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Schistosomiasis remains a major neglected tropical disease. The treatment and control of schistosomiasis rely on a single drug, praziquantel (PZQ). Despite its efficacy, treatment with PZQ presents some major drawbacks including an inability of the chemotherapy to reverse disease-induced fibrosis and the prospect of the emergence of drug resistance. Here, we investigated a novel therapeutic approach with antioxidant biomolecules in combination with PZQ against the adult developmental stage of Schistosoma mansoni and oviposition in vitro, given that this therapeutic approach achieved synergistic/additive activity against larval schistosomes. The antioxidants curcumin and oxadiazole per se exhibited antischistosomal activity against adult worms leading to severe morphological alterations and death. Additionally, the antioxidant flavone combined with vandetanib or imatinib improved antischistosomal activity against adult forms. By contrast, however, these antioxidant-anthelmintic combinations were not as effective against adults in comparison to larval schistosomes. Nevertheless, the antioxidants alone or combined with drugs inhibited oviposition. [ABSTRACT FROM AUTHOR]

The availability of genome and transcriptome data of the liver fluke Opisthorchis viverrini provides the foundation for exploration of gene function and its effect on host-parasite interactions and pathogenesis of O. viverrini-associated bile duct cancer. Functional genomics approaches address the function of DNA at levels of the gene, RNA transcript and protein product using informative manipulations of the genome, epigenome, transcriptome, proteome, microbiome and metabolome. Advances in functional genomics for O. viverrini have thus far focused on RNA interference. The flukes have been transfected with double-stranded RNAs aiming to silence target gene expression. In general, this approach for functional genomics investigation of this pathogen has been found to be tractable and efficient: suppression of messenger RNA expression in O. viverrini results in reduction of protein activity and phenotypic changes. Future perspectives for functional genomics of this liver fluke and close phylogenetic relatives are also discussed. [ABSTRACT FROM AUTHOR]

The article focuses on aspects of the snail or schistosome relationship elucidating common pathways to enable both snails and humans to accommodate parasitism by schistosomes in view of physiological and immunological environments. It notes that the excretory or secretory products (ESPs) of the miracidium include the stress-inducing factor. Gene repositioning in B. glabrata by schistosomes exemplifies how a eukaryotic pathogen influences hijack of the genome behavior of its host.

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. [ABSTRACT FROM AUTHOR]

The article discusses a research on Helminth pathogens infection-induced malignancy. It mentions how infection with helminths leads to cholangiocarcinoma and squamous cell carcinoma of the urinary bladder. It also mentions impact of ingestion of undercooked freshwater fish infected with the metacercaria stage of species of liver flukes. It mentions Cancer occur in the DNA of the genome of the target cell, while the mutations lead to uncontrolled cellular proliferation and metastasis.

Liver fluke infection caused by Opisthorchis viverrini is a major public health problem in Thailand and adjacent countries. In addition to infection-associated morbidity, infection with O. viverrini and the related Clonorchis sinensis are unarguable risk factors for cholangiocarcinoma (CAA, bile-duct cancer). Here we review the pathogenesis of opisthorchiasis and the association between O. viverrini infection and bile-duct cancer, focusing on the molecular parallels between wound healing, chronic inflammation, and cancer development. We review a schema for human disease progression from fluke infection, chronic opisthorchiasis, advanced periductal fibrosis, and cholangiocarcinogenesis, and present a rationale for biomarker discovery to facilitate early intervention. We conclude by addressing post-genomic advances with a view to developing new control strategies to combat this infectious cancer. [Copyright &y& Elsevier]

Abstract: A cathepsin B-like cysteine protease belonging to family C1 is abundantly expressed in the transcriptome and proteome of the carcinogenic liver fluke of humans, Opisthorchis viverrini. This enzyme is present in excretory/secretory (ES) products released by parasites cultured in vitro. This study evaluated the performance of recombinant O. viverrini cathepsin B1 (rOv-CB-1) as an antigen for immunodiagnosis of opisthorchiasis. The full length Ov-CB-1 cDNA was cloned and recombinant protein was produced in catalytically active form in Pichia pastoris. The recombinant Ov-CB-1 (rOv-CB-1) was affinity purified via nickel-NTA chromatography and tested in enzyme-linked immunosorbent assays (ELISA) with human sera from an opisthorchiasis endemic area. Sera from egg-positive O. viverrini infections produced a strong IgG antibody response to rOv-CB-1 both in ELISA and immunoblot analysis. The sensitivity and specificity of the ELISA test was 67% and 81%, respectively. These findings support the feasibility of using recombinant Ov-CB-1 in ELISA for the serodiagnosis of human opisthorchiasis. [Copyright &y& Elsevier]

Abstract: Peptides, bound to the tegument of live Schistosoma japonicum schistosomula, were differentially screened by phage display in vitro using three rounds of reverse absorption and bio-panning. Three M13 phage peptides were isolated and identified by determination of their recovery rate, immunohistochemical localization, immunoblot analysis, and their anti-schistosomal effects in vivo and in vitro. Of the three, M13 phage peptide ZL4 (MppZL4, YSGLQDSSLRLR, 1.4kDa, pI 8.8) bound to the tegument of mechanically transformed schistosomula and to other developmental stages of S. japonicum from the mammalian host. By contrast, MppZL4 did not bind to the surface of cercariae. To further examine its binding properties, MppZL4 was conjugated to Rhodamine B (RhB-YSGLQDSSLRLR, RhB-ZL4) and a peptide control (RhB-AIPYFSGILQWR, RhB-12P) was similarly synthesized. The binding capacities of RhB-ZL4 to the surface membrane of S. japonicum schistosomula in vitro and of S. japonicum adult worms in vivo were examined and revealed specificity for binding. When examined for anti-parasite activity, both MppZL4 and RhB-ZL4 exhibited a potent schistosomicidal effect in vitro. Further MppZL4 also affected the growth and development of schistosomula in vivo. These findings extend previous studies showing that phage display techniques can recover polypeptides that bind specifically to living schistosomes and, moreover, that these bound peptides have the potential to inhibit key physiological processes in these parasites. Our findings suggest further that ectogenic polypeptides, which can bind to the tegument of S. japonicum, might be adapted as vectors to deliver experimental probes and/or pharmacologically relevant compounds to the schistosome tegument, including drugs and immunological mediators. [Copyright &y& Elsevier]

Abstract: Although draft genome sequences of two of the major human schistosomes, Schistosoma japonicum and Schistosoma mansoni are available, the structures and characteristics of most genes and the influence of exogenous genes on the metabolism of schistosomes remain uncharacterized. Furthermore, which functional genomics approaches will be tractable for schistosomes are not yet apparent. Here, the vesicular stomatitis virus glycoprotein (VSVG)-pseudotyped pantropic retroviral vector pBABE-puro was modified to incorporate the human telomerase reverse transcriptase gene (hTERT) as a reporter, under the control of the retroviral long terminal repeat (LTR). Pseudotyped virions were employed to transduce S. japonicum to investigate the utility of retrovirus-mediated transgenesis of S. japonicum and the activity of human telomerase reverse transcriptase as a reporter transgene in schistosomes. Schistosomules perfused from experimentally infected rabbits were cultured for 6 days after exposure to the virions after which genomic DNAs from virus exposed and control worms were extracted. Analysis of RNA from transduced parasites and immunohistochemistry of thin parasite sections revealed expression of hTERT in the transduced worms. Expression of hTERT was also confirmed by immunoblot analysis. These findings indicated that S. japonicum could be effectively transduced by VSVG-pseudotyped retrovirus carrying the hTERT gene. Given the potential of hTERT to aid in derivation of immortalized cells, these findings suggest that this pantropic retroviral approach can be employed to transduce cells from specific tissues and organs of schistosomes to investigate the influence of transgene hTERT on growth and proliferation of schistosome cells. [ABSTRACT FROM AUTHOR]

More than two billion people (one-third of humanity) are infected with parasitic roundworms or flatworms, collectively known as helminth parasites. These infections cause diseases that are responsible for enormous levels of morbidity and mortality, delays in the physical development of children, loss of productivity among the workforce, and maintenance of poverty. Genomes of the major helminth species that affect humans, and many others of agricultural and veterinary significance, are now the subject of intensive genome sequencing and annotation. Draft genome sequences of the filarial worm Brugia malayi and two of the human schistosomes, Schistosoma japonicum and S. mansoni, are now available, among others. These genome data will provide the basis for a comprehensive understanding of the molecular mechanisms involved in helminth nutrition and metabolism, host-dependent development and maturation, immune evasion, and evolution. They are likely also to predict new potential vaccine candidates and drug targets. In this review, we present an overview of these efforts and emphasize the potential impact and importance of these new findings. [ABSTRACT FROM AUTHOR]

More than two billion people (one-third of humanity) are infected with parasitic roundworms or flatworms, collectively known as helminth parasites. These infections cause diseases that are responsible for enormous levels of morbidity and mortality, delays in the physical development of children, loss of productivity among the workforce, and maintenance of poverty. Genomes of the major helminth species that affect humans, and many others of agricultural and veterinary significance, are now the subject of intensive genome sequencing and annotation. Draft genome sequences of the filarial worm Brugia malayi and two of the human schistosomes, Schistosoma japonicum and S. mansoni, are now available, among others. These genome data will provide the basis for a comprehensive understanding of the molecular mechanisms involved in helminth nutrition and metabolism, host-dependent development and maturation, immune evasion, and evolution. They are likely also to predict new potential vaccine candidates and drug targets. In this review, we present an overview of these efforts and emphasize the potential impact and importance of these new findings. [ABSTRACT FROM AUTHOR]

Schistosomiasis, caused mainly by Schistosoma japonicum, S. mansoni, and S. hematobium, remains one of the most prevalent and serious parasitic diseases worldwide. The blood flukes have a complex life cycle requiring adaptation for survival in fresh water as free-living forms and as parasites in snail intermediate and vertebrate definitive hosts. Functional genomics analyses, including transcriptomic and proteomic approaches, have been performed on schistosomes, in particular S. mansoni and S. japonicum, using powerful high-throughput methodologies. These investigations have not only chartered gene expression profiles across genders and developmental stages within mammalian and snail hosts, but have also characterized the features of the surface tegument, the eggshell and excretory-secretory proteomes of schistosomes. The integration of the genomic, transcriptomic, and proteomic information, together with genetic manipulation on individual genes, will provide a global insight into the molecular architecture of the biology, pathogenesis, and host-parasite interactions of the human blood flukes. Importantly, these functional genomics analyses lay a foundation on which to develop new antischistosome vaccines as well as drug targets and diagnostic markers for treatment and control of schistosomiasis. [ABSTRACT FROM AUTHOR]

Helminths are parasitic worms. They are the most common infectious agents of humans in developing countries and produce a global burden of disease that exceeds better-known conditions, including malaria and tuberculosis. As we discuss here, new insights into fundamental helminth biology are accumulating through newly completed genome projects and the nascent application of transgenesis and RNA interference technologies. At the same time, our understanding of the dynamics of the transmission of helminths and the mechanisms of the Th2-type immune responses that are induced by infection with these parasitic worms has increased markedly. Ultimately, these advances in molecular and medical helminth biology should one day translate into a new and robust pipeline of drugs, diagnostics, and vaccines for targeting parasitic worms that infect humans. [ABSTRACT FROM AUTHOR]

Because tropical medicine and parasitology research has moved into the postgenomic era, an enormous amount of gene sequence information for parasitic helminths is now accumulating. These sequences undoubtedly hold information that can be used for new interventions and control. However, to exploit the new resource, methods for gene manipulation and transformation of parasitic worms are needed. Until recently, gene manipulation approaches had not been seriously addressed. This situation is now changing in response to the availability of genome sequences and other advances. In this article, we review advances in the transgenesis and gene silencing of parasitic worms. [Copyright &y& Elsevier]

Abstract: In contrast to the situations with model organisms and parasitic protozoa, progress with gene manipulation with schistosomes has been delayed by impediments that include our inability to maintain the life cycle in vitro, absence of immortalized cell lines, large genome sizes, unavailability of drug resistance markers and other difficulties. However, in the past few years, tangible progress has been reported towards development of tools for gene manipulation and transgenesis of schistosomes, and there is reason to believe that the field is on the verge of transformation into an era where genetic manipulation is routine. Recent reports dealing with approaches and tools to manipulate the genome and gene expression in schistosomes are reviewed here. [Copyright &y& Elsevier]

Twenty years ago, an article by Carter and Colley was published in an early issue of this journal. The report outlined pioneering studies by several laboratories into schistosome molecular biology and molecular genetics. To commemorate that prescient report and, in like fashion, to provide a brief (and non-comprehensive) synopsis of progress in this field up to the present time, I will outline some key aspects of the molecular biology of schistosomes that have been reported in the intervening years. [Copyright &y& Elsevier]

Abstract: Schistosoma mansoni is an important flatworm parasite of man that has remained intractable to experimental analyses of gene function. We have developed an approach for using dsRNA to target schistosome transcripts for RNA interference, and used it to address the role of cathepsin B (SmCB1), a cysteine protease that has been proposed to play a central role in hemoglobin digestion in the schistosome gut. Electroporation of 3h old larval schistosomes with SmCB1-specific dsRNA (SmCB1-dsRNA) resulted in a greater than 10-fold reduction in SmCB1 transcript levels that persisted for >20 days. RNAi mediated reductions in transcript levels led to associated reductions in SmCB1 enzyme activity. Schistosomes treated with SmCB1-dsRNA were viable and developed intestinal heme pigmentation indicative of hemoglobin digestion, but showed significant growth retardation when compared to control parasites, indicating that SmCB1 function is not essential for hemoglobin digestion but is necessary for normal parasite growth. This effect on growth was apparent when parasites were maintained in culture or introduced into mammalian hosts. The report sheds new light on the role of SmCB1 and provides a template for using RNAi to examine gene function in the mammal-parasitic stages of schistosomes during early development in vitro and in vivo. [Copyright &y& Elsevier]

Schistosomiasis is one of the most serious parasitic diseases. More than 250 million people are infected with schistosomes in the tropics or subtropics. The parasitic flukes have some unique biological features: dioecism, complex life cycles, mechanisms to avoid host immune responses, and an apparent reliance on host endocrine and immune signals to complete their development, maturation and egg production. Recently, a large dataset of expressed sequence tags (ESTs) were generated from Schistosoma japonicum and Schistosoma mansoni, from which numerous novel genes were identified. The transcriptome analyses provide the basis for a comprehensive understanding of the molecular mechanisms involved in schistosome nutrition and metabolism, host-dependent development and maturation, immune evasion and invertebrate evolution. In addition, new potential vaccine candidates and drug targets have been predicted. [Copyright &y& Elsevier]

Blood-feeding parasites employ a battery of proteolytic enzymes to digest the contents of their bloodmeal. Host haemoglobin is a major substrate for these proteases and, therefore, a driving force in the evolution of parasite-derived proteolytic enzymes. This review will focus on the digestive proteases of the major blood-feeding nematodes – hookworms (Ancylostoma spp. and Necator americanus) and the ruminant parasite, Haemonchus contortus – but also compares and contrasts these proteases with recent findings from schistosomes and malaria parasites. Haematophagous nematodes express proteases of different mechanistic classes in their intestines, many of which have proven or putative roles in degradation of haemoglobin and other proteins involved in nutrition. Moreover, the fine specificity of the relationships between digestive proteases and their substrate proteins provides a new molecular paradigm for understanding host–parasite co-evolution. Numerous laboratories are actively investigating these molecules as antiparasite vaccine targets. [Copyright &y& Elsevier]

The genome of Schistosoma mansoni contains a proviral form of a retrovirus-like long terminal repeat (LTR) retrotransposon, designated Boudicca. Sequence and structural characterization of the new mobile genetic element, which was found in bacterial artificial chromosomes prepared from S. mansoni genomic DNA, revealed the presence of three putative open reading frames (ORFs) bounded by direct LTRs of 328 bp in length. ORF1 encoded a retrovirus-like major homology region and a Cys/His box motif, also present in Gag polyproteins of related retrotransposons and retroviruses. ORF2 encoded enzymatic domains and motifs characteristic of a retrovirus-like polyprotein, including aspartic protease, reverse transcriptase, RNase H, and integrase, in that order, a domain order similar to that of the gypsy/Ty3 retrotransposons. An additional ORF at the 3' end of the retrotransposon may encode an envelope protein. Phylogenetic comparison based on the reverse transcriptase domain of ORF2 confirmed that Boudicca was a gypsy-like retrotransposon and showed that it was most closely related to CsRnl from the Oriental liver fluke Clonorchis sinensis and to kabuki from Bombyx mori. Bioinformatics approaches together with Southern hybridization analysis of genomic DNA of S. mansoni and the screening of a bacterial artificial chromosome library representing ≈8-fold coverage of the S. mansoni genome revealed that numerous copies of Boudicca were interspersed throughout the schistosome genome. By reverse transcription-PCR, mRNA transcripts were detected in the sporocyst, cercaria, and adult developmental stages of S. mansoni, indicating that Boudicca is actively transcribed in this trematode. [ABSTRACT FROM AUTHOR]

The control of helminth diseases of people and livestock continues to rely on the widespread use of anti-helminthic drugs. However, concerns with the appearance of drug resistant parasites and the presence of pesticide residues in food and the environment, has given further incentive to the goal of discovering molecular vaccines against these pathogens. The exponential rate at which gene and protein sequence information is accruing for many helminth parasites requires new methods for the assimilation and analysis of the data and for the identification of molecules capable of inducing immunological protection. Some promising vaccine candidates have been discovered, in particular cathepsin L proteases from Fasciola hepatica, aminopeptidases from Haemonchus contortus, and aspartic proteases from schistosomes and hookworms, all of which are secreted into the host tissues or into the parasite intestine where they play important roles in host-parasite interactions. Since secreted proteins, in general, are exposed to the immune system of the host they represent obvious candidates at which vaccines could be targeted. Therefore, in this article, we consider the potential values and uses of algorithms for characterising cDNAs amongst the collated helminth genomic information that encode secreted proteins, and methods for their selective isolation and cloning. We also review the variety of prokaryotic and eukaryotic cell expression systems that have been employed for the production and downstream purification of recombinant proteins in functionally active form, and provide an overview of the parameters that must be considered if these recombinant proteins are to be commercialised as vaccine therapeutics in humans and/or animals. [Copyright &y& Elsevier]

Hookworms are voracious blood-feeders. The cloning and functional expression of an aspartic protease, Na-APR-2, from the human hookworm Necator americanus are described here. Na-APR-2 is more similar to a family of nematode-specific, aspartic proteases than it is to cathepsin D or pepsin, and the term "nemepsins" for members of this family of nematode-specific hydrolases is proposed. Na-apr-2 mRNA was detected in blood-feeding, developmental stages only of N. americanus, and the protease was expressed in the intestinal lumen, amphids, and excretory glands. Recombinant Na-APR-2 cleaved human hemoglobin (Hb) and serum proteins almost twice as efficiently as the orthologous substrates from the nonpermissive dog host. Moreover, only 25% of the Na-APR-2 cleavage sites within human Hb were shared with those generated by the related N. americanus cathepsin D, Na-APR-1. Antiserum against Na-APR-2 inhibited migration of 50% of third-stage N. americanus larvae through skin, which suggests that aspartic proteases might be effective vaccines against human hookworm disease. [ABSTRACT FROM AUTHOR]

A substantial fraction of the genome of most eukaryotes, including those of metazoan parasites, is predicted to comprise repetitive sequences. Mobile genetic elements (MGEs) will make up much of these repetitive sequences, particularly the interspersed sequences. This article reviews information on MGEs that have colonized the genomes of metazoan parasites (i.e. parasites of parasites). Helminth and mosquito genomes, in particular, are compared with those of better-understood model organisms. MGEs from the genomes of metazoan parasites can be expected to have practical uses in transgenesis and epidemiological studies. [Copyright &y& Elsevier]

A new RTE-like, non-long terminal repeat retrotransposon, termed SjR2, from the human blood fluke, Schistosoma japonicum, is described. SjR2 is ∼3.9 kb in length and is constituted of a single open reading frame encoding a polyprotein with apurinic/apyrimidinic endonuclease and reverse transcriptase domains. The open reading frame is bounded by 5′- and 3′-terminal untranslated regions and, at its 3′-terminus, SjR2 bears a short (TGAC)3 repeat. Phylogenetic analyses based on conserved domains of reverse transcriptase or endonuclease revealed that SjR2 belonged to the RTE clade of non-long terminal repeat retrotransposons. Further, SjR2 was homologous, but probably not orthologous, to SR2 from the African blood fluke, Schistosoma mansoni; this RTE-like family of non-long terminal repeat retrotransposons appears to have arisen before the divergence of the extant schistosome species. Hybridisation analyses indicated that ∼10,000 copies of SjR2 were dispersed throughout the S. japonicum chromosomes, accounting for up to 14% of the nuclear genome. Messenger RNAs encoding the reverse transcriptase and endonuclease domains of SjR2 were detected in several developmental stages of the schistosome, indicating that the retrotransposon was actively replicating within the genome of the parasite. Exploration of the coding and non-coding regions of SjR2 revealed two notable characteristics. First, the recombinant reverse transcriptase domain of SjR2 expressed in insect cells primed reverse transcription of SjR2 mRNA in vitro. By contrast, recombinant SjR2-endonuclease did not appear to cleave schistosome or plasmid DNA. Second, the 5′-untranslated region of SjR2 was >80% identical to the 3′-untranslated region of a schistosome heat shock protein-70 gene (hsp-70) in the antisense orientation, indicating that SjR2-like elements were probably inserted into the non-coding regions of ancestral S. japonicum HSP-70, probably after the species diverged from S. mansoni. [Copyright &y& Elsevier]

A newly described non-long terminal repeat (non-LTR) retrotransposon element was isolated from the genome of the Oriental schistosome, Schistosoma japonicum. At least 1000 partial copies of the element, which was named pido, were dispersed throughout the genome of S. japonicum. As is usual with non-LTR retrotransposons, it is expected that many pido elements will be 5′-truncated. A consensus sequence of 3564 bp of the truncated pido element was assembled from several genomic fragments that contained pido-hybridizing sequences. The sequence encoded part of the first open reading frame (ORF), the entire second ORF and, at its 3′-terminus, a tandemly repetitive, A-rich (TA6TA5TA8) tail. The ORF1 of pido encoded a nucleic acid binding protein and ORF2 encoded a retroviral-like polyprotein that included apurinic/apyrimidinic endonuclease (EN) and reverse transcriptase (RT) domains, in that order. Based on its sequence and structure, and phylogenetic analyses of both the RT and EN domains, pido belongs to the chicken repeat 1 (CR1)-like lineage of elements known from the chicken, turtle, puffer fish, mosquitoes and other taxa. pido shared equal similarity with CR1 from chicken, an uncharacterized retrotransposon from Caenorhabditis elegans and SR1 (a non-LTR retrotransposon) from the related blood fluke Schistosoma mansoni; the level of similarity between pido and SR1 indicated that these two schistosome retrotransposons were related but not orthologous. The findings indicate that schistosomes have been colonized by at least two discrete CR1-like elements. Whereas pido did not appear to have a tight target site specificity, at least one copy of pido has inserted into the 3′-untranslated region of a protein-encoding gene (GenBank AW736757) of as yet unknown identity. mRNA encoding the RT of pido was detected by reverse transcription–polymerase chain reaction in the egg, miracidium and adult developmental stages of S. japonicum, indicating that the RT domain was transcribed and suggesting that pido was replicating actively and mobile within the S. japonicum genome. [Copyright &y& Elsevier]

The article discusses the newly completed whole genome sequence of Schistosoma haematobium, the leading cause of human schistosomiasis in Africa. It highlights the importance of this research in developing new tools to eliminate the disease, which affects over 90% of the roughly 200 million cases of schistosomiasis worldwide. The article also emphasizes the significant impact of urogenital schistosomiasis, caused by S. haematobium, on public health in Africa, including its association with AIDS and cancer. Despite its importance, research on S. haematobium has been limited compared to other schistosomes, but recent breakthroughs in animal models, in vitro systems, and omics technologies offer promising opportunities for further research and development. The article calls for international cooperation and increased support to advance S. haematobium research and address the disease burden in Africa. [Extracted from the article]

The newly completed whole genome sequence of Schistosoma haematobium, the leading cause of human schistosomiasis and an emerging cofactor in Africa's AIDS and cancer epidemics, together with rapidly advancing genetic manipulation technologies, is providing new insights that could lead to the development of a new generation of tools for eliminating this ancient scourge. [ABSTRACT FROM AUTHOR]

Background: Infections classified as group 1 biological carcinogens include the helminthiases caused by Schistosoma haematobium and Opisthorchis viverrini. The molecular mediators underlying the infection with these parasites and cancer remain unclear. Although carcinogenesis is a multistep process, we have postulated that these parasites release metabolites including oxysterols and estrogen-like metabolites that interact with host cell DNA. How and why the parasite produce/excrete these metabolites remain unclear. A gene encoding a CYP enzyme was identified in schistosomes and opisthorchiids. Therefore, it is reasonable hypothesized that CYP 450 might play a role in generation of pro-inflammatory and potentially carcinogenic compounds produced by helminth parasites such as oxysterols and catechol estrogens. Here, we performed enzymatic assays using several isoforms of CYP 450 as CYP1A1, 2E1 and 3A4 which are involved in the metabolism of chemical carcinogens that have been associated with several cancer. The main aim was the analysis of the role of these enzymes in production of helminth-associated metabolites and DNA-adducts. Method: The effect of cytochrome P450 enzymes CYP 1A1, 2E1 and 3A4 during the interaction between DNA, glycocholic acid and taurochenodeoxycholate sodium on the formation of DNA-adducts and metabolites associated with urogenital schistosomiasis (UGS) and opisthorchiasis was investigated in vitro. Liquid chromatography/mass spectrometry was used to detect and identify metabolites. Main findings: Through the enzymatic assays we provide a deeper understanding of how metabolites derived from helminths are formed and the influence of CYP 450. The assays using compounds similar to those previously observed in helminths as glycocholic acid and taurochenodeoxycholate sodium, allowed the detection of metabolites in their oxidized form and their with DNA. Remarkably, these metabolites were previously associated with schistosomiaisis and opisthorchiasis. Thus, in the future, it may be possible to synthesize this type of metabolites through this methodology and use them in cell lines to clarify the carcinogenesis process associated with these diseases. Principal conclusions: Metabolites similar to those detected in helminths are able to interact with DNA in vitro leading to the formation of DNA adducts. These evidences supported the previous postulate that imply helminth-like metabolites as initiators of helminthiases-associated carcinogenesis. Nonetheless, studies including these kinds of metabolites and cell lines in order to evaluate its potential carcinogenic are required. [ABSTRACT FROM AUTHOR]

Background: Treatment of schistosomiasis has relied on the anthelmintic drug praziquantel (PZQ) for more than a generation. Despite its celebrated performance for treatment and control of schistosomiasis and other platyhelminth infections, praziquantel has some shortcomings and the inability of this drug to counteract disease sequelae prompts the need for novel therapeutic strategies. Methods: Using a host-parasite model involving Biomphalaria glabrata and Schistosoma mansoni we established mechanical transformation of S. mansoni cercariae into newly transformed schistosomula (NTS) and characterized optimal culture conditions. Thereafter, we investigated the antischistosomal activity and ability of the antioxidants N-acetylcysteine (NAC) and resveratrol (RESV) to augment the performance of praziquantel and/or artesunate (AS) against larval stages of the parasite. Drug effects were evaluated by using an automated microscopical system to study live and fixed parasites and by transmission electron microscopy (TEM). Results: Transformation rates of cercariae to schistosomula reached ~ 70% when the manipulation process was optimized. Several culture media were tested, with M199 supplemented with HEPES found to be suitable for S. mansoni NTS. Among the antioxidants studied, RESV alone or combined with anthelminthic drugs achieved better results rather N-acetylcysteine (NAC). TEM observations demonstrated that the combination of AS + RESV induced severe, extensive alterations to the tegument and subtegument of NTS when compared to the constituent compounds alone. Two anthelmintic–antioxidant combinations, praziquantel-resveratrol [combination index (CI) = 0.74] and artesunate-resveratrol (CI = 0.34) displayed moderate and strong synergy, respectively. Conclusions: The use of viability markers including staining with propidium iodide increased the accuracy of drug screening assays against S. mansoni NTS. The synergies observed might be the consequence of increased action by RESV on targets of AS and PZQ and/or they may act through concomitantly on discrete targets to enhance overall antischistosomal action. Combinations of active agents, preferably with discrete modes of action including activity against developmental stages and/or the potential to ameliorate infection-associated pathology, might be pursued in order to identify novel therapeutic interventions. [ABSTRACT FROM AUTHOR]

Schistosomiasis is a major neglected tropical disease. Treatment for schistosomiasis with praziquantel (PZQ), which is effective against the parasite, by itself is not capable to counteract infection-associated disease lesions including hepatic fibrosis. There is a pressing need for novel therapies. Due to their biological properties, antioxidant biomolecules might be useful in treating and reverting associated pathological sequelae. Here, we investigated a novel therapy approach based on a combination of anthelmintic drugs with antioxidant biomolecules. We used a host-parasite model involving Bioamphalaria glabrata and newly transformed schistosomula (NTS) of Schistosoma mansoni. For in vitro drug screening assays, was selected several antioxidants and evaluated not only antischistosomal activity but also ability to enhance activity of the anthelmintic drugs praziquantel (PZQ) and artesunate (AS). The morphological alterations induced by compounds alone/combined were assessed on daily basis using an inverted and automated microscope to quantify NTS viability by a fluorometric-based method. The findings indicated that not only do some antioxidants improve antischistosomal activity of the two anthelmintics, but they exhibit activity per se, leading to high mortality of NTS post-exposure. The combination index (CI) of PZQ + Mel (CI = 0.80), PZQ + Resv (CI = 0.74), AS + Resv (CI = 0.34), AS + NAC (CI = 0.89), VDT + Flav (CI = 1.03) and VDT + Resv (CI = 1.06) reveal that they display moderate to strong synergism. The combination of compounds with discrete mechanisms of action might provide a valuable adjunct to contribution for treatment of schistosomiasis-associated disease. [ABSTRACT FROM AUTHOR]

Background: The human liver fluke Opisthorchis viverrini is a food-borne trematode that causes hepatobiliary disease in humans throughout Southeast Asia. People become infected by consuming raw or undercooked fish containing metacercariae. Development of a vaccine to prevent or minimize pathology would decrease the risk of severe morbidity, including the development of bile duct cancer.Methods: We produced an oral vaccine based on recombinant Bacillus subtilis spores expressing the large extracellular loop (LEL) of O. viverrini tetraspanin-2 (Ov-TSP-2), a protein that is abundant on the surface of O. viverrini secreted extracellular vesicles (EVs). Recombinant spores expressing Ov-TSP-2-LEL were orally administered to hamsters prior to challenge infection with O. viverrini metacercariae.Results: Vaccinated hamsters generated serum IgG as well as bile IgG and IgA responses to Ov-TSP-2-LEL, and serum IgG from vaccinated hamsters blocked the uptake of fluke EVs by a human bile duct epithelial cell line. Vaccinated hamsters had 56% reductions in both adult flukes and fecal eggs compared to the control group.Conclusions: These findings indicate that oral vaccination of hamsters with recombinant B. subtilis spores expressing Ov-TSP-2-LEL is efficacious at reducing infection intensity and could form the basis of a vaccine for control of carcinogenic liver fluke infection in humans. [ABSTRACT FROM AUTHOR]

In this article the authors discusses aspects of infections of parasitic worms called helminths. Topics include the prevalence of parasitic flatworm infections worldwide from hydatid tapeworms and blood fluke schistosomes, advances in genetics and biotechnology in the study of blood fluke schistosomes, innovations in parasitic flatworm cell culture, and a strategy in genetics research called clustered regulatory interspaced short palindromic repeats (CRISPR)-Cas9 endonuclease system.

The World Health Organization (WHO) currently classifies 20 diseases and conditions as neglected tropical diseases (NTDs). However, since its inception in 2007, PLOS Neglected Tropical Diseases has considered an expanded list that includes additional diseases with the chronic and/or debilitating, and poverty-promoting features of NTDs. Described here is an update of our current scope, which attempts to embrace all of the NTDs, and a discussion of the status of some of the more debated medical conditions in terms of whether or not they constitute an NTD. [ABSTRACT FROM AUTHOR]

January 30, 2020 is the first-ever World Neglected Tropical Diseases Day (World NTD Day), a day when we celebrate the achievements made towards control of the world's NTDs, yet recognize the daunting challenges we face in the control and elimination of these conditions. [ABSTRACT FROM AUTHOR]

The article offers information on the natural selection act on parasites to compromise barriers to cancer risks. Topics discussed the factors that disrupt the cellular barriers to cancer as cell-cycle arrest, apoptosis, repression of telomerase, and cell adhesion; highlights high prevalence of microbes with oncogenic potential and focuses that parasites can modulate the oncogenicity of host-associated microbes.

Infection with the food-borne liver fluke Opisthorchis viverrini causes cholangiocarcinoma (CCA). Whereas the cause of CCA in the West remains obscure, the principal risk factor in Thailand is opisthorchiasis. Here, we review recent findings on the pathogenesis of opisthorchiasis and CCA focusing on helminth molecules/toxic metabolites, host-parasite interaction, endocytosis, immunopathology/inflammatory responses, free radical production, molecular genetic alterations, and multifactorial including coinfections driving to CCA development. [ABSTRACT FROM AUTHOR]

The liver flukes Opisthorchis viverrini, O. felineus, and Clonorchis sinensis are closely related fish-borne trematodes endemic in East Asia, Eurasia, and Siberia. Following ingestion, the parasites locate to the biliary tree, where chronic infection frequently leads to cholangiocarcinoma (CCA). Infection with C. sinensis or O. viverrini is classified as a Group 1 carcinogen by the International Agency for Research on Cancer. Infection with O. felineus may also be carcinogenic. The mechanism(s) by which infection with these liver flukes culminates in CCA remain elusive, although they are likely to be multi-factorial. Not yet well studied is the influence of opisthorchiasis on the microbiome of the host despite reports that helminth parasites are capable of affecting the microbiome, potentially modulating gastrointestinal inflammation in response to the appearance of pathogenic strains of bacteria. Here, we review recent findings related to opisthorchiasis and the microbiome and related issues. In the hamster, a tractable model of infection with liver fluke and of infection-induced biliary morbidity and CCA, infection with O. viverrini perturbs the microbiome of the gastrointestinal tract, including increasing numbers of Lachnospiraceae, Ruminococcaceae, Lactobacillaceae, and others, while decreasing Porphyromonadaceae, Erysipelotrichaceae, and Eubacteriaceae. In addition, a complex microbial community associates with the parasites within the biliary tree, including Helicobacter pylori and related bacteria. Moreover, higher rates of infection with Helicobacter occur in Thailand in persons with opisthorchiasis in a liver fluke infection intensity-dependent manner. Experimental infection of hamsters with Opisthorchis felineus results in increased alpha diversity of the microbiota diversity in the biliary tract. In humans, infection with O. felineus modifies the composition of the biliary microbiome, with increasing numbers of species of Klebsiella, Aggregatibacter, Lactobacillus, Treponema, and others. Several phylotypes of Archaea occurred solely in bile from persons infected with O. felineus. [ABSTRACT FROM AUTHOR]

Infection with the fish-borne liver fluke Opisthorchis viverrini is classified by the International Agency for Research on Cancer as a Group 1 carcinogen: definitely carcinogenic in humans. Cofactors likely contribute to bile duct cancer (cholangiocarcinoma) caused by this infection. Here we review recent findings that address the role of liver fluke associated H . pylori in hepatobiliary disease and malignancy. We hypothesize that co-infection by O . viverrini and the bacillus Helicobacter pylori is central of liver fluke infection associated cholangiocarcinoma. [ABSTRACT FROM AUTHOR]

Over the last decade, research interest in defining how extracellular vesicles (EVs) shape cross‐species communication has grown rapidly. Parasitic helminths, worm species found in the phyla Nematoda and Platyhelminthes, are well‐recognised manipulators of host immune function and physiology. Emerging evidence supports a role for helminth‐derived EVs in these processes and highlights EVs as an important participant in cross‐phylum communication. While the mammalian EV field is guided by a community‐agreed framework for studying EVs derived from model organisms or cell systems [e.g., Minimal Information for Studies of Extracellular Vesicles (MISEV)], the helminth community requires a supplementary set of principles due to the additional challenges that accompany working with such divergent organisms. These challenges include, but are not limited to, generating sufficient quantities of EVs for descriptive or functional studies, defining pan‐helminth EV markers, genetically modifying these organisms, and identifying rigorous methodologies for in vitro and in vivo studies. Here, we outline best practices for those investigating the biology of helminth‐derived EVs to complement the MISEV guidelines. We summarise community‐agreed standards for studying EVs derived from this broad set of non‐model organisms, raise awareness of issues associated with helminth EVs and provide future perspectives for how progress in the field will be achieved. [ABSTRACT FROM AUTHOR]

Infection with the food-borne liver fluke Opisthorchis viverrini is the principal risk factor for cholangiocarcinoma (CCA) in the Mekong Basin countries of Thailand, Lao PDR, Vietnam, Myanmar and Cambodia. Using a novel model of CCA, involving infection with gene-edited liver flukes in the hamster during concurrent exposure to dietary nitrosamine, we explored the role of the fluke granulin-like growth factor Ov-GRN-1 in malignancy. We derived RNA-guided gene knockout flukes (ΔOv-grn-1) using CRISPR/Cas9/gRNA materials delivered by electroporation. Genome sequencing confirmed programmed Cas9-catalyzed mutations of the targeted genes, which was accompanied by rapid depletion of transcripts and the proteins they encode. Gene-edited parasites colonized the biliary tract of hamsters and developed into adult flukes. However, less hepatobiliary tract disease manifested during chronic infection with ΔOv-grn-1 worms in comparison to hamsters infected with control gene-edited and mock-edited parasites. Specifically, immuno- and colorimetric-histochemical analysis of livers revealed markedly less periductal fibrosis surrounding the flukes and less fibrosis globally within the hepatobiliary tract during infection with ΔOv-grn-1 genotype worms, minimal biliary epithelial cell proliferation, and significantly fewer mutations of TP53 in biliary epithelial cells. Moreover, fewer hamsters developed high-grade CCA compared to controls. The clinically relevant, pathophysiological phenotype of the hepatobiliary tract confirmed a role for this secreted growth factor in malignancy and morbidity during opisthorchiasis. Author summary: Infection with the human liver flukes, Opisthorchis viverrini, O. felineus and Clonorchis sinensis remains a public health concern in regions where these parasites are endemic. O. viverrini is endemic in the Mekong River drainage countries including Thailand and the Lao People's Democratic Republic. Infection follows the consumption of undercooked freshwater fish harboring the parasite. Liver fluke infection, opisthorchiasis, is associated with diseases of the liver and bile ducts including cancer of the biliary tract, cholangiocarcinoma, a cancer with a poor prognosis. This report characterizes, for the first time, experimental infection with gene-edited O. viverrini liver flukes during concurrent exposure to a dietary nitrosamine in a rodent model of liver fluke infection-associated cancer. Cancer development was slowed in hamsters infected with the parasite following CRISPR-based knock-out mutation and loss of a parasite gene known to stimulate growth of cells lining the bile ducts. These findings definitely link a parasite factor to cancer etiology, and present a new laboratory model to investigate risk factors for infection-associated cholangiocarcinoma and to assess efficacy of anti-infection/anti-cancer vaccines. [ABSTRACT FROM AUTHOR]

Genetic variability within and among four geographical strains of Schistosoma japonicum was examined using a novel repetitive element. The element, termed Sjrh1.0, was isolated from genomic DNA of a Philippine strain of S. japonicum using a combination of restriction fragment PCR and band-stab PCR. Sjrh1.0 is a tandemly repeated element, the sequence of which appears to be species-specific, in that it hybridized to DNA from S. japonicum but not to DNA from S. mansoni. Its sequence does not match previously deposited sequences in GenBank. When employed as a probe in Southern hybridization analysis, radiolabelled Sjrh1.0 revealed sex-specific and strain-specific differences in genomic DNA of individual worms. We also found individual genetic variation within geographical isolates of the Asian schistosome. [ABSTRACT FROM AUTHOR]

An estrogen-DNA adduct mediated pathway may be involved in the pathogenesis of the squamous cell carcinoma of the bladder associated with infection with the blood fluke Schistosoma haematobium . Extracts from developmental stages of S. haematobium , including eggs, induce tumor-like phenotypes in cultured cells. In addition, estrogen-derived, reactive metabolites occur in this pathogen and in sera of infected persons. Liquid chromatography-mass spectrometry analysis was performed on urine from 40 Angolans diagnosed with urogenital schistosomiasis (UGS), half of who also presented UGS-associated squamous cell carcinoma and/or urothelial cell carcinoma. The analysis revealed numerous estrogen-like metabolites, including seven specifically identified in UGS cases, but not reported in the database of metabolites in urine of healthy humans. These schistosome infection-associated metabolites included catechol estrogen quinones (CEQ) and CEQ-DNA-adducts, two of which had been identified previously in S. haematobium . In addition, novel metabolites derived directly from 8-oxo-7, 8-dihydro-2′-deoxyguanosine (8-oxodG) were identified in urine of all 40 cases of UGS. These metabolites can be expected to provide deeper insights into the carcinogenesis UGS-induced bladder cancer, and as biomarkers for diagnosis and/or prognosis of this neglected tropical disease-linked cancer. [ABSTRACT FROM AUTHOR]

• Opisthorchis viverrini, one of three helminths classified as group 1 biological carcinogens • Rapid detection of anti–O. viverrini IgG antibodies in patients with cholangiocarcinoma • Anti–O. viverrini IgG antibody titre higher in sera of cholangiocarcinoma than other cancers • Diagnostic biomarker to predict risk of O. viverrini–associated cholangiocarcinoma • Reduce the costs of screening tools toward the planning for prevention of disease Opisthorchiasis is caused by an infection with fish-borne liver flukes of the genus Opisthorchis. Opisthorchiasis frequently leads to chronic inflammation in the biliary tract and is classified as a group 1 biological carcinogen by the International Agency for Research on Cancer: a definitive risk for cholangiocarcinoma (CCA). We used the rapid immunochromatographic test (ICT) to detect anti- Opisthorchis viverrini IgG and IgG4 subclass antibodies in sera of patients with CCA. The ICT kits were developed based on soluble antigens excreted and secreted by O. viverrini adult worms. ICT indicated sera was positive for IgG and IgG4 antibodies, respectively, in 22 (61.1%) and 15 (41.6%) participants of the 36 study participants diagnosed with CCA (P > 0.05). Our study also included groups with other cancers and with liver cirrhosis, where the IgG ICT and IgG4 ICT kits were 27.7% (13/47) and 25.5% (12/47) positive, respectively (P > 0.05). Neither total the IgG ICT nor the IgG4 ICT yielded positive results in a control group of 20 healthy participants. Moreover, the percentage positivity rate using the ICT for total IgG between the CCA group and the other cancers and liver cirrhosis group was significantly different (P < 0.05). By contrast, no significant difference between these groups was apparent in the ICT for IgG4 antibody. The CCA group was 6.53 times more likely to have positive anti– O. viverrini IgG antibody (odds ratio 6.53, P < 0.001) and 3.27 times more likely to have positive anti– O. viverrini IgG4 antibody (odds ratio 3.27, P = 0.010) than the non-CCA group. This information is of potential value for the development of a diagnostic biomarker to predict risk for O. viverrini infection-associated CCA. [ABSTRACT FROM AUTHOR]

Urogenital schistosomiasis is caused by the blood fluke Schistosoma haematobium and is one of the most neglected tropical diseases worldwide, afflicting > 100 million people. It is characterised by granulomata, fibrosis and calcification in urogenital tissues, and can lead to increased susceptibility to HIV/AIDS and squamous cell carcinoma of the bladder. To complement available treatment programs and break the transmission of disease, sound knowledge and understanding of the biology and ecology of S. haematobium is required. Hybridisation/introgression events and molecular variation among members of the S. haematobium-group might effect important biological and/or disease traits as well as the morbidity of disease and the effectiveness of control programs including mass drug administration. Here we report the first chromosome-contiguous genome for a well-defined laboratory line of this blood fluke. An exploration of this genome using transcriptomic data for all key developmental stages allowed us to refine gene models (including non-coding elements) and annotations, discover 'new' genes and transcription profiles for these stages, likely linked to development and/or pathogenesis. Molecular variation within S. haematobium among some geographical locations in Africa revealed unique genomic 'signatures' that matched species other than S. haematobium, indicating the occurrence of introgression events. The present reference genome (designated Shae.V3) and the findings from this study solidly underpin future functional genomic and molecular investigations of S. haematobium and accelerate systematic, large-scale population genomics investigations, with a focus on improved and sustained control of urogenital schistosomiasis. Author summary: More than 100 million people are infected with the carcinogenic blood fluke Schistosoma haematobium, the aetiological agent of urogenital schistosomiasis—a neglected tropical disease (NTD). In spite of its major significance, little is known about this fluke, its interactions with the human and snail intermediate hosts and the pathogenesis of the urogenital form of schistosomiasis at the molecular and biochemical levels. To enable research in these areas, we report the first chromosome-level genome and markedly enhanced gene models for S. haematobium. Comparative genomic analyses also reveal evidence of past introgression events between or among closely related schistosome species. This present reference genome for S. haematobium and the findings from this study should underpin future functional genomic and molecular investigations of S. haematobium and accelerate systematic, large-scale population genomics investigations, with a focus on improved control of urogenital schistosomiasis. [ABSTRACT FROM AUTHOR]

Background Opisthorchiasis and Opisthorchis viverrini-associated bile duct cancer represent major public health threats in Thailand and Laos. The tegument of this food borne fluke plays pivotal roles in parasite metabolism, homeostasis and osmoregulation. Excretory/secretory products also pass from the fluke to the biliary environment, products that likely underlie pathogenesis of liver fluke infection. Aquaporins (AQPs), belong to the major intrinsic protein superfamily of integral plasma membrane channel proteins that selectively transport water across cell membranes. AQPs play key roles as water and ion transport channels through the tegument of helminth parasites. Methods Here, two forms of AQP mRNAs from the adult developmental stage of O. viverrini, termed O. viverrini aquaporin-1 and -2 (Ov-aqp-1 and -2) were investigated. Roles of Ov-aqp-1 and -2 in the movement of water across the tegument of this carcinogenic liver fluke were investigated using RNA interference. Results Ov-AQP-1 and Ov-AQP-2 contain unique characteristic asparagine-proline-alanine (NPA) motifs of AQP transmembrane proteins. Phylogenetic analysis indicated that Ov-AQPs belong to an expanding group of aquaglyceroporin-like water channel proteins characterized from helminth and protozoan parasites, which is pivotal to the specialized requirements of water and solute control during parasitism. Elevated transcription of Ov-aqp-1 was evident in the egg, cercaria, metacercaria and adult stages of O. viverrini, whereas Ov-aqp-2 transcripts were detected at higher level in egg, metacercaria, cercaria and adult stage, respectively. RNA interference using electroporated dsRNA suppressed transcript levels of Ov-aqp-1 and Ov-aqp-2 in adult worms by 58-99% over periods of up to 16 days in vitro. Suppression of Ov-aqp- 1 and Ov-aqp-2 in vitro disabled water transport in adult flukes. Conclusion The apparently pivotal roles of Ov-AQP in solute homeostasis at the fluke surface suggest that deeper investigation will be informative for the pathophysiology of O. viverrini, and may uncover intervention targets, particularly in view of the singularly notable predilection of this pathogen for residence within ducts of the biliary tree. [ABSTRACT FROM AUTHOR]