Plastoquinone-Derivative SkQ1 Improved the Biliary Intraepithelial Neoplasia during Liver Fluke Infection.

Carcinogenic food-borne liver fluke infections are a serious epidemiological threat worldwide. The major complications of Opisthorchis felineus infection are chronic inflammation and biliary intraepithelial neoplasia. Although evidence has accumulated that increased reactive oxygen species production is observed in liver fluke infection, a direct relationship between the oxidative stress and biliary intraepithelial neoplasia has not been shown. Quinones and SkQ1, a derivative of plastoquinone, have been demonstrated to be cytoprotective in numerous liver injuries due to their potent antioxidant properties. This study is aimed to assess the level of biliary intraepithelial neoplasia in O. felineus-infected hamsters after treatment with mitochondria-targeted SkQ1. SkQ1 significantly reduced the biliary intraepithelial neoplasia, which was accompanied by a decrease in lipid and DNA oxidation byproducts, mRNA expression and level of proteins associated with inflammation (TNF-α, CD68) and fibrogenesis (CK7, αSMA), and was also associated with an activation of the Keap1-Nrf2 pathway. Thus, a direct relationship was found between oxidative stress and the severity of biliary intraepithelial neoplasia in O. felineus-infected hamsters. The hepatoprotective effect of plastoquinone-derivative SkQ1 was established; therefore, this compound is a promising agent in complex therapy in the treatment of opisthorchiasis.

FASN-mediated fatty acid biosynthesis remodels immune environment in Clonorchis sinensis infection-related intrahepatic cholangiocarcinoma.

BACKGROUND & AIMS: Intrahepatic cholangiocarcinoma (iCCA) is the second most common primary liver cancer and is highly lethal. Clonorchis sinensis (C. sinensis) infection is an important risk factor for iCCA. Here we investigated the clinical impact and underlying molecular characteristics of C. sinensis infection-related iCCA. METHODS: We performed single-cell RNA sequencing, whole-exome sequencing, RNA sequencing, metabolomics and spatial transcriptomics in 251 patients with iCCA from three medical centers. Alterations in metabolism and the immune microenvironment of C. sinensis-related iCCAs were validated through an in vitro co-culture system and in a mouse model of iCCA. RESULTS: We revealed that C. sinensis infection was significantly associated with iCCA patients' overall survival and response to immunotherapy. Fatty acid biosynthesis and the expression of fatty acid synthase (FASN), a key enzyme catalyzing long-chain fatty acid synthesis, were significantly enriched in C. sinensis-related iCCAs. iCCA cell lines treated with excretory/secretory products of C. sinensis displayed elevated FASN and free fatty acids. The metabolic alteration of tumor cells was closely correlated with the enrichment of tumor-associated macrophage (TAM)-like macrophages and the impaired function of T cells, which led to formation of an immunosuppressive microenvironment and tumor progression. Spatial transcriptomics analysis revealed that malignant cells were in closer juxtaposition with TAM-like macrophages in C. sinensis-related iCCAs than non-C. sinensis-related iCCAs. Importantly, treatment with a FASN inhibitor significantly reversed the immunosuppressive microenvironment and enhanced anti-PD-1 efficacy in iCCA mouse models treated with excretory/secretory products from C. sinensis. CONCLUSIONS: We provide novel insights into metabolic alterations and the immune microenvironment in C. sinensis infection-related iCCAs. We also demonstrate that the combination of a FASN inhibitor with immunotherapy could be a promising strategy for the treatment of C. sinensis-related iCCAs. IMPACT AND IMPLICATIONS: Clonorchis sinensis (C. sinensis)-infected patients with intrahepatic cholangiocarcinoma (iCCA) have a worse prognosis and response to immunotherapy than non-C. sinensis-infected patients with iCCA. The underlying molecular characteristics of C. sinensis infection-related iCCAs remain unclear. Herein, we demonstrate that upregulation of FASN (fatty acid synthase) and free fatty acids in C. sinensis-related iCCAs leads to formation of an immunosuppressive microenvironment and tumor progression. Thus, administration of FASN inhibitors could significantly reverse the immunosuppressive microenvironment and further enhance the efficacy of anti-PD-1 against C. sinensis-related iCCAs.

Four successive cases of human fasciolosis in Japan.

Fasciolosis is a food-borne parasitic disease, caused by the large liver fluke, Fasciola. Humans acquire infection by ingesting fresh or undercooked water plants, on which infective metacercaria encyst. In spite of the rarity of the disease in Japan, we encountered four successive fasciolosis patients within a short period, who were all living in the same area. The patients were 70-82 years old, three females and the husband of one of the female patients. They started complaining of non-specific symptoms, such as fever, general fatigue, appetite loss, and abdominal pain, almost at the same time. All patients showed prominent peripheral blood eosinophilia, and the medical imaging indicated multiple hepatic lesions. No parasite eggs or worms were detected in any of the patients. Diagnosis was made serologically and they were treated with praziquantel and/or triclabendazole. No cattle or sheep were farmed in the area, but the wild sika deer, Cervus nippon, inhabited adjacent to the residential area. The intermediate host snail, Austropeplea ollula, were found near the residence of the patients, and one of the collected snails was positive for F. hepatica/gigantica hybrid type rediae. Our report should alarm the medical professionals for this rare and unfamiliar parasitic disease.

Environmental influence on abundance and infection patterns of snail intermediate hosts of liver and intestinal flukes in North and Central Vietnam.

Liver and intestinal flukes (LIF) are important groups of foodborne zoonotic trematodes (FZTs) in Southeast Asia, including Vietnam. Their complex life cycles require specific freshwater snail species as the obligatory first intermediate hosts. In 2019, we conducted a longitudinal study in Yen Bai and Thanh Hoa provinces in North and Central Vietnam, respectively, to investigate the diversity of LIF and their infection prevalence in relation to snail host abundance and environmental factors. Using a combination of morphological and molecular identification techniques, we identified 10 LIF species infecting 11 snail host species. We observed significant seasonal variation in the mean abundance of several snail host species, with the majority of snails collected during the spring. We also detected seasonal changes in LIF species composition, with the highest species richness reported in the spring. Clonorchis sinensis and Fasciola gigantica, two medically important human liver flukes in Asia, were found only in the spring in Yen Bai. Our study revealed that not all snail host species have the same probability of becoming infected, and we recorded seasonal variations in the prevalence of LIF infection in different snail species in relation to water parameters.

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.

HMGN3 represses transcription of epithelial regulators to promote migration of cholangiocarcinoma in a SNAI2-dependent manner.

High mobility group nucleosome-binding protein 3 (HMGN3), a member of the HMGN family, modulates the structure of chromatin and regulates transcription through transcription factors. HMGN3 has been implicated in the development of various cancers; however, the underlying mechanisms remain unclear. We herein demonstrated that the high expression of HMGN3 correlated with the metastasis of liver fluke infection-induced cholangiocarcinoma (CCA) in patients in northeastern Thailand. The knockdown of HMGN3 in CCA cells significantly impaired the oncogenic properties of colony formation, migration, and invasion. HMGN3 inhibited the expression of and blocked the intracellular polarities of epithelial regulator genes, such as the CDH1/E-cadherin and TJAP1 genes in CCA cells. A chromatin immunoprecipitation sequencing analysis revealed that HMGN3 required the transcription factor SNAI2 to bind to and repress the expression of epithelial regulator genes, at least in part, due to histone deacetylases (HDACs), the pharmacological inhibition of which reactivated these epithelial regulators in CCA, leading to impairing the cell migration capacity. Therefore, the overexpression of HMGN3 represses the transcription of and blocks the polarities of epithelial regulators in CCA cells in a manner that is dependent on the SNAI2 gene and HDACs.

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.

The knowledge, attitudes, and practices of smallholder cattle farmers concerning the epidemiology of bovine fasciolosis in the North West Province, South Africa.

Bovine fasciolosis has negative impacts on cattle production worldwide, more so on the African continent and especially in smallholder farming areas with limited level of awareness. A cross-sectional questionnaire-based survey was conducted to investigate the knowledge, attitudes, and practices concerning bovine fasciolosis among smallholder cattle farmers in the North West Province of South Africa. A total of 153 farmers were interviewed from three villages of the Moretele Local Municipality in Bojanala District. The majority of respondents were male (84%) farm owners (81%) that had low education levels (56% primary school or less) and employed extensive cattle management systems (84%). A large number of farms lacked infrastructure including calving pens (88%), restraining equipment (85%), and weight determination equipment (92%) while sourcing drinking water for cattle from rivers or dams (58%). No evaluated factors were significantly associated with a positive fasciolosis epidemiological knowledge score. However, education level (P = 0.046), some cattle breeds (P = 0.022), and management system (P < 0.001) of the smallholder farmers were associated with a positive practice score concerning bovine fasciolosis prevention. We therefore recommend that education programs be introduced that focus on the mode of transmission, risk factors, zoonotic importance, and practices associated with the prevention and control of bovine fasciolosis.

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.

Body condition scores, fluke intensity, liver pathology, and carcass quality of different dairy cattle genotypes infected with Fasciola species at high throughput abattoirs in South Africa.

Milk is an essential commodity whose demand far exceeds supply. However, dairy animal productivity is constantly hampered by parasitic diseases such as fasciolosis, affecting milk production. Despite the negative impact of liver fluke on milk production, there is little information on liver fluke infection and associated abattoir losses (body weight, condition score, liver pathology, and carcass quality) in culled dairy cattle. This study aimed to determine body condition scores, fluke intensity, liver pathology, and carcass quality of different cattle genotypes infected with Fasciola species at three commercial abattoirs. A longitudinal study was conducted from September 2019 to October 2020 to determine body condition score, liver fluke intensity, liver pathology in 3065 dairy cattle slaughtered in CA1, CA2, and CA3, of the Eastern Cape Province South Africa. Liver fluke intensity significantly increased with cattle age (P < 0.0001). Cattle ≥ 7 years old (59.93 ± 6.42) and those 4 to 6 years old (49.78 ± 9.98) had higher infection than those 2 to 3 years old (27.55 ± 13.68). The liver fluke infection was significantly (P < 0.001) the highest when sampling was conducted in summer, followed by autumn and winter, and least for spring. The differences in carcass weights or body condition scores decreased by 0.99 units (P < 0.0001) or 0.97 units (P < 0.0001) respectively. Therefore, this study suggests that fluke infection could be responsible for considerable economic and production losses mainly due to condemnation and weight loss in dairy cattle. This study recommended a combination of holistic and grazing management to control infection rates in dairy herds.

Identification and expression of a transforming growth factor beta (TGF-ß) homologue in the tropical liver fluke Fasciola gigantica.

Liver flukes, Fasciola spp., are veterinary and medically important parasites infecting numerous species of economically important animals in addition to humans on a global scale. The components of transforming growth factor beta (TGF-ß) signalling are widely distributed throughout the animal kingdom and are considerably conserved. Through shared common signal transduction mechanisms, crosstalk of TGF-ß signalling between a host and the parasite during infection is possible. Herein, we have identified and undertaken the molecular characterisation of a putative TGF-ß homologue from the tropical liver fluke F. gigantica (FgTLM). A FgTLM cDNA was 3557 bp in length, it encoded for 620 amino acid polypeptide which consisted of 494 amino acids of prodomain and 126 amino acids comprising the mature protein. FgTLM displayed characteristic structures of mammalian TGF-ß ligands that were unique to the inhibin-ß chain, monomer of activin. A phylogenetic analysis revealed the high degree of conservation with TGF-ß molecules from trematode species. Interestingly, the sequence of amino acid in the active domain of FgTLM was completely identical to FhTLM from F. hepatica. FgTLM expressed throughout the lifecycle of F. gigantica but was highly expressed in developmental active stages. The dynamics of expression of FgTLM during the developmental stages of F. gigantica was comparable to the pattern of TGF-ß expression in F. hepatica. Our findings demonstrated that FgTLM exhibits a high level of similarity to FhTLM in the context of both amino acid sequence and the life stage expression patterns. These similarities underline the possibility that the FgTLM molecule might have the same properties and functions as FhTLM in biological processes of the immature parasites and host immune evasion. Consequently, the specific biological functions of FgTLM on either parasite or relevant hosts need to be defined experimentally.

High-quality reference genome for Clonorchis sinensis.

The Chinese liver fluke, Clonorchis sinensis, causes the disease clonorchiasis, affecting ~35 million people in regions of China, Vietnam, Korea and the Russian Far East. Chronic clonorchiasis causes cholangitis and can induce a malignant cancer, called cholangiocarcinoma, in the biliary system. Control in endemic regions is challenging, and often relies largely on chemotherapy with one anthelmintic, called praziquantel. Routine treatment carries a significant risk of inducing resistance to this anthelmintic in the fluke, such that the discovery of new interventions is considered important. It is hoped that the use of molecular technologies will assist this endeavour by enabling the identification of drug or vaccine targets involved in crucial biological processes and/or pathways in the parasite. Although draft genomes of C. sinensis have been published, their assemblies are fragmented. In the present study, we tackle this genome fragmentation issue by utilising, in an integrated way, advanced (second- and third-generation) DNA sequencing and informatic approaches to build a high-quality reference genome for C. sinensis, with chromosome-level contiguity and curated gene models. This substantially-enhanced genome provides a resource that could accelerate fundamental and applied molecular investigations of C. sinensis, clonorchiasis and/or cholangiocarcinoma, and assist in the discovery of new interventions against what is a highly significant, but neglected disease-complex.

Triclabendazole Treatment Failure for Fasciola hepatica Infection among Preschool and School-Age Children, Cusco, Peru1.

We conducted a retrospective cohort study of children who had chronic fascioliasis in the highlands of Peru to determine triclabendazole treatment efficacy. Children passing Fasciola eggs in stool were offered directly observed triclabendazole treatment (>1 doses of 10 mg/kg). Parasitologic cure was evaluated by using microscopy of stool 1-4 months after each treatment. A total of 146 children who had chronic fascioliasis participated in the study; 53% were female, and the mean ± SD age was 10.4 ± 3.1 years. After the first treatment, 55% of the children achieved parasitologic cure. Cure rates decreased after the second (38%), third (30%), and fourth (23%) treatments; 17 children (11.6%) did not achieve cure after 4 treatments. Higher baseline egg counts and lower socioeconomic status were associated with triclabendazole treatment failure. Decreased triclabendazole efficacy in disease-endemic communities threatens control efforts. Further research on triclabendazole resistance and new drugs to overcome it are urgently needed.

Acute fasciolosis in an alpaca: a case report.

BACKGROUND: The popularity of new world camelids, particularly alpacas, is growing rapidly in Ireland, presenting a clinical challenge to veterinary practitioners who may not have worked with these species previously. To the authors' knowledge, the clinical course of a case of acute fasciolosis in an alpaca has not previously been reported, and fasciolosis has not been reported at all in alpacas in Ireland, making this case report a valuable addition to the current literature. CASE PRESENTATION: A three-year-old male castrated huacaya alpaca was admitted to UCD Veterinary Hospital with a two-day history of colic and tenesmus. He had been treated with albendazole, dexamethasone and potentiated amoxycillin by the referring veterinary practitioner with no response. On initial clinical exam, sensitivity to abdominal palpation was the only abnormality. However, the alpaca proceeded to show abnormal lying positions, tenesmus and reduced faecal output over the next 24 h. A general blood panel demonstrated moderate anaemia, marked hyperglobulinaemia and moderately increased hepatocellular and hepatobiliary enzyme activity. Abdominal radiography revealed enlargement of the first forestomach compartment without evidence of gastrointestinal obstruction or peritonitis. An abdominal ultrasound exam revealed an elongated, heterogenous mass in the caudoventral abdomen that appeared to be contiguous with the liver. FNA of this mass revealed that it was in fact a liver lobe with biliary stasis and inflammation. Faecal sedimentation demonstrated Fasciola hepatica eggs. In spite of treatment with triclabendazole and supportive treatment including blood transfusion, the alpaca's condition continued to deteriorate and he was euthanised. On post-mortem exam, acute fasciolosis was diagnosed. CONCLUSIONS: The clinical presentation and course of a case of acute fasciolosis in an individual alpaca is described, including the results of a range of diagnostic tests that were carried out. The final diagnosis is supported by a description of post-mortem findings. This information will serve as a resource for veterinary practitioners involved in the diagnosis and treatment of similar cases.

Assessing the role of Filopaludina martensi martensi as a biocontrol agent of Bithynia siamensis goniomphalos, the first intermediate host of Opisthorchis viverrini.

The freshwater snail Bithynia siamensis goniomphalos serves as the first intermediate host of liver fluke Opisthorchis viverrini, a foodborne parasite, of which human infection has persisted in Southeast Asia for decades. The snail Filopaludina martensi martensi has been proposed as a biological control agent against B.s. goniomphalos, but knowledge on the snail ecology and population dynamics between the two species remains rudimentary. This study investigated selected abiotic and biotic factors influencing the distribution and abundance of B.s. goniomphalos and F.m. martensi. Water quality, soils, and snails were collected from 34 localities in Northeast Thailand. Soil properties and snail soft tissue elemental concentrations were analyzed. Experiments were performed to examine interspecific competition. Statistical analysis was conducted to explore the associations between water and soil properties and soft tissue elemental concentrations. The results showed that B.s. goniomphalos had the highest mean dominance in streams and red-yellow podzolic soils, while F.m. martensi snails preferred ponds and latosol soils. Negative correlation in species abundances was found between the two species. Interspecific competition was detected, with B.s. goniomphalos growth rates hampered by the presence of F.m. martensi. Despite the possibility of using F.m. martensi to control B.s. goniomphalos, B.s. goniomphalos exhibited a greater adaptability to different water and soil properties, suggesting that the species could colonize a wide range of environmental conditions. This study provides further insights into the ecology of the two snail species, underscoring the importance of considering abiotic factors when assessing the possible biological control agent to control O. viverrini transmission.

Animation as Supplementary Learning Material About Carcinogenic Liver Fluke in Classes for Primary Schoolchildren.

Carcinogenic liver fluke is still an issue of great concern in some countries of Southeast Asia, particularly in Thailand, Cambodia, the Lao People's Democratic Republic, and Vietnam. The infection, caused by Opisthorchis viverrini, is associated to cholangiocarcinoma and is endemic among human populations for whom raw fish is frequently consumed. Prevention and health education are required. Therefore, this study aimed to evaluate the effectiveness of educational intervention to improve knowledge among primary schoolchildren based on animation-assisted education. In this study, 80 participants (40 participants in the experimental group and 40 participants in the comparison group) were selected in 2018. The effectiveness of an interactive animation program in improving the knowledge of students studying liver fluke was determined based on scores on tests given before and immediately after completion of a 4.29-min animated program on the liver fluke life cycle, risk factors, disease, diagnosis, treatment, prevention, and control. Data were analyzed using SPSS-22 via paired t tests and independent samples t tests at a significance level of 0.05. A marked and significant improvement was observed in the immediate posttest compared with the pretest scores. More importantly, the students who had used the animated program achieved a significantly higher score on the final test than the comparison group. The results offered in the first report show that the use of the animated program facilitated education about liver fluke. It is strongly believed that animations are good supplementary learning materials for students, particularly for learning about serious concepts.

Structural basis of urea-induced unfolding of Fasciola gigantica glutathione S-transferase.

Glutathione S-transferases (GSTs) are enzymes that are involved in the detoxification of harmful electrophilic endogenous and exogenous compounds by conjugating with glutathione (GSH). The liver fluke GSTs have multifunctional roles in the host-parasite interaction, such as general detoxification and bile acid sequestration to synthase activity. The GSTs have been highlighted as vaccine candidates towards parasitic flukes. In this study, we have thoroughly examined the urea-induced unfolding of a mu-class Fasciola gigantica GST1 (FgGST1) using spectroscopic techniques and molecular dynamic simulations. FgGST1 is a highly cooperative molecule, because during urea-induced equilibrium unfolding, a concurrent unfolding of the protein without stabilization of any folded intermediate was observed. The protein was stabilized with conformational free energy of about ~12.36 kcal/mol. The protein loses its activity with increasing urea concentration, as the GSH molecule is not able to bind to the protein. We also studied the fluorescence quenching of Trp residues and the obtained K SV data that provided additional information on the unfolding of FgGST1. Molecular dynamic trajectories simulated in different urea concentrations and temperatures indicated that urea destabilizes FgGST1 structure by weakening hydrophobic interactions and the hydrogen bond network. We observed a precise correlation between the in vitro and in silico studies.

Low-Grade Endemicity of Opisthorchiasis, Yangon, Myanmar.

We performed an epidemiologic survey of opisthorchiasis in Yangon, Myanmar. The fecal egg-positive rate of residents was 0.7%, and we recovered an adult fluke after chemotherapy and purging of an egg-positive resident. We detected Opisthorchis viverrini metacercariae in freshwater fish. We found the Yangon area to have low-grade endemicity of opisthorchiasis.

Pooled Population Pharmacokinetic Analysis of Tribendimidine for the Treatment of Opisthorchis viverrini Infections.

Opisthorchiasis, caused by the foodborne trematode Opisthorchis viverrini, affects more than 8 million people in Southeast Asia. In the framework of a phase 2b clinical trial conducted in Lao People's Democratic Republic, pharmacokinetic samples were obtained from 125 adult and adolescent O. viverrini-infected patients treated with 400 mg tribendimidine following the design of a sparse sampling scheme at 20 min and 2, 7.75, 8, and 30 h after treatment using dried blood spot sampling. Pharmacokinetic data for the metabolites deacetylated amidantel (dADT) and acetylated dADT (adADT) were pooled with data from two previous ascending-dose trials and evaluated using nonlinear mixed-effects modeling. The observed pharmacokinetic data were described using a flexible transit absorption model for the active metabolite dADT, followed by one-compartment disposition models for both metabolites. Significant covariates were age, body weight, formulation, and breaking of the enteric coating on the tablets. There were significant associations between O. viverrini cure and both the dADT maximum concentration and the area under the concentration-time curve (P < 0.001), with younger age being associated with a higher probability of cure. Modeling and simulation of exposures in patients with different weight and age combinations showed that an oral single dose of 400 mg tribendimidine attained therapeutic success in over 90% of adult patients. Our data confirmed that tribendimidine could be a valuable novel alternative to the standard treatment, praziquantel, for the treatment of O. viverrini infections.

Conserved Arg451 residue is critical for maintaining the stability and activity of thioredoxin glutathione reductase.

Thioredoxin glutathione reductase (TGR), a potential anthelminthic drug target causes NADPH-dependent transfer of electrons to both thioredoxins and glutathione systems. In the present study, we showed that a single point mutation conserved at Arg451 position is critical for maintaining the structure-function of FgTGR. The current biochemical results showed that R451A mutation significantly decreases both oxidoreductase activities (glutathione reductase and thioredoxin reductase) of the enzyme. Computational analyses using molecular dynamics simulation provided an in-depth insight into the structural alterations caused as a result of the mutation. Furthermore, the different regions of the mutant FgTGR structure were found to be altered in flexibility/rigidity as a result of the mutation. This led to mutant-specific conformational alterations and dominant differential motions that contributed to the abrogated function of mutant FgTGR. These results were confirmed using GdnHCl-induced denaturation-based stability studies. Moreover, mutation reduced the free energy of stabilization of the protein, thereby destabilizing the mutant protein structure. Therefore, these findings displayed differential dynamics in the FgTGR structure and highlighted the relevance of residue-level interactions in the protein. Thus, the current study provided a basis for exploiting regions other than the active site of TGR for inhibitory effect and development of novel antihelminthics.