FLBZ induced a 90% reduction in cyst weight in comparison to those collected from untreated control mice (P < 0.05). However, no differences in cyst weight were observed between the ABZ-treated (8.2 g) and unmedicated control (10.5 g) groups. Due to these results, we consider flubendazole to have great potential to become a drug of choice in the treatment of cystic echinococcosis.

Flubendazole in cystic echinococcosis therapy: pharmaco-parasitological evaluation in mice

Cystic echinococcosis (CE) caused by the parasite Echinococcus granulosus is an important public health problem worldwide. Flubendazole has shown poor in vivo efficacy against CE in humans and mice. However, flubendazole causes marked in vitro damage on E. granulosus protoscoleces. The goals of the current work were: a) to compare the plasma pharmacokinetic behaviour of flubendazole formulated as a hydroxipropyl-beta-cyclodextrin aqueous solution or as a carboxymethyl celullose suspension, both given by the oral route to mice, b) to compare flubendazole clinical efficacy in secondary CE in mice after its administration as both formulations, c) to evaluate the flubendazole-induced morphological changes in hydatid cysts recovered from infected mice treated with both drug formulations. Flubendazole administration as a solution resulted in significantly higher plasma maximum concentration (C(max)) and area under the concentration-time curve (AUC) values compared to those obtained after the flubendazole-suspension treatment. This enhanced drug availability correlated with an increased efficacy against secondary CE in mice observed for the flubendazole-solution formulation, while the suspension formulation did not reach differences with the untreated control group. Similar ultrastructural changes were observed in cysts recovered from flubendazole (both formulations) treated mice after 3, 6 and 9months of infection, although the damage extension was greater after treatment with the flubendazole-solution formulation.

Albendazole treatment in cystic echinococcosis: pharmacokinetics and clinical efficacy of two different aqueous formulations

The pharmacokinetic (PK) behaviour and clinical efficacy of albendazole (ABZ) against hydatid cysts in mice were assessed after treatment with two different ABZ pharmaceutical formulations. BalbC mice received ABZ (0.5 mg/kg) prepared either as solution or suspension (50 microg/ml) for oral administration (PK study). Blood samples were collected up to 16 h post-treatment and processed to measure ABZ/metabolites concentrations in plasma. The clinical efficacy assessment was performed in BalbC mice infected 8 months earlier with Echinococcus granulosus protoscoleces. Infected animals were allocated into three experimental treatment groups: (a) untreated control, (b) ABZ-solution treated, (c) ABZ-suspension treated. Both treated groups received ABZ (0.5 mg/kg) administered under two different therapeutic schemes: dosing every 48 h over 30 days (regimen I) or treated every 12 h during 15 days (regimen II). Experimental mice were sacrificed 12 h after treatment, and cysts were recovered, weighed and processed for transmission electron microscopy. Enhanced ABZ sulphoxide (the main ABZ metabolite) concentration profiles were measured in animals treated with the ABZ solution. Any positive clinical response was obtained after treatment every 48 h (30 days therapy). However, consistent with the observed PK results, both ABZ formulations were clinically effective in infected mice treated with a 12-h dosing interval (15 days therapy).

In vitro and in vivo effects of flubendazole on Echinococcus granulosus metacestodes

The aim of the present work was to determine the efficacy of flubendazole (FLBZ) against Echinococcus granulosus metacestodes by using in vitro and in vivo models. Groups of 50 microcysts developed in vitro, and groups of 10 peritoneal cysts were obtained from Balb C mice with experimental secondary infections of 8 months. The cysts were placed in Leighton tubes containing 10 ml of culture medium. FLBZ was added to the medium resulting in final concentrations of 5 and 1 microg/ml for mycrocysts treatment and 10, 5, and 1 microg/ml for murine cysts treatment. In vivo treatment was performed on 20 mice that developed an experimental secondary hydatid disease over a period of 11 months. FLBZ was given (1.5 mg/kg) by the oral route once a day for 50 days. A loss of turgidity was detected in all in vitro drug treated cysts irrespective of the drug concentration or parasite origin. Inspection of treated cysts by scanning electron microscopy (SEM) revealed that the germinal layer lost it characteristic multicelular structure. These results were confirmed on the ultrastructural level by transmission electron microscopy (TEM), treated metacestodes had undergone considerable degenerative changes after the in vitro treatment. The results obtained after the in vivo treatment with FLBZ showed no significant difference between the control and treated groups related to the weight of cyst masses. However, the ultrastructural study at TEM of cysts that developed in mice from the treated group revealed alterations in the germinal layer with the presence of numerous vacuoles. With regard to the ultrastructural study at SEM, only cellular debris of the germinal layer could be seen. In conclusion, the data obtained clearly demonstrate that in vitro and in vivo treatment with FLBZ is effective against E. granulosus metacestodes.