The potential of artemether for the control of schistosomiasis

Unrevealing the therapeutic potential of artesunate against emerging zoonotic Babesia microti infection in the murine model

Babesiosis, a zoonotic blood protozoal disease, threatens humans and animals and is difficult to treat due to growing antimicrobial resistance. The study aimed to investigate the therapeutic efficacy of artesunate (AS), a well-known derivative of artemisinin, against Babesia microti (B. microti) using a murine infection model. Male BALB/c mice (6 weeks old; 15 per group) were chosen and randomly divided into 1) the control group, 2) the B. microti group, and 3) the B. microti + artesunate treatment groups. AS treatment at 2 mg/kg, 4 mg/kg, and 8 mg/kg of body weight significantly (p < 0.05) reduced the B. microti load in blood smears in a dose-dependent manner. Additionally, AS treatment mitigated the decrease in body weight and restored the normal state of the liver and spleen viscera index compared to the B. microti-infected group after 28 days. Hematological analysis revealed significant increases in RBC, WBC, and PLT counts post-AS treatment compared to the B. microti-infected group. Furthermore, AS administration resulted in significant reductions in total protein, bilirubin, ALT, AST, and ALP levels, along with reduced liver and spleen inflammation and lesions as observed through histopathological analysis. AS also elicited dose-dependent changes in mRNA and protein expression levels of apoptotic, proinflammatory, and anti-inflammatory cytokines in the liver compared to the control and B. microti-infected groups. Immunolabeling revealed decreased expression of apoptotic and inflammation-related proteins in AS-treated hepatic cytoplasm compared to the B. microti-infected group. AS also in dose-dependent manner decreased apoptotic protein and increased Bcl-2. Overall, these findings underscore the potential of AS as an anti-parasitic candidate in combating B. microti pathogenesis in an in vivo infection model, suggesting its promise for clinical trials as a treatment for babesiosis.

Resolution of systemic complications in Schistosoma mansoni-infected mice by concomitant treatment with praziquantel and Schisandrin B

Schistosomiasis is a tropical parasitic disease, in which the major clinical manifestation includes hepatosplenomegaly, portal hypertension, and organs fibrosis. Clinically, treatment of schistosomiasis involves the use of praziquantel (PZQ) and supportive care, which does not improve the patient's outcome as liver injuries persist. Here we show the beneficial effects of using PZQ in combination with Schisandrin B (Sch B). Concomitant treatment with PZQ and Sch B resulted in a significant improvement of hepatosplenomegaly and fibrosis, compared with single-agent treatment. We also demonstrated that PZQ-Sch B treatment ameliorates injuries in the lungs and intestine better than the sole use of PZQ or Sch B. In addition, PZQ-Sch B treatment improves the survival of S. mansoni-infected mice, and the treatment combination yields better therapeutic outcomes, as indicated by a partial improvement in neurological function. These results were accompanied by a reduction in neurological injuries. Collectively, we suggest that PZQ-Sch B concomitant therapy may be useful to alleviate schistosomiasis-associated liver injuries and prevent systemic complications.

Alkaloids in Contemporary Drug Discovery to Meet Global Disease Needs

An overview is presented of the well-established role of alkaloids in drug discovery, the application of more sustainable chemicals, and biological approaches, and the implementation of information systems to address the current challenges faced in meeting global disease needs. The necessity for a new international paradigm for natural product discovery and development for the treatment of multidrug resistant organisms, and rare and neglected tropical diseases in the era of the Fourth Industrial Revolution and the Quintuple Helix is discussed.

Molecular basis of inhibition of Schistosoma japonicum glutathione transferase by ellagic acid: Insights into biophysical and structural studies

Schistosoma japonicum glutathione transferase (Sj26GST), an enzyme central to detoxification of electrophilic compounds in the parasite, is upregulated in response to drug treatment. Therefore, Sj26GST may serve as a potential therapeutic target for the treatment of schistosomiasis. Herewith, we describe the structural basis of inhibition of Sj26GST by ellagic acid (EA). Using 1-chloro-2,4-dinitrobenzene and reduced glutathione (GSH) as Sj26GST substrates, EA was shown to inhibit Sj26GST activity by 66 % with an IC50 of 2.4 μM. Fluorescence spectroscopy showed that EA altered the polarity of the environment of intrinsic tryptophan and that EA decreased (in a dose-dependent manner) the interaction between Sj26GST and 8-Anilino-1-naphthalenesulfonate (ANS), which is a known GST H-site ligand. Thermodynamic studies indicated that the interaction between Sj26GST and EA is spontaneous (ΔG = -29.88 ± 0.07 kJ/mol), enthalpically-driven (ΔH = -9.48 ± 0.42 kJ/mol) with a favourable entropic change (ΔS = 20.40 ± 0.08 kJ/mol/K), and with a stoichiometry of four EA molecules bound per Sj26GST dimer. The 1.53 Å-resolution Sj26GST crystal structure (P 21 21 21 space group) complexed with GSH and EA shows that EA binds primarily at the dimer interface, stabilised largely by Van der Waal forces and H-bonding. Besides, EA bound near the H-site and less than 3.5 Å from the ε-NH2 of the γ-glutamyl moiety of GSH, in each subunit.

In vitro activities of crude extracts and triterpenoid constituents of Dichapetalum crassifolium Chodat against clinical isolates of Schistosoma haematobium

Dichapetalum crassifolium Chodat (Dichapetalaceae) is widely distributed in Africa, Tropical Asia and Latin America. As part of our quest for potential bioactive lead compounds for various neglected tropical diseases, we report the anti-schistosomal potential of the crude extracts and chemical constituents of the stems and roots of Dichapetalum crassifolium. Column chromatography of extracts of the stems and roots led to the isolation and identification of three oleanane-type triterpenoids, friedelan-3β-ol (1), friedelan-3-one (2), and maslinic acid (3); the ursane-type tritepenoid, pomolic acid (4) and the dammarane-type tetracyclic triterpenoids, dichapetalin A (5) and dichapetalin M (6). Dichapetalin A was isolated from only the roots. Isolated compounds were identified by comparison of their physico-chemical and spectral data with published data. The highest in vitro anti-schistosomal activity (IC₅₀) of the crude extracts against clinical isolates of Schistosoma haematobium (Bilharz 1852) was 248.6 μg/ml for the ethyl acetate extract of the root while dichapetalin A gave the highest activity at 151.1 μg/ml among the compounds compared with the 15.5 μg/ml for the standard drug, praziquantel. The rest of the compounds showed activities in the order 177.9, 191.0, and 378.1 μg/ml respectively for mixture of β-sitosterol/stigmasterol, dichapetalin M and friedelan-3-one. The least active extract was the methanol extract of the stem (893.7 μg/ml). The constituents of D. crassifolium showed activity against the S. haematobium that are below praziquantel. It is envisaged that the presence of multiple layers and the minute sizes of pores in the egg shells, may preclude penetration of eggs by the compounds.

Therapeutic efficacy of a newly synthesized benzimidazole compound BTP-OH against murine schistosomiasis mansoni

Because of the increasingly emerging praziquantel resistance, there is a crucial need to develop new anti-schistosomal agents. This work was conducted to assess the therapeutic efficacy of a new benzimidazole compound (BTP-OH) in mice experimentally infected with Schistosoma mansoni. A total of 40 Swiss albino female mice were divided into an infected untreated group and three infected treated groups (using praziquantel and BTP-OH). The compound activity was evaluated through parasitological, histopathological and scanning electron microscopy studies. Praziquantel and BTP-OH at both doses significantly reduced male (75%, 42.67% and 61.08%, respectively), female (71.45%, 48.94% and 68.13%, respectively) and total worm burden (75.21%, 42.42% and 62.28%, respectively), as well as tissue egg load in the liver (71.22%, 42.12% and 66.04%, respectively). In oogram, praziquantel significantly increased the percentage of dead eggs (65.89%), while BTP-OH significantly reduced the percentage of immature eggs (30.43% and 19.64%). BTP-OH significantly diminished granuloma count (33.87% and 44.77%) and diameter (39.23% and 49.40%), and caused ultrastructural changes in the tegument of adult schistosomes. This study provides evidence for the schistosomicidal efficacy of BTP-OH. However, future studies are needed to elucidate the full mechanisms of action and effects of BTP-OH on other human schistosomes.

Proteomic analysis of adult Schistosoma mekongi somatic and excretory-secretory proteins

Schistosoma mekongi is a causative agent of human schistosomiasis. There is limited knowledge of the molecular biology of S. mekongi and very few studies have examined drug targets, vaccine candidates and diagnostic biomarkers for S. mekongi. To explore the biology of S. mekongi, computational as well as experimental approaches were performed on S. mekongi males and females to identify excretory-secretory (ES) proteins and proteins that are differentially expressed between genders. According to bioinformatic prediction, the S. mekongi ES product was approximately 4.7% of total annotated transcriptome sequences. The classical secretory pathway was the main process to secrete proteins. Mass spectrometry-based quantification of male and female adult S. mekongi proteins was performed. We identified 174 and 156 differential expression of proteins in male and female worms, respectively. The dominant male-biased proteins were involved in actin filament-based processes, microtubule-based processes, biosynthetic processes and homeostatic processes. The major female-biased proteins were related to biosynthetic processes, organelle organization and signal transduction. An experimental approach identified 88 proteins in the S. mekongi secretome. The S. mekongi ES proteins mainly contributed to nutrient uptake, essential substance supply and host immune evasion. This research identifies proteins in the S. mekongi secretome and provides information on ES proteins that are differentially expressed between S. mekongi genders. These findings will contribute to S. mekongi drug and vaccine development. In addition, the study enhances our understanding of basic S. mekongi biology.

Searching for drugs for Chagas disease, leishmaniasis and schistosomiasis: a review

Chagas disease, leishmaniasis and schistosomiasis are neglected diseases (NDs) and are a considerable global challenge. Despite the huge number of people infected, NDs do not create interest from pharmaceutical companies because the associated revenue is generally low. Most of the research on these diseases has been conducted in academic institutions. The chemotherapeutic armamentarium for NDs is scarce and inefficient and better drugs are needed. Researchers have found some promising potential drug candidates using medicinal chemistry and computational approaches. Most of these compounds are synthetic but some are from natural sources or are semi-synthetic. Drug repurposing or repositioning has also been greatly stimulated for NDs. This review considers some potential drug candidates and provides details of their design, discovery and activity.

Pre-clinical study of iron oxide nanoparticles fortified artesunate for efficient targeting of malarial parasite

BACKGROUND

Artesunate the most potent antimalarial is widely used for the treatment of multidrug-resistant malaria. The antimalarial cytotoxicity of artesunate has been mainly attributed to its selective, irreversible and iron- radical-mediated damage of parasite biomolecules. In the present research, iron oxide nanoparticle fortified artesunate was tested in P. falciparum and in an experimental malaria mouse model for enhancement in the selectivity and toxicity of artesunate towards parasite. Artesunate was fortified with nontoxic biocompatible surface modified iron oxide nanoparticle which is specially designed and synthesized for the sustained pH-dependent release of Fe2+ within the parasitic food vacuole for enhanced ROS spurt.

METHODS

Antimalarial efficacy of Iron oxide nanoparticle fortified artesunate was evaluated in wild type and artemisinin-resistant Plasmodium falciparum (R539T) grown in O + ve human blood and in Plasmodium berghei ANKA infected swiss albino mice. Internalization of nanoparticles, the pH-dependent release of Fe2+, production of reactive oxygen species and parasite biomolecule damage by iron oxide nanoparticle fortified artesunate was studied using various biochemical, biophysical, ultra-structural and fluorescence microscopy. For determining the efficacy of ATA-IONP+ART on resistant parasite ring survival assay was performed.

RESULTS

The nanoparticle fortified artesunate was highly efficient in the 1/8th concentration of artesunate IC50 and led to retarded growth of P. falciparum with significant damage to macromolecules mediated via enhanced ROS production. Similarly, preclinical In vivo studies also signified a radical reduction in parasitemia with ~8-10-fold reduced dosage of artesunate when fortified with iron oxide nanoparticles. Importantly, the ATA-IONP combination was efficacious against artemisinin-resistant parasites.

INTERPRETATION

Surface coated iron-oxide nanoparticle fortified artesunate can be developed into a potent therapeutic agent towards multidrug-resistant and artemisinin-resistant malaria in humans. FUND: This study is supported by the Centre for Study of Complex Malaria in India funded by the National Institute of Health, USA.

Association between Schistosoma mansoni infection and access to improved water and sanitation facilities in Mwea, Kirinyaga County, Kenya

Background

Schistosomiasis remains a public health problem in Central Kenya despite concerted control efforts. Access to improved water and sanitation has been emphasized as important control measures. Few studies have assessed the association between access to improved water sources and sanitation facilities with Schistosoma mansoni infection in different environmental settings. This study assessed the association between S. mansoni infection and household access to improved water sources and sanitation facilities in Mwea, Kirinyaga County, Kenya.

Methods

A cross sectional study was conducted between the months of August and October 2017. A total of 905 household heads from seven villages were interviewed and their stool samples screened for S. mansoni using the Kato Katz technique. Comparisons of demographic factors by S. mansoni infection were tested for significance using the chi-square test (χ2) or the Fisher exact test for categorical variables. Variables associated with S. mansoni infection were analyzed using univariable analysis and the strength of the association measured as odds ratio (OR) using mixed effects logistic regression at 95% CI, with values considered significant at p < 0.05.

Results

The overall prevalence of S. mansoni was, 23.1% (95% CI: 20.5–26.0%), with majority of the infections being of light intensity. Rurumi village had the highest prevalence at 33.3%, with Kirogo village having the least prevalence at 7.0%. Majority (84.1%) of the households lacked access to improved water sources but had access to improved sanitation facilities (75%). Households with access to piped water had the lowest S. mansoni infections. However, there was no significant association between S. mansoni infections with either the main source of water in the household (Odds Ratio (OR) =0.782 (95% CI: 0.497–1.229) p = 0.285 or sanitation facilities (OR = 1.018 (95% CI: 0.705–1.469) p = 0.926.

Conclusion

Our study suggests that S. mansoni is still a public health problem among all age groups in Mwea irrigation scheme, Kirinyaga County, Central Kenya. Majority of the households lacks access to improved water sources but have access to improved sanitation facilities. This study recommends initiatives to ensure adequate provision of improved water sources, and the inclusion of the adult community in preventive chemotherapy programs.

Electronic supplementary material

The online version of this article (10.1186/s12879-019-4105-1) contains supplementary material, which is available to authorized users.

Schistosomiasis in Malaysia: A review

Schistosomiasis, a neglected tropical parasitic disease caused by the trematode flatworms of the genus Schistosoma, affects approximately 207 million people worldwide. Among the five main species infecting humans, Schistosoma mansoni and S. japonicum are responsible for the majority of hepatointestinal schistosomiasis. Human settlements near fresh water sites that lack proper sanitary systems often contribute to the transmission of disease. This risk particularly impacts on travellers or immigrants who come into contact with larvae-contaminated water. This review discusses the central features of schistosomiasis; including clinical manifestations, diagnosis, treatments, and the preventive measures available for the control of this disease. The description of the Malaysian schistosome species Schistosoma malayensis and the current status of schistosomiasis in Malaysia including the compilation of cases diagnosed from 1904 to 2015 are also discussed in this paper.

In vitro and in vivo evaluation of six artemisinin derivatives against Schistosoma mansoni

Schistosomiasis is a tropical neglected disease whose socioeconomic impact is surpassed only by malaria. Until recently, praziquantel (PZQ) has been the only available drug, raising concerns that tolerant/resistant strains may appear. Since the discovery of the schistosomicidal potential of artemisinin (ART), new derivatives have been produced and evaluated. In this work, we evaluated the activity of ART derivatives against Schistosoma mansoni, both in vitro and in vivo. In the in vitro assay, worm survival, oviposition, and morphological alterations were evaluated. Further analysis of morphological alterations and membrane integrity was conducted using scanning electron microscopy and a cell-permeable, benzimidazole dye (Hoescht 33258) that binds to the minor groove of double stranded DNA. For the in vivo assay, artesunic acid (AcART) and dihydroartemisinin acetate (AcDQHS) were selected, since they showed the best in vitro results. Infected mice treated 21, 45, or 60 days post-infection (dpi), with a concentration of 100 mg/kg of either AcART or AcDQHS, showed a significant worm reduction (particularly in females), fewer eggs eliminated in feces, and a decrease of immature eggs in the intestinal tissues. Our results indicate that AcART and AcDQHS have some schistosomicidal activity against juvenile and adult stages of S. mansoni.

Nanomedicine Approaches Against Parasitic Worm Infections

Nanomedicine approaches have the potential to transform the battle against parasitic worm (helminth) infections, a major global health scourge from which billions are currently suffering. It is anticipated that the intersection of two currently disparate fields, nanomedicine and helminth biology, will constitute a new frontier in science and technology. This progress report surveys current innovations in these research fields and discusses research opportunities. In particular, the focus is on: (1) major challenges that helminth infections impose on mankind; (2) key aspects of helminth biology that inform future research directions; (3) efforts to construct nanodelivery platforms to target drugs and genes to helminths hidden in their hosts; (4) attempts in applying nanotechnology to enable vaccination against helminth infections; (5) outlooks in utilizing nanoparticles to enhance immunomodulatory activities of worm-derived factors to cure allergy and autoimmune diseases. In each section, achievements are summarized, limitations are explored, and future directions are assessed.

Identification of Peptide Antagonists to Thioredoxin Glutathione Reductase of Schistosoma japonicum

Schistosomiasis is one of the world's major public health problems. Praziquantel is currently the only effective drug against schistosomiasis. As resistance of praziquantel has emerged in some endemic areas, development of new antischistosomal agents should be a high priority. In this study, a phage display peptide library was used for screening for peptide antagonists of thioredoxin glutathione reductase of Schistosoma japonicum (SjTGR), which has been identified as an alternative drug target. Three rounds of panning produced four different fusion phages. ELISA proved that all four phages could bind to SjTGR. One peptide, JIPDys1 (aa, WPHNWWPHFKVK), reduced enzyme activity of SjTGR by more than 50%. 2 μM of the synthesized peptide of JIPDys1 inhibited the activity of TrxR, GR, and Grx of SjTGR by 32.5%, 100%, and 100%, respectively. The IC₅₀ values of the synthetic peptide JIPDys1 for TrxR, GR, and Grx were 3.67 μM, 0.11 μM, and 0.97 μM, respectively. Based on computer simulation, it appeared that JIPDys1 binds to the substrate binding sites of glutathione reductase (GR) and glutaredoxin (Grx). Our data show that the peptide, JIPDys1 (aa, WPHNWWPHFKVK), is a promising candidate to develop novel drugs against S. japonicum which acts by binding with SjTGR and reduces enzyme activity of SjTGR.

Drug Repurposing for Schistosomiasis: Combinations of Drugs or Biomolecules

Schistosomiasis is a major neglected tropical disease. Control of schistosomiasis currently relies on a single drug, praziquantel, and despite its efficacy against the all schistosome species that parasitize humans, it displays some problematic drawbacks and alone is ineffective in counteracting adverse pathologies associated with infection. Moreover, due to the development of the potential emergence of PZQ-resistant strains, the search for additional or alternative antischistosomal drugs have become a public health priority. The current drug discovery for schistosomiasis has been slow and uninspiring. By contrast, repurposing of existing approved drugs may offer a safe, rapid and cost-effective alternative. Combined treatment with PZQ and other drugs with different mode of action, i.e., antimalarials, shows promise results. In addition, a combination of anthelminthic drugs with antioxidant might be advantageous for modulating oxidative processes associated with schistosomiasis. Herein, we review studies dealing with combination therapies that involve PZQ and other anthelminthic drugs and/or antioxidant agents in treatment of schistosomiasis. Whereas PZQ combined with antioxidant agents might or might not interfere with anthelminthic efficacy, combinations may nonetheless ameliorate tissue damage and infection-associated complications. In fact, alone or combine with other drugs, antioxidants might be a valuable adjuvant to reduce morbidity and mortality of schistosomiasis. Therefore, attempting new combinations of anthelmintic drugs with other biomolecules such as antioxidants provides new avenues for discovery of alternatives to PZQ.

Real-time PCR diagnosis of Schistosoma japonicum in low transmission areas of China

Background

Schistosomiasis in the People’s Republic of China (PRC) can be traced back to antiquity. In the past 60 years, the Chinese government has made great efforts to control this persistent disease with elimination slated by 2020 through the implementation of a comprehensive control strategy. This strategy aims to reduce the role of bovines and humans as sources of infection as a pre-requisite for elimination through transmission interruption. The goal of elimination will be achievable only by the implementation of a sustainable surveillance and control system, with sensitive diagnosis a key feature so that the true disease burden is not underestimated. Currently used diagnostics lack the necessary sensitivity to accurately determine the prevalence of Schistosoma japonicum infection in areas with low infection intensities. It is of critical importance to find and treat people and to identify animals with low-level infections if the National Control Programme for China is to achieve schistosomiasis elimination.

Methods

We evaluated a real-time polymerase chain reaction (qPCR) assay using 633 human stool samples collected from five villages in Hunan, Anhui, Hubei, and Jiangxi provinces, and 182 bovine (70 cattle and 112 buffalo) stool samples obtained from four villages in Hunan, Anhui, and Jiangxi provinces in the PRC. All stool samples were subjected to the miracidium hatching test (MHT, a diagnostic procedure used in the National Schistosomiasis Control Programme) and the qPCR assay. Samples positive by MHT were subjected to either the Kato-Katz technique for humans, or the formalin-ethyl acetate sedimentation-digestion (FEA-SD) procedure for bovines, to determine infection intensities.

Results

The qPCR assay exhibited a high level of sensitivity in the detection of S. japonicum infections. With both the human and bovine samples, a significantly higher prevalence was determined using the qPCR assay (11.06% humans, 24.73% bovines) than with the MHT (0.93% humans, 7.69% bovines). The animal contamination index (calculated using data obtained with the qPCR technique) for all positive bovines was 27 618 000 eggs per day, indicating a considerable amount of environmental egg contamination that would be underestimated using less sensitive diagnostic procedures.

Conclusions

The qPCR assay we have evaluated will be applicable as a future field diagnostic and surveillance tool in low-transmission zones where schistosomiasis elimination is targeted and for monitoring post-intervention areas to verify that elimination has been maintained.

Electronic supplementary material

The online version of this article (10.1186/s40249-018-0390-y) contains supplementary material, which is available to authorized users.

Antischistosomal agents: state of art and perspectives

Praziquantel has remained the drug of choice for schistosomiasis chemotherapy for almost 40 years. The pressing need to develop a new antischistosomal drug may necessitate exploring and filtering chemotherapeutic history to search for the most promising ones. In this context, this review attempts to summarize all progress made in schistosomiasis chemotherapy from the early 20th century (mid-1910s) to 2016. We gathered almost 100 compounds providing information on therapeutic action, specifically covering at least first in vivo studies in animal model and in vitro. Pharmacokinetic and toxicity profiles of antischistosomal agents were also described. Preclinical studies indicate a handful of promising future candidates.

Peroxides with Anthelmintic, Antiprotozoal, Fungicidal and Antiviral Bioactivity: Properties, Synthesis and Reactions

The biological activity of organic peroxides is usually associated with the antimalarial properties of artemisinin and its derivatives. However, the analysis of published data indicates that organic peroxides exhibit a variety of biological activity, which is still being given insufficient attention. In the present review, we deal with natural, semi-synthetic and synthetic peroxides exhibiting anthelmintic, antiprotozoal, fungicidal, antiviral and other activities that have not been described in detail earlier. The review is mainly concerned with the development of methods for the synthesis of biologically active natural peroxides, as well as its isolation from natural sources and the modification of natural peroxides. In addition, much attention is paid to the substantially cheaper biologically active synthetic peroxides. The present review summarizes 217 publications mainly from 2000 onwards.

The Role of Natural Products in Drug Discovery and Development against Neglected Tropical Diseases

Endemic in 149 tropical and subtropical countries, neglected tropical diseases (NTDs) affect more than 1 billion people annually, including 875 million children in developing economies. These diseases are also responsible for over 500,000 deaths per year and are characterized by long-term disability and severe pain. The impact of the combined NTDs closely rivals that of malaria and tuberculosis. Current treatment options are associated with various limitations including widespread drug resistance, severe adverse effects, lengthy treatment duration, unfavorable toxicity profiles, and complicated drug administration procedures. Natural products have been a valuable source of drug regimens that form the cornerstone of modern pharmaceutical care. In this review, we highlight the potential that remains untapped in natural products as drug leads for NTDs. We cover natural products from plant, marine, and microbial sources including natural-product-inspired semi-synthetic derivatives which have been evaluated against the various causative agents of NTDs. Our coverage is limited to four major NTDs which include human African trypanosomiasis (sleeping sickness), leishmaniasis, schistosomiasis and lymphatic filariasis.

Implication of artemisinin nematocidal activity on experimental trichinellosis: In vitro and in vivo studies

Benzimidazole drugs are used for treatment of trichinellosis, but they have a limited effect against encapsulated larval stages of Trichinella spiralis. Hence, there is a considerable interest in developing new anthelmintic drugs. Our aim is to investigate the possible effect of artemisinin on T. spiralis in in vitro and in vivo studies. T. spiralis worms were isolated from infected mice and transferred to 3 culture media; group I: with no drugs, group II: contained artemisinin and group III: contained mebendazole, then they were subjected to electron microscopic study. An in vivo study was done where mice were divided into three groups; group I: infected and untreated, group II: received artemisinin and group III: received mebendazole. The efficacy of treatment was assessed by adult and total larval counts, histopathological study of the small intestinal and muscle tissues and immunohistochemical staining of cyclooxygenase-2 (COX-2) and vascular endothelial growth factor (VEGF) in muscles. Adult worm teguments showed significant degeneration and destruction with both drugs. Also, significant reduction of total adult and larval counts occurred in treated groups in comparison to the control group. Histopathological examination of the small intestine and muscles showed marked improvement with reduction in the inflammatory infiltrates with both drugs. COX-2 and VEGF expressions were reduced in both treated groups with more reduction in the artemisinin-treated group. This study revealed that artemisinin has the potential to be an alternative drug against trichinellosis.

Case Report of a Pituitary Macroadenoma Treated With Artemether

Introduction: This report describes the case of a male patient with pituitary macroadenoma treated with the artemisinin analog artemether. Patient and Methods: A 75 year-old male patient presented with vision, hearing, and locomotion-related problems. Artemether was administered orally to the patient over a period of 12 months. Results: Although the tumor remained consistent in size, CT scan shows a reduction in its density, and clinically, the related symptoms and signs resolved significantly as therapy progressed. Discussion: Overall, the artemether treatment was beneficial in improving the patient's quality of life. Artemether and other artemisinin analogs offer promise for cancer therapy.

Prophylactic effect of artemether on human schistosomiasis mansoni among Egyptian children: A randomized controlled trial

A double-blind, randomized controlled trial was conducted in an endemic focus for Schistosoma mansoni in Kafr El-Sheikh Governorate, Northern Nile Delta, Egypt, to evaluate the prophylactic effect of artemether (ART) given in conjunction with praziquantel (PZQ). The study encompassed 913 primary school children randomly assigned to two treatment groups PZQ/ART and PZQ/ART-placebo. At baseline, both groups received 40 mg/kg body weight of PZQ twice four weeks apart, after which one group received 6 mg/kg body weight of ART every 3 weeks in 5 cycles during the transmission season and the other group received ART-placebo. At the end of the study, prevalence of infection among the PZQ/ART was approximately half that of the PZQ/ART-placebo group, i.e. 6.7% versus 11.6%, and incidence of new infections for the PZQ/ART was 2.7% versus 6.5% for the PZQ/ART-placebo. In conclusion, PZQ/ART combined therapy might be considered as an adjunct measure against human schistosomiasis, by specifically reducing transmission and therefore contribute to disease elimination.

Extent of morbidity associated with schistosomiasis infection in Malawi: a review paper

Data on the extent of the burden due to schistosomiasis is sparse in most Sub-Saharan African countries. However, this data is crucial for triggering medical attention. A review of extent of morbidity and determinants associated with schistosomiasis in Malawi was therefore conducted to quantify the infection in order to concretise the need for medical intervention. A systematic and traditional search strategy was used to find literature for the review, whilst exclusion and inclusion criteria were used to identify appropriate articles. Logistic regression curves of epidemiological model Y = (a + bx (c) )/(1 + bx (c) ) and the recommendation that schistosomiasis prevalence can be used to estimate morbidity were employed to quantify morbidity at various infection stages. Morbidity was quantified as a direct proportion of the population and the respective national schistosomiasis prevalence. Findings showed that both S. mansoni and S. haematobium are present in Malawi with the latter highly prevalent (50%). Furthermore, out of the estimated population of 16,829 million, approximately 8.4 million have schistosomiasis, with about 4.4 million of these aged 18 years and below. The most frequent manifestation is Katayama syndrome, while ascites is the lowest, impacting about 3.0 million and 960 individuals, respectively. Localised studies on association of schistosomiasis infection to risk factors such as occupation, age and gender found odds ratio (OR) ranging from 1.29 to 5.37. Morbidity due to schistosomiasis is high in Malawi. It is therefore recommended that a more detailed study on the determinants of high schistosomiasis and re-evaluation of the current control measures be conducted if the current morbidity statistics are to be remarkably reduced.

Natural products with antischistosomal activity

In recent years, natural product groups have been gaining prominence as possible sources of new drugs for schistosomiasis. This review attempts to update the antischistosomal natural compounds, or natural product-derived compounds, from the mid-1980s. Some of the main metabolites obtained from plants (e.g., terpenes, alkaloids, phenolic compounds and peptides) with in vitro and/or in vivo antischistosomal properties are discussed. Less thoroughly, due to scarcity of data in the literature, molecules from animals (e.g., peptides) are also described. Special mention of the anthelmintic activity against different parasitic stages of schistosomes is made; the mechanism of action of most of the metabolites is discussed, and a number of bioassay procedures are listed.

The roles of water, sanitation and hygiene in reducing schistosomiasis: a review

Schistosomiasis is a disease caused by infection with blood flukes of the genus Schistosoma. Transmission of, and exposure to, the parasite result from faecal or urinary contamination of freshwater containing intermediate host snails, and dermal contact with the same water. The World Health Assembly resolution 65.21 from May 2012 urges member states to eliminate schistosomiasis through preventive chemotherapy (i.e. periodic large-scale administration of the antischistosomal drug praziquantel to school-aged children and other high-risk groups), provision of water, sanitation and hygiene (WASH) and snail control. However, control measures focus almost exclusively on preventive chemotherapy, while only few studies made an attempt to determine the impact of upgraded access to safe water, adequate sanitation and good hygiene on schistosome transmission. We recently completed a systematic review and meta-analysis pertaining to WASH and schistosomiasis and found that people with safe water and adequate sanitation have significantly lower odds of a Schistosoma infection. Importantly though, the transmission of schistosomiasis is deeply entrenched in social-ecological systems, and hence is governed by setting-specific cultural and environmental factors that determine human behaviour and snail populations. Here, we provide a comprehensive review of the literature, which explores the transmission routes of schistosomes, particularly focussing on how these might be disrupted with WASH-related technologies and human behaviour. Additionally, future research directions in this area are highlighted.

Efficacy of Synriam™, a new antimalarial combination of OZ277 and piperaquine, against different developmental stages of Schistosoma mansoni

Control of schistosomiasis relies on a single drug, praziquantel (PZQ). Given the rising concerns about the potential emergence of PZQ-resistant strains, it has now become necessary to search for novel therapeutics. However, the current pace for anti-schistosomal drug discovery is slow; hence, repositioning of existing approved drugs can offer a safe, rapid and cost-effective solution. The anti-malarial synthetic artemisinin-derivatives trioxolanes demonstrated anti-schistosomal efficacies against the three major species infecting humans and, unlike PZQ, showed activities against both juvenile and adult worm stages. The 1,2,4-trioxolane/OZ277 (arterolane maleate) in combination with a partner drug: piperaquine phosphate was recently developed as an anti-malarial drug and manufactured by Ranbaxy (India) as Synriam™ (SYN). Herein, the in vivo activities of SYN were investigated in a mouse model of Schistosoma mansoni (S. mansoni), compared to PZQ. We show that a single fixed dose of 240mg/kg SYN (40mg/kg arterolane and 200mg/kg piperaqine) induced significant protective effects in mice, in terms of reduction in worm and tissue egg burdens, which were evident against all schistosome developmental stages. Extensive alterations in the tegument and subtegumental tissues of SYN-exposed worms were revealed by both scanning and transmission electron microscopes. Progressive decrease in worm activity and occurrence of death were noticed in vitro upon exposure to the drug - more pronounced in the presence of haemin. This report provides the first evidence of the efficacy of a combination of 1,2,4-trioxolane and piperaquine against S. mansoni in mice. Being effective against young stages, SYN could be used to prevent early Schistosoma infection.

An artemisinin derivative of praziquantel as an orally active antischistosomal agent

Background

Schistosomiasis is a major health problem in tropical and sub-tropical areas caused by species of trematode belonging to the genus Schistosoma. The treatment and control of this disease has been relying on the use of a single drug praziquantel. However, the drug resistance concern urged the development of new drugs against schistosoma. Here, we report our systematic biological evaluation of DW-3-15, a new lead compound developed based on our conjugation design rationale as an effective anti-schistosomal agent.

Methodology/Principal Findings

The antischistosomal activity of DW-3-15 was systematically evaluated in S. japonicum infected mouse model for its stage-sensitivity and dose response. The results revealed that DW-3-15 exhibited 60–85% worm reduction rate against different development stage of worm. Scanning electron microscopy (SEM) observation indicated that DW-3-15 may damage to the tegument of male schistosomes.

Conclusions/Significance

Our results demonstrated that DW-3-15 showed potent anti-schistosomal activities in vivo. The results strongly support our conjugation design strategy of artemisinin analogs and further development of DW-3-15 as a new lead compound as anti-schistosomal agent.

Drugs for treating urinary schistosomiasis

BACKGROUND

Urinary schistosomiasis is caused by an intravascular infection with parasitic Schistosoma haematobium worms. The adult worms typically migrate to the venous plexus of the human bladder and excrete eggs which the infected person passes in their urine. Chronic infection can cause substantial morbidity and long-term complications as the eggs become trapped in human tissues causing inflammation and fibrosis. We summarised evidence of drugs active against the infection. This is new edition of a review first published in 1997.

OBJECTIVES

To evaluate the efficacy and safety of drugs for treating urinary schistosomiasis.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register, MEDLINE, CENTRAL, EMBASE and LILACS and reference lists of articles up to 23 May 2014.

SELECTION CRITERIA

Randomized controlled trials (RCTs) of antischistosomal drugs and drug combinations compared to placebo, no intervention, or each other.

DATA COLLECTION AND ANALYSIS

Two researchers independently screened the records, extracted the data and assessed risk of bias. The primary efficacy outcomes were parasitological failure (defined as the continued presence of S. haematobium eggs in the urine at time points greater than one month after treatment), and percent reduction of egg counts from baseline. We presented dichotomous data as risk ratios (RR), and continuous data as mean difference (MD), alongside their 95% confidence intervals (CIs). Where appropriate we combined trials in meta analyses or tables. We assessed the quality of evidence using the GRADE approach.

MAIN RESULTS

We included 30 RCTs enrolling 8165 participants in this review. Twenty-four trials were conducted in children in sub-Saharan Africa, and 21 trials were over 20 years old. Many studies were assessed as being at unclear risk of bias due to inadequate descriptions of study methods. PraziquantelOn average, a single 40 mg/kg dose of praziquantel reduced the proportion of people still excreting eggs in their urine by around 60% compared to placebo at one to two months after treatment (treatment failure: RR 0.42, 95% CI 0.29 to 0.59, 864 participants, seven trials, high quality evidence). The proportion of people cured with praziquantel varied substantially between trials, from 22.5% to 83.3%, but was higher than 60% in five of the seven trials. At one to two months following praziquantel treatment at 40 mg/kg, the mean number of schistosome eggs in the urine was reduced by over 95% in five out of six trials (678 participants, six trials, high quality evidence).Splitting praziquantel 40 mg/kg into two doses over 12 hours probably has no benefits over a single dose, and in a single trial of 220 participants the split dose caused more vomiting (RR 0.5, 95% CI 0.29 to 0.86) and dizziness (RR 0.39, 95% CI 0.16 to 0.94). MetrifonateA single dose of metrifonate 10 mg/kg reduced egg excretion (210 participants, one trial, at eight months), but was only marginally better than placebo at achieving cure at one month (RR 0.83, 95% CI 0.74 to 0.94, 142 participants, one trial). In a single trial comparing one, two and three doses, the absolute number of participants cured improved from 47% after one dose to 81% after three doses (93 participants, one trial, low quality evidence).Two small trials compared 40 mg/kg single dose praziquantel with two or three doses of 10 mg/kg metrifonate and found no clear evidence of differences in cure (metrifonate 2 x 10 mg/kg at one month: RR 1.03, 95% CI 0.8 to 1.34, 72 participants, one trial; metrifonate 3 x 10 mg/kg at three months: RR 0.33, 95% CI 0.07 to 1.57, 100 participants, one trial. In one trial both drugs performed badly and in one trial both performed well. Other drugsThree trials have evaluated the antimalarial artesunate; with inconsistent results. Substantial antischistosomal effects were only seen in one of the three trials, which was at unclear risk of bias due to poor reporting of the trial methods. Similarly, another anti-malarial mefloquine has been evaluated in two small trials with inconsistent effects.Adverse events were described as mild for all evaluated drugs, but adverse event monitoring and reporting was generally of low quality.

AUTHORS' CONCLUSIONS

Praziquantel 40 mg/kg is the most studied drug for treating urinary schistosomiasis, and has the strongest evidence base.Potential strategies to improve future treatments for schistosomiasis include the combination of praziquantel with metrifonate, or with antimalarial drugs with antischistosomal properties such as artesunate and mefloquine. Evaluation of these combinations requires rigorous, adequately powered trials using standardized outcome measures.

Efficacy of artemether and artesunate in mice infected with praziquantel non-susceptible isolate of Schistosoma japonicum

Praziquantel is currently the only drug of choice for the treatment of human Schistosoma japonicum infections, and praziquantel-based chemotherapy has been proved to be generally effective to control the morbidity and reduce the prevalence and intensity of S. japonicum infections. However, the potential emergence of praziquantel resistance in S. japonicum seriously threatens the elimination of this neglected tropical disease in China. The purpose of this study was designed, in mouse animals, to evaluate the in vivo efficacy of artemether and artesunate against praziquantel non-susceptible S. japonicum. Mice infected with a praziquantel non-susceptible isolate and a praziquantel-susceptible isolate of S. japonicum were treated with artemether and artesunate at a single oral dose of 300 mg/kg given once on each of days 7-8 and 35-36 post-infection to assess the efficacy against juvenile and adult worms. Administration with artemether and artesunate at a single oral dose of 300 mg/kg on each of days 7-8 post-infection resulted in total worm burden reductions of 72.8 and 73.5% in mice infected with praziquantel-susceptible S. japonicum, and 77.9 and 74.1% in mice infected with the non-susceptible isolate (both P values >0.05), while the same treatments given on days 35-36 post-infection reduced total worm burdens by 71.4 and 69.6% in mice infected with the susceptible isolate, and 75.3 and 69.6% in mice infected with the non-susceptible parasite (both P values >0.05). It is concluded that there is no evidence for reduced susceptibility of artemether and artesunate in praziquantel non-susceptible S. japonicum.

Research gaps for three main tropical diseases in the People's Republic of China

This scoping review analyzes the research gaps of three diseases: schistosomiasis japonica, malaria and echinococcosis. Based on available data in the P.R. China, we highlight the gaps between control capacity and prevalence levels, and between diagnostic/drug development and population need for treatment at different stages of the national control programme. After reviewing the literature from 848 original studies and consultations with experts in the field, the gaps were identified as follows. Firstly, the malaria research gaps include (i) deficiency of active testing in the public community and no appropriate technique to evaluate elimination, (ii) lack of sensitive diagnostic tools for asymptomatic patients, (iii) lack of safe drugs for mass administration. Secondly, gaps in research of schistosomiasis include (i) incongruent policy in the implementation of integrated control strategy for schistosomiasis, (ii) lack of effective tools for Oncomelania sp. snail control, (iii) lack of a more sensitive and cheaper diagnostic test for large population samples, (iv) lack of new drugs in addition to praziquantel. Thirdly, gaps in research of echinococcosis include (i) low capacity in field epidemiology studies, (ii) lack of sanitation improvement studies in epidemic areas, (iii) lack of a sensitivity test for early diagnosis, (iv) lack of more effective drugs for short-term treatment. We believe these three diseases can eventually be eliminated in mainland China if all the research gaps are abridged in a short period of time.

Efficacy of artesunate in the treatment of urinary schistosomiasis, in an endemic community in Nigeria

The efficacy and tolerability of oral artesunate for the treatment of urinary schistosomiasis was assessed among schoolchildren aged 5-18 years in Adim community, Nigeria. Overall, 500 children, randomly selected from those attending the Presbyterian primary school, were each invited to provide two consecutive urine samples. Using standard parasitological procedures, Schistosoma haematobium ova were found in the samples from 145 (29.0%) of the subjects. Most (87) of the infected subjects were then treated orally with artesunate, using two doses, each of 6 mg/kg, given 2 weeks apart. When the treated children were re-examined 4 weeks after the second dose of artesunate, 61 (70.1%) appeared egg-negative and were therefore considered cured. Post-treatment, the geometric mean egg count (GMEC) for the treated subjects who were not cured was significantly lower than the pre-treatment GMEC for all the treated subjects, with log10[(eggs/10 ml urine) + 1] values of 0.9 v. 1.75 (t = 4.45; P < 0.05). The cure 'rate' for the subjects aged > or = 10 years was slightly higher than that among the younger subjects. It was lowest for the heavier subjects (70% for those weighing 41-50 kg) and highest (79%) for the subjects who weighed 31-40 kg. The artesunate was well tolerated. This observation of a therapeutic effect of artesunate against S. haematobium in Nigeria confirms recent observations from Senegal. In the Adim community at least, it would be more cost-effective to treat urinary schistosomiasis with artesunate than with praziquantel. The wide-spread use of artesunate against schistosomiasis has to be considered carefully, however, if it is not to compromise the efficacy of the drug as an antimalarial, by increasing the risk of resistance developing in local Plasmodium.

Drugs for treating Schistosoma mansoni infection

BACKGROUND

Schistosoma mansoni is a parasitic infection common in the tropics and sub-tropics. Chronic and advanced disease includes abdominal pain, diarrhoea, blood in the stool, liver cirrhosis, portal hypertension, and premature death.

OBJECTIVES

To evaluate the effects of antischistosomal drugs, used alone or in combination, for treating S. mansoni infection.

SEARCH METHODS

We searched MEDLINE, EMBASE and LILACS from inception to October 2012, with no language restrictions. We also searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (The Cochrane Library 2012) and mRCT. The reference lists of articles were reviewed and experts were contacted for unpublished studies.

SELECTION CRITERIA

Randomized controlled trials of antischistosomal drugs, used alone or in combination, versus placebo, different antischistosomal drugs, or different doses of the same antischistosomal drug for treating S. mansoni infection.

DATA COLLECTION AND ANALYSIS

One author extracted data and assessed eligibility and risk of bias in the included studies, which were independently checked by a second author. We combined dichotomous outcomes using risk ratio (RR) and continuous data weighted mean difference (WMD); we presented both with 95% confidence intervals (CI). We assessed the quality of evidence using the GRADE approach.

MAIN RESULTS

Fifty-two trials enrolling 10,269 participants were included. The evidence was of moderate or low quality due to the trial methods and small numbers of included participants.Praziquantel: Compared to placebo, praziquantel 40 mg/kg probably reduces parasitological treatment failure at one month post-treatment (RR 3.13, 95% CI 1.03 to 9.53, two trials, 414 participants, moderate quality evidence). Compared to this standard dose, lower doses may be inferior (30 mg/kg: RR 1.52, 95% CI 1.15 to 2.01, three trials, 521 participants, low quality evidence; 20 mg/kg: RR 2.23, 95% CI 1.64 to 3.02, two trials, 341 participants, low quality evidence); and higher doses, up to 60 mg/kg, do not appear to show any advantage (four trials, 783 participants, moderate quality evidence).The absolute parasitological cure rate at one month with praziquantel 40 mg/kg varied substantially across studies, ranging from 52% in Senegal in 1993 to 92% in Brazil in 2006/2007. Oxamniquine: Compared to placebo, oxamniquine 40 mg/kg probably reduces parasitological treatment failure at three months (RR 8.74, 95% CI 3.74 to 20.43, two trials, 82 participants, moderate quality evidence). Lower doses than 40 mg/kg may be inferior at one month (30 mg/kg: RR 1.78, 95% CI 1.15 to 2.75, four trials, 268 participants, low quality evidence; 20 mg/kg: RR 3.78, 95% CI 2.05 to 6.99, two trials, 190 participants, low quality evidence), and higher doses, such as 60 mg/kg, do not show a consistent benefit (four trials, 317 participants, low quality evidence).These trials are now over 20 years old and only limited information was provided on the study designs and methods. Praziquantel versus oxamniquine: Only one small study directly compared praziquantel 40 mg/kg with oxamniquine 40 mg/kg and we are uncertain which treatment is more effective in reducing parasitological failure (one trial, 33 participants, very low quality evidence). A further 10 trials compared oxamniquine at 20, 30 and 60 mg/kg with praziquantel 40 mg/kg and did not show any marked differences in failure rate or percent egg reduction.Combination treatments: We are uncertain whether combining praziquantel with artesunate reduces failures compared to praziquantel alone at one month (one trial, 75 participants, very low quality evidence).Two trials also compared combinations of praziquantel and oxamniquine in different doses, but did not find statistically significant differences in failure (two trials, 87 participants). Other outcomes and analyses: In trials reporting clinical improvement evaluating lower doses (20 mg/kg and 30 mg/kg) against the standard 40 mg/kg for both praziquantel or oxamniquine, no dose effect was demonstrable in resolving abdominal pain, diarrhoea, blood in stool, hepatomegaly, and splenomegaly (follow up at one, three, six, 12, and 24 months; three trials, 655 participants).Adverse events were not well-reported but were mostly described as minor and transient.In an additional analysis of treatment failure in the treatment arm of individual studies stratified by age, failure rates with 40 mg/kg of both praziquantel and oxamniquine were higher in children.

AUTHORS' CONCLUSIONS

Praziquantel 40 mg/kg as the standard treatment for S. mansoni infection is consistent with the evidence. Oxamniquine, a largely discarded alternative, also appears effective.Further research will help find the optimal dosing regimen of both these drugs in children.Combination therapy, ideally with drugs with unrelated mechanisms of action and targeting the different developmental stages of the schistosomes in the human host should be pursued as an area for future research.

Natural products as a source for treating neglected parasitic diseases

Infectious diseases caused by parasites are a major threat for the entire mankind, especially in the tropics. More than 1 billion people world-wide are directly exposed to tropical parasites such as the causative agents of trypanosomiasis, leishmaniasis, schistosomiasis, lymphatic filariasis and onchocerciasis, which represent a major health problem, particularly in impecunious areas. Unlike most antibiotics, there is no "general" antiparasitic drug available. Here, the selection of antiparasitic drugs varies between different organisms. Some of the currently available drugs are chemically de novo synthesized, however, the majority of drugs are derived from natural sources such as plants which have subsequently been chemically modified to warrant higher potency against these human pathogens. In this review article we will provide an overview of the current status of plant derived pharmaceuticals and their chemical modifications to target parasite-specific peculiarities in order to interfere with their proliferation in the human host.

Enhanced IL-12p40 production in LPS-stimulated macrophages by inhibiting JNK activation by artemisinin

Artemisinin can be isolated from Artemisia annua L. In addition to its well-known anti-malarial activity, artemisinin has antitumor and anti-microbial effects. In this study, we investigated the effect of artemisinin on the production of IL-12p40, which is important in the generation of T helper 1 responses. Artemisinin significantly induced IL-12p40 production in LPS-stimulated RAW264.7 macrophage cells. To elucidate the signaling molecules regulated by artemisinin in induced IL-12p40 production, the DNA-binding activity of several transcription factors and activation of mitogen-activated protein kinase (MAPK)s were investigated. The band intensities of NF-κB, AP-1, and SP1, and the activation of p38 MAPK and ERK were not changed by artemisinin. However, the induced phosphorylation of JNK was significantly decreased by artemisinin, and inhibition of the JNK signaling pathway further increased IL-12p40 production in LPS-stimulated RAW264.7 macrophage cells. Taken together, these data suggest that artemisinin induces the production of IL-12p40 in LPS-stimulated macrophage cells by inhibiting JNK activity.

Pharmacodynamics of mefloquine and praziquantel combination therapy in mice harbouring juvenile and adult Schistosoma mansoni

Praziquantel (PZQ) is currently the only drug widely used for the treatment of schistosomiasis, but the antimalarial drug mefloquine (Mef) possesses interesting antischistosomal properties. Combination therapy with these two drugs has been suggested as a strategy for transmission control, as PZQ is active against adult worms and Mef is active against schistosomula. To examine the efficacy of combination therapy, Schistosoma mansoni-reinfected mice were separated into seven groups: untreated (I), treated with PZQ in doses of 200 mg/kg (II) or 1,000 mg/kg (III), treated with Mef in doses of 200 mg/kg (IV) or 400 mg/kg (V); each dose was divided equally and given on two consecutive days. Group VI was treated with doses of PZQ + Mef as in groups II and IV, respectively, while group VII was treated with PZQ + Mef as in groups III and V, respectively. PZQ + Mef at the reduced doses of 200 mg/kg each enhanced the therapeutic efficacy over the reduced PZQ dose alone as shown by a very high reduction in the total numbers of mature worms (95% vs. 49%), immature worms (96% vs. 29%) and the complete eradication of immature females, mature females and immature eggs. The reduction in worm burden was associated with the healing of hepatic granulomatous lesions and the normalisation of all liver enzymes. Therefore, the use of Mef with PZQ is more effective than PZQ alone and should be considered for clinical trials in humans as a potential treatment regimen to prevent treatment failures in areas with high rates of schistosomiasis.

Identification of the Schistosoma mansoni molecular target for the antimalarial drug artemether

Plasmodium falciparum and Schistosoma mansonii are the parasites responsible for most of the malaria and schistosomiasis cases in the world. Notwithstanding their many differences, the two agents have striking similarities in that they both are blood feeders and are targets of an overlapping set of drugs, including the well-known artemether molecule. Here we explore the possibility of using the known information about the mode of action of artemether in Plasmodium to identify the molecular target of the drug in Schistosoma and provide evidence that artemether binds to SmSERCA, a putative Ca²⁺-ATPase of Schistosoma . We also predict the putative binding mode of the molecule for both its Plasmodium and Schistosoma targets. Our analysis of the mode of binding of artemether to Ca²⁺-ATPases also provides an explanation for the apparent paradox that, although the molecule has no side effect in humans, it has been shown to possess antitumoral activity.

Efficacy of praziquantel and artemisinin derivatives for the treatment and prevention of human schistosomiasis: a systematic review and meta-analysis

Background

Praziquantel has been used as first-line drug for chemotherapy of schistosomiasis since 1984. Besides praziquantel, artemether and artesunate have also been used for the control of this infectious disease since late 1990s. In this article, we conducted a systematic review and meta-analysis to evaluate the antischistosomal efficacy of different medication strategies including monotherapy or combination therapies of these drugs.

Results

A number of 52 trials from 38 articles published in peer-reviewed journals before July 2011 were selected for analysis after searching the following literature databases: the Cochrane Library, PubMed/Medline, ISI Web of Science, Chinese Biomedicine Literature Database, and China National Knowledge Infrastructure. Our meta-analyses showed that a dosage of 30-60 mg/kg praziquantel compared with placebo produced a protection rate of about 76% (95% CI: 67%-83%) for treating human schistosomiasis, which varied from 70% to 76% with no significant differences among the subspecies S. haematobium, S. japonicum or S. mansoni. Protection rates were higher when praziquantel doses were elevated, as concluded from the nRCTs results: the protection rate of praziquantel at 40 mg/kg was 52% (95% CI: 49%-55%), and it increased to 91% (95% CI: 88%-92%) when the dosages were elevated to 60/80/100 mg/kg divided two or more doses. Multiple doses of artemether or artesunate over 1- or 2-week intervals resulted in protection rates of 65% to 97% for preventing schistosomiasis, and increased doses and shorter medication intervals improved their efficacies. Praziquantel and artemisinin derivatives (artemether or artesunate) in combination resulted in a higher protection rate of 84% (95% CI: 64%-91%) than praziquantel monotherapy for treatment. praziquantel and artesunate in combination had a great protection rate of 96% (95% CI: 78%-99%) for preventing schistosomes infection.

Conclusions

According to the results, praziquantel remains effective in schistosomiasis treatment, and multiple doses would improve its efficacy; meanwhile, praziquantel is also a good drug for preventing acute schistosomiasis morbidity. It's better to use multiple doses of artemether or artesunate with 1- or 2-week intervals for prevention against schistosome infection. Praziquantel and artemether or artesunate in combination perform better in treatment than praziquantel monotherapy, and they are especially suitable for treating the patients with repeated exposure to infected water.

Structural changes of Schistosoma mansoni adult worms recovered from C57BL/6 mice treated with radiation-attenuated vaccine and/or praziquantel against infection

Although the current treatment of schistosomiasis relies largely on praziquantel (PZQ), it has not significantly reduced the overall number of disease cases, perhaps due to inevitable resistance to PZQ. Previous studies showed that radiation-attenuated vaccine gives protection levels for Schistosoma mansoni in host various species. In the present study, we evaluated the effect of various vaccination strategies in C57BL/6 mice, including single or multiple vaccination strategy, subcurative dose (20 mg/kg) of PZQ, and a combination of single vaccination with subcurative dose of PZQ. Groups of five mice were sacrificed postinfection in 42 days and schistosomes were collected by perfusion and examined by scanning electron microscopy. Treatment either with subcurative dose of PZQ or with a single vaccination of attenuated cercariae (500 per mouse), caused significant reduction in total worm burden, hepatic and intestinal ova counts 43.03%, 73.2%, 59.5% and 37.97%, 52.02%, 26.3%, respectively. Furthermore, tegumental changes were observed, including severe swelling, fusion of tegumental folds, vesicle formation, and loss or shortening of the spines on the tubercles. However, multiple vaccination strategy resulted in much higher reduction in total worm burden, hepatic and intestinal ova count. However, multiple vaccination strategy resulted in high reduction of worm burden, hepatic and intestinal ova counts 72.5%, 90.7%, 65.79%, respectively, and further causing swollen, disruption of tubercles teguments and erosion, extensive peeling, fusion of tegumental folds. Our findings suggest that multiple vaccination strategy is the most effective strategy to clear schistosomal infection, indicating its potential in guiding the design of appropriate therapeutic strategy against schistosomes.

Interactions of mefloquine with praziquantel in the Schistosoma mansoni mouse model and in vitro

OBJECTIVES

Mefloquine has interesting antischistosomal properties, hence it might be an attractive partner drug for combination treatment with praziquantel. The aim of this study was to evaluate activities of mefloquine/praziquantel combinations against Schistosoma mansoni in vitro and in vivo.

METHODS

Dose-response relationships were established following exposure of adult S. mansoni to mefloquine, praziquantel and fixed dose combinations of mefloquine/praziquantel in vitro. S. mansoni-infected mice were treated orally with selected doses of single drugs and drug combinations 7 weeks post-infection.

RESULTS

We calculated in vitro LC(50) values of 0.024 and 1.9 μg/mL for praziquantel and mefloquine, respectively. Mefloquine/praziquantel combinations showed synergistic effects, with combination index (CI) values <1 when adult S. mansoni were simultaneously incubated with both drugs in vitro. Reduced viabilities were also observed when schistosomes were first exposed to mefloquine followed by praziquantel in vitro. ED(50)s of 62 mg/kg and 172 mg/kg were determined for mefloquine and praziquantel against adult S. mansoni in vivo, respectively. Combinations of praziquantel (50 or 100 mg/kg) followed the next day by mefloquine (50 or 100 mg/kg) treatment revealed only moderate total worm burden reductions of 47.8%-54.7%. On the other hand, when both drugs (100 mg/kg each) were either given simultaneously or mefloquine was given prior to praziquantel, high total and female worm burden reductions of 86.0%-93.1% were observed. For the later treatment regimen, synergistic effects (CI < 1) were calculated when mefloquine and praziquantel were combined using a fixed dose ratio based on their ED(50)s.

CONCLUSIONS

Combinations of mefloquine and praziquantel may have clinical utility in the treatment of schistosomiasis.

Schistosoma mansoni: N-acetylcysteine downregulates oxidative stress and enhances the antischistosomal activity of artemether in mice

Artemether (Art), a derivative of the antimalarial artemisinin, also exhibit antischistosomal properties. N-acetylcysteine (NAC) has a diversity of applications, largely because of the chemical properties of the thiol moiety present in its structure. The ability of this moiety to sweep reactive oxygen species is well-established with NAC. This study investigates the ability of NAC to enhance the therapeutic potential of Art against adult Schistosoma mansoni infection and evaluates the protective role of this antioxidant on S. mansoni-induced oxidative stress. Mice were divided into five groups; normal (i), infected control (ii), infected treated with NAC, 300mg/kg 5 days a week/4weeks (iii), infected treated with Art (300mg/kg) 7 weeks post infection (iv) and infected treated with both NAC and Art (v). Results showed that Art produced a significant reduction in total number of worms when used alone. Also, it decreased hepatic ova count significantly accompanied with an increase in the percentage of dead ova. Treatment with NAC alone increased the percentage of dead ova; meanwhile, it enhanced the decrease in total number of worms and hepatic ova count when used with Art. Infection with S. mansoni significantly increased tissue GSH, GR, SOD and serum ALT and GGT, while decreased the activities of GST, GPx and the levels of proteins and albumin compared to normal control. Treatment with NAC alone approximately recovered the contents of GSH, activities of GPx and levels of serum albumin, ALT and GGT relative to normal control. A tendency for normalization in activities of the antioxidant enzymes mentioned above and serum levels of liver function tests was observed in the groups treated with Art alone or Art+NAC.

CONCLUSION

NAC downregulates oxidative stress induced by S. mansoni infection and enhances the therapeutic potential of artemether against adult schistosomes.