Whipworms and blood flukes combined infect almost one billion people in developing countries. Only a handful of anthelmintic drugs are currently available to treat these infections effectively; there is therefore an urgent need for new generations of anthelmintic compounds. Medicinal plants have presented as a viable source of new parasiticides. Ajania nubigena, the Bhutanese daisy, has been used in Bhutanese traditional medicine for treating various diseases and our previous studies revealed that small molecules from this plant have antimalarial properties. Encouraged by these findings, we screened four major compounds isolated from A. nubigena for their anthelmintic properties.

Parasitic nematodes threaten the health of humans and livestock and cause a major financial and socioeconomic burden to modern society. Given the widespread distribution of diseases caused by parasitic nematodes there is an urgent need to develop tools that will elucidate the genetic complexity of host-parasite interactions. Heterorhabditis bacteriophora is a parasitic nematode that allows simultaneous monitoring of nematode infection processes and host immune function, and offers potential as a tractable model for parasitic nematode infections. However, molecular tools to investigate these processes are required prior to its widespread acceptance as a robust model organism. In this paper we describe microinjection in adult H. bacteriophora as a suitable means of dsRNA delivery to knockdown gene transcripts.

Hookworms infect nearly 700 million people, causing anemia and developmental stunting in heavy infections. Little is known about the genomic structure or gene regulation in hookworms, although recent publication of draft genome assemblies has allowed the first investigations of these topics to be undertaken. The transcription factor DAF-16 mediates multiple developmental pathways in the free living nematode Caenorhabditis elegans, and is involved in the recovery from the developmentally arrested L3 in hookworms. Identification of downstream targets of DAF-16 will provide a better understanding of the molecular mechanism of hookworm infection.

Gastrointestinal (GI) parasites, hookworms in particular, have evolved to cause minimal harm to their hosts, allowing them to establish chronic infections. This is mediated by creating an immunoregulatory environment. Indeed, hookworms are such potent suppressors of inflammation that they have been used in clinical trials to treat inflammatory bowel diseases (IBD) and celiac disease. Since the recent description of helminths (worms) secreting extracellular vesicles (EVs), exosome-like EVs from different helminths have been characterized and their salient roles in parasite-host interactions have been highlighted. Here, we analyze EVs from the rodent parasite Nippostrongylus brasiliensis, which has been used as a model for human hookworm infection. N. brasiliensis EVs (Nb-EVs) are actively internalized by mouse gut organoids, indicating a role in driving parasitism. We used proteomics and RNA-Seq to profile the molecular composition of Nb-EVs. We identified 81 proteins, including proteins frequently present in exosomes (like tetraspanin, enolase, 14-3-3 protein, and heat shock proteins), and 27 sperm-coating protein-like extracellular proteins. RNA-Seq analysis revealed 52 miRNA species, many of which putatively map to mouse genes involved in regulation of inflammation. To determine whether GI nematode EVs had immunomodulatory properties, we assessed their potential to suppress GI inflammation in a mouse model of inducible chemical colitis. EVs from N. brasiliensis but not those from the whipworm Trichuris muris or control vesicles from grapes protected against colitic inflammation in the gut of mice that received a single intraperitoneal injection of EVs. Key cytokines associated with colitic pathology (IL-6, IL-1β, IFNγ, and IL-17a) were significantly suppressed in colon tissues from EV-treated mice. By contrast, high levels of the anti-inflammatory cytokine IL-10 were detected in Nb-EV-treated mice. Proteins and miRNAs contained within helminth EVs hold great potential application in development of drugs to treat helminth infections as well as chronic non-infectious diseases resulting from a dysregulated immune system, such as IBD.

The liver fluke Opisthorchis viverrini is a food-borne, zoonotic pathogen endemic to Thailand and adjacent countries in Southeast Asia. The adult developmental stage of the O. viverrini parasite excretes and secretes numerous proteins within the biliary tract including the gall bladder. Lesions caused by the feeding activities of the liver fluke represent wounds that undergo protracted cycles of healing and re-injury during chronic infection, which can last for decades. Components of the excretory/secretory (ES) complement released by the worms capably drive proliferation of bile duct epithelial cells and are implicated in establishing the oncogenic milieu that leads to bile duct cancer, cholangiocarcinoma. An ES protein, the secreted granulin-like growth factor termed Ov-GRN-1, accelerates wound resolution in mice and in vitro. To investigate angiogenesis (blood vessel development) that may contribute to wound healing promoted by liver fluke granulin and, by implication, to carcinogenesis during chronic opisthorchiasis, we employed an in vitro tubule formation assay (TFA) where human umbilical vein endothelial cells were grown on gelled basement matrix. Ten and 40 nM Ov-GRN-1 significantly stimulated angiogenesis as monitored by cellular proliferation and by TFA in real time. This demonstration of potent angiogenic property of Ov-GRN-1 bolsters earlier reports on the therapeutic potential for chronic non-healing wounds of diabetics, tobacco users, and the elderly and, in addition, showcases another of the hallmark of cancer characteristic of this carcinogenic liver fluke.

Hookworms infect more people than HIV and malaria combined, predominantly in third world countries. Treatment of infection with chemotherapy can have limited efficacy and re-infections after treatment are common. Heavy infection often leads to debilitating diseases. All these factors suggest an urgent need for development of vaccine. In an attempt to develop a vaccine targeting the major human hookworm, Necator americanus, a B-cell peptide epitope was chosen from the apical enzyme in the hemoglobin digestion cascade, the aspartic protease Na-APR-1. The A(291)Y alpha helical epitope is known to induce neutralizing antibodies that inhibit the enzymatic activity of Na-APR-1, thus reducing the capacity for hookworms to digest hemoglobin and obtain nutrients. A(291)Y was engineered such that it was flanked on both termini by a coil-promoting sequence to maintain native conformation, and subsequently incorporated into a Lipid Core Peptide (LCP) self-adjuvanting system. While A(291)Y alone or the chimeric epitope with or without Freund's adjuvants induced negligible IgG responses, the LCP construct incorporating the chimeric peptide induced a strong IgG response in mice. Antibodies produced were able to bind to and completely inhibit the enzymatic activity of Na-APR-1. The results presented show that the new chimeric LCP construct can induce effective enzyme-neutralising antibodies in mice, without the help of any additional toxic adjuvants. This approach offers promise for the development of vaccines against helminth parasites of humans and their livestock and companion animals.

No abstract available

The snail Bithynia siamensis goniomphalos acts as the first intermediate host for the human liver fluke Opisthorchis viverrini, the major cause of cholangiocarcinoma (CCA) in Northeast Thailand. The undisputed link between CCA and O. viverrini infection has precipitated efforts to understand the molecular basis of host-parasite interactions with a view to ultimately developing new control strategies to combat this carcinogenic infection. To date most effort has focused on the interactions between the parasite and its human host, and little is known about the molecular relationships between the liver fluke and its snail intermediate host. In the present study we analyse the protein expression changes in different tissues of B. siamensis goniomphalos induced by infection with larval O. viverrini using iTRAQ labelling technology. We show that O. viverrini infection downregulates the expression of oxidoreductases and catalytic enzymes, while stress-related and motor proteins are upregulated. The present work could serve as a basis for future studies on the proteins implicated in the susceptibility/resistance of B. siamensis goniomphalos to O. viverrini, as well as studies on other pulmonate snail intermediate hosts of various parasitic flukes that infect humans.

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.

The hookworm Necator americanus is the predominant soil-transmitted human parasite. Adult worms feed on blood in the small intestine, causing iron-deficiency anemia, malnutrition, growth and development stunting in children, and severe morbidity and mortality during pregnancy in women. We report sequencing and assembly of the N. americanus genome (244 Mb, 19,151 genes). Characterization of this first hookworm genome sequence identified genes orchestrating the hookworm's invasion of the human host, genes involved in blood feeding and development, and genes encoding proteins that represent new potential drug targets against hookworms. N. americanus has undergone a considerable and unique expansion of immunomodulator proteins, some of which we highlight as potential treatments against inflammatory diseases. We also used a protein microarray to demonstrate a postgenomic application of the hookworm genome sequence. This genome provides an invaluable resource to boost ongoing efforts toward fundamental and applied postgenomic research, including the development of new methods to control hookworm and human immunological diseases.

The liver fluke Opisthorchis viverrini infects 10 million people in Southeast Asia and causes cholangiocarcinoma (CCA). Fluke secreted and tegumental proteins contribute to the generation of a tumorigenic environment and are targets for drug and vaccine-based control measures. Herein, we identified two tetraspanins belonging to the CD63 family (Ov-TSP-2 and Ov-TSP-3) that are abundantly expressed in the tegument proteome of O. viverrini. Ov-tsp-2 and tsp-3 transcripts were detected in all developmental stages of O. viverrini. Protein fragments corresponding to the large extracellular loop (LEL) of each TSP were produced in recombinant form and antibodies were raised in rabbits. Ov-TSP-2 and TSP-3 were detected in whole worm extracts and excretory/secretory products of O. viverrini and reacted with sera from infected hamsters and humans. Antibodies confirmed localization of Ov-TSP-2 and TSP-3 to the adult fluke tegument. Using RNA interference, Ov-tsp-2 and tsp-3 mRNA expression was significantly suppressed for up to 21 days in vitro. Ultrastructural observation of tsp-2 and tsp-3 dsRNA-treated flukes resulted in phenotypes with increased tegument thickness, increased vacuolation (tsp-2) and reduced electron density (tsp-3). These studies confirm the importance of CD63 family tegument tetraspanins in parasitic flukes and support efforts to target these proteins for vaccine development.

Parasitic hookworms and the free-living model nematode Caenorhabtidis elegans share a developmental arrested stage, called the dauer stage in C. elegans and the infective third-stage larva (L3) in hookworms. One of the key transcription factors that regulate entrance to and exit from developmental arrest is the forkhead transcription factor DAF-16/FoxO. During the dauer stage, DAF-16 is activated and localized in the nucleus. DAF-16 is negatively regulated by phosphorylation by the upstream kinase AKT, which causes DAF-16 to localize out of the nucleus and the worm to exit from dauer. DAF-16 is conserved in hookworms, and hypothesized to control recovery from L3 arrest during infection. Lacking reverse genetic techniques for use in hookworms, we used C. elegans complementation assays to investigate the function of Ancylostoma caninum DAF-16 during entrance and exit from L3 developmental arrest. We performed dauer switching assays and observed the restoration of the dauer phenotype when Ac-DAF-16 was expressed in temperature-sensitive dauer defective C. elegans daf-2(e1370);daf-16(mu86) mutants. AKT phosphorylation site mutants of Ac-DAF-16 were also able to restore the dauer phenotype, but surprisingly allowed dauer exit when temperatures were lowered. We used fluorescence microscopy to localize DAF-16 during dauer and exit from dauer in C. elegans DAF-16 mutant worms expressing Ac-DAF-16, and found that Ac-DAF-16 exited the nucleus during dauer exit. Surprisingly, Ac-DAF-16 with mutated AKT phosphorylation sites also exited the nucleus during dauer exit. Our results suggest that another mechanism may be involved in the regulation DAF-16 nuclear localization during recovery from developmental arrest.

Hookworms infect 730 million people in developing countries where they are a leading cause of intestinal blood loss and iron-deficiency anemia. At the site of attachment to the host, adult hookworms ingest blood and lyse the erythrocytes to release hemoglobin. The parasites subsequently digest hemoglobin in their intestines using a cascade of proteolysis that begins with the Ancylostoma caninum aspartic protease 1, APR-1.

It is becoming apparent that perhaps as much as half of the genome of the human blood fluke Schistosoma mansoni is constituted of mobile genetic element-related sequences. Non-long terminal repeat (LTR) retrotransposons, related to the LINE elements of mammals, comprise much of this repetitive component of the schistosome genome. Of more than 12 recognized clades of non-LTR retrotransposons, only members of the CR1, RTE, and R2 clades have been reported from the schistosome genome.

The liver fluke Opisthorchis viverrini is classified as a class I carcinogen due to the association between cholangiocarcinoma and chronic O. viverrini infection. During its feeding activity within the bile duct, the parasite secretes several cathepsin F cysteine proteases that may induce or contribute to the pathologies associated with hepatobiliary abnormalities.

Ac-MTP-2 is an astacin-like metalloprotease secreted by adult Ancylostoma caninum hookworms. Ac-mtp-2 cDNA was cloned by immunoscreening a cDNA library with antisera prepared against adult A. caninum excretory/secretory (ES) products. The full-length Ac-mtp-2 contains 850 bp cDNA encoding a 233 amino acid open reading frame (ORF) with 32% amino acid identity to Ce-NSP-4, a pharyngeal cell-derived secreted metalloprotease of the nematode Caenorhabditis elegans. The predicted ORF contained a conserved Met-turn sequence (SXMHY), but only a partial zinc-binding signature sequence (GXXXEHXRXER instead of HEXXHXXGXXHEXXRXDR) found in other astacins. However, by both gelatin gel electrophoresis and azocasein digestion, the recombinant Ac-MTP-2 exhibited proteolytic activity that was inhibited by the zinc chelator 1,10-phenanthroline and Ac-TMP, a putative tissue inhibitor of metalloprotease that was previously shown to be a highly abundant component of adult A. caninum ES products. By RT-PCR, Western blot Ac-MTP-2 was found only expressed in adult hookworms and secreted in the adult ES products. Immunolocalization with antisera shows that Ac-MTP-2 is located to the esophageal glands (confirming its role as a secretory protein), as well as to the parasite uterus. It is hypothesized that Ac-MTP-2 functions in the extracorporeal digestion of the intestinal mucosal plug lodged in the buccal capsule of the adult parasite.

A reduced diversity of the gastrointestinal commensal microbiota is associated with the development of several inflammatory diseases. Recent reports in humans and animal models have demonstrated the beneficial therapeutic effects of infections by parasitic worms (helminths) in some inflammatory disorders, such as inflammatory bowel disease (IBD) and coeliac disease (CeD). Interestingly, these studies have described how helminths may alter the intestinal microbiota, potentially representing a mechanism by which they regulate inflammation. However, for practical reasons, these reports have primarily analysed the faecal microbiota. In the present investigation, we have assessed, for the first time, the changes in the microbiota at the site of infection by a parasitic helminth (hookworm) and gluten-dependent inflammation in humans with CeD using biopsy tissue from the duodenum. Hookworm infection and gluten exposure were associated with an increased abundance of species within the Bacteroides phylum, as well as increases in the richness and diversity of the tissue-resident microbiota within the intestine, results that are consistent with previous reports using other helminth species in humans and animal models. Hence, this may represent a mechanism by which parasitic helminths may restore intestinal immune homeostasis and exert a therapeutic benefit in CeD, and potentially other inflammatory disorders.

The dynamic host-parasite mechanisms underlying hookworm infection establishment and maintenance in mammalian hosts remain poorly understood but are primarily mediated by hookworm's excretory/secretory products (ESPs), which have a wide spectrum of biological functions. We used ultra-high performance mass spectrometry to comprehensively profile and compare female and male ESPs from the zoonotic human hookworm Ancylostoma ceylanicum, which is a natural parasite of dogs, cats, and humans. We improved the genome annotation, decreasing the number of protein-coding genes by 49% while improving completeness from 92 to 96%. Compared to the previous genome annotation, we detected 11% and 10% more spectra in female and male ESPs, respectively, using this improved version, identifying a total of 795 ESPs (70% in both sexes, with the remaining sex-specific). Using functional databases (KEGG, GO and Interpro), common and sex-specific enriched functions were identified. Comparisons with the exclusively human-infective hookworm Necator americanus identified species-specific and conserved ESPs. This is the first study identifying ESPs from female and male A. ceylanicum. The findings provide a deeper understanding of hookworm protein functions that assure long-term host survival and facilitate future engineering of transgenic hookworms and analysis of regulatory elements mediating the high-level expression of ESPs. Furthermore, the findings expand the list of potential vaccine and diagnostic targets and identify biologics that can be explored for anti-inflammatory potential.

Helminth parasites secrete extracellular vesicles (EVs) into their environment that have potential roles in host-parasite communication, and thus represent potentially useful targets for novel control strategies. Here, we carried out a comprehensive proteomic analysis of two different populations of EVs - 15k pellet and 120k pellet EVs - from Schistosoma mansoni adult worms. We characterised the proteins present in the membranes of the EVs (including external trypsin-liberated peptides, integral membrane proteins (IMPs) and peripheral membrane proteins (PMPs)), as well as cargo proteins, using LC-MS/MS. A total of 286 and 716 proteins were identified in 15k and 120k pellets, respectively. Some of the most abundant proteins identified from both 15k and 120k pellets include known vaccine candidates such as Sm-TSP-2, saponin B domain-containing proteins, calpain glutathione-S-transferase, Sm29 and cathepsin domain-containing proteins. Other abundant proteins that have not been tested as vaccines include DM9 domain-containing protein, 13 kDa tegumental antigen and histone H4-like protein. Sm23, a member of the tetraspanin family with known vaccine efficacy, was identified in the cargo and IMP compartments of only 15k pellet vesicles. Moreover, a collection of proteins with known or potential relevance in host-parasite communication including proteases, antioxidants and EV biogenesis/trafficking of both vesicle types were identified. Our results provide the first report of a comprehensive compartmental proteomic analysis of adult S. mansoni-derived EVs. Future research should investigate recombinant forms of these proteins as vaccine and serodiagnostic antigens as well as the roles of EV proteins in host-parasite communication.

Alternatively activated macrophages are essential effector cells during type 2 immunity and tissue repair following helminth infections. We previously showed that Ym1, an alternative activation marker, can drive innate IL-1R-dependent neutrophil recruitment during infection with the lung-migrating nematode, Nippostrongylus brasiliensis, suggesting a potential role for the inflammasome in the IL-1-mediated innate response to infection. Although inflammasome proteins such as NLRP3 have important proinflammatory functions in macrophages, their role during type 2 responses and repair are less defined. We therefore infected Nlrp3 -/- mice with N. brasiliensis Unexpectedly, compared with wild-type (WT) mice, infected Nlrp3 -/- mice had increased neutrophilia and eosinophilia, correlating with enhanced worm killing but at the expense of increased tissue damage and delayed lung repair. Transcriptional profiling showed that infected Nlrp3 -/- mice exhibited elevated type 2 gene expression compared with WT mice. Notably, inflammasome activation was not evident early postinfection with N. brasiliensis, and in contrast to Nlrp3 -/- mice, antihelminth responses were unaffected in caspase-1/11-deficient or WT mice treated with the NLRP3-specific inhibitor MCC950. Together these data suggest that NLRP3 has a role in constraining lung neutrophilia, helminth killing, and type 2 immune responses in an inflammasome-independent manner.