Helminth infection-induced malignancy

CRISPR/Cas genome editing, functional genomics, and diagnostics for parasitic helminths

Functional genomics using CRISPR (Clustered Regulatory Interspaced Short Palindromic Repeats)/Cas (CRISPR-associated endonuclease)-based approaches has revolutionized biomedical sciences. Gene editing is also widespread in parasitology generally and its use is increasing in studies on helminths including flatworm and roundworm parasites. Here, we survey the progress, specifically with experimental CRISPR-facilitated functional genomics to investigate helminth biology and pathogenesis, and also with the burgeoning use of CRISPR-based methods to assist in diagnosis of helminth infections. We also provide an historical timeline of the introduction and uses of CRISPR in helminth species to date.

How Do Trematodes Induce Cancer? A Possible Evolutionary Adaptation of an Oncogenic Agent Transmitted by Flukes

There is strong epidemiological evidence that development of various cancer types is linked to infection with flukes (Platyhelminthes: Trematoda) in Africa, Asia and the Middle East. The exact nature of the mechanism by which cancer is induced by these parasites is unknown. Here, we provide a new hypothesis suggesting that flukes are not the primary cause of cancer but act as vectors of cancer-inducing microbial pathogens. These pathogens adaptively induce tumours to attract and help flukes to feed on blood from the tumour. Pathogen take-up by fluke vectors also takes place in the tumour; therefore, tumour formation in this case is the result of a mutualistic and adaptive relationship between the microbe and the helminth parasite. The suggested mechanism for cancer induction provided here may help us gain deeper understanding about cancer in general and its relationship with microbes and parasites. By further elaborating the unique nexus between flukes, carcinogenic microbes and cancer, in the future it will also help us to broaden our oncological perspective to reduce human death and suffering from this serious disease group.

Reinventing type 2 immunity in cancer

Our understanding of type 2 immunity has undergone a substantial transformation in recent years, revealing previously unknown functions. Beyond its canonical role in defence against parasitic helminth infections, type 2 immunity safeguards the host through additional mechanisms, including the suppression of excessive type 1 immune responses, regulation of tissue repair and maintenance of adipose tissue homeostasis. However, unlike type 1 immune responses, type 2 immunity is perceived as a potential promoter of tumorigenesis. Emerging evidence challenges this perspective, painting a more nuanced picture in which type 2 immunity might protect against or even actively suppress tumour growth and progression. In this Review, we explore discoveries that highlight the potential of type 2 immunity in reshaping the landscape of cancer immunotherapies.

Comparative liver transcriptome analysis in hamsters infected with food-borne trematodes Opisthorchis felineus, Opisthorchis viverrini, or Clonorchis sinensis

BACKGROUND

Epidemiologically important food-borne trematodes Opisthorchis viverrini and Clonorchis sinensis are recognized as biological carcinogens of Group 1A, while Opisthorchis felineus is in Group 3 as noncarcinogenic to humans. Mechanisms of the biological carcinogenesis are still elusive. Some studies highlight chronic inflammation as a key factor and common pathway for cancer initiation and progression. Nonetheless, the chronic inflammation alone does not explain why these three species differ in carcinogenicity. We focused this study on genome-wide landscapes of liver gene expression and activation of cellular pathways in Mesocricetus auratus golden hamsters infected with C. sinensis (South Korea), O. viverrini (Thailand), or O. felineus (Russia) at 1 and 3 months after infection initiation.

METHODOLOGY/PRINCIPAL FINDINGS

Liver transcriptomes of golden hamsters (HiSeq Illumina, 2X150 bp) were sequenced at 1 and 3 months postinfection. Data processing was carried out using the following bioinformatic and experimental approaches: analysis of differential gene expression, estimates of proportions of affected liver cell types, liver histopathology, and examination of weighted gene coexpression networks. All infections caused enrichment with inflammatory response signaling pathways, fibrogenesis and cell proliferation, and IL2-STAT5, TNF-NF-κB, TGF-β, Hippo, MAPK, and PI3K-Akt signaling pathways. Nevertheless, species-specific responses to each infection were noted too. We also identified species-specific responses of liver cell types, differentially expressed gene clusters, and cellular pathways associated with structural liver damage (such as periductal fibrosis, epithelial neoplasia, and inflammation).

CONCLUSIONS/SIGNIFICANCE

This is the first comparative analysis of gene expression landscapes in the liver of experimental animals infected with O. viverrini, O. felineus, or C. sinensis. The trematodes have species-specific effects on the hepatobiliary system by triggering signaling pathways, thereby leading to differences in the severity of hepatobiliary structural lesions and contributing to the pathogenicity of closely related foodborne trematodes.

Mechanistic insights into liver-fluke-induced bile-duct cancer

Liver fluke infection is a major risk for cholangiocarcinoma (CCA). It has been established that the Asian liver flukes, Clonorchis sinensis and Opisthorchis viverrini secrete growth factors, digestive enzymes, and extracellular vesicles (EVs) which contribute to abnormal cell development in the bile ducts where the worms reside. These secretions - combined with aberrant inflammation and repeated cycles of chronic wounding at the site of parasite attachment and grazing on the epithelium - promote biliary hyperplasia and fibrosis and ultimately malignant transformation. Application of post-genomic and gene-editing tools to the study of liver fluke immunobiology and pathogenesis has accelerated the discovery of essential virulence factors to which targeted therapies and diagnostics can be directed.

Unveiling Drimenol: A Phytochemical with Multifaceted Bioactivities

Drimenol, a phytochemical with a distinct odor is found in edible aromatic plants, such as Polygonum minus (known as kesum in Malaysia) and Drimys winteri. Recently, drimenol has received increasing attention owing to its diverse biological activities. This review offers the first extensive overview of drimenol, covering its sources, bioactivities, and derivatives. Notably, drimenol possesses a wide spectrum of biological activities, including antifungal, antibacterial, anti-insect, antiparasitic, cytotoxic, anticancer, and antioxidant effects. Moreover, some mechanisms of its activities, such as its antifungal effects against human mycoses and anticancer activities, have been investigated. However, there are still several crucial issues in the research on drimenol, such as the lack of experimental understanding of its pharmacokinetics, bioavailability, and toxicity. By synthesizing current research findings, this review aims to present a holistic understanding of drimenol, paving the way for future studies and its potential utilization in diverse fields.

Repurposing methuosis-inducing anticancer drugs for anthelmintic therapy

Drug-resistant parasitic nematodes pose a grave threat to plants, animals, and humans. An innovative paradigm for treating parasitic nematodes is emphasized in this opinion. This approach relies on repurposing methuosis (a death characterized by accumulation of large vacuoles) inducing anticancer drugs as anthelmintics. We review drugs/chemicals that have shown to kill nematodes or cancerous cells by inducing multiple vacuoles that eventually coalesce and rupture. This perspective additionally offers a succinct summary on Structure-Activity Relationship (SAR) of methuosis-inducing small molecules. This strategy holds promise for the development of broad-spectrum anthelmintics, shedding light on shared molecular mechanisms between cancer and nematodes in response to these inducers, thereby potentially transforming both therapeutic domains.

Inflammatory responses to Opisthorchis viverrini infection in animal models: A comparison between susceptible and nonsusceptible hosts in different anatomical locations

Background

Inflammation caused by Opisthorchis viverrini infection increases the risk of cholangitis, cholecystitis, and leads to bile duct cancer (cholangiocarcinoma or CCA). However, only certain infected individuals are susceptible to CCA, suggesting the involvement of host factors in cancer development. In addition, there are reports indicating differences in the locations of CCA.

Aim

This study aims to investigate cellular inflammatory responses in the common bile duct (CB), intrahepatic bile duct (IHB), and gallbladder (GB) in susceptible and non-susceptible hosts following O. viverrini infection.

Methods

Thirty Syrian golden hamsters (a susceptible host) and 30 BALB/c mice (a non-susceptible host) infected with O. viverrini were studied at six time points (five animals per group). Histopathological evaluations were conducted on samples from the IHB, CB, and GB. Inflammatory cell infiltration was quantitatively assessed and compared between groups and time points. Statistical analysis was performed using one-way ANOVA, with a significance level of p < 0.05.

Results

Inflammation was significantly more pronounced in the IHB compared to the other two biliary locations. In comparison between susceptible and non-susceptible hosts, the intensity of inflammation was higher in the OV+H group than in the OV+M group (p < 0.05).

Conclusion

This study highlights the association between host response to inflammation, tissue location, and host susceptibility, with the IHB showing particular susceptibility to inflammation and pathological changes. These findings contribute to our understanding of the increased risk of CCA in susceptible hosts.

Trematode Genomics and Proteomics

Trematode infections stand out as one of the frequently overlooked tropical diseases, despite their wide global prevalence and remarkable capacity to parasitize diverse host species and tissues. Furthermore, these parasites hold significant socio-economic, medical, veterinary and agricultural implications. Over the past decades, substantial strides have been taken to bridge the information gap concerning various "omic" tools, such as proteomics and genomics, in this field. In this edition of the book, we highlight recent progress in genomics and proteomics concerning trematodes with a particular focus on the advances made in the past 5 years. Additionally, we present insights into cutting-edge technologies employed in studying trematode biology and shed light on the available resources for exploring the molecular facets of this particular group of parasitic helminths.

Unraveling the relationship among inflammatory responses, oxidative damage, and host susceptibility to Opisthorchis viverrini infection: A comparative analysis in animal models

Background and Aim

Opisthorchis viverrini infection-induced inflammation contributes to cholangiocarcinoma (CCA) development in humans and animals. Inflammation generates free radicals, such as reactive oxygen species and reactive nitrogen species (RNS), which damage the host's DNA. However, only 5% of O. viverrini-infected individuals develop malignancy, suggesting that variations in the inflammatory response of individuals to the parasite may influence susceptibility. Due to limitations in studying human susceptibility, we used an animal model to investigate the profiles of inflammatory reactions, oxidative burst, and irreversible DNA damage. This study aimed to explore the potential role of inflammation and RNS in causing DNA damage that may predispose susceptible hosts and non-susceptible animal models to cancer development in O. viverrini infection.

Materials and Methods

This experimental study was conducted on 30 Syrian golden hamsters (OV-H) and 30 BALB/c mice (OV-M) infected with O. viverrini, representing susceptible and non-susceptible models, respectively. Five animals per group were examined at six predetermined time points during the experiment. Biliary tract samples were systematically investigated using histopathological evaluation for inflammatory cell infiltration and immunohistochemical staining for RNS production and markers of DNA damage, including nitrotyrosine and 8-hydroxy-2'-deoxyguanosine. These features were quantified and compared among the experimental groups. Mann-Whitney U-test was used for statistical analysis, with p < 0.05 considered statistically significant.

Results

The comparison revealed that the OV-M group exhibited significantly earlier and higher rates of inflammatory cell infiltration during the acute phase, whereas the OV-H group exhibited chronic and more severe inflammation (p < 0.020). Intracellular RNS production and DNA damage were closely associated with the inflammatory response.

Conclusion

This study demonstrates differential responses in susceptible and non-susceptible models of O. viverrini infection regarding disease onset and duration, as well as intracellular RNS production and DNA damage caused by inflammation. Persistent inflammation generated oxidatively damaged DNA, which is a distinct pathological characteristic of susceptible hosts and may be critical for CCA development.

Cancerogenic parasites in veterinary medicine: a narrative literature review

Parasite infection is one of the many environmental factors that can significantly contribute to carcinogenesis and is already known to be associated with a variety of malignancies in both human and veterinary medicine. However, the actual number of cancerogenic parasites and their relationship to tumor development is far from being fully understood, especially in veterinary medicine. Thus, the aim of this review is to investigate parasite-related cancers in domestic and wild animals and their burden in veterinary oncology. Spontaneous neoplasia with ascertained or putative parasite etiology in domestic and wild animals will be reviewed, and the multifarious mechanisms of protozoan and metazoan cancer induction will be discussed.

Peptide derived from progranulin of the carcinogenic liver fluke, Opisthorchis viverrini stimulates cell hyperproliferation and proinflammatory cytokine production

Purpose

Progranulin (PGRN) is a secreted glycoprotein growth factor with roles in wound healing, inflammation, angiogenesis and malignancy. An orthologue of the gene encoding human PGRN was identified in the carcinogenic liver fluke Opisthorchis viverrini.

Methods

Sequence structure, general characteristics and possible function of O. viverrini PGRN was analyzed using bioinformatics. Expression profiles were investigated with quantitative RT-PCR, western blot and immunolocalization. A specific peptide of Ov-PGRN was used to investigate a role for this molecule in pathogenesis.

Results

The structure of the gene coding for O. viverrini PGRN was 36,463 bp in length, and comprised of 13 exons, 12 introns, and a promoter sequence. The Ov-pgrn mRNA is 2,768 bp in length and encodes an 846 amino acids with a predicted molecular mass of 91.61 kDa. Ov-PGRN exhibited one half and seven complete granulin domains. Phylogenetic analysis revealed that Ov-PGRN formed its closest relationship with PGRN of liver flukes in the Opisthorchiidae. Transcripts of Ov-pgrn were detected in several developmental stages, with highest expression in the metacercaria, indicating that Ov-PGRN may participate as a growth factor in the early development of O. viverrini. Western blot analysis revealed the presence of detected Ov-PGRN in both soluble somatic or excretory/secretory products, and immunolocalization indicated high levels of expression in the tegument and parenchyma of the adult fluke. Co-culture of a human cholangiocyte cell line and a peptide fragment of Ov-PGRN stimulated proliferation of cholangiocytes and upregulation of expression of the cytokines IL6 and IL8.

Conclusion

Ov-PGRN is expressed throughout the life cycle of liver fluke, and likely plays a key role in development and growth.

Opisthorchis Felineus Infection is a Risk Factor for Cholangiocarcinoma in Western Siberia: A Hospital-based Case-control Study

BACKGROUND

Cholangiocarcinoma (CCA), a fatal bile duct cancer, has a high incidence in Western Siberia, Russian Federation. In addition, Opisthorchis felineus, a bile duct-dwelling trematode liver fluke is highly endemic. Closely related species have been shown to be cancerogenic agents in Asia. We therefore examined the association between O felineus infection and CCA in Western Siberia.

METHODS

We conducted a hospital-based, individually matched case-control study between January 2017 and August 2020 in Tomsk Oblast and Khanty-Mansiysk Autonomous Okrug, Yugra, Russian Federation. Histologically confirmed CCA patients (cases) were compared with matched age, sex, and place of residence hospital controls. The examination of study participants included the diagnosis of current and past O felineus infection, abdominal ultrasonographical assessment, physical examination, and interview on exposures to potential risk factors.

RESULTS

We identified 40 patients with CCA and 160 controls. Exposures to O felineus infection was strongly associated with CCA (odds ratio [OR], 3.9; 95% confidence interval [CI], 1.4-10.8; P = .008). Also, cases reported more often that they were currently or in the past were infected by O felineus compared with controls (OR, 4.03; 95% CI, 1.7-9.5; P = .001). Furthermore, cases reported river fish consumption and fishing habits significantly more often than controls (OR, 5.5; 95% CI, 1.5-19.8; P = .009 and OR, 3.3; 95% CI, 1.4-7.7; P = .005).

CONCLUSIONS

The study results revealed a strong significantly increased risk for CCA development in O felineus-infected individuals. Elaboration of the guidelines on screening programs for early CCA diagnosis, prevention, and treatment is socially important in endemic regions.

microRNAs: Critical Players during Helminth Infections

microRNAs (miRNAs) are a group of small non-coding RNAs that regulate gene expression post-transcriptionally through their interaction with the 3' untranslated regions (3' UTR) of target mRNAs, affecting their stability and/or translation. Therefore, miRNAs regulate biological processes such as signal transduction, cell death, autophagy, metabolism, development, cellular proliferation, and differentiation. Dysregulated expression of microRNAs is associated with infectious diseases, where miRNAs modulate important aspects of the parasite-host interaction. Helminths are parasitic worms that cause various neglected tropical diseases affecting millions worldwide. These parasites have sophisticated mechanisms that give them a surprising immunomodulatory capacity favoring parasite persistence and establishment of infection. In this review, we analyze miRNAs in infections caused by helminths, emphasizing their role in immune regulation and its implication in diagnosis, prognosis, and the development of therapeutic strategies.

Inflammatory Response in Caco-2 Cells Stimulated with Anisakis Messengers of Pathogenicity

Background: Anisakis spp. third-stage larvae (L3) are the causative agents of human zoonosis called anisakiasis. The accidental ingestion of L3 can cause acute and chronic inflammation at the gastric, intestinal, or ectopic levels. Despite its relevance in public health, studies on pathogenetic mechanisms and parasite-human interplay are scarce. The aim of this study was to investigate the human inflammatory response to different Anisakis vehicles of pathogenicity. Methods: Human colorectal adenocarcinoma (Caco-2) cells were exposed to Anisakis L3 (the initial contact with the host), extracellular vesicles (EVs, Anisakis-host communication), and crude extract (CE, the larval dying). The protein quantity and gene expression of two pro-inflammatory cytokines (IL-6 and IL-8) were investigated using an ELISA test (6 h and 24 h) and a qReal-Time PCR (1 h, 6 h, and 24 h), respectively. Results: The L3 and EVs induced a downregulation in both the Il-6 and Il-8 gene expression and protein quantity. On the contrary, the CE stimulated IL-6 gene expression and its protein release, not affecting IL-8. Conclusions: The Caco-2 cells seemed to not react to the exposure to the L3 and EVs, suggesting a parasite's immunomodulating action to remain alive in an inhospitable niche. Conversely, the dying larva (CE) could induce strong activation of the immune strategy of the host that, in vivo, would lead to parasite expulsion, eosinophilia, and/or granuloma formation.

Helminth infection and helminth-derived products: A novel therapeutic option for non-alcoholic fatty liver disease

Non-alcoholic fatty liver disease (NAFLD) is closely related to obesity, diabetes, and metabolic syndrome (MetS), and it has become the most common chronic liver disease. Helminths have co-evolved with humans, inducing multiple immunomodulatory mechanisms to modulate the host's immune system. By using their immunomodulatory ability, helminths and their products exhibit protection against various autoimmune and inflammatory diseases, including obesity, diabetes, and MetS, which are closely associated with NAFLD. Here, we review the pathogenesis of NAFLD from abnormal glycolipid metabolism, inflammation, and gut dysbiosis. Correspondingly, helminths and their products can treat or relieve these NAFLD-related diseases, including obesity, diabetes, and MetS, by promoting glycolipid metabolism homeostasis, regulating inflammation, and restoring the balance of gut microbiota. Considering that a large number of clinical trials have been carried out on helminths and their products for the treatment of inflammatory diseases with promising results, the treatment of NAFLD and obesity-related diseases by helminths is also a novel direction and strategy.

Comorbidities involving parasitic diseases: A look at the benefits and complications

Parasitic infections acquired by the population cause substantial morbidity worldwide, with individuals from developing countries being most affected. Some parasites remain in the host for long periods, settling in different organs, manipulating the flow of nutrients and metabolites, and influencing the immune response, favoring their adaptation. The host attempts to counteract the metabolic and immunological alterations and the possible damage caused by infection. These metabolic and immunological changes experienced by the host can influence the progression of other existing morbidities or those that will be acquired in the future. Cancer and metabolic diseases are also frequent causes of morbidity in the world population. The large numbers of individuals affected by cancer and metabolic diseases and the high prevalence of morbidity caused by parasitic diseases favor the development of comorbidity involving these pathologies. This review provides an overview of major advances in research on cancer and metabolic diseases associated with parasitic infections. Information about hosts and parasites such as alterations of the immune response, metabolism and adaptation mechanisms of the parasites, and parasitic molecules with therapeutic potential is provided, as well as the beneficial results or complications related to the comorbidities discussed herein. We emphasize the need to conduct additional studies addressing comorbidities associated with parasitic infections to improve the understanding of the impact of this association on the progression of morbidities, as well as the possibility of the therapeutic use of and therapeutic approaches involving parasites.

Knockout of liver fluke granulin, Ov-grn-1, impedes malignant transformation during chronic infection with Opisthorchis viverrini

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.

Intestinal epithelial tuft cell induction is negated by a murine helminth and its secreted products

Helminth parasites are adept manipulators of the immune system, using multiple strategies to evade the host type 2 response. In the intestinal niche, the epithelium is crucial for initiating type 2 immunity via tuft cells, which together with goblet cells expand dramatically in response to the type 2 cytokines IL-4 and IL-13. However, it is not known whether helminths modulate these epithelial cell populations. In vitro, using small intestinal organoids, we found that excretory/secretory products (HpES) from Heligmosomoides polygyrus blocked the effects of IL-4/13, inhibiting tuft and goblet cell gene expression and expansion, and inducing spheroid growth characteristic of fetal epithelium and homeostatic repair. Similar outcomes were seen in organoids exposed to parasite larvae. In vivo, H. polygyrus infection inhibited tuft cell responses to heterologous Nippostrongylus brasiliensis infection or succinate, and HpES also reduced succinate-stimulated tuft cell expansion. Our results demonstrate that helminth parasites reshape their intestinal environment in a novel strategy for undermining the host protective response.

Rapid assessment of Opisthorchis viverrini IgG antibody in serum: a potential diagnostic biomarker to predict risk of cholangiocarcinoma in regions endemic for opisthorchiasis

Background:

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).

Methods:

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.

Results:

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.

Conclusion:

This information is of potential value for the development of a diagnostic biomarker to predict risk for O. viverrini infection-associated CCA.

Helminth extracellular vesicles: Interactions with the host immune system

As long-lived parasites, helminths depend upon immunomodulation of their hosts for survival. The release of excretory-secretory (ES) products, including proteins, lipids and RNAs is how successful host manipulation is achieved. It has recently been discovered that the ES products of helminths contain extracellular vesicles (EVs), with every species investigated found to secrete these lipid-bound structures. EVs are perfect for packaging and delivering immune modulators to target cell types. This review outlines the research carried out on helminth EVs and their constituents thus far, as well as their interaction with components of the mammalian immune system. We discuss how targeting EVs will aid treatment of helminth infection and consider how EVs and their immunomodulatory cargo could be used as therapeutics as we progress through this exciting era.

Promising Technologies in the Field of Helminth Vaccines

Helminths contribute a larger global burden of disease than both malaria and tuberculosis. These eukaryotes have caused human infections since before our earliest recorded history (i.e.: earlier than 1200 B.C. for Schistosoma spp.). Despite the prevalence and importance of these infections, helminths are considered a neglected tropical disease for which there are no vaccines approved for human use. Similar to other parasites, helminths are complex organisms which employ a plethora of features such as: complex life cycles, chronic infections, and antigenic mimicry to name a few, making them difficult to target by conventional vaccine strategies. With novel vaccine strategies such as viral vectors and genetic elements, numerous constructs are being defined for a wide range of helminth parasites; however, it has yet to be discussed which of these approaches may be the most effective. With human trials being conducted, and a pipeline of potential anti-helminthic antigens, greater understanding of helminth vaccine-induced immunity is necessary for the development of potent vaccine platforms and their optimal design. This review outlines the conventional and the most promising approaches in clinical and preclinical helminth vaccinology.

Immunological and Biochemical Interplay between Cytokines, Oxidative Stress and Schistosomiasis

The host–parasite schistosome relationship relies heavily on the interplay between the strategies imposed by the schistosome worm and the defense mechanisms the host uses to counter the line of attack of the parasite. The ultimate goal of the schistosome parasite entails five important steps: evade elimination tactics, survive within the human host, develop into adult forms, propagate in large numbers, and transmit from one host to the next. The aim of the parasitized host on the other hand is either to cure or limit infection. Therefore, it is a battle between two conflicting aspirations. From the host’s standpoint, infection accompanies a plethora of immunological consequences; some are set in place to defend the host, while most end up promoting chronic disease, which ultimately crosses paths with oxidative stress and cancer. Understanding these networks provides attractive opportunities for anti-schistosome therapeutic development. Hence, this review discusses the mechanisms by which schistosomes modulate the human immune response with ultimate links to oxidative stress and genetic instability.

Hepatobiliary morbidities detected by ultrasonography in Opisthorchis viverrini-infected patients before and after praziquantel treatment: a five-year follow up study

Infection of the liver fluke, Opisthorchis viverrini (OV) is an important public health problem in northeast Thailand and adjacent countries, where people have a habit of eating raw or undercooked fish. A community case-control study was carried out with 8,936 participants from 89 villages, in Khon Kaen province, Thailand. There were 3,359 OV-infected participants all of whom underwent ultrasonography of upper abdomen for the evaluation of hepatobiliary morbidity. The participants with advanced periductal fibrosis (APF) by ultrasound (n = 785) were invited to undergo annual follow-up ultrasonography for five years after praziquantel treatment. The sonographer was blinded with respect to status of OV infection at each visit. The study findings revealed variability in the study population profile of the hepatobiliary morbidities before and after praziquantel treatment over the follow up interval. At the end of the study, 32 (30.8%) out of 104 participants showed no relapse of APF whereas, by contrast, 39 (37.5%) participants showed relapse or persistent APF since the outset of the study (≥ two consecutive visits). The APF in most follow-up visits was significantly associated with male sex, with intrahepatic duct stones, with the width of the gallbladder "pre" minus "post" fatty meal, and with the ratio of left lobe of the liver to aorta. Five cases of suspected cholangiocarcinoma were observed over the five years of follow-up. This long-term ultrasound follow-up study demonstrates a significant incidence of persistent APF in over one-third of opisthorchiasis cases after praziquantel treatment, findings that support the prospect of ongoing cholangiocarcinogenesis long after successful elimination of liver fluke infection among the population.

Control Strategies for Carcinogenic-Associated Helminthiases: An Integrated Overview

Helminthiases are extremely prevalent in the developing world. In addition, the chronic infection with some parasitic worms are classified as carcinogenic. Therefore, it is utmost importance to understand the parasite-host interactions, the mechanisms underlay carcinogenesis and how they could be counteracted. This knowledge may ultimately guide novel control strategies that include chemotherapy-based approaches targeting these pathogens and associated pathologies caused by their infections. Little is known on how some helminthiases are associated with cancer; however, it has been hypothesized that chemical carcinogenesis may be involved in the process. Here, we summarize the current knowledge on chemical carcinogenesis associated with helminthiases, along with available therapeutic options and potential therapeutic alternatives including chemotherapy and/or immunotherapy. Ideally, the treatment of the carcinogenic helminthiases should target both the parasite and associated pathologies. The success of any chemotherapeutic regimen often depends on the host immune response during the infection and nutritional status among other factors. The close association between chemotherapy and cell-mediated immunity suggests that a dual therapeutic approach would be advantageous. In addition, there is a pressing need for complementary drugs that antagonize the carcinogenesis process associated with the helminth infections.

Spirocerca lupi Proteomics and Its Role in Cancer Development: An Overview of Spirocercosis-Induced Sarcomas and Revision of Helminth-Induced Carcinomas

Spirocerca lupi is a parasitic nematode of canids that induces a myriad of clinical manifestations in its host and, in 25% of infections, leads to the formation of sarcomas. The description of the protein composition of the excretory and secretory products (Sl-ESP) of S. lupi has shed light on its possible interactions with the host environment, including migration within the host and mechanisms of immunomodulation. Despite this, the process by which S. lupi induces cancer in the dog remains poorly understood, and some hypotheses have arisen regarding these possible mechanisms. In this review, we discuss the role of specific ESP from the carcinogenic helminths Clonorchis sinensis, Opisthorchis viverrini and Schistosoma haematobium in inducing chronic inflammation and cancer in their host’s tissues. The parasitic worms Taenia solium, Echinococcus granulosus, Heterakis gallinarum, Trichuris muris and Strongyloides stercoralis, which have less-characterized mechanisms of cancer induction, are also analyzed. Based on the pathological findings in spirocercosis and the mechanisms by which other parasitic helminths induce cancer, we propose that the sustained inflammatory response in the dog´s tissues produced in response to the release of Sl-ESP homologous to those of other carcinogenic worms may lead to the malignant process in infected dogs.

Infection with Helicobacter pylori Induces Epithelial to Mesenchymal Transition in Human Cholangiocytes

Recent reports suggest that the East Asian liver fluke infection, caused by Opisthorchis viverrini, which is implicated in opisthorchiasis-associated cholangiocarcinoma, serves as a reservoir of Helicobacter pylori. The opisthorchiasis-affected cholangiocytes that line the intrahepatic biliary tract are considered to be the cell of origin of this malignancy. Here, we investigated interactions in vitro among human cholangiocytes, Helicobacter pylori strain NCTC 11637, and the congeneric bacillus, Helicobacter bilis. Exposure to increasing numbers of H. pylori at 0, 1, 10, 100 bacilli per cholangiocyte of the H69 cell line induced phenotypic changes including the profusion of thread-like filopodia and a loss of cell-cell contact, in a dose-dependent fashion. In parallel, following exposure to H. pylori, changes were evident in levels of mRNA expression of epithelial to mesenchymal transition (EMT)-encoding factors including snail, slug, vimentin, matrix metalloprotease, zinc finger E-box-binding homeobox, and the cancer stem cell marker CD44. Analysis to quantify cellular proliferation, migration, and invasion in real-time by both H69 cholangiocytes and CC-LP-1 line of cholangiocarcinoma cells using the xCELLigence approach and Matrigel matrix revealed that exposure to 10 H. pylori bacilli per cell stimulated migration and invasion by the cholangiocytes. In addition, 10 bacilli of H. pylori stimulated contact-independent colony establishment in soft agar. These findings support the hypothesis that infection by H. pylori contributes to the malignant transformation of the biliary epithelium.

A comparative proteomics analysis of the egg secretions of three major schistosome species

Morbidity associated with hepatic and urogenital schistosomiasis stems primarily from the host immune response directed against schistosome eggs. When eggs become entrapped in host tissues, the development of fibrotic plaques drives downstream pathology. These events occur due to the antigenic nature of egg excretory/secretory products (ESPs). Both Schistosoma mansoni and S. japonicum ESPs have been shown to interact with several cell populations in the host liver including hepatocytes, macrophages, and hepatic stellate cells, with both immunomodulatory and pathological consequences. Several protein components of the ESPs of S. mansoni and S. japonicum eggs have been characterised; however, studies into the collective contents of schistosome egg ESPs are lacking. Utilising shotgun mass spectrometry and an array of in silico analyses, we identified 266, 90 and 50 proteins within the S. mansoni, S. japonicum and S. haematobium egg secretomes respectively. We identified numerous proteins with already established immunomodulatory activities, vaccine candidates and vesicle markers. Relatively few common orthologues within the ESPs were identified by BLAST, indicating that the three egg secretomes differ in content significantly. Having a clearer understanding of these components may lead to the identification of new proteins with uncharacterised immunomodulatory potential or pathological relevance. This will enhance our understanding of host-parasite interactions, particularly those occurring during chronic schistosomiasis, and pave the way towards novel therapeutics and vaccines.

Estrogen receptors in urogenital schistosomiasis and bladder cancer: Estrogen receptor alpha-mediated cell proliferation

Estrogen-like metabolites have been identified in S. haematobium, the helminth parasite that causes urogenital schistosomiasis (UGS) and in patients´ blood and urine during UGS. Estrogen receptor (ER) activation is enriched in the luminal molecular subtype bladder cancer (BlaCa). To date, the significance of ER to these diseases remains elusive. We evaluated ERα and ERβ expression in UGS-related BlaCa (n = 27), UGS-related non-malignant lesions (n = 35), and noninfected BlaCa (n = 80). We investigated the potential of ERα to recognize S. haematobium-derived metabolites by docking and molecular dynamics simulations and studied ERα modulation in vitro using 3 BlaCa cell lines, T24, 5637 and HT1376. ERα was expressed in tumor and stromal cells in approximately 20% noninfected cases and in 30% of UGS-related BlaCa, predominantly in the epithelial cells. Overall, ERα expression was associated with features of tumor aggressiveness such as high proliferation and p53 positive expression. ERα expression correlated with presence of schistosome eggs. ERβ was widely expressed in both cohorts but weaker in UGS-related cases. molecular dynamics simulations of the 4 most abundant S. haematobium-derived metabolites revealed that smaller metabolites have comparable affinity for the ERα active state than 17β-estradiol, while the larger metabolites present higher affinity. Our in vitro findings suggested that ERα activation promotes proliferation in ERα expressing BlaCa cells and that this can be reverted with anti-estrogenic therapy. In summary, we report differential ER expression between UGS-related BlaCa and noninfected BlaCa and provide evidence supporting a role of active ERα during UGS and UGS-induced carcinogenesis.

Liver fluke granulin promotes extracellular vesicle-mediated crosstalk and cellular microenvironment conducive to cholangiocarcinoma

Crosstalk between malignant and neighboring cells contributes to tumor growth. In East Asia, infection with the liver fluke is a major risk factor for cholangiocarcinoma (CCA). The liver fluke Opisthorchis viverrini secretes a growth factor termed liver fluke granulin, a homologue of the human progranulin, which contributes significantly to biliary tract fibrosis and morbidity. Here, extracellular vesicle (EV)-mediated transfer of mRNAs from human cholangiocytes to naïve recipient cells was investigated following exposure to liver fluke granulin. To minimize the influence of endogenous progranulin, its cognate gene was inactivated using CRISPR/Cas9-based gene knock-out. Several progranulin-depleted cell lines, termed ΔhuPGRN-H69, were established. These lines exhibited >80% reductions in levels of specific transcript and progranulin, both in gene-edited cells and within EVs released by these cells. Profiles of extracellular vesicle RNAs (evRNA) from ΔhuPGRN-H69 for CCA-associated characteristics revealed a paucity of transcripts for estrogen- and Wnt-signaling pathways, peptidase inhibitors and tyrosine phosphatase related to cellular processes including oncogenic transformation. Several CCA-specific evRNAs including MAPK/AKT pathway members were induced by exposure to liver fluke granulin. By comparison, estrogen, Wnt/PI3K and TGF signaling and other CCA pathway mRNAs were upregulated in wild type H69 cells exposed to liver fluke granulin. Of these, CCA-associated evRNAs modified the CCA microenvironment in naïve cells co-cultured with EVs from ΔhuPGRN-H69 cells exposed to liver fluke granulin, and induced translation of MAPK phosphorylation related-protein in naïve recipient cells in comparison with control recipient cells. Exosome-mediated crosstalk in response to liver fluke granulin promoted a CCA-specific program through MAPK pathway which, in turn, established a CCA-conducive disposition.

Inflammation and Progression of Cholangiocarcinoma: Role of Angiogenic and Lymphangiogenic Mechanisms

Cholangiocarcinoma (CCA), or cancer of the biliary epithelium is a relatively rare but aggressive form of biliary duct cancer which has a 5-year survival rate post metastasis of 2%. Although a number of risk factors are established for CCA growth and progression, a careful evaluation of the existing literature on CCA reveals that an inflammatory environment near the biliary tree is the most common causal link between the risk factors and the development of CCA. The fact that inflammation predisposes affected individuals to CCA is further bolstered by multiple observations where the presence and maintenance of an inflammatory microenvironment at the site of the primary tumor plays a significant role in the development and metastasis of CCA. In addition, mechanisms activating the tumor vasculature and enhancing angiogenesis and lymphangiogenesis significantly contribute to CCA aggressiveness and metastasis. This review aims to address the role of an inflammatory microenvironment-CCA crosstalk and will present the basic concepts, observations, and current perspectives from recent research studies in the field of tumor stroma of CCA.

Neglected Agent Eminent Disease: Linking Human Helminthic Infection, Inflammation, and Malignancy

Helminthic parasitic infection is grossly prevalent across the globe and is considered a significant factor in human cancer occurrence induced by biological agents. Although only three helminths (Schistosoma haematobium, Clonorchis sinensis, and Opisthorchis viverrini) so far have been directly associated with carcinogenesis; there are evidence suggesting the involvement of other species too. Broadly, human helminthiasis can cause chronic inflammation, genetic instability, and host immune modulation by affecting inter- and intracellular communications, disruption of proliferation-anti-proliferation pathways, and stimulation of malignant stem cell progeny. These changes ultimately lead to tumor development through the secretion of soluble factors that interact with host cells. However, the detailed mechanisms by which helminths introduce and promote malignant transformation of host cells are still not clear. Here, we reviewed the current understanding of immune-pathogenesis of helminth parasites, which have been associated with carcinogenesis, and how these infections initiate carcinogenesis in the host.

Inhibition of the Formation In Vitro of Putatively Carcinogenic Metabolites Derived from S. haematobium and O. viverrini by Combination of Drugs with Antioxidants

Infections caused by Schistosoma haematobium and Opisthorchis viverrini are classified as carcinogenic. Although carcinogenesis might be a multifactorial process, it has been postulated that these helminth produce/excrete oxysterols and estrogen-like metabolites that might act as initiators of their infection-associated carcinogenesis. Current treatment and control of these infections rely on a single drug, praziquantel, that mainly targets the parasites and not the pathologies related to the infection including cancer. Thus, there is a need to search for novel therapeutic alternatives that might include combinations of drugs and drug repurposing. Based on these concepts, we propose a novel therapeutic strategy that combines drugs with molecule antioxidants. We evaluate the efficacy of a novel therapeutic strategy to prevent the formation of putative carcinogenic metabolites precursors and DNA adducts. Firstly, we used a methodology previously established to synthesize metabolites precursors and DNA adducts in the presence of CYP450. Then, we evaluated the inhibition of their formation induced by drugs and antioxidants alone or in combination. Drugs and resveratrol alone did not show a significant inhibitory effect while N-acetylcysteine inhibited the formation of most metabolite precursors and DNA adducts. Moreover, the combinations of classical drugs with antioxidants were more effective rather than compounds alone. This strategy might be a valuable tool to prevent the initiation of helminth infection-associated carcinogenesis.

Differential responses of epithelial cells from urinary and biliary tract to eggs of Schistosoma haematobium and S. mansoni

Chronic urogenital schistosomiasis can lead to squamous cell carcinoma of the bladder. The International Agency for Research on Cancer classifies the infection with S. haematobium as a group 1 carcinogen, a definitive cause of cancer. By contrast, hepatointestinal schistosomiasis due to the chronic infection with S. mansoni or S. japonicum associated with liver periportal fibrosis, does not apparently lead to malignancy. The effects of culturing human epithelial cells, HCV29, established from normal urothelium, and H69, established from cholangiocytes, in the presence of S. haematobium or S. mansoni eggs were investigated. Cell growth of cells co-cultured with schistosome eggs was monitored in real time, and gene expression analysis of oncogenesis, epithelial to mesenchymal transition and apoptosis pathways was undertaken. Schistosome eggs promoted proliferation of the urothelial cells but inhibited growth of cholangiocytes. In addition, the tumor suppressor P53 pathway was significantly downregulated when exposed to schistosome eggs, and downregulation of estrogen receptor was predicted in urothelial cells exposed only to S. haematobium eggs. Overall, cell proliferative responses were influenced by both the tissue origin of the epithelial cells and the schistosome species.

In-depth proteomic characterization of Schistosoma haematobium: Towards the development of new tools for elimination

BACKGROUND

Schistosomiasis is a neglected disease affecting hundreds of millions worldwide. Of the three main species affecting humans, Schistosoma haematobium is the most common, and is the leading cause of urogenital schistosomiasis. S. haematobium infection can cause different urogenital clinical complications, particularly in the bladder, and furthermore, this parasite has been strongly linked with squamous cell carcinoma. A comprehensive analysis of the molecular composition of its different proteomes will contribute to developing new tools against this devastating disease.

METHODS AND FINDINGS

By combining a comprehensive protein fractionation approach consisting of OFFGEL electrophoresis with high-throughput mass spectrometry, we have performed the first in-depth characterisation of the different discrete proteomes of S. haematobium that are predicted to interact with human host tissues, including the secreted and tegumental proteomes of adult flukes and secreted and soluble egg proteomes. A total of 662, 239, 210 and 138 proteins were found in the adult tegument, adult secreted, soluble egg and secreted egg proteomes, respectively. In addition, we probed these distinct proteomes with urine to assess urinary antibody responses from naturally infected human subjects with different infection intensities, and identified adult fluke secreted and tegument extracts as being the best predictors of infection.

CONCLUSION

We provide a comprehensive dataset of proteins from the adult and egg stages of S. haematobium and highlight their utility as diagnostic markers of infection intensity. Protein composition was markedly different between the different extracts, highlighting the distinct subsets of proteins that different development stages present in their different niches. Furthermore, we have identified adult fluke ES and tegument extracts as best predictors of infection using urine antibodies of naturally infected people. This study provides the first steps towards the development of novel tools to control this important neglected tropical disease.

Programmed knockout mutation of liver fluke granulin attenuates virulence of infection-induced hepatobiliary morbidity

Infection with the food-borne liver fluke Opisthorchis viverrini is the principal risk factor (IARC Working Group on the Evaluation of Carcinogenic Risks to Humans, 2012) for cholangiocarcinoma (CCA) in the Lower Mekong River Basin countries including Thailand, Lao PDR, Vietnam and Cambodia. We exploited this link to explore the role of the secreted growth factor termed liver fluke granulin (Ov-GRN-1) in pre-malignant lesions by undertaking programmed CRISPR/Cas9 knockout of the Ov-GRN-1 gene from the liver fluke genome. Deep sequencing of amplicon libraries from genomic DNA of gene-edited parasites revealed Cas9-catalyzed mutations within Ov-GRN-1. Gene editing resulted in rapid depletion of Ov-GRN-1 transcripts and the encoded Ov-GRN-1 protein. Gene-edited parasites colonized the biliary tract of hamsters and developed into adult flukes, but the infection resulted in reduced pathology as evidenced by attenuated biliary hyperplasia and fibrosis. Not only does this report pioneer programmed gene-editing in parasitic flatworms, but also the striking, clinically-relevant pathophysiological phenotype confirms the role for Ov-GRN-1 in virulence morbidity during opisthorchiasis.

Trematode Genomics and Proteomics

Trematode infections are among the most neglected tropical diseases despite their worldwide distribution and extraordinary ability to parasitise many different host species and host tissues. Furthermore, these parasites are of great socioeconomic, medical, veterinary and agricultural importance. During the last 10 years, there have been increasing efforts to overcome the lack of information on different "omic" resources such as proteomics and genomics. Herein, we focus on the recent advances in genomics and proteomics from trematodes of human importance, including liver, blood, intestinal and lung flukes. We also provide information on the latest technologies applied to study the biology of trematodes as well as on the resources available for the study of the molecular aspects of this group of helminths.

RNA Interference as an Approach to Functional Genomics Genetic Manipulation of Opisthorchis viverrini

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.

Bioassay-guided isolation of active substances from Semen Torreyae identifies two new anthelmintic compounds with novel mechanism of action

ETHNOPHARMACOLOGICAL RELEVANCE

Semen Torreyae, the seeds of Torreya grandis Fortune ex Lindley (Cephalotaxaceae) is a well-known traditional Chinese medicinal plant recorded in the Chinese Pharmacopeia (2010 version). It is widely used for treating intestinal parasites in China, owing to its desirable efficacy and safety. However, the anthelmintic compounds in Semen Torreyae have not yet been identified.

AIM OF THE STUDY

This study aims to identify the compounds active against helminths from Semen Torreyae. In addition, we tested whether C. elegans strains resistant to currently-used anthelmintic drugs showed cross-resistance to these compounds.

METHODS

A bioassay-guided isolation of anthelmintic compounds from Semen Torreyae was performed using a Caenorhabditis elegans (C. elegans) testing model. The structures of active compounds were elucidated by a combination of GC-MS, high resolution MS, and NMR. The median-effect method was employed to generate a combination index (CI) to evaluate the synergistic effect of the anthelmintic compounds. A panel of C. elegans mutant strains resistant against the major anthelmintic drug classes was used to study the cross-resistance to currently-used anthelmintic drugs. A panel of transient receptor potential (TRP) channel mutant strains was also tested to explore the possible mechanisms of action of the anthelmintic compounds.

RESULTS

The bioassay-guided isolation led to two active compounds, i.e. galangal acetate (IC₅₀: 58.5 ± 8.9 μM) and miogadial (IC₅₀: 25.1 ± 5.4 μM). The combination of galangal acetate and miogadial resulted in a synergistic effect at IC₅₀, IC₇₀, and IC₉₀ levels (CIs < 1). Galangal acetate and miogadial demonstrated similar activity against drug-resistant C. elegans strains compared to the wild-type strain. In addition, none of the TRP mutants was significantly resistant to galangal acetate or miogadial compared to wild type worms.

CONCLUSIONS

We identified the bioactive compounds from Semen Torreyae responsible for its anthelmintic activity: galangal acetate and miogadial. The two anthelmintic compounds demonstrated a synergistic effect against C. elegans. Galangal acetate and miogadial are unlikely to act on the targets of currently-used anthelmintics (ivermectin, levamisole, benomyl and aldicarb), and an action on TRP channels appears to be ruled out as well. In summary, galangal acetate and miogadial are promising anthelmintic hits worth further investigation.

Bioassay-guided isolation of three anthelmintic compounds from Warburgia ugandensis Sprague subspecies ugandensis, and the mechanism of action of polygodial

Parasitic helminths continue to pose problems in human and veterinary medicine, as well as in agriculture. Resistance to current anthelmintics has prompted the search for new drugs. Anthelmintic metabolites from medicinal plants could be good anthelmintic drug candidates. However, the compounds active against nematodes have not been identified in most medicinal plants with anthelmintic activity. In this study, we aimed to identify the active compounds against helminths in Warburgia ugandensis Sprague subspecies ugandensis (Canellaceae) and study the underlying mechanism of action. A bioassay-guided isolation of anthelmintic compounds from the plant was performed using a Caenorhabditis elegans (C. elegans) test model with a WMicrotracker instrument to monitor motility. Three active compounds were purified and identified by nuclear magnetic resonance and high resolution MS: warburganal (IC₅₀: 28.2 ± 8.6 μM), polygodial (IC₅₀: 13.1 ± 5.3 μM) and alpha-linolenic acid (ALA, IC₅₀: 70.1 ± 17.5 μM). A checkerboard assay for warburganal and ALA as well as polygodial and ALA showed a fractional inhibitory concentration index of 0.41 and 0.37, respectively, suggesting that polygodial and ALA, as well as warburganal and ALA, have a synergistic effect against nematodes. A preliminary structure-activity relationship study for polygodial showed that the α,β-unsaturated 1,4-dialdehyde structural motif is essential for the potent activity. None of a panel of C. elegans mutant strains, resistant against major anthelmintic drug classes, showed significant resistance to polygodial, implying that polygodial may block C. elegans motility through a mechanism which differs from that of currently marketed drugs. Further measurements showed that polygodial inhibits mitochondrial ATP synthesis of C. elegans in a dose-dependent manner (IC₅₀: 1.8 ± 1.0 μM). Therefore, we believe that the underlying mechanism of action of polygodial is probably inhibition of mitochondrial ATP synthesis. In conclusion, polygodial could be a promising anthelmintic drug candidate worth considering for further development.

Co-occurrence of opisthorchiasis and diabetes exacerbates morbidity of the hepatobiliary tract disease

Complications arising from infection with the carcinogenic liver fluke Opisthorchis viverrini cause substantial morbidity and mortality in Thailand and adjacent lower Mekong countries. In parallel, the incidence rate of diabetes mellitus (DM) is increasing in this same region, and indeed worldwide. Many residents in opisthorchiasis-endemic regions also exhibit DM, but the hepatobiliary disease arising during the co-occurrence of these two conditions remains to be characterized. Here, the histopathological profile during co-occurrence of opisthorchiasis and DM was investigated in a rodent model of human opisthorchiasis in which diabetes was induced with streptozotocin. The effects of excretory/secretory products from the liver fluke, O. viverrini (OVES) on hepatocyte and cholangiocyte responses during hyperglycemic conditions also were monitored. Both the liver fluke-infected hamsters (OV group) and hamsters with DM lost weight compared to control hamsters. Weight loss was even more marked in the hamsters with both opisthorchiasis and DM (OD group). Hypertrophy of hepatocytes, altered biliary canaliculi, and biliary hyperplasia were more prominent in the OD group, compared with OV and DM groups. Profound oxidative DNA damage, evidenced by 8-oxo-2'-deoxyguanosine, proliferating cell nuclear antigen, and periductal fibrosis characterized the OD compared to OV and DM hamsters. Upregulation of expression of cytokines in response to infection and impairment of the pathway for insulin receptor substrate (IRS)/phosphatidylinositol-3-kinases (PI3K)/protein kinase B (AKT) signaling attended these changes. In vitro, OVES and glucose provoked time- and dose-dependent effects on the proliferation of both hepatocytes and cholangiocytes. In overview, the co-occurrence of opisthorchiasis and diabetes exacerbated pathophysiological damage to the hepatobiliary tract. We speculate that opisthorchiasis and diabetes together aggravate hepatobiliary pathogenesis through an IRS/PI3K/AKT-independent pathway.

Helminths and Cancers From the Evolutionary Perspective

Helminths include free-living and parasitic Platyhelminthes and Nematoda which infect millions of people worldwide. Some Platyhelminthes species of blood flukes (Schistosoma haematobium, Schistosoma japonicum, and Schistosoma mansoni) and liver flukes (Clonorchis sinensis and Opisthorchis viverrini) are known to be involved in human cancers. Other helminths are likely to be carcinogenic. Our main goals are to summarize the current knowledge of human cancers caused by Platyhelminthes, point out some helminth and human biomarkers identified so far, and highlight the potential contributions of phylogenetics and molecular evolution to cancer research. Human cancers caused by helminth infection include cholangiocarcinoma, colorectal hepatocellular carcinoma, squamous cell carcinoma, and urinary bladder cancer. Chronic inflammation is proposed as a common pathway for cancer initiation and development. Furthermore, different bacteria present in gastric, colorectal, and urogenital microbiomes might be responsible for enlarging inflammatory and fibrotic responses in cancers. Studies have suggested that different biomarkers are involved in helminth infection and human cancer development; although, the detailed mechanisms remain under debate. Different helminth proteins have been studied by different approaches. However, their evolutionary relationships remain unsolved. Here, we illustrate the strengths of homology identification and function prediction of uncharacterized proteins from genome sequencing projects based on an evolutionary framework. Together, these approaches may help identifying new biomarkers for disease diagnostics and intervention measures. This work has potential applications in the field of phylomedicine (evolutionary medicine) and may contribute to parasite and cancer research.

Granulin Secreted by the Food-Borne Liver Fluke Opisthorchis viverrini Promotes Angiogenesis in Human Endothelial Cells

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.

Opisthorchis viverrini Proteome and Host-Parasite Interactions

The omics technologies have improved our understanding of the molecular events that underpin host-parasite interactions and the pathogenesis of parasitic diseases. In the last decade, proteomics and genomics in particular have been used to characterize the surface and secreted products of the carcinogenic liver fluke Opisthorchis viverrini and revealed important roles for proteins at the host-parasite interface to ensure that the flukes can migrate, feed and reproduce in a hostile environment. This review summarizes the advances made in this area, primarily focusing on discoveries enabled by the publication of the fluke secreted proteomes over the last decade. Protein families that will be covered include proteases, antioxidants, oncogenic proteins and the secretion of exosome-like extracellular vesicles. Roles of these proteins in host-parasite interactions and pathogenesis of fluke-induced hepatobiliary diseases, including cholangiocarcinogenesis, are discussed. Future directions for the application of this knowledge to control infection and disease will also be discussed.

Update on Pathogenesis of Opisthorchiasis and Cholangiocarcinoma

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.

Extracellular vesicles as a target for the development of anti-helminth vaccines

There is a rapidly growing body of evidence that production of extracellular vesicles (EVs) is a universal feature of cellular life. More recently, EVs have been identified in a broad range of both unicellular and multicellular parasites where they play roles in parasite-parasite intercommunication as well as parasite-host interactions. Parasitic helminth-derived EVs traverse host target cell membranes whereupon they offload their molecular cargo - proteins, lipids, and genetic information such as mRNAs and miRNAs - which are thought to hijack the target cell and modulate its gene expression to promote parasite survival. As such, EVs represent a novel mechanism of intercellular communication that could be targeted for vaccine-mediated interruption, given the abundance of surface antigens expressed on helminth EVs, and the ability of antibodies to block their uptake by target cells. In this Perspective article, we review recent developments in the field of helminth-derived EVs and highlight their roles in helminth vaccine discovery and development.