Current drug strategies for the treatment and control of schistosomiasis

INTRODUCTION

Schistosomiasis, one of the current Neglected Tropical Diseases (NTDs) affects over 230 million people globally, with nearly 700 million at risk in more than 74 countries. Praziquantel (PZQ) has served as the primary treatment for the past four decades; however, its effectiveness is limited as it solely eliminates adult worms. In regions where infections are frequent, PZQ exhibits only temporary efficacy and has restricted potential to disrupt the prolonged transmission of the disease.

AREAS COVERED

A comprehensive exploration using the PubMed database was conducted to review current pharmacotherapy approaches for schistosomiasis. This review also encompasses recent research findings related to potential novel therapeutics and the repurposing of existing drugs.

EXPERT OPINION

Current schistosoma treatment strategies, primarily relying on PZQ, face challenges like temporary effectiveness and limited impact on disease transmission. Drug repurposing, due to economic constraints, is decisive for NTDs. Despite PZQ's efficacy, its failure to prevent reinfection highlights the need for complementary strategies, especially in regions with persistent environmental foci. Integrating therapies against diverse schistosome stages boosts efficacy and impedes resistance. Uncovering novel agents is essential to address resistance concerns in tackling this neglected tropical disease. Integrated strategies present a comprehensive approach to navigate the complex challenges.

Anti-fibrotic Effect of Oral Versus Intraperitoneal Administration of Gold Nanoparticles in Hepatic Schistosoma mansoni-Infected Mice

BACKGROUND

Schistosomiasis significantly impacts public health, as it causes severe morbidity. Infections caused by Schistosoma mansoni (S. mansoni) can be treated with gold nanoparticles (AuNPs). This study aims to determine the most effective route of AuNPs administration and the magnitude of its anti-fibrotic effect.

METHODS

In the five groups' in vivo assay design, AuNPs were administered intraperitoneally (1 mg/kg) and orally (1 mg/100 g) to S. mansoni-infected mice. Biochemical parameters (serum levels of albumin and liver enzymes alanine aminotransferase (ALT), and aspartate aminotransferase (AST) were measured. The histological changes of the liver in distinct groups were evaluated using Hematoxylin and Eosin, Masson's trichrome, and immunohistochemical stains.

RESULTS

Infection with S. mansoni was associated with substantial changes in the histological architecture of liver tissue and abnormal levels of hepatic function tests (albumin, AST, and ALT). Schistosoma infected hepatocytes exhibited an abnormal microscopic morphology, granuloma formation and aggressive fibrosis. AuNPs restored the liver histological architecture with a highly significant anti-fibrotic effect and significantly corrected hepatic function test levels. Intraperitoneal administration of AuNPs resulted in the most significant anti-fibrotic effect against hepatic S. mansoni infection as observed in all histological sections with Masson's trichrome being the best stain to represent this fact.

CONCLUSION

For treating S. mansoni-induced chronic liver fibrosis, intraperitoneal administration of AuNPs is a successful and effective route of administration that can be recommended.

Non-covalent inhibitors of thioredoxin glutathione reductase with schistosomicidal activity in vivo

Only praziquantel is available for treating schistosomiasis, a disease affecting more than 200 million people. Praziquantel-resistant worms have been selected for in the lab and low cure rates from mass drug administration programs suggest that resistance is evolving in the field. Thioredoxin glutathione reductase (TGR) is essential for schistosome survival and a validated drug target. TGR inhibitors identified to date are irreversible and/or covalent inhibitors with unacceptable off-target effects. In this work, we identify noncovalent TGR inhibitors with efficacy against schistosome infections in mice, meeting the criteria for lead progression indicated by WHO. Comparisons with previous in vivo studies with praziquantel suggests that these inhibitors outperform the drug of choice for schistosomiasis against juvenile worms.

Human Schistosomiasis Vaccines as Next Generation Control Tools

Human schistosomiasis remains one of the most important yet neglected tropical diseases, with the latest estimates from the Global Burden of Disease Study indicating that over 140 million people are infected with schistosomes [...]

Comparison of intestinal flora between patients with chronic and advanced Schistosoma japonicum infection

Background

Schistosoma japonicum infection is an important public health problem, imposing heavy social and economic burdens in 78 countries worldwide. However, the mechanism of transition from chronic to advanced S. japonicum infection remains largely unknown. Evidences suggested that gut microbiota plays a role in the pathogenesis of S. japonicum infection. However, the composition of the gut microbiota in patients with chronic and advanced S. japonicum infection is not well defined. In this study, we compared the composition of the intestinal flora in patients with chronic and advanced S. japonicum infection.

Methods

The feces of 24 patients with chronic S. japonicum infection and five patients with advanced S. japonicum infection from the same area were collected according to standard procedures, and 16S rRNA sequencing technology was used to analyze the intestinal microbial composition of the two groups of patients.

Results

We found that alteration occurs in the gut microbiota between the groups of patients with chronic and advanced S. japonicum infections. Analysis of alpha and beta diversity indicated that the diversity and abundance of intestinal flora in patients with advanced S. japonicum infection were lower than those in patients with chronic S. japonicum infection. Furthermore, Prevotella 9, Subdoligranulum, Ruminococcus torques, Megamonas and Fusicatenibacter seemed to have potential to discriminate different stages of S. japonicum infection and to act as biomarkers for diagnosis. Function prediction analysis revealed that microbiota function in the chronic group was focused on translation and cell growth and death, while that in the advanced group was concentrated on elevating metabolism-related functions.

Conclusions

Our study demonstrated that alteration in gut microbiota in different stages of S. japonicum infection plays a potential role in the pathogenesis of transition from chronic to advanced S. japonicum infection. However, further validation in the clinic is needed, and the underlying mechanism requires further study.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-022-05539-6.

De Novo Design of Cathepsin B1 Inhibitors as Potential Anti-Schistosomal Agents Using Computational Studies

Background

Schistosomiasis is the world’s second most devastating disease after malaria and the leading cause of disease and mortality for more than 200 million people in developing countries. Cysteine proteases, in particular SmCB1, are the most well-researched biological targets for this disorder.

Objective

To apply computational techniques to design new antischistosomal agents against SmCB1 protein with favorable pharmacokinetic properties.

Methods

The smCB1 receptor-based pharmacophore model was created and used to screen 567,000 fragments from the Enamine library. The best scoring fragments have been linked to build novel compounds that were subjected to molecular docking, MM-GBSA free energy estimation, ADME prediction, and molecular dynamics.

Results

A seven-point pharmacophore hypothesis ADDDRRR was created. The developed hypothesis was used to screen 1.3 M fragment conformations. Among them, 23,732 fragments matched the hypothesis and screened against the protein. The top 50 fragments were used to design new 7745 compounds using the Breed ligand panel which were subjected to docking and MMGBSA binding energy. This led to the identification of 10 compounds with better docking scores (−8.033– −7.483 kcal/mol) and lower-bound free energies (−58.49 – −40.02 kcal/mol) compared to the reference bound ligand. Most of the designed compounds demonstrated good drug-like properties. Concerning Molecular dynamics (MD) simulation results, a low root mean square deviation (RMSD) range (0.25–1.2 Å) was found for the top 3 complexes which indicated their stability.

Conclusion

We identified compounds that could be potential candidates in the search for novel Schistosoma mansoni inhibitors by targeting SmCB1 utilizing various computational tools. Three newly designed compounds namely breed 1, 2, and 3 showed promising affinity to the target as well as favorable drug-like properties which might be considered potential anti-schistosomal agents.

Cervical lesion proportion measure using a digital gridded imaging technique to assess cervical pathology in women with genital schistosomiasis

Female genital schistosomiasis (FGS) is characterized by a pattern of lesions which manifest at the cervix and the vagina, such as homogeneous and grainy sandy patches, rubbery papules in addition to neovascularization. A tool for quantification of the lesions is needed to improve FGS research and control programs. Hitherto, no tools are available to quantify clinical pathology at the cervix in a standardized and reproducible manner. This study aimed to develop and validate a cervical lesion proportion (CLP) measure for quantification of cervical pathology in FGS. A digital imaging technique was applied in which a grid containing 424 identical squares was positioned on high resolution digital images from the cervix of 70 women with FGS. CLP was measured for each image by observers counting the total number of squares containing at least one type of FGS associated lesion. For assessment of inter- and intra-observer reliability, three different observers measured CLP independently. In addition, a rubbery papule count (RPC) was determined in a similar manner. The intraclass correlation coefficient was 0.94 (excellent) for the CLP inter-rater reliability and 0.90 (good) for intra-rater reliability and the coefficients for the RPC were 0.88 and 0.80 (good), respectively. The CLP facilitated a reliable and reproducible quantification of FGS associated lesions of the cervix. In the future, grading of cervical pathology by CLP may provide insight into the natural course of schistosome egg-induced pathology of the cervix and may have a role in assessing praziquantel treatment efficacy against FGS.

Trial Registration: ClinicalTrials.gov, trial number NCT04115072; trial URL https://clinicaltrials.gov/ct2/show/NCT04115072?term=Female+genital+schistosomiasis+AND+Madagascar&draw=2&rank=1.

Female genital schistosomiasis (FGS) is characterized by development of egg-induced chronic inflammatory lesions of the cervix and the vagina. FGS causes various symptoms such vaginal discharge, genital itch, pelvic pain and post-coital bleeding, and the disease is further associated with reproductive complications such as ectopic pregnancy and infertility. Moreover, FGS is today hypothesized as a risk factor for transmission of HIV in Sub-Saharan Africa. General prevention directed against Schistosoma infection and use of praziquantel as anthelmintic drug therapy are cornerstones in the FGS control strategy. The aim of the study was to test inter- and intra-rater reliability using a cervical lesion proportion (CLP) measure in a series of digital images from women living in a Schistosoma haematobium hyperendemic area in Madagascar”. In that overall context, we have developed a digital image-based tool for quantitative assessment of FGS associated cervical lesions, which enables evaluation of treatment outcome at individual as well as community level with particular focus on resolution of cervical pathology, but also on risk of recurrence. The tool will also provide new information in understanding the natural history of FGS including development of clinical pathology.

Schistosome AMPK Is Required for Larval Viability and Regulates Glycogen Metabolism in Adult Parasites

On entering the mammalian host, schistosomes transition from a freshwater environment where resources are scarce, to an environment where there is an unlimited supply of glucose, their preferred energy substrate. Adult schistosome glycolytic activity consumes almost five times the parasite's dry weight in glucose per day to meet the parasite's energy demands, and the schistosome glycolytic enzymes and mechanisms for glucose uptake that sustain this metabolic activity have previously been identified. However, little is known of the parasite processes that regulate schistosome glucose metabolism. We previously described the Schistosoma mansoni ortholog of 5' AMP-Activated Protein Kinase (AMPK), which is a central regulator of energy metabolism in eukaryotes, and characterized the developmental regulation of its expression and activity in S. mansoni. Here we sought to explore the function of AMPK in schistosomes and test whether it regulates parasite glycolysis. Adult schistosomes mounted a compensatory response to chemical inhibition of AMPK α, resulting in increased AMPK α protein abundance and activity. RNAi inhibition of AMPK α expression, however, suggests that AMPK α is not required for adult schistosome viability in vitro. Larval schistosomula, on the other hand, are sensitive to chemical AMPK α inhibition, and this correlates with inactivity of the AMPK α gene in this life cycle stage that precludes a compensatory response to AMPK inhibition. While our data indicate that AMPK is not essential in adult schistosomes, our results suggest that AMPK regulates adult worm glycogen stores, influencing both glycogen utilization and synthesis. AMPK may therefore play a role in the ability of adult schistosomes to survive in vivo stressors such as transient glucose deprivation and oxidative stress. These findings suggest that AMPK warrants further investigation as a potential drug target, especially for interventions aimed at preventing establishment of a schistosome infection.

Clinical interventions for tungiasis (sand flea disease): a systematic review

Tungiasis (sand flea disease) is an epidermal parasitic skin disease occurring in resource-limited communities. There is no standard treatment for tungiasis, and available treatment options are scarce. To our knowledge, this is the first systematic review aimed to assess randomised controlled trials (RCTs) investigating interventions for tungiasis. We systematically searched databases including MEDLINE (EBSCOhost), CENTRAL, CINAHL, PubMed, Web of Science, SciELO, LILACS and Embase (Scopus) for RCTs in any language, from inception of the databases until June 12, 2021. RCTs exploring preventive and therapeutic interventions for tungiasis were eligible. We used the revised Cochrane Collaboration's risk of bias tool to assess the risk of bias and Jadad scale to quantify the methodological quality of the RCTs. Of the 1839 identified records, only eight RCTs involving 808 participants were included, and several methodological deficiencies were identified in most of the trials. Trial interventions included: oral drugs niridazole and ivermectin and topical interventions of ivermectin lotion, metrifonate lotion, thiabendazole lotion, thiabendazole ointment, dimeticones (NYDA), and a neem seed and coconut oils-based mixture for treatment and coconut oil-based lotion (Zanzarin) for prevention. The coconut oil-based lotion for prevention and dimeticones for treatment of tungiasis have displayed the most promise. Most of the RCTs included in this study had low methodological quality. There is a clear unmet need for high-quality RCTs examining safe and effective prevention and treatment alternatives of tungiasis in endemic settings.

Synthesis and therapeutic delivery approaches for praziquantel: a patent review (2010-present)

INTRODUCTION

: Among all the anti-schistosomal drugs, praziquantel has been the most widely used. However, some major challenges have been faced using the drug in the treatment of schistosome infections.

AREAS COVERED

: Several approaches used in the synthesis of praziquantel aimed at reducing the time and cost of production, the toxicity and experimental harsh conditions are discussed. Also, patented methods involved in the pharmaceutical reformulation of praziquantel in the treatment of diverse endoparasitic infestations are reported. Additionally, future perspectives in terms of nanomedicine approach in the formulation of praziquantel are highlighted.

EXPERT OPINION

: Lipid-based nanosystems (LBNSs) formulations can be used to overcome the shortcomings associated with the use of praziquantel in the schistosomiasis treatment due to their amphipathic nature. This could be a promising vehicle for the delivery of praziquantel, which could in turn improve the bioavailability, as well as reduce the frequent dose of the drug and improve patient compliance. This may sustain the release of the drug and improve the rapid conversion of the drug into inactive metabolite due to rapid metabolism. Additionally, LBNSs approach could increase and improve the lipophilicity of the drug, which could make it easier to interact with the hydrophobic cores of the worm tegument.

Structure, Immunoreactivity, and In Silico Epitope Determination of SmSPI S. mansoni Serpin for Immunodiagnostic Application

The human parasitic disease Schistosomiasis is caused by the Schistosoma trematode flatworm that infects freshwaters in tropical regions of the world, particularly in Sub-Saharan Africa, South America, and the Far-East. It has also been observed as an emerging disease in Europe, due to increased immigration. In addition to improved therapeutic strategies, it is imperative to develop novel, rapid, and sensitive diagnostic tests that can detect the Schistosoma parasite, allowing timely treatment. Present diagnosis is difficult and involves microscopy-based detection of Schistosoma eggs in the feces. In this context, we present the 3.22 Å resolution crystal structure of the circulating antigen Serine protease inhibitor from S. mansoni (SmSPI), and we describe it as a potential serodiagnostic marker. Moreover, we identify three potential immunoreactive epitopes using in silico-based epitope mapping methods. Here, we confirm effective immune sera reactivity of the recombinant antigen, suggesting the further investigation of the protein and/or its predicted epitopes as serodiagnostic Schistosomiasis biomarkers.

Current and Novel Therapies Against Helminthic Infections: The Potential of Antioxidants Combined with Drugs

Infections caused by Schistosoma haematobium and Opisthorchisviverrini are classified as Group 1 biological carcinogen and it has been postulated that parasites produce oxysterol and estrogen-like metabolites that might be considered as initiators of infection-associated carcinogenesis. Chemotherapy for these helminthic infections relies on a single drug, praziquantel, (PZQ) that mainly targets the parasite. Additionally, PZQ has some major drawbacks as inefficacy against juvenile form and alone it is not capable to counteract pathologies associated to infections or prevent carcinogenesis. There is an urgent need to develop novel therapeutic approaches that not only target the parasite but also improve the pathologies associated to infection, and ultimately, counteract or/and prevent the carcinogenesis processes. Repurposing the drug in combination of compounds with different modes of action is a promising strategy to find novel therapeutics approaches against these helminthic infections and its pathologies. Here, we emphasized that using antioxidants either alone or combined with anthelmintic drugs could ameliorate tissue damage, infection-associated complications, moreover, could prevent the development of cancer associated to infections. Hence, antioxidants represent a potential adjuvant approach during treatment to reduce morbidity and mortality. Despite the success of some strategies, there is a long way to go to implement novel therapies for schistosomiasis.

Praziquantel ameliorates CCl4 -induced liver fibrosis in mice by inhibiting TGF-β/Smad signalling via up-regulating Smad7 in hepatic stellate cells

BACKGROUND AND PURPOSE

Praziquantel is a schistosomicide, which has been used for more than 30 years due to its efficiency, safety, and mild side effects. Previous studies showed that prolonged treatment with praziquantel suppressed the development of liver fibrosis in mice with schistosomiasis. In this study, we investigated the potential mechanisms underlying the antifibrotic effects of praziquantel.

EXPERIMENTAL APPROACH

To avoid the effect of schistosomicidal activity of praziquantel against liver fibrosis induced by Schistosoma japonicum infection, we established a mouse model of carbon tetrachloride (CCl₄ )-induced liver fibrosis for in vivo studies and used TGF-β1-stimulated human hepatic stellate cell line (LX-2) in addition to other fibroblast-like cell line (MES13) and fibroblast cell line (NIH3T3) in vitro. Western blotting, immunohistochemistry, quantitative real-time PCR, siRNA, and immunofluorescence staining were utilized to assess the expression of key molecules in liver fibrosis and the TGF-β/Smad pathway.

KEY RESULTS

Praziquantel significantly attenuated CCl₄ -induced liver fibrosis by inhibiting the activation of hepatic stellate cells (HSCs) and expression of collagen matrix via enhancement of Smad7 expression, which were confirmed in LX-2, MES13, and NIH3T3 cells in vitro. In contrast, knockdown of Smad7 in LX-2 cells prevented praziquantel-mediated inhibition of LX-2 cell activation and TGF-β1-mediated collagen type I α1 induction, revealing the critical role of Smad7 in the antifibrotic effect of praziquantel during liver fibrosis.

CONCLUSIONS AND IMPLICATIONS

PZQ exhibited a strong efficacy against liver fibrosis by inhibiting activation of HSCs via Smad7 up-regulation, suggesting potential broad utility in treatment of diseases characterized by liver fibrosis.

PZQ Therapy: How Close are we in the Development of Effective Alternative Anti-schistosomal Drugs?

Today schistosomiasis, caused mainly by the three major schistosome species (S. mansoni, S. haematobium and S. japonicum), has for many decades and still continues to be on a rapid and swift rise globally, claiming thousands of lives every year and leaving 800 million people at the risk of infection. Due to the high prevalence of this disease and the steady increase in the infection rates, praziquantel (PZQ) remains the only effective drug against this acute disease although it has no effect on the juvenile schistosome parasite. However, no significant approaches have been made in recent years in the discovery of new or alternative drugs and unfortunately, resistance to this drug has been reported in some parts of the world. Therefore, it is imperative to develop a new drug for this debilitating disease. In this review, a brief history of past, present, and new promising anti-schistosomal drugs is presented.

Schistosomiasis

Schistosomiasis (bilharzia) is a neglected tropical disease caused by parasitic flatworms (blood flukes) of the genus Schistosoma, with considerable morbidity in parts of the Middle East, South America, Southeast Asia and, particularly, in sub-Saharan Africa. Infective larvae grow in an intermediate host (fresh-water snails) before penetrating the skin of the definitive human host. Mature adult worms reside in the mesenteric (Schistosoma mansoni and Schistosoma japonicum) or pelvic (Schistosoma haematobium) veins, where female worms lay eggs, which are secreted in stool or urine. Eggs trapped in the surrounding tissues and organs, such as the liver and bladder, cause inflammatory immune responses (including granulomas) that result in intestinal, hepato-splenic or urogenital disease. Diagnosis requires the detection of eggs in excreta or worm antigens in the serum, and sensitive, rapid, point-of-care tests for populations living in endemic areas are needed. The anti-schistosomal drug praziquantel is safe and efficacious against adult worms of all the six Schistosoma spp. infecting humans; however, it does not prevent reinfection and the emergence of drug resistance is a concern. Schistosomiasis elimination will require a multifaceted approach, including: treatment; snail control; information, education and communication; improved water, sanitation and hygiene; accurate diagnostics; and surveillance-response systems that are readily tailored to social-ecological settings.

Prevalence and intensity of Schistosoma haematobium infection among schoolchildren in central Zambia before and after mass treatment with a single dose of praziquantel

Introduction

Urinary schistosomiasis caused by Schistosoma haematobium is common in some parts of Lusaka Province, Zambia, where water contact activity is high and sanitation is poor. We conducted a longitudinal study in Ng'ombe Compound of Lusaka, between 2007 and 2015, to observe the prevalence and intensity of S. haematobium infection among community primary school children, before and after receiving a single dose of praziquantel.

Materials and Methods

A total of 975 (445 females and 530 males) pupils, aged 9-16 years, were tested for S. haematobium at baseline. After mass treatment with praziquantel in 2010, 1570 pupils (785 females and 785 males), aged 9-15 years, were examined for S. haematobium eggs, from 2011 to 2015.

Results

At baseline, 279 out of 975 of the children were infected, with light infections constituting 84.9% and 15.1% classified as heavy infection. After mass treatment with praziquantel, the prevalence rate dropped, slightly, to 20.3% (63 out of 310) in 2011. However, it increased the following years up to 38% (133 out of 350) in 2015, with prevalence rates higher in males than females. The average number of heavy infection cases increased to 24.3% (120 out of 494) after treatment, reducing cases of light infections to 75.7% (374 out of 494).

Conclusion

This study revealed that mass treatment with a single dose of praziquantel was not sufficient to significantly reduce the transmission of schistosomiasis. Further studies will need to evaluate whether multiple praziquantel treatments will be more therapeutically effective in limiting future incidences.

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.

Elimination of Schistosoma mansoni in infected mice by slow release of artemisone

The current treatment of schistosomiasis is based on the anti-helminthic drug praziquantel (PZQ). PZQ affects only the adult stages of schistosomes. In addition, resistance to PZQ is emerging. We suggest a drug, which could serve as a potential alternative or complement to PZQ, and as a means of treating infections at earlier, pre-granuloma stage. Derivatives of the peroxidic antimalarial drug artemisinin have been indicated as alternatives, because both plasmodia and schistosomes are blood-feeding parasites. The mechanism of action of artemisinins is related to oxidative effects of the artemisinins on intracellular reductants leading to formation of cytotoxic reactive oxygen species. We used artemisone, which has improved pharmacokinetics and anti-plasmodial activity, and reduced toxicity compared to other artemisinins in clinical use against malaria. We infected adult mice by subcutaneous injection of S. mansoni cercariae (about 200) and treated them at various times post infection by the following methods: i. artemisone suspension administered by gavage (400-450 mg/kg); ii. subcutaneous injection of a gel containing a known concentration of artemisone (115-120 mg/kg); iii. subcutaneous insertion of the drug incorporated in a solid polymer (56-60 mg/kg); iv. intraperitoneal injection of the drug solubilized in DMSO (115-120 mg/kg). Drug administration in polymers was performed to enable slow release of the artemisone that was verified in vivo and in vitro bioassays using drug-sensitive malaria parasites. We found superior strong anti-schistosome effects up to a total reduction of worm number, mainly following repetitive treatments with the drug absorbed in the polymers (73.1% and 95.9% reduction in mice treated with artemisone in gel 7 and 14, and 21, 28 and 35 days post infection, respectively). The results indicate that artemisone has a potent anti-schistosome activity. Its main importance in this context is its effectiveness in treating hosts harboring juvenile schistosomes, before egg-deposition and induction of deleterious immune responses.

Histone deacetylase inhibition modulates histone acetylation at gene promoter regions and affects genome-wide gene transcription in Schistosoma mansoni

BACKGROUND

Schistosomiasis is a parasitic disease infecting hundreds of millions of people worldwide. Treatment depends on a single drug, praziquantel, which kills the Schistosoma spp. parasite only at the adult stage. HDAC inhibitors (HDACi) such as Trichostatin A (TSA) induce parasite mortality in vitro (schistosomula and adult worms), however the downstream effects of histone hyperacetylation on the parasite are not known.

METHODOLOGY/PRINCIPAL FINDINGS

TSA treatment of adult worms in vitro increased histone acetylation at H3K9ac and H3K14ac, which are transcription activation marks, not affecting the unrelated transcription repression mark H3K27me3. We investigated the effect of TSA HDACi on schistosomula gene expression at three different time points, finding a marked genome-wide change in the transcriptome profile. Gene transcription activity was correlated with changes on the chromatin acetylation mark at gene promoter regions. Moreover, combining expression data with ChIP-Seq public data for schistosomula, we found that differentially expressed genes having the H3K4me3 mark at their promoter region in general showed transcription activation upon HDACi treatment, compared with those without the mark, which showed transcription down-regulation. Affected genes are enriched for DNA replication processes, most of them being up-regulated. Twenty out of 22 genes encoding proteins involved in reducing reactive oxygen species accumulation were down-regulated. Dozens of genes encoding proteins with histone reader motifs were changed, including SmEED from the PRC2 complex. We targeted SmEZH2 methyltransferase PRC2 component with a new EZH2 inhibitor (GSK343) and showed a synergistic effect with TSA, significantly increasing schistosomula mortality.

CONCLUSIONS/SIGNIFICANCE

Genome-wide gene expression analyses have identified important pathways and cellular functions that were affected and may explain the schistosomicidal effect of TSA HDACi. The change in expression of dozens of histone reader genes involved in regulation of the epigenetic program in S. mansoni can be used as a starting point to look for possible novel schistosomicidal targets.

Protective immune responses against Schistosoma mansoni infection by immunization with functionally active gut-derived cysteine peptidases alone and in combination with glyceraldehyde 3-phosphate dehydrogenase

BACKGROUND

Schistosomiasis, a severe disease caused by parasites of the genus Schistosoma, is prevalent in 74 countries, affecting more than 250 million people, particularly children. We have previously shown that the Schistosoma mansoni gut-derived cysteine peptidase, cathepsin B1 (SmCB1), administered without adjuvant, elicits protection (>60%) against challenge infection of S. mansoni or S. haematobium in outbred, CD-1 mice. Here we compare the immunogenicity and protective potential of another gut-derived cysteine peptidase, S. mansoni cathepsin L3 (SmCL3), alone, and in combination with SmCB1. We also examined whether protective responses could be boosted by including a third non-peptidase schistosome secreted molecule, glyceraldehyde 3-phosphate dehydrogenase (SG3PDH), with the two peptidases.

METHODOLOGY/PRINCIPAL FINDINGS

While adjuvant-free SmCB1 and SmCL3 induced type 2 polarized responses in CD-1 outbred mice those elicited by SmCL3 were far weaker than those induced by SmCB1. Nevertheless, both cysteine peptidases evoked highly significant (P < 0.005) reduction in challenge worm burden (54-65%) as well as worm egg counts and viability. A combination of SmCL3 and SmCB1 did not induce significantly stronger immune responses or higher protection than that achieved using each peptidase alone. However, when the two peptidases were combined with SG3PDH the levels of protection against challenge S. mansoni infection reached 70-76% and were accompanied by highly significant (P < 0.005) decreases in worm egg counts and viability. Similarly, high levels of protection were achieved in hamsters immunized with the cysteine peptidase/SG3PDH-based vaccine.

CONCLUSIONS/SIGNIFICANCE

Gut-derived cysteine peptidases are highly protective against schistosome challenge infection when administered subcutaneously without adjuvant to outbred CD-1 mice and hamsters, and can also act to enhance the efficacy of other schistosome antigens, such as SG3PDH. This cysteine peptidase-based vaccine should now be advanced to experiments in non-human primates and, if shown promise, progressed to Phase 1 safety trials in humans.

Immunomodulatory effects of metal salts at sub-toxic concentrations

Because different metals are used in complementary medicine for the treatment of diseases related to a dysfunction of the immune system, this study aimed at determining the immunomodulatory potential of Pb(NO₃ )₂ , AuCl₃ , Cu(NO₃ )₂ , HgCl₂ , AgNO₃ , SnCl₂ , AsCl₃ and SbCl₃ at sub-toxic concentrations and at assessing possible toxic side effects of low-concentrated metal preparations. The influence of the metal salts on primary human mononuclear cells was analyzed by measuring cell viability using the water-soluble tetrazolium salt assay, apoptosis and necrosis induction by annexin V/propidium iodide staining and proliferation by carboxyfluorescein diacetate succinimidyl ester staining and flow cytometry. Effects on T-cell activation were assessed with CD69 and CD25 expression using flow cytometry whereas CD83, CD86 and CD14 expression was measured to evaluate the influence on dendritic cell maturation. Alterations of interleukin-2 and interferon-γ secretion were detected by enzyme-linked immunosorbent assay and genotoxic effects were analyzed using the comet assay. At sub-toxic concentrations retardation of T-cell proliferation was caused by Pb(NO₃ )₂ , AuCl₃ and Cu(NO₃ )₂ and inhibitory effects on interleukin-2 secretion were measured after incubation with Pb(NO₃ )₂ , AuCl₃ , Cu(NO₃ )₂ , HgCl₂ and AsCl_3. Cu(NO₃ )₂ had immunosuppressive activity at dosages within the serum reference range for copper. All other metal salts showed effects at dosages above upper serum limits of normal. Therefore, only low-concentrated copper preparations are promising to have immunomodulatory potential. Toxic side effects of metal preparations used in complementary medicine are improbable because upper limits of metals set in the drinking water ordinance are either not exceeded or the duration of their application is limited. Copyright © 2016 John Wiley & Sons, Ltd.

Discovery of Antischistosomal Drug Leads Based on Tetraazamacrocyclic Derivatives and Their Metal Complexes

Praziquantel (PZQ) is the only drug available for the treatment of schistosomiasis, and since its large-scale use might be associated with the onset of resistance, new antischistosomal drugs should be developed. A series of 26 synthetic tetraazamacrocyclic derivatives and their metal complexes were synthesized, characterized, and screened for antischistosomal activity by application of a phased screening program. The compounds were first screened against newly transformed schistosomula (NTS) of harvested Schistosoma mansoni cercariae, then against adult worms, and finally, in vivo using the mouse model of S. mansoni infection. At a concentration of 33 μM, incubation with a total of 12 compounds resulted in the mortality of NTS at the 62% to 100% level. Five of these showing 100% inhibition of viability of NTS at 10 μM were selected for further screening for determination of the 50 inhibitory concentrations (IC50s) against both NTS and adult worms. Against NTS, all 5 compounds showed IC50s comparable to the IC50 of the standard drug, PZQ (0.87 to 9.65 μM for the 5 compounds versus 2.20 μM for PZQ). Three of these, which are the bisquinoline derivative of cyclen and its Fe(2+) and Mn(2+) complexes, showed micromolar IC50s (1.62 μM, 1.34 μM, and 4.12 μM, respectively, versus 0.10 μM for PZQ) against adult worms. In vivo, the worm burden reductions were 12.3%, 88.4%, and 74.5%, respectively, at a single oral dose of 400 mg/kg of body weight. The Fe(2+) complex exhibited activity in vivo comparable to that of PZQ, pointing to the discovery of a novel drug lead for schistosomiasis.