Update on Pathogenesis of Opisthorchiasis and Cholangiocarcinoma

Clonorchis sinensis and Cholangiocarcinoma

Clonorchiasis is a parasitic disease caused by Clonorchis sinensis, a trematode that inhabits the intrahepatic bile ducts of humans and mammals. C. sinensis is one of common food-borne trematodes, prevalent in East Asia including Korea. The International Agency for Research on Cancer reclassified C. sinensis as the Group 1 biological carcinogen of human cholangiocarcinoma (CCA). Evidence supporting the carcinogenicity of C. sinensis includes epidemiological studies showing increased prevalence and odds ratio (OR) of CCA in clonorchiasis patients, the development of CCA in experimental animals, and molecular studies. Approximately 10% of CCA in Korea are believed to be solely caused by clonorchiasis, with an OR of 4.7 for CCA risk among clonorchiasis patients. All hamsters exposed to both of C. sinensis and N-nitrosodimethylamine (NDMA) developed CCA while those exposed to either C. sinensis or NDMA alone did not. In vitro studies using cell models investigated carcinogenetic changes of the intracellular molecules and genes following stimulation with a soluble extract of C. sinensis. The in vitro stimulated cells showed a significant shift to G2/M phage, produced oncogenic molecules, changed expression of oncogenes, increased cell proliferation and suppressed apoptosis. Additionally, the gap-junction proteins between cells, such as connexin (Cx) 43, Cx 26, and Cx 32, were changed significantly, disrupting intercellular homeostasis. These findings suggest that C. sinensis and nitrogen compounds synergistically stimulate the cholangiocytes to become neoplastic. C. sinensis is a biological carcinogen of human CCA, and the World Health Organization guidelines enlist food-borne trematodes as one of target neglected tropical diseases to be eliminated by 2030. The present article reviews and updates perspectives on clonorchiasis, focusing on carcinogenesis.

Synthesis and Characterization of a Novel All-in-One Graphene Oxide-Nafion Polymer Bioconjugate for Application in Electrochemical Biosensing of the Opisthorchis viverrini Antigen

Bioconjugates in electrochemical biosensors can significantly enhance the detection process and sensitivity. In this study, we synthesized a monoclonal antibody-conjugated nanocomposite of graphene oxide and Nafion (GO-Nf-mAb) for application in an electrochemical biosensor as a novel all-in-one bioreceptor. The incorporation of Nafion (Nf) improved the stability, dispersity, and antibody immobilization on the GO surface, thereby increasing the sensitivity of the biosensor. The impact of Nafion on GO stability and antibody conjugation was thoroughly investigated and compared to that of Nafion-free conjugation via various characterization techniques, including X-ray photoelectron spectroscopy (XPS) and synchrotron radiation near-edge X-ray absorption fine structure. The presence of Nafion during monoclonal antibody (mAb) conjugation resulted in an increased peak intensity of the NH2 band in XPS analysis and the highest intensity of C=O groups in O-K edge analysis, indicating a greater yield of the antibody. This innovative electrochemical biosensor exhibited a low detection limit of 1.68 ng mL-1 in spiked urine, a wide linear range, and high reproducibility, outperforming conventional detection methods for Opisthorchis viverrini (OV) antigen detection. Our developed electrochemical biosensor introduces a novel and straightforward fabrication process using an all-in-one bioconjugate that serves as a bioreceptor, transducer, and blocking reagent simultaneously. Overall, this study offers a new insight on Nafion application in bioconjugation, and the GO-Nf-mAb conjugate-based electrochemical biosensor promises high sensitivity and a hassle-free immobilization process for OV antigen quantification.

Factors Contributing to the High Malignancy Level of Cholangiocarcinoma and Its Epidemiology: Literature Review and Data

CCA is a highly desmoplastic malignant cancer and is the second most common primary liver malignancy after hepatocellular carcinoma (HCC), accounting for approximately 15% of all primary liver tumors. CCA has a poor prognosis, with an average five-year survival rate of 9%, which is lower than that of pancreatic cancer. Although considerable efforts have been invested into the genomics, epigenetics, and risk factors, very little is known about what might have been the key causes for the high malignancy level of CCA. In this review, we analyze the incidence and mortality of CCA in different regions based on data from 1994 to 2022 obtained from the International Agency for Research on Cancer (IARC), discuss the current status of treatment of the disease, and focus on what might be the main factors contributing to the high malignancy level of CCA: alkalosis caused by the Fenton reaction, hypoxia, and the TIME. The review includes studies published from 1979 to 2024, aiming to provide an updated synthesis of basic early classical theoretical knowledge and current knowledge about CCA. By revealing the epidemiological characteristics of CCA, the potential mechanisms of high malignancy, and the current challenges of treatment, this review aims to provide new directions for future cancer research, promote the development of personalized treatment strategies, and facilitate a deeper understanding and the more effective management of CCA worldwide.

Goblet cell metaplasia and mucin alterations in biliary epithelial cells during Opisthorchis viverrini infection in rodent models: Insights into host susceptibility and defense mechanisms

Background and Aim

Chronic Opisthorchis viverrini (OV) infection induces significant biliary changes and is a major risk factor for cholangiocarcinoma. However, the role of goblet cell metaplasia (GCM) and mucin dynamics in host defense and parasite persistence remains poorly understood. This study aims to characterize biliary histological changes, particularly mucin types, and compare responses between susceptible (hamsters) and non-susceptible (mice) hosts during early to chronic OV infection.

Materials and Methods

Thirty-five male golden Syrian hamsters and 35 male BALB/c mice were divided into infected and control groups. Infected animals received 50 OV metacercariae through gastric intubation and were sacrificed on days 1, 2, 7, 14, 28, and 56 post-infection. Histological, histochemical (Alcian Blue, periodic Acid-Schiff, and high iron diamine), and immunohistochemical (Bromodeoxyuridine [BrdU]) analyses were performed to assess mucin production, GCM, and bile duct proliferation.

Results

Mice demonstrated an early, robust biliary response with pronounced hyperplasia and GCM characterized by acid mucin overproduction during the acute phase (days 1-28). Conversely, hamsters exhibited delayed biliary proliferation and GCM, with predominant sulfated mucins appearing during the chronic phase (days 28-56). BrdU immunoreactivity indicated earlier and stronger bile duct epithelial proliferation in mice, correlating with worm clearance by day 28. In hamsters, mucosal changes supported worm survival, as evidenced by continued parasite presence and egg production. Statistical analyses confirmed significant differences in mucin types and hyperplasia between species across infection stages.

Conclusion

Distinct mucosal responses in hamsters and mice reflect their susceptibility to OV infection. Acid mucins in mice facilitate worm expulsion, while sulfated mucins in hamsters appear to promote parasite persistence. These findings highlight the dual roles of mucins in host defense and parasite survival, providing insight into mechanisms underlying susceptibility and resistance in OV infections.

Differential circulating miRNA profiles identified miR-423-5p, miR-93-5p, and miR-4532 as potential biomarkers for cholangiocarcinoma diagnosis

Background

Cholangiocarcinoma (CCA) is high in morbidity and mortality rates which may be due to asymptomatic and effective diagnostic methods not available. Therefore, an effective diagnosis is urgently needed.

Methods

Investigation of plasma circulating miRNA (cir-miRNA) was divided into two phases, including the discovery phase (pooled 10 samples each from three pools in each group) and the validation phase (17, 16, and 35 subjects of healthy control (HC), O. viverrini (OV), and CCA groups, respectively). The plasma from healthy control subjects, O. viverrini infected subjects, and CCA subjects was used. In the discovery phase, plasma was pooled by adding an equal volume of plasma, and cir-miRNA was isolated and analyzed with the nCounter® SPRINT Profiler. The significantly different cir-miRNAs were selected for the validation phase. In the validation phase, cir-miRNA was isolated and analyzed using real time-quantitative polymerase chain reaction (RT-qPCR). Subsequently, statistical analysis was conducted, and diagnostic parameters were calculated.

Results

Differential plasma cir-miRNA profile showed at least three candidates including miR-423-5p, miR-93-5p, and miR-4532 as potential biomarkers. From validation of these cir-miRNAs by RT-qPCR, the result showed that the satisfied sensitivity and specificity to differential CCA group from HC and OV group was obtained from miR-4532 (P < 0.05) while miR-423-5p and miR-93-5p can be used for differential CCA from OV and HC group (P < 0.05) with high specificity but limited the sensitivity. In conclusion, candidate cir-miRNAs have been identified as potential biomarkers including miR-423-5p, miR-93-5p and miR-4532. Screening by miR-4532 and confirmed with miR-423-5p, miR-93-5p were suggested for differential CCA patients in the endemic area of O. viverrini.

Species-specific renal and liver responses during infection with food-borne trematodes Opisthorchis felineus, Opisthorchis viverrini, or Clonorchis sinensis

Three food-borne trematodes-Opisthorchis felineus, Opisthorchis viverrini, and Clonorchis sinensis-are closely related epidemiologically important species. Despite the similarity of their life cycles, these liver flukes also have marked differences in the geographical range, helminth biology, and hepatobiliary disorders. O. viverrini and C. sinensis are classified as Group 1 biological carcinogens while O. felineus is not. Direct comparisons of systemic response to the liver fluke infections are unexplored aspects. This study was carried out to identify species-specific liver and kidney responses in the hamster models after the infection with one of the three liver flukes. Liver periductal-fibrosis development was similar between hamsters infected with O. felineus or C. sinensis, whereas biliary intraepithelial neoplasia development was noticed predominantly in O. viverrini-infected ones. Species-specific renal damage was detected, including progression of interstitial fibrosis and IgA deposition in glomeruli of O. felineus-infected hamsters and C. sinensis-infected ones. A strong correlation (R = 0.63; P = 0.0001) was found between periductal fibrosis in the liver and kidney interstitial fibrosis. Future comparative studies are needed to elucidate the development of serious complications during the long term of the infection, as well as under the influence of additional factors, including concomitant infections and the use of dimethylnitrosamine to clarify the mechanisms underlying the liver fluke-associated carcinogenesis. Thus, our findings may stimulate new comparative studies on the pathogenicity.

Advances in targeted therapy of cholangiocarcinoma

Cholangiocarcinoma (CCA) is a malignant tumor originating in the bile duct and its branching epithelium. Due to its high heterogeneity, there are no specific clinical indications at the early stage, the diagnosis is often in advanced CCA. With surgical resection, the 5-year postoperative survival rate (long-term survival rate) is very poor. The regimen of gemcitabine combined with platinum has been used as the first-line chemotherapy for advanced patients. In recent years, targeted therapy for a variety of malignant tumors has made great progress, showing good efficacy and safety in advanced CCA. However, the current targeted therapy of CCA still has many challenges, such as adverse reactions, drug resistance, and individual differences. Therefore, the researches need to further explore the targeted therapy mechanism of CCA malignancies in depth, develop more effective and safe drugs, and accurately formulate plans based on patient characteristics to further improve patient prognosis in the future. This article reviews the recent progress of targeted therapy for CCA, aiming to provide a strategy for the research and clinical work of targeted therapy for CCA.

MicroRNAs in opisthorchiids and their definitive hosts: Current Status and Perspectives

Opisthorchis felineus, Opisthorchis viverrini, and Clonorchis sinensis (family Opisthorchiidae) are parasitic flatworms that pose serious threats to humans in certain countries and cause opisthorchiasis/clonorchiasis. Opisthorchiid flukes parasitize the biliary tract of the host, causing cholangitis, cholecystitis, cholelithiasis and cholangiocarcinoma. In this review, we primarily focus on recent microRNAs (miRNAs) studies of opisthorchiid flukes and their definitive hosts. Many miRNAs are conserved and expressed in a developmentally stage specific manner in the three opisthorchiid flukes, which play important roles in the growth and development of Opisthorchiidae spp., as well as host-pathogen interactions. Some miRNAs might be potential biomarkers related to carcinogenesis of cholangiocarcinoma. Therefore, this review provides the basis for further investigating the roles of miRNAs in opisthorchiid flukes and their definitive hosts, as well as promoting the development of novel approaches to prevent and treat opisthorchiasis/clonorchiasis.

Study of the population genetic structure of Opisthorchis-like eggs in northern Thailand using mitochondrial genes

BACKGROUND

Opisthorchis-like eggs are a public health problem in northern and northeastern Thailand. However, the genetic epidemiology and structure of these parasites in northern Thailand are unknown. Thus, this study investigated their population genetic structure using cytochrome c oxidase subunit 1 (cox1) and NADH dehydrogenase subunit 1 (nad1) nucleotide sequences.

METHODOLOGY/PRINCIPAL FINDINGS

A study was conducted in the hill tribe regions of Chiang Mai Province, northern Thailand. Internal transcribed spacer 2 polymerase chain reaction and restriction fragment length polymorphism were used to distinguish 205 positive feces samples for Opisthorchis-like eggs. The results showed that the prevalence of O. viverrini and Haplorchis taichui was 10.5% and 38.2%, respectively, and the co-infection rate was 37.2%. To determine the genetic structure of O. viverrini and H. taichui using cox1 and nad1 genes, genetic analysis was performed using 30 randomly chosen fecal samples for Opisthorchis-like eggs. Pairwise FST analysis indicated that O. viverrini and H. taichui displayed nonsignificant genetic differentiation within Chiang Mai Province and between interpopulations from different geographic areas. Moreover, within the intrapopulation in Chiang Mai Province, cox1 presented higher gene flow than nad1 in O. viverrini, while nad1 demonstrated higher gene flow than cox1 in H. taichui. The neutrality tests based on Fu's Fs indicated population expansion and selective sweep from bottleneck or hitchhiking in O. viverrini and H. taichui populations, supported by haplotype network patterns. Phylogenetic tree analysis based on cox1 and nad1 revealed the monophyly of O. viverrini and H. taichui and genetic relationships with other isolates collected from Thailand, Lao People's Democratic Republic (PDR), and Vietnam.

CONCLUSIONS/SIGNIFICANCE

This study investigated the molecular discrimination and genetic structure of Opisthorchis-like eggs in northern Thailand. The genetic information derived from this study could be associated with the background, molecular epidemiology, and disease severity of these parasites.

Identification and functional analysis of mitogenic miRNA of the carcinogenic liver fluke Opisthorchis viverrini

Opisthorchis viverrini is a pathogenic liver fluke that is known to cause cholangiocarcinoma in chronic infections. The underlying mechanism for this carcinogenesis is believed to be multifactorial, with parasite-derived excretory-secretory (ES) products potentially playing major roles. A recent study on these ES products has identified microRNAs (miRNA) that originate from O. viverrini but their influence on carcinogenesis remains understudied. Hence, we aimed to investigate the role of these miRNAs in the carcinogenesis of O. viverrini-associated cholangiocarcinoma. The mature miRNA sequences were retrieved from published data. Bioinformatics analysis was employed to identify miRNA targets and to identify potentially mitogenic miRNAs. An in vitro study was conducted to test the effects of miRNA on the bile duct epithelial cell lines. The miRNA target prediction analysis revealed that Ov_miRNA_EV_36/ovi-miR-3479a targets cancer-associated pathways. Hence, it was selected and used to assess its effect on the cell proliferation rate of H69 and MMNK-1 cholangiocyte cell lines. The results showed that Ov_miRNA_EV_36/ovi-miR-3479a induced significant cell proliferation in both cell lines when compared to negative controls. These results indicate that Ov_miRNA_EV_36/ovi-miR-3479a may play an essential role in the carcinogenesis of O. viverrini and therefore warrant further investigations.

Bioengineered Organoids Offer New Possibilities for Liver Cancer Studies: A Review of Key Milestones and Challenges

Hepatic cancer is widely regarded as the leading cause of cancer-related mortality worldwide. Despite recent advances in treatment options, the prognosis of liver cancer remains poor. Therefore, there is an urgent need to develop more representative in vitro models of liver cancer for pathophysiology and drug screening studies. Fortunately, an exciting new development for generating liver models in recent years has been the advent of organoid technology. Organoid models hold huge potential as an in vitro research tool because they can recapitulate the spatial architecture of primary liver cancers and maintain the molecular and functional variations of the native tissue counterparts during long-term culture in vitro. This review provides a comprehensive overview and discussion of the establishment and application of liver organoid models in vitro. Bioengineering strategies used to construct organoid models are also discussed. In addition, the clinical potential and other relevant applications of liver organoid models in different functional states are explored. In the end, this review discusses current limitations and future prospects to encourage further development.

Opisthorchis viverrini excretory-secretory products suppress GLUT8 of cholangiocytes

Opisthorchis viverrini infection and the subsequent bile duct cancer it induces remains a significant public health problem in Southeast Asia. Opisthorchiasis has been reported to cause reduced plasma glucose levels among infected patients. The underlying mechanism for this phenomenon is unclear. In the present study, evidence is presented to support the hypothesis that O. viverrini exploits host cholangiocyte glucose transporters (GLUTs) in a similar manner to that of rodent intestinal nematodes, to feed on unabsorbed glucose in the bile for survival. GLUT levels in a cholangiocyte H69 cell line co-cultured with excretory-secretory products of O. viverrini were examined using qPCR and immunoblotting. GLUT 8 mRNA and expressed proteins were found to be downregulated in H69 cells in the presence of O. viverrini. This suggests that O. viverrini alters glucose metabolism in cells within its vicinity by limiting transporter expression resulting in increased bile glucose that it can utilize and potentially explains the previously reported anti-insulin effect of opisthorchiasis.

Fish and Food-Fatale: Food-borne Trematode Opisthorchis viverrini and Cholangiocarcinoma

Neglected Tropical Diseases (NTDs) are a group of communicable diseases with a long history with human beings. NTDs are the proxy of poverty since they affect those in low-income and extreme-poverty populations, as those populations lack access to proper health care, clean water, sanitary conditions, and hygiene. NTDs create losses for a nation that come from the health and the economic sectors as well since the costs of diagnosis, prevention, and treatment strain the national purse strings. One of the 20 different forms of NTDs on the list is food-borne trematodes, comprises of Fasciola, Paragonimus, Clonorchis, and Opisthorchis. Currently, it is estimated that food-borne trematodes can cause a devastating effect on mortality and morbidity. All of them are zoonotic, as humans become infected by ingestion of a second intermediate host, such as freshwater snails, fish, or water vegetables. Opisthorchis viverrini, one of the food-borne trematodes that can be found mostly in South East Asia regions, especially in the Mekong basin, is regarded as a group 1 carcinogen leading to cholangiocarcinoma (CCA). This study aims to present the updated review of Opisthorchis viverrini and CCA.

Curcumin-loaded nanocomplexes alleviate the progression of fluke-related cholangiocarcinoma in hamsters

Background

Curcumin-loaded nanocomplexes (CNCs) previously demonstrated lower toxicity and extended release better than is the case for free curcumin. Here, we evaluated the efficacy of CNCs against opisthorchiasis-associated cholangiocarcinoma (CCA) in hamsters.

Method

Dose optimization (dose and frequency) was performed over a 1-month period using hamsters, a model that is widely used for study of opisthorchiasis-associated cholangiocarcinoma. In the main experimental study, CCA was induced by a combination of fluke, Opisthorchis viverrini (OV), infection and N-nitrosodimethylamine (NDMA) treatment. Either blank (empty) nanocomplexes (BNCs) or different concentrations of CNCs (equivalent to 10 and 20 mg cur/kg bw) were given to hamsters thrice a week for 5 months. The histopathological changes, biochemical parameters, and the expression of inflammatory/oncogenic transcription factors were investigated. In addition, the role of CNCs in attenuating CCA genesis, as seen in an animal model, was also confirmed in vitro using CCA cell lines.

Results

The optimization study revealed that treatment with CNCs at a dose equivalent to 10 mg cur/kg bw, thrice a week for 1 month, led to a greater reduction of inflammation and liver injury induced in hamsters by OV + NDMA than did treatments at other dose rates. Oral administration with CNCs (10 mg cur/kg bw), thrice a week for 5 months, significantly increased survival rate, reduced CCA incidence, extent of tumor development, cholangitis, bile duct injury and cholangiofibroma. In addition, this treatment decreased serum ALP and ALT activities and suppressed expression of NF-κB, FOXM1, HMGB1, PCNA and formation of 8-nitroguanine. Treatment of CCA cell lines with CNCs also reduced cell proliferation and colony formation, similar to those treated with NF-κB and/or FOXM1 inhibitors.

Conclusion

CNCs (10 mg cur/kg bw) attenuate the progression of fluke-related CCA in hamsters partly via a NF-κB and FOXM1-mediated pathway.

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.

Interplay between the Human Microbiome and Biliary Tract Cancer: Implications for Pathogenesis and Therapy

Biliary tract cancer, encompassing intrahepatic and extrahepatic cholangiocarcinoma as well as gallbladder carcinoma, stands as a prevalent malignancy characterized by escalating incidence rates and unfavorable prognoses. The onset of cholangiocarcinoma involves a multitude of risk factors and could potentially be influenced by microbial exposure. The human microbiome, encompassing the entirety of human microbial genetic information, assumes a pivotal role in regulating key aspects such as host digestion, absorption, immune responses, and metabolism. The widespread application of next-generation sequencing technology has notably propelled investigations into the intricate relationship between the microbiome and diseases. An accumulating body of evidence strongly suggests a profound interconnection between biliary tract cancer and the human microbiome. This article critically appraises the existing evidence pertaining to the microbiome milieu within patients afflicted by biliary tract cancer. Furthermore, it delves into potential mechanisms through which dysregulation of the human microbiome could contribute to the advancement of biliary tract cancer. Additionally, the article expounds on its role in the context of chemotherapy and immunotherapy for biliary tract cancer.

Secreted and surface proteome and transcriptome of Opisthorchis felineus

Introduction

Opisthorchis felineus, Opisthorchis viverrini, and Clonorchis sinensis are the most medically important species of fish-borne zoonotic trematodes. O. felineus is endemic to the river plains of Western Siberia and Eastern Europe, and it is estimated that more than 1.6 million people could be infected with this parasite. Chronic opisthorchiasis may lead to significant gastrointestinal and hepatobiliary pathology. This study aimed to identify and characterize proteins from the secreted and tegumental proteomes of O. felineus.

Methods

Adult flukes were collected from experimentally infected hamsters and cultured in vitro in serum-free media. We extracted proteins from different compartments of the O. felineus secretome, including (i) soluble excretory/secretory (ES) products; (ii) secreted 15K-extracellular vesicles (EVs); and (iii) tegument.

Results

We also generated a transcriptome using long-read sequencing, and when this was combined with high-resolution mass spectrometry, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) separation, and protein digestion, we identified 686, 894, 389, 324, and 165 proteins from the ES, 15K-EV, and the three sequentially extracted tegument (TEG) protein fractions, respectively. We conducted in-depth gene ontology and protein family analyses on the identified proteins and discussed comparisons against similar proteome data sets acquired for the Southeast Asian liver fluke O. viverrini and the Chinese liver fluke C. sinensis.

Discussion

The information from this study will form a biologically relevant data set of O. felineus proteins that could be used to develop diagnostic and therapeutic tools to manage the human cost of O. felineus infection and its associated comorbidities.

Advances in the Early Detection of Hepatobiliary Cancers

Hepatocellular cancer (HCC) and biliary tract cancers (BTCs) have poor survival rates and a low likelihood of a cure, especially in advanced-stage disease. Early diagnosis is crucial and can significantly improve survival rates through curative treatment approaches. Current guidelines recommend abdominal ultrasonography (USG) and alpha-fetoprotein (AFP) monitoring for HCC screening in high-risk groups, and abdominal USG, magnetic resonance imaging (MRI), and magnetic resonance cholangiopancreatography (MRCP) monitoring for biliary tract cancer. However, despite this screening strategy, many high-risk individuals still develop advanced-stage HCC and BTC. Blood-based biomarkers are being developed for use in HCC or BTC high-risk groups. Studies on AFP, AFP-L3, des-gamma-carboxy prothrombin, glypican-3 (GPC3), osteopontin (OPN), midkine (MK), neopterin, squamous cell carcinoma antigen (SCCA), Mac-2-binding protein (M2BP), cyclic guanosine monophosphate (cGMP), and interleukin-6 biomarkers for HCC screening have shown promising results when evaluated individually or in combination. In the case of BTCs, the potential applications of circulating tumor DNA, circulating microRNA, and circulating tumor cells in diagnosis are also promising. These biomarkers have shown potential in detecting BTCs in early stages, which can significantly improve patient outcomes. Additionally, these biomarkers hold promise for monitoring disease progression and evaluating response to therapy in BTC patients. However, further research is necessary to fully understand the clinical utility of these biomarkers in the diagnosis and management of HCC and BTCs.

Distinct antibody response in susceptible and non-susceptible hosts of the carcinogenic liver fluke Opisthorchis viverrini infection

Opisthorchis viverrini is a carcinogenic parasite that can cause bile duct cancer called cholangiocarcinoma. A study of the immune response of this parasite in susceptible and non-susceptible hosts may provide a clue to develop vaccines and immunodiagnostic markers, which are currently not available. Here, we compared the antibody response in susceptible Golden Syrian hamsters and non-susceptible BALB/c mice infected by the liver fluke. In mice, the antibody was detected between 1 and 2 weeks post-infection, whereas it was positive between 2 and 4 weeks post-infection in hamsters. Immunolocalization revealed that the antibody from mice reacts strongly with the tegumental surface and gut epithelium of the worm, while hamster antibody showed a weak signal in the tegument and a comparable signal in the gut of the worm. Immunoblot of the tegumental proteins demonstrated that while hamster antibody showed a broad specificity, mice strongly reacted with a single protein band. Mass spectrometry revealed these immunogenic targets. Recombinant proteins of the reactive targets were produced in the bacterial expression system. The immunoblot of these recombinant proteins confirm the reactivity of their native form. In summary, there is a different antibody response against O. viverrini infection in susceptible and non-susceptible hosts. The non-susceptible host reacts quicker and stronger than the susceptible host.

Curcumin and Its Supramolecular Complex with Disodium Glycyrrhizinate as Potential Drugs for the Liver Fluke Infection Caused by Opisthorchis felineus

Opisthorchiosis is a parasitic liver disease found in mammals that is widespread throughout the world and causes systemic inflammation. Praziquantel remains the drug of choice for the treatment of opisthorchiosis, despite its many adverse effects. An anthelmintic effect is attributed to the main curcuminoid of Curcuma longa L. roots-curcumin (Cur)-along with many other therapeutic properties. To overcome the poor solubility of curcumin in water, a micellar complex of curcumin with the disodium salt of glycyrrhizic acid (Cur:Na₂GA, molar ratio 1:1) was prepared via solid-phase mechanical processing. In vitro experiments revealed a noticeable immobilizing effect of curcumin and of Cur:Na₂GA on mature and juvenile Opisthorchis felineus individuals. In vivo experiments showed that curcumin (50 mg/kg) had an anthelmintic effect after 30 days of administration to O. felineus-infected hamsters, but the effect was weaker than that of a single administration of praziquantel (400 mg/kg). Cur:Na₂GA (50 mg/kg, 30 days), which contains less free curcumin, did not exert this action. The complex, just as free curcumin or better, activated the expression of bile acid synthesis genes (Cyp7A1, Fxr, and Rxra), which was suppressed by O. felineus infection and by praziquantel. Curcumin reduced the rate of inflammatory infiltration, whereas Cur:Na₂GA reduced periductal fibrosis. Immunohistochemically, a decrease in liver inflammation markers was found, which is determined by calculating the numbers of tumor-necrosis-factor-positive cells during the curcumin treatment and of kynurenine-3-monooxygenase-positive cells during the Cur:Na₂GA treatment. A biochemical blood test revealed a normalizing effect of Cur:Na₂GA (comparable to that of curcumin) on lipid metabolism. We believe that the further development and investigation of therapeutics based on curcuminoids in relation Opisthorchis felineus and other trematode infections will be useful for clinical practice and veterinary medicine.

Small extracellular vesicles but not microvesicles from Opisthorchis viverrini promote cell proliferation in human cholangiocytes

Chronic infection with O. viverrini has been linked to the development of cholangiocarcinoma (CCA), which is a major public health burden in the Lower Mekong River Basin countries, including Thailand, Lao PDR, Vietnam and Cambodia. Despite its importance, the exact mechanisms by which O. viverrini promotes CCA are largely unknown. In this study, we characterized different extracellular vesicle populations released by O. viverrini (OvEVs) using proteomic and transcriptomic analyses and investigated their potential role in host-parasite interactions. While 120k OvEVs promoted cell proliferation in H69 cells at different concentrations, 15k OvEVs did not produce any effect compared to controls. The proteomic analysis of both populations showed differences in their composition that could contribute to this differential effect. Furthermore, the miRNAs present in 120k EVs were analysed and their potential interactions with human host genes was explored by computational target prediction. Different pathways involved in inflammation, immune response and apoptosis were identified as potentially targeted by the miRNAs present in this population of EVs. This is the first study showing specific roles for different EV populations in the pathogenesis of a parasitic helminth, and more importantly, an important advance towards deciphering the mechanisms used in establishment of opisthorchiasis and liver fluke infection-associated malignancy.

Omega-Class Glutathione Transferases Protect DNA from Oxidative Stress in Pathogenic Helminth Reproductive Cells

Pathogenic helminths have evolved mechanisms to preserve reproductive function while surviving long-term in the host via robust protective responses. A protective role of antioxidant enzymes in preventing DNA degradation has long been proposed, but little evidence has been provided. Here, we show that omega-class glutathione transferases (GSTOs) are critical for maintaining viability by protecting the reproductive cell DNA of the carcinogenic liver fluke, Clonorchis sinensis. Clonorchis sinensis GSTO (CsGSTO) activities modified by changes in the GSH/GSSG and NADPH/NADP+ molar ratios suppressed the overproduction of reactive oxygen species. CsGSTO1 and CsGSTO2 catalyzed deglutathionylation under physiologic and low-stress conditions (GSH/GSSG ratio of 23:1 or higher) but promoted glutathionylation under high-stress conditions (GSH/GSSG ratio of 3:1 or lower). Gliotoxin-induced functional disruption of CsGSTOs in living C. sinensis reduced the GSH/GSSG molar ratio and increased the production of protein glutathionylation (PSSG) under physiologic and low-stress conditions, indicating that suppression of GSTO function did not affect deglutathionylation. However, the perturbation of CsGSTOs decreased the GSH/GSSG ratio but also reduced PSSG production under high oxidative stress, demonstrating that glutathionylation was impeded. In response to oxidative stimuli, C. sinensis decreased GSTO-specific dehydroascorbate reductase and thiol transferase activities and the GSH/GSSG ratio, while it increased the NADPH/NADP+ ratio and PSSG. CsGSTOs utilized GSH to regulate GSH/GSSG and NADPH/NADP+ recycling and triggered a redox signal leading to nuclear translocation. Nuclear-imported CsGSTOs were modified by glutathionylation to prevent DNA damage. Antibodies specific to CsGSTOs dose-dependently inhibited this process. Disruption of CsGSTOs or the depletion of GSH caused glutathionylation defects, leading to DNA degradation. Our results demonstrate that CsGSTOs and the GSH system play a previously unappreciated role in protecting DNA from oxidative stress.

Lactic acidosis induces metabolic and phenotypic reprogramming in cholangiocarcinoma cells via the upregulation of thrombospondin-1

The high glycolytic activity of cancer cells leads to lactic acidosis (LA) in the tumor microenvironment. LA is not merely a consequence of metabolic activities but also has functional roles in metabolic reprogramming and cancer progression. Cholangiocarcinoma (CCA) cells exhibit a high dependency on glycolysis for survival and growth, but the specific effects of LA on cellular characteristics remain unknown. Here, we demonstrate that long-term LA (LLA) reprograms the metabolic phenotype of CCA cells from glycolytic to oxidative and enhances their migratory activity. In CCA cell culture, short-term LA (24 h) showed a growth inhibitory effect, while extended LA exposure for more than 2 weeks (LLA) led to enhanced cell motility. Coincidentally, LLA enhanced the respiratory capacity with an increase in mitochondrial mass. Inhibition of mitochondrial function abolished LLA-induced cell motility, suggesting that metabolic remodeling affects the phenotypic outcomes. RNA-sequencing analysis revealed that LLA upregulated genes associated with cell migration and epithelial-mesenchymal transition (EMT), including thrombospondin-1 (THBS1), which encodes a pro-EMT-secreted protein. Inhibition of THBS1 resulted in the suppression of both LLA-induced cell motility and respiratory capacity. Moreover, high THBS1 expression was associated with poor survival in patients with CCA. Collectively, our study suggests that the increased expression of THBS1 by LLA promotes phenotypic alterations, leading to CCA progression.

A New Role for Old Friends: Effects of Helminth Infections on Vaccine Efficacy

Vaccines are one of the most successful medical inventions to enable the eradication or control of common and fatal diseases. Environmental exposure of hosts, including helminth infections, plays an important role in immune responses to vaccines. Given that helminth infections are among the most common infectious diseases in the world, evaluating vaccine efficiency in helminth-infected populations may provide critical information for selecting optimal vaccination programs. Here, we reviewed the effects of helminth infections on vaccination and its underlying immunological mechanisms, based on findings from human studies and animal models. Moreover, the potential influence of helminth infections on SARS-CoV-2 vaccine was also discussed. Based on these findings, there is an urgent need for anthelmintic treatments to eliminate helminth suppressive impacts on vaccination effectiveness during implementing mass vaccination in parasite endemic areas.

Foodborne trematodes: old foes, new kids on the block and research perspectives for control and understanding host-parasite interactions

Foodborne trematodes (FBTs) have a worldwide distribution (with particular prevalence in south-east Asia) and are believed to infect almost 75 million people, with millions more living at risk of infection. Although mortality due to trematodiasis is low, these infections cause considerable morbidity and some species are associated with the development of cancer in hyperendemic regions. Despite this, FBTs are often side-lined in terms of research funding and have been dubbed neglected tropical diseases by the World Health Organisation. Thus, the aim of this special issue was to provide an update of our understanding of FBT infections, to shine a light on current work in the field and to highlight some research priorities for the future. With contributions from leading researchers, many from endemic regions, we review the major FBT species. In doing so we revisit some old foes, uncover emerging infections and discover how outbreaks are being dealt with as a result of new approaches to parasite control. We also report advances in our understanding of the interactions of FBTs with their mammalian hosts and uncover new interplay between trematodes and host microbiome components. We hope that this article collection will stimulate discussion and further research on the FBTs and help raise them from their neglected status.

General overview of the current status of human foodborne trematodiasis

Foodborne trematodes (FBT) of public health significance include liver flukes (Clonorchis sinensis, Opisthorchis viverrini, O. felineus, Fasciola hepatica and F. gigantica), lung flukes (Paragonimus westermani and several other Paragonimus spp.) and intestinal flukes, which include heterophyids (Metagonimus yokogawai, Heterophyes nocens and Haplorchis taichui), echinostomes (Echinostoma revolutum, Isthmiophora hortensis, Echinochasmus japonicus and Artyfechinostomum malayanum) and miscellaneous species, including Fasciolopsis buski and Gymnophalloides seoi. These trematode infections are distributed worldwide but occur most commonly in Asia. The global burden of FBT diseases has been estimated at about 80 million, however, this seems to be a considerable underestimate. Their life cycle involves a molluscan first intermediate host, and a second intermediate host, including freshwater fish, crustaceans, aquatic vegetables and freshwater or brackish water gastropods and bivalves. The mode of human infection is the consumption of the second intermediate host under raw or improperly cooked conditions. The major pathogenesis of C. sinensis and Opisthorchis spp. infection includes inflammation of the bile duct which leads to cholangitis and cholecystitis, and in a substantial number of patients, serious complications, such as liver cirrhosis and cholangiocarcinoma, may develop. In lung fluke infections, cough, bloody sputum and bronchiectasis are the most common clinical manifestations. However, lung flukes often migrate to extrapulmonary sites, including the brain, spinal cord, skin, subcutaneous tissues and abdominal organs. Intestinal flukes can induce inflammation in the intestinal mucosa, and they may at times undergo extraintestinal migration, in particular, in immunocompromised patients. In order to control FBT infections, eating foods after proper cooking is strongly recommended.

Persistent advanced periductal fibrosis is associated with cagA-positive Helicobacter pylori infection in post-praziquantel treatment of opisthorchiasis

BACKGROUND

Liver fluke infection caused by Opisthorchis viverrini is associated with several hepatobiliary diseases including advanced periductal fibrosis (APF) and cholangiocarcinoma. Recently, we demonstrated a persistent APF in over one-third of opisthorchiasis patients after worm removal by praziquantel (PZQ) treatment. However, the underlying mechanism(s) of this phenomena is unclear. Given a co-infection with Helicobacter pylori (H. pylori) especially cagA-positive strain enhances APF, we hypothesized that H. pylori with CagA virulent factor contributes to persistent APF.

MATERIALS AND METHODS

Seventy-five opisthorchiasis patients who underwent ultrasonography and treatment with PZQ were recruited in the 2-year follow-up study. Helicobacter and its cagA in the feces were examined by conventional and qPCR. Correlations between prevalence or bacterial loads of Helicobacter spp., H. pylori, and cagA-positive H. pylori before and after PZQ treatment were analyzed among resolved, slowly resolved, relapsed, and persistent APF groups.

RESULTS

Overall, prevalence of Helicobacter spp., H. pylori, and cagA-positive H. pylori declined after PZQ treatment. However, only the prevalence and bacterial loads of cagA-positive H. pylori detected at 2-year post-treatment were significantly lower than those before treatment (p < .05). In addition, both prevalence and bacterial loads of cagA-positive H. pylori were significantly lower in the resolved APF group after PZQ treatment, while there were no significant changes in the slowly resolved, relapsed, and persistent APF groups. Among the APF subgroups, cagA-positive H. pylori prevalence in both relapsed and persistent APF groups were significantly higher than the resolved APF group.

CONCLUSION

The results support our hypothesis that H. pylori, especially cagA-positive strain, contributes to the relapsed and persistent APF. A supplementary antibiotic treatment for H. pylori to reduce persistent APF and eventually CCA is warranted.

Silencing of Opisthorchis viverrini Tetraspanin Gene Expression Results in Reduced Secretion of Extracellular Vesicles

Inter-phylum transfer of molecular information is exquisitely exemplified in the uptake of parasite extracellular vesicles (EVs) by their target mammalian host tissues. The oriental liver fluke, Opisthorchis viverrini is the major cause of bile duct cancer in people in Southeast Asia. A major mechanism by which O. viverrini promotes cancer is through the secretion of excretory/secretory products which contain extracellular vesicles (OvEVs). OvEVs contain microRNAs that are predicted to impact various mammalian cell proliferation pathways, and are internalized by cholangiocytes that line the bile ducts. Upon uptake, OvEVs drive relentless proliferation of cholangiocytes and promote a tumorigenic environment, but the underlying mechanisms of this process are unknown. Moreover, purification and characterization methods for helminth EVs in general are ill defined. We therefore compared different purification methods for OvEVs and characterized the sub-vesicular compartment proteomes. Two CD63-like tetraspanins (Ov-TSP-2 and TSP-3) are abundant on the surface of OvEVs, and could serve as biomarkers for these parasite vesicles. Anti-TSP-2 and -TSP-3 IgG, as well as different endocytosis pathway inhibitors significantly reduced OvEV uptake and subsequent proliferation of cholangiocytes in vitro. Silencing of Ov-tsp-2 and tsp-3 gene expression in adult flukes using RNA interference resulted in substantial reductions in OvEV secretion, and those vesicles that were secreted were deficient in their respective TSP proteins. Our findings shed light on the importance of tetraspanins in fluke EV biogenesis and/or stability, and provide a conceivable mechanism for the efficacy of anti-tetraspanin subunit vaccines against a range of parasitic helminth infections.

Current status of human liver fluke infections in the Greater Mekong Subregion

The Greater Mekong Subregion (GMS) is a trans-national region of the Mekong River basin in Southeast Asia comprising Cambodia, the People's Republic of China (specifically Yunnan Province and Guangxi Zhuang Autonomous Region), Lao People's Democratic Republic (Lao PDR), Myanmar, Thailand, and Vietnam home to more than 340 million people or almost 4.5% of the global population. Human liver fluke infections caused by Opisthorchis viverrini and Clonorchis sinensis have been major public health problems in this region for decades. Opisthorchiasis caused by O. viverrini is prevalent in Thailand, Lao PDR, Cambodia and central-southern Vietnam with more than 12 million people infected. Clonorchiasis caused by C. sinensis is endemic in northern Vietnam and Guangxi with estimated 3.5 -5 million infected. The infections can cause several liver and biliary diseases such as cholangitis, periductal fibrosis, gallstones, and cholangiocarcinoma (CCA), a fatal bile duct cancer. Key determinants of the geographical distribution differences of the two liver fluke species are snail species and geographic barriers. Main risk behaviour of the infections is the culture of eating raw fish "the raw attitude" of people in the GMS, especially the Tai/Dai/Thai/Laos ethnic groups, the major population in the GMS. Over the past 20 years, there is a big change in prevalence of the infections. Opisthorchiasis has long been endemic, particularly in northern and northeastern Thailand and Lao PDR with over 8-10 million cases estimated. However, after several rounds of national campaign against opisthorchiasis using integrated control approach in Thailand over the past three decades, the prevalence of O. viverrini infection has reduced from over 15% in 1996 to 2.2% in 2019. High prevalence of O. viverrini infection continues in Lao PDR and central Vietnam. Emerging high prevalence, up to a maximum of 47.5%, has been noted in Cambodia during the past 10 years possibly due to more studies being conducted rather than increasing prevalence. O. viverrini infection has now also been reported in Lower Myanmar in recent years. Clonorchiasis has been known in northern Vietnam and southern China for a long time. Several surveys have reported infections in Guangxi in the last 10 years, and until now liver fluke infected cases have not been reported in Yunnan. Overall, nowadays, there is a shift in high risk areas for GMS liver fluke infection from northeastern Thailand to Lao PDR, Cambodia, Vietnam, Myanmar, and Guangxi P.R. China. Urgent systematic disease mapping and integrated liver fluke control using One Health approaches should be implemented nationwide in GMS countries.

Cholangiocarcinoma

Cholangiocarcinoma (CCA) is a highly lethal adenocarcinoma of the hepatobiliary system, which can be classified as intrahepatic, perihilar and distal. Each anatomic subtype has distinct genetic aberrations, clinical presentations and therapeutic approaches. In endemic regions, liver fluke infection is associated with CCA, owing to the oncogenic effect of the associated chronic biliary tract inflammation. In other regions, CCA can be associated with chronic biliary tract inflammation owing to choledocholithiasis, cholelithiasis, or primary sclerosing cholangitis, but most CCAs have no identifiable cause. Administration of the anthelmintic drug praziquantel decreases the risk of CCA from liver flukes, but reinfection is common and future vaccination strategies may be more effective. Some patients with CCA are eligible for potentially curative surgical options, such as resection or liver transplantation. Genetic studies have provided new insights into the pathogenesis of CCA, and two aberrations that drive the pathogenesis of non-fluke-associated intrahepatic CCA, fibroblast growth factor receptor 2 fusions and isocitrate dehydrogenase gain-of-function mutations, can be therapeutically targeted. CCA is a highly desmoplastic cancer and targeting the tumour immune microenvironment might be a promising therapeutic approach. CCA remains a highly lethal disease and further scientific and clinical insights are needed to improve patient outcomes.

Helicobacter pylori GroEL Seropositivity Is Associated with an Increased Risk of Opisthorchis viverrini-Associated Hepatobiliary Abnormalities and Cholangiocarcinoma

Despite the synergistic effect of Opisthorchis viverrini and Helicobacter pylori co-infection on pathogenesis of severe hepatobiliary abnormalities (HBA) including advanced periductal fibrosis and replace with cholangiocarcinoma (CCA) have been established, the immune response to H. pylori in O. viverrini infected population has never been explored. Hence, this study aimed to investigate the antibody responses to 2 immunogenic H. pylori proteins in O. viverrini-infected patients with HBA and CCA. The risk analysis by multinomial logistic regression revealed that GroEL seropositivity was associated with higher risks of hepatobiliary abnormalities and CCA with adjusted odds ratios (95% confidence intervals) of 2.11 (95% CI=1.20-3.71, P=0.008) and 2.13 (95% CI=1.21-3.75, P=0.009), respectively. These findings indicate that GroEL seropositivity might be a biomarker for early detection of O. viverrini associated HBA and CCA.

Biliary Migration, Colonization, and Pathogenesis of O. viverrini Co-Infected with CagA+ Helicobacter pylori

Co-infection with the cagA strain of Helicobacter pylori exacerbates the pathology of human liver fluke Opisthorchis viverrini (OV) infection leading to cholangiocarcinoma. However, underlying mechanisms remain unclear. We report a significant increase in cagA-positive and cagA-negative H. pylori in the stomach, blood, bile, and in the OV worms of co-infected Syrian golden hamsters at one hour, three hours, and one month, post-infection, compared to hamsters infected with either OV or H. pylori alone. Except in the worms, H. pylori numbers declined at three months post-infection, particularly in the bile fluid of co-infected animals. Both strains of H. pylori were immunohistochemically detected in the tegument of the worm, as well as in the bile duct epithelium when co-infected with O. viverrine, but not in H. pylori infection alone. Interestingly, only the cagA-positive strain was detected in the gut of the worm. Co-infection between cagA-positive H. pylori and O. viverrini resulted in a more severe biliary pathology and decreased E-cadherin expression in vivo and in vitro than those of the cagA-negative strain. These data suggest that O. viverrini acts as a carrier of cagA-positive H. pylori and co-migrates to the bile ducts, whereas O. viverrini facilitates H. pylori colonization and enhances the biliary pathogenesis and carcinogenesis.

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.

Omega-Class Glutathione Transferases of Carcinogenic Liver Fluke, Clonorchis sinensis, Modulate Apoptosis and Differentiation of Host Cholangiocytes

The small liver fluke Clonorchis sinensis causes hepatobiliary ductal infections in humans. Clonorchiasis is characterized histopathologically by ductal dysplasia, hyperplasia and metaplasia, which closely resembles cholangiocarcinoma (CCA). The disruption of programmed cell death is critical for malignant transformation, while molecular events underlying these phenomena have poorly been understood in clonorchiasis-related CCA tumorigenesis. We incorporated recombinant C. sinensis omega-class glutathione transferase (rCsGSTo) 1 or 2 into human intrahepatic biliary epithelial cells (HIBECs) and analyzed pathophysiological alterations of HIBECs upon the application of oxidative stress. rCsGSTos partially but significantly rescued HIBECs from cell death by inhibiting oxidative stress-induced apoptosis (p < 0.01). rCsGSTos modulated transcriptional levels of numerous genes. We analyzed 13 genes involved in programmed cell death (the upregulation of five antiapoptotic and two apoptotic genes, and the downregulation of one antiapoptotic and five apoptotic genes) and 11 genes associated with cell differentiation (the increase in seven and decrease in four genes) that showed significant modifications (p < 0.05). The induction profiles of the mRNA and proteins of these differentially regulated genes correlated well with each other, and mostly favored apoptotic suppression and/or cell differentiation. We detected increased active, phosphorylated forms of Src, PI3K/Akt, NF-κB p65, MKK3/6 and p38 MAPK, but not JNK and ERK1/2. CsGSTos were localized in the C. sinensis-infected rat cholangiocytes, where cytokeratin 19 was distributed. Our results demonstrated that CsGSTos excreted to the biliary lumen are internalized and accumulated in the host cholangiocytes. When cholangiocytes underwent oxidative stressful condition, CsGSTos appeared to be critically involved in both antiapoptotic process and the differentiation of host cholangiocytes through the regulation of target genes following the activation of responsible signal molecules.

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.

Orally Administered Bacillus Spores Expressing an Extracellular Vesicle-Derived Tetraspanin Protect Hamsters Against Challenge Infection With Carcinogenic Human Liver Fluke

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.

High prevalence of opisthorchiasis in rural populations from Khammouane Province, central Lao PDR: serological screening using total IgG- and IgG4-based ELISA

BACKGROUND

Human opisthorchiasis, caused by Opisthorchis viverrini, is a public health problem in Southeast Asia and a major risk factor for cholangiocarcinoma. In Lao PDR, seroprevalence and the relationship between the number of O. viverrini eggs in infected people and specific antibody responses are still unknown. We evaluated and compared parasitological and serological screening methods in the community in an endemic area of opisthorchiasis in Lao PDR.

METHODS

Seroprevalence of O. viverrini-specific total IgG and IgG4 antibodies and their relationships with O. viverrini egg intensities were evaluated in Khammouane Province, central Lao PDR, using ELISA and a modified formalin ethyl-acetate concentration technique (FECT).

RESULTS

FECT stool examination revealed O. viverrini eggs in 70.3% (90/128) of individuals (95% CI 61.6 to 78.1%) while ELISA (based on total IgG and on IgG4 antibodies to O. viverrini) found 98.4% (95% CI 94.5 to 99.8%) and 89.8% (95% CI 83.3 to 94.5%) of sera, respectively. There was a positive and significant correlation between numbers of O. viverrini eggs per gram and levels of both IgG (R2=0.168, p<0.001) and IgG4 (R2=0.219, p<0.001) antibodies.

CONCLUSIONS

A high prevalence of human opisthorchiasis in Lao PDR was found using a new platform, serological screening in the community. This points to a need for sustainable control of this liver fluke infection.

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.

Impact of environmental changes on infectious diseases: Key findings from an international conference in Trieste, Italy in May 2017

Elsevier's 2nd conference on "Impact of Environmental Changes on Infectious Diseases" (IECID), convened in May 2017 in Trieste, Italy, brought together some 120 researchers from more than 20 countries. They presented the latest findings and discussed the impact of current and predicted future environmental changes on infectious disease dynamics in humans, livestock and wildlife in different parts of the world. Particular emphasis was placed on food-, vector- and water-borne diseases within the general theme of infectious diseases of poverty and emerging and re-emerging diseases. The potential impact of mobility, travel, population growth, trade and globalization on infectious disease dynamics against the background of a changing climate, land use, air quality and urbanization on individual, population, ecosystem and planetary health were addressed. Speakers at the conference were encouraged to put forth their talks into stand-alone manuscripts, which resulted in a unique collection of 13 articles, now brought together into a thematic issue of Acta Tropica. In this umbrella piece, we synthesize key findings from the published articles and highlight potential actions that might be taken forward to prevent and mitigate the impact of environmental change on infectious diseases. The work presented is salient in the current era of the Sustainable Development Goals.

Synergistic effects of cagA+ Helicobacter pylori co-infected with Opisthorchis viverrini on hepatobiliary pathology in hamsters

Human liver fluke infection caused by Opisthorchis viverrini is associated with several biliary diseases including cholangiocarcinoma (CCA). Recently, it was discovered that the liver fluke is a reservoir of Helicobacter pylori, particularly the cagA-positive strain (cytotoxin-associated gene A) in its gut. Given that two carcinogenic pathogens are associated with CCA development, however, the role of cagA-positive H. pylori in opisthorchiasis has not been clarified. The present study was therefore aimed to investigate histopathological changes of the biliary system in hamsters co-infected with O. viverrini and cagA-positive H. pylori or O. viverrini and cagA-negative H. pylori, with controls of O. viverrini, cagA-positive H. pylori, or cagA-negative H. pylori alone, over time. Major histopathological changes were systematically investigated. All pathological features were quantified/semi-quantified and compared among the experimental groups. The results showed that O. viverrini infection groups (O. viverrini, cagA-positive H. pylori and cagA-negative H. pylori) showed a high degree of eosinophil and mononuclear cell infiltration, lymphoid aggregation and granuloma. Specifically, O. viverrini co-infected with cagA-positive H. pylori presented significantly higher inflammatory scores than O. viverrini and O. viverrini with cagA-positive H. pylori. Proliferation and adaptive lesions such as hyperplasia, goblet cell metaplasia and dysplasia were detected only in O. viverrini infection groups. Dysplasia, the precancerous lesion of CCA, was observed in the first-order bile ducts, especially where the inflammation existed and was found earlier and more severely in O. viverrini with cagA-positive H. pylori than other groups. Similarly, the BrdU (bromodeoxyuridine) proliferation index was significantly higher in O. viverrini co-infected with cagA-positive H. pylori than O. viverrini and O. viverrini with cagA-negative H. pylori groups. Periductal fibrosis was a prominent histopathologic feature in chronic infection in O. viverrini infection groups. Multiple logistic regression showed that O. viverrini co-infected with cagA-positive H. pylori and the duration of infection were the most important factors associated with periductal fibrosis (OR 3.02, 95% CI 1.02-9.29, p = 0.04 and OR 3.82, 95% CI 2.61-5.97, p<0.001). This study demonstrates that the liver fluke co-infected with cagA-positive H. pylori induces severe biliary pathology that may predispose to cholangiocarcinogenesis.

Intrahepatic cholangiocarcinoma: Morpho-molecular pathology, tumor reactive microenvironment, and malignant progression

Intrahepatic cholangiocarcinoma (iCCA) is a relatively rare, but highly lethal and biologically complex primary biliary epithelial cancer arising within liver. After hepatocellular carcinoma, iCCA is the second most common primary liver cancer, accounting for approximately 10-20% of all primary hepatic malignancies. Over the last 10-20 years, iCCA has become the focus of increasing concern largely due to its rising incidence and high mortality rates in various parts of the world, including the United States. The challenges posed by iCCA are daunting and despite recent progress in the standard of care and management options for iCCA, the prognosis for this cancer continues to be dismal. In an effort to provide a framework for advancing our understanding of iCCA malignant aggressiveness and therapy resistance, this review will highlight key etiological, biological, molecular, and microenvironmental factors hindering more effective management of this hepatobiliary cancer. Particular focus will be on critically reviewing the cell origins and morpho-molecular heterogeneity of iCCAs, providing mechanistic insights into high risk fibroinflammatory cholangiopathies associated with iCCA development, and notably discussing the deleterious role played by the tumor reactive desmoplastic stroma in regulating iCCA malignant progression, lymphangiogenesis, and tumor immunobiology.

Mast cell hyperplasia in Opisthorchis viverrini-associated cholecystitis

Despite significant advances in understanding the role of the immune response in Opisthorchis viverrini-associated carcinogenesis, little is known about how infection induces gall bladder disease. This study investigated whether mast cells are activated in cholecystitis associated with O. viverrini, gall bladder specimens from ninety-two patients who had undergone cholecystectomy at the Khon Kaen Regional Hospital, Khon Kaen, Thailand. Two representative sections from the body of fresh gall bladder tissue were fixed in Carnoy's solution and embedded in paraffin wax. The paraffin sections were stained for mast cells and IgE plasma cells by the double histochemical and immunohistochemical method. The cells in the epithelium, lamina propria, muscular layer, and subserosa were counted and expressed as cells per square millimeter. The gall bladder bile was examined for the presence of O. viverrini eggs. Significantly higher mean mast cell numbers were found in the lamina propria (221.41 ± 16.01 vs 116.97 ± 14.61 cells per mm²; P < 0.005) of egg positive compared to egg negative groups, respectively. No comparable differences in mast cell number were observed in other layers. IgE plasma cells were rarely seen. The results suggest that mast cell hyperplasia occurs during cholecystitis in association with opisthorchiasis and may play a role in the pathogenesis of the disease.

Production and characterization of monoclonal antibodies against highly immunogenic Opisthorchis viverrini proteins and development of coproantigen detection

Opisthorchis viverrini and other foodborne trematode infections are major health concerns in the Greater Mekong Subregion. Currently, the gold-standard diagnostic method for opisthorchiasis is conventional stool examination for the presence of parasite eggs. This method lacks sensitivity and needs an experienced technician. We therefore produced monoclonal antibodies to highly immunogenic O. viverrini proteins aiming at detecting specific antigens in the feces. In this study, BALB/C mice were immunized using semi-purified somatic antigens and spleen cells were fused with a Sp2/0 myeloma cell line. Four hybridomas (1A2, 1E12, 2C7 and 8D6) were selected and cloned due to their strong reaction against O. viverrini somatic protein, resulting in three IgM clones and one IgG2 clone. Immunohistochemistry showed that 1A2, 1E12, 2C7 and 8D6 stained the parenchyma cells, gut, tegument and muscles, respectively. Western-blot analysis revealed that only antibody 1A2 could detect coproantigen (approx. 73 kDa protein) in feces of hamsters infected with O. viverrini. The 1A2 monoclonal antibody may be of value in the diagnosis of opisthorchiasis by coproantigen detection.

Mustard oil consumption, cooking method, diet and gallbladder cancer risk in high- and low-risk regions of India

The current study aimed to investigate the role of cooking with mustard oil and other dietary factors in relation to gallbladder cancer (GBC) in high- and low-incidence regions of India. A case-control study was conducted including 1,170 histologically confirmed cases and 2,525 group-matched visitor controls from the largest cancer hospital in India. Dietary data were collected through a food frequency questionnaire. For oil consumption, we enquired about monthly consumption of 11 different types of cooking oil per family and the number of individuals usually sharing the meal to estimate per-individual consumption of oil. Information about method of cooking was also requested. Odds ratios (ORs) and 95% confidence intervals (CIs) quantifying the association of GBC risk consumption of different types of oil, method of cooking, and dietary food items, were estimated using logistic regression models, after adjusting for potential confounders. High consumption of mustard oil was associated with GBC risk in both high- and low-risk regions (OR = 1.33, 95% CI = 0.99-1.78; OR = 3.01, 95% CI = 1.66-5.45), respectively. An increased risk of GBC was observed with deep frying of fresh fish in mustard oil (OR = 1.57, 95% CI = 0.99-2.47, p-value = 0.052). A protective association was observed with consumption of leafy vegetables, fruits, onion and garlic. No association was observed between consumption of meat, spicy food, turmeric, pulses or with any other oil as a cooking medium. The effect of high consumption of mustard oil on GBC risk, if confirmed, has implications for the primary prevention of GBC, via a reduced consumption.

N-glycosylation profiling of serum immunoglobulin in opisthorchiasis patients

Alteration of immunoglobulin glycosylation correlates with inflammatory diseases and infectious diseases including parasitic infections. Immunoglobulin glycosylation patterns may be implicated in disease development and have also been proposed as diagnostic tools for several diseases. Previous studies have reported the immunoglobulin profiles in experimental animals and in patients infected with the carcinogenic human liver fluke, Opisthorchis viverrini. However, the N-glycosylation profiles of immunoglobulins and their subclass-specific glycoforms in opisthorchiasis patients have never been elucidated. Here, N-glycosylation patterns of immunoglobulins and their subclass-specific glycoforms in sera of O. viverrini-infected patients were investigated using triple quadrupole mass spectrometry coupled with multiple reaction monitoring. Peptide fragmentation was utilized to quantify the immunoglobulin glycoforms normalized to the unique peptide of each subclass. Overall, serum levels of IgG and IgA in O. viverrini patients were significantly increased compared to uninfected controls. Twenty-seven glycoforms were detected based on analysis of detached glycans in all immunoglobulin subclasses. The abundance of immunoglobulin glycopeptides in serum of opisthorchiasis patients deviated significantly from controls. Immunoglobulin glycosylation patterns were associated with both pro- and anti-inflammatory properties. In conclusion, O. viverrini infection alters the serum immunoglobulin glycosylation profile and these changes could distinguish between O. viverrini-infected individuals and healthy controls. SIGNIFICANCE: We demonstrated that both quantities and glycoforms of serum immunoglobulin subclasses were altered in Opisthorchis viverrini-infected individuals as investigated by the QqQ-MS-MRM method. Patterns of immunoglobulin with a specific glycoform might contribute to immune responses to O. viverrini infection.

Curcumin enhances chemotherapeutic effects and suppresses ANGPTL4 in anoikis-resistant cholangiocarcinoma cells

Anoikis resistance is a critical feature involved in tumor progression and chemoresistance. Finding approaches to improve the effect of chemotherapy on anoikis-resistant cancer cells is therefore critically important. In this study, we examined the effects of curcumin in anoikis-resistant cholangiocarcinoma (CCA) cells, including HuCCT1 and TFK-1 that were anchorage-independently cultured (AI-cells) using poly (2-hydroxyethyl methacrylate). The AI-CCA cells were treated with curcumin alone or in combination with anti-cancer agents and their responses to each treatment were determined by cell viability assay. Gene expression in AI-cells was determined by quantitative real-time PCR. The potential involvement of angiopoietin-like 4 (ANGPTL4) in anoikis resistance was examined by gene knockdown. It was found that AI-cells tended to resist anti-cancer agents tested, especially AI-HuCCT1, which significantly resisted gemcitabine and suberoylanilide hydroxamic acid (SAHA). Curcumin alone significantly inhibited viability and colony formation of AI-cells. Moreover, curcumin combination significantly enhanced the treatment effect of SAHA on AI-HuCCT1 and AI-TFK-1 cells. Gene expression analysis revealed that ANGPTL4 was markedly upregulated in AI-CCA cells and its knockdown tended to sensitize AI-cells to cell death and treatments. In addition, curcumin treatment decreased phosphorylated STAT3 and expression levels of Mcl-1, HDACs and ANGPTL4. Altogether, these findings reveal the beneficial property of curcumin to potentiate chemotherapeutic effects on anoikis-resistant CCA cells, which might suggest the potential use of curcumin for cancer treatment.

Zoonotic transmission of intestinal helminths in southeast Asia: Implications for control and elimination

Intestinal helminths are extremely widespread and highly prevalent infections of humans, particularly in rural and poor urban areas of low and middle-income countries. These parasites have chronic and often insidious effects on human health and child development including abdominal problems, anaemia, stunting and wasting. Certain animals play a fundamental role in the transmission of many intestinal helminths to humans. However, the contribution of zoonotic transmission to the overall burden of human intestinal helminth infection and the relative importance of different animal reservoirs remains incomplete. Moreover, control programmes and transmission models for intestinal helminths often do not consider the role of zoonotic reservoirs of infection. Such reservoirs will become increasingly important as control is scaled up and there is a move towards interruption and even elimination of parasite transmission. With a focus on southeast Asia, and the Philippines in particular, this review summarises the major zoonotic intestinal helminths, risk factors for infection and highlights knowledge gaps related to their epidemiology and transmission. Various methodologies are discussed, including parasite genomics, mathematical modelling and socio-economic analysis, that could be employed to improve understanding of intestinal helminth spread, reservoir attribution and the burden associated with infection, as well as assess effectiveness of interventions. For sustainable control and ultimately elimination of intestinal helminths, there is a need to move beyond scheduled mass deworming and to consider animal and environmental reservoirs. A One Health approach to control of intestinal helminths is proposed, integrating interventions targeting humans, animals and the environment, including improved access to water, hygiene and sanitation. This will require coordination and collaboration across different sectors to achieve best health outcomes for all.

Identification, recombinant protein production, and functional analysis of a M60-like metallopeptidase, secreted by the liver fluke Opisthorchis viverrini

The carcinogenic liver fluke Opisthorchis viverrini (O. viverrini) is endemic in Thailand and neighboring countries including Laos PDR, Vietnam and Cambodia. Infections with O. viverrini lead to hepatobiliary abnormalities including bile duct cancer-cholangiocarcinoma (CCA). Despite decades of extensive studies, the underlying mechanisms of how this parasite survives in the bile duct and causes disease are still unclear. Therefore, this study aims to identify and characterize the most abundant protein secreted by the parasite. Proteomics and bioinformatics analysis revealed that the most abundant secretory protein is a metallopeptidase, named Ov-M60-like-1. This protein contains an N-terminal carbohydrate-binding domain and a C-terminal M60-like domain with a zinc metallopeptidase HEXXH motif. Further analysis by mass spectrometry revealed that Ov-M60-like-1 is N-glycosylated. Recombinant Ov-M60-like-1 (rOv-M60-like-1) expressed in Escherichia coli (E. coli) was able to digest bovine submaxillary mucin (BSM). The mucinase activity was inhibited by the ion chelating agent EDTA, confirming its metallopeptidase identity. The enzyme was active at temperatures ranging 25-37 °C in a broad pH range (pH 2-10). The identification of Ov-M60-like-1 mucinase as the major secretory protein of O. viverrini worms warrants further research into the role of this glycoprotein in the pathology induced by this carcinogenic worm.

How globalization and climate change could affect foodborne parasites

Foodborne parasites, most of which are zoonotic, represent an important human health hazard. These pathogens which include both protozoa (e.g., Cryptosporidium spp., Cyclospora cayetanensis, Toxoplasma gondii) and helminths (e.g., liver and intestinal flukes, Fasciola spp., Paragonimus spp., Echinococcus spp., Taenia spp., Angiostrongylus spp., Anisakis spp., Ascaris spp., Capillaria spp., Toxocara spp., Trichinella spp., Trichostrongylus spp.), have accompanied the human species since its origin and their spread has often increased due to their behavior. Since both domesticated and wild animals play an important role as reservoirs of these pathogens the increase/decrease of their biomasses, migration, and passive introduction by humans can change their epidemiological patterns. It follows that globalization and climate change will have a tremendous impact on these pathogens modifying their epidemiological patterns and ecosystems due to the changes of biotic and abiotic parameters. The consequences of these changes on foodborne parasites cannot be foreseen as a whole due to their complexity, but it is important that biologists, epidemiologists, physicians and veterinarians evaluate/address the problem within a one health approach. This opinion, based on the author's experience of over 40 years in the parasitology field, takes into consideration the direct and indirect effects on the transmission of foodborne parasites to humans.

Inhibition of Opisthorchis felineus glutathione-dependent prostaglandin synthase by resveratrol correlates with attenuation of cholangiocyte neoplasia in a hamster model of opisthorchiasis

Food-borne trematodiases represent major neglected parasitic diseases. Trematodes of the family Opisthorchiidae including Opisthorchis felineus, Opisthorchis viverrini and Clonorchis sinensis are ranked eight on the global list of the 24 most prevalent food-borne parasites. Chronic O. felineus infection symptoms include precancerous lesions with the potential for malignancy. In recent decades, liver flukes of the family Opisthorchiidae have been extensively scientifically explored, however despite this the molecular mechanisms of O. felineus pathogenicity and its carcinogenic potential have not been studied. Opisthorchis felineus glutathione-dependent prostaglandin synthase (GST σ) is the major component of the excretory-secretory product of this liver fluke. We hypothesised that the activity of this enzyme is involved in the infection pathogenesis, including the formation of precancerous lesions. To test this hypothesis and to gain insights into the mechanisms of precancerous lesion formation, we (i) investigated whether excretory parasitic GST σ retains its enzymatic activity, (ii) tested resveratrol (RSV) as a possible inhibitor of this enzyme, and (iii) assessed biliary neoplasia and oxidative DNA damage as well as the expression of neoplasia and fibrogenesis marker genes after prolonged administration of RSV in a hamster model. RSV was found to inhibit GST σ enzymatic activity in a dose-dependent manner (R = 0.85, P < 0.001; half-maximal effective dose (ED₅₀) = 48.6 μM). Prolonged administration of RSV significantly suppressed high-grade biliary neoplasia (P = 0.008), attenuated upregulation of hyperplasia and fibrogenesis-related genes (Tgfb, α-SMA and CK7), and decreased the elevated oxidative DNA damage. Taking into account that RSV can influence a wide range of pathways, further research is needed to confirm the role of GST σ in O. felineus pathogenicity. Nevertheless, the chemopreventive effect of RSV targeting biliary neoplasia formation might be useful for improving the outcomes in infected populations and represents a compelling rationale for RSV testing in combination chemotherapy of opisthorchiasis.