Amino acids serve as an important energy source for adult flukes of Clonorchis sinensis.

Clonorchiasis, caused by chronic infection with Clonorchis sinensis (C. sinensis), is an important food-borne parasitic disease that seriously afflicts more than 35 million people globally, resulting in a socioeconomic burden in endemic regions. C. sinensis adults long-term inhabit the microaerobic and limited-glucose environment of the bile ducts. Energy metabolism plays a key role in facilitating the adaptation of adult flukes to crowded habitat and hostile environment. To understand energy source for adult flukes, we compared the component and content of free amino acids between C. sinensis-infected and uninfected bile. The results showed that the concentrations of free amino acids, including aspartic acid, serine, glycine, alanine, histidine, asparagine, threonine, lysine, hydroxylysine, and urea, were significantly higher in C. sinensis-infected bile than those in uninfected bile. Furthermore, exogenous amino acids could be utilized by adult flukes via the gluconeogenesis pathway regardless of the absence or presence of exogenous glucose, and the rate-limiting enzymes, such as C. sinensis glucose-6-phosphatase, fructose-1,6-bisphosphatase, phosphoenolpyruvate carboxykinase, and pyruvate carboxylase, exhibited high expression levels by quantitative real-time PCR analysis. Interestingly, no matter whether exogenous glucose was present, inhibition of gluconeogenesis reduced the glucose and glycogen levels as well as the viability and survival time of adult flukes. These results suggest that gluconeogenesis might play a vital role in energy metabolism of C. sinensis and exogenous amino acids probably serve as an important energy source that benefits the continued survival of adult flukes in the host. Our study will be a cornerstone for illuminating the biological characteristics of C. sinensis and the host-parasite interactions.

A Clonorchiasis Case of a Leopard Cat, Prionailurus bengalensis euptilurus, Diagnosed by Ultrasonography and Egg Detection in Republic of Korea.

A clonorchiasis case in a captive leopard cat, Prionailurus bengalensis euptilurus, was confirmed by ultrasonographic findings and egg morphologies found in the bile juice sample in the Korea. The leopard cat was introduced from the wild habitat of Gyeongsangnam-do, to Cheongju Zoo in Cheongju-si, Chungcheongbuk-do, Korea in August 2014. Physical examinations were basically performed for quarantine and check-up health. The cat was comparatively good in health except anorexia. The cyst-like bile duct dilation and the increased echogenicity of gall bladder wall and hepatic parenchyma were observed by ultrasonography. Ultrasound-guided needle biopsy was conducted for collecting bile juice and the specimens were observed under light microscope. The numerous small trematode eggs were detected in the bile juice sample of the light microscopy. The eggs were 25-33 (28±3) µm by 18-22 (20±1) µm in size and showed typical characteristics of Clonorchis sinensis egg, i.e., a dominantly developed operculum, shoulder rim and dust-like wrinkles in surface. To treat the liver fluke infection, 20 mg/kg of praziquantel was orally administered only once to the case. Follow-up studies including fecal examinations were conducted during 2 years after treatment. But no more eggs were detected from the case. In the present study, we described the first clonorchiasis case of leopard cat, which was confirmed by ultrasonographic findings and egg morphologies from the bile juice sample in Korea.

Chinese liver fluke Clonorchis sinensis infection changes the gut microbiome and increases probiotic Lactobacillus in mice.

Chinese liver fluke Clonorchis sinensis changes the host's immune system. Recently, it has been reported that helminths including C. sinensis can ameliorate immune-related diseases such as allergy. In addition, recent studies showed that helminth infection can alleviate immune-mediated disorders by altering the gut microbiome. However, changes in the gut microbiome due to C. sinensis have not been reported yet. In this study, changes in the gut microbiome of C57BL/6 mice infected with C. sinensis metacercariae were evaluated over time. Stool was analyzed by 16S rRNA amplicon analysis using high-throughput sequencing technology. There was no apparent difference in species richness and diversity between the infected and control groups. However, the composition of the microbiome was different between the infected and control groups at 20 days and 30 days post-infection, and the difference disappeared at 50 days post-infection. In particular, this microbiome alteration was associated with a change in the relative abundance of genus Lactobacillus and the probiotic Lactobacillus species that are known to have an immune-modulation role in immune-mediated diseases.

TLR2 signal influences the iNOS/NO responses and worm development in C57BL/6J mice infected with Clonorchis sinensis.

BACKGROUND: Although the responses of inducible nitric oxide synthase (iNOS) and associated cytokine after Clonorchis sinensis infection have been studied recently, their mechanisms remain incompletely understood. In this study, we investigated the effects of toll-like receptor 2 (TLR2) signals on iNOS/nitric oxide (NO) responses after C. sinensis infection. We also evaluated the correlations between iNOS responses and worm development, which are possibly regulated by TLR2 signal. METHODS: TLR2 wild-type and mutant C57BL/6 J mice were infected with 60 C. sinensis metacercariae, and the samples were collected at 30, 60, 90 and 120 days post-infection (dpi). The total serum NO levels were detected using Griess reagent after nitrate was reduced to nitrite. Hepatic tissue samples from the infected mice were sliced and stained with hematoxylin and eosin (HE) to observe worm development in the intrahepatic bile ducts. The iNOS mRNA transcripts in the splenocytes were examined by real time reverse transcriptase polymerase chain reaction (qRT-PCR), and iNOS expression was detected by immunohistochemistry. RESULTS: Developing C. sinensis juvenile worms were more abundant in the intrahepatic bile ducts of TLR2 mutant mice than those of TLR2 wild-type mice. However, no eggs were found in the faeces of both mice samples. The serum levels of total NO significantly increased in TLR2 mutant mice infected with C. sinensis at 30 (t (5) = 2.595, P = 0.049), 60 (t (5) = 7.838, P = 0.001) and 90 dpi (t (5) = 3.032, P = 0.029). Meanwhile, no changes occurred in TLR2 wild-type mice compared with uninfected controls during the experiment. The iNOS expression in splenocytes showed unexpected higher background levels in TLR2 mutant mice than those in TLR2 wild-type mice. Furthermore, the iNOS mRNA transcripts in splenocytes were significantly increased in the TLR2 wild-type mice infected with C. sinensis at 30 (t (5) = 5.139, P = 0.004), 60 (t (5) = 6.138, P = 0.002) and 90 dpi (t (5) = 6.332, P = 0.001). However, the rising of iNOS transcripts dropped under the uninfected control level in the TLR2 mutant mice at 120 dpi (t (5) = -9.082, P < 0.0001). Both total NO and iNOS transcripts were significantly higher in the TLR2 mutant mice than those in the TLR2 wild-type mice at 30 (t (5) = 3.091/2.933, P = 0.027/0.033) and 60 dpi (t (5) = 2.667/6.331, P = 0.044/0.001), respectively. In addition, the remarkable increase of iNOS expressions was immunohistochemically detected in the splenic serial sections of TLR2 wild-type mice at 30 and 60 dpi. However, the expressions of iNOS were remarkably decreased in the splenocytes of both TLR2 wild-type and mutant mice at 120 dpi. CONCLUSIONS: These results demonstrate that TLR2 signal plays an important role in the regulation of iNOS expression after C. sinensis infection. TLR2 signal is also beneficial to limiting worm growth and development and contributing to the susceptibility to C. sinensis in which the iNOS/NO reactions possibly participate.

C3H/He Mice as an Incompatible Cholangiocarcinoma Model by Clonorchis sinensis, Dicyclanil and N-Nitrosodimethylamine.

Clonorchis sinensis is a Group-I bio-carcinogen, associated with cholangiocarcinoma (CCA). The hamster is the only experimental model of C. sinensis-mediated CCA, but we oblige another animal model. The present study intended to develop a C. sinensis (Cs) mediated CCA model using C3H/He mice, co-stimulated with N-nitrosodimethyl-amine (NDMA) and dicyclanil (DC). The mice were divided into 8 groups with different combinations of Cs, NDMA, and DC. Six months later the mice were sacrificed and subjected to gross and histopathological examination. The body weights were significantly reduced among the groups treated with 2 or more agents (eg. Cs+NDMA, Cs+DC, NDMA+DC, and Cs+NDMA+DC). In contrast, liver weight percentages to body weight were increased in above groups by 4.1% to 4.7%. A Change of the spleen weight was observed only in Cs+NDMA group. Though C. sinensis infection is evident from hyperplastic changes, only 1 worm was recovered. T wo mice, 1 from Cs and the other from Cs+DC group, showed mass forming lesions; 1 (281.2 mm(3)) from the Cs group was a hepatocellular adenoma and the other (280.6 mm(3)) from the Cs+DC group was a cystic mass (peliosis). Higher prevalence of gray-white nodules was observed in Cs group (42.9%) followed by Cs+NDMA+DC group (21.4%). The mice of the Cs+NDMA+DC group showed hyper-proliferation of the bile duct with fibrotic changes. No characteristic change for CCA was recognized in any of the groups. In conclusion, C3H/He mice produce no CCA but extensive fibrosis when they are challenged by Cs, NDMA, and DC together.

Characterization and identification of differentially expressed microRNAs during the process of the peribiliary fibrosis induced by Clonorchis sinensis.

Clonorchis sinensis (C. sinensis) infection can lead to biliary fibrosis. MicroRNAs (miRNAs) play important roles in regulation of genes expression in the liver diseases. However, the differential expression of miRNAs that probably regulates the portal fibrogenesis caused by C. sinensis has not yet been investigated. Hepatic miRNAs expression profiles from C. sinensis-infected mice at different time-points were analyzed by miRNA microarray and validated by quantitative real-time PCR (qRT-PCR). 349 miRNAs were differentially expressed in the liver of the C. sinensis-infected mice at 2, 8 or 16weeks post infection (p.i.), compared with those at 0week p.i., and there were 143 down-regulated and 206 up-regulated miRNAs among them. These all dysregulated miRNAs were potentially involved in the pathological processes of clonorchiasis by regulation of cancer-related signaling pathway, TGF-ß signaling pathway, MAPK signaling pathway, Toll-like receptor signaling pathway, PI3K /AKT signaling pathway, etc. 169 of these dysregulated miRNAs were predicted to be involved in the TGF/Smads signaling pathway which plays an important role in the biliary fibrosis caused by C. sinensis. Additionally, miRNA-32, miRNA-34a, miRNA-125b and miRNA-497 were negatively correlated with Smad7 expression, indicating these miRNAs may specifically down-regulate Smad7 expression and participate in regulation of biliary fibrosis caused by C. sinensis. The results of the present study for the first time demonstrated that miRNAs were differentially expressed in the liver of mice infected by C. sinensis, and these miRNAs may play important roles in regulation of peribiliary fibrosis caused by C. sinensis, which may provide possible therapeutic targets for clonorchiasis.

The importance of wild fish in the epidemiology of Clonorchis sinensis in Vietnam.

Preliminary findings of a high prevalence of Clonorchis sinensis in wild-caught fish in a North Vietnam reservoir (Thac Ba reservoir, Yen Bai Province) prompted a longitudinal epidemiological study of fish infections. Monthly collections of fish from September 2014 to August 2015 were processed for recovery of metacercariae; 1219 fish, representing 22 species, were examined. Seven species were infected with C. sinensis metacercariae. Four species, Toxabramis houdemeri, Hemiculter leucisculus, Cultrichthys erythropterus, and Culter recurvirostris, had high prevalence (31.1 to 76.7 %); metacercarial intensities ranged from 3.9 to 65.7 metacercariae/fish. A seasonal variation of C. sinensis prevalence was observed in T. houdemeri. Variation in intensity of infection occurred in C. erythropterus and H. leucisculus. Intensity and prevalence of C. sinensis in the most highly infected species, T. houdemeri, varied by fish size; prevalence was higher in fish weighing more than 3 g, and intensity was higher in fish weighing more than 5 g. The distribution of metacercariae in the body region of T. houdemeri was significantly higher in the caudal fin (14.7 metacercariae/g), compared to the body and head regions (0.7 and 1.4 metacercariae/g, respectively). Further epidemiological investigations on C. sinensis in this reservoir region should include assessing the relative risk of the different fish species for humans based on the latter's food preferences, and the prevalence of C. sinensis in the community. The snail intermediate host(s) in the reservoir should also be identified along with the ecological factors influencing its exposure to C. sinensis eggs and its subsequent transmission of cercariae to fish. Also needed are investigations on the relative importance of wild and domestic reservoir hosts as sources of egg contamination of the reservoir.

Evaluation of Modified Formalin-Ether Concentration Method Using Para Tube in Clinical Settings.

Conventional formalin-ether concentration method is a gold standard for the diagnosis of parasite infection. However, it may be time-consuming and laborious. We aimed to reveal the clinical usefulness of a modified formalin-ether concentration method using the Para Tube (KS Corporation, Korea) compared with the conventional method. A total of 117 fresh, unpreserved fecal samples composed to 90 negative controls and 27 positive controls with ova of Diphyllobothrium latum/D. nihonkaiense, ova of Clonorchis sinensis and cysts of Giardia lamblia were used in this study. Both methods showed comparable correct identification rate (87.2% for the Para Tube vs. 86.3% for the conventional method).When five samples were examined at once, the Para Tube method reduced the procedure time compared with the conventional method (19 min 58 sec vs. 23 min 18 sec, P=0.0286). We concluded that the modified formalin-ether concentration method using the Para Tube is a rapid, simple, and reliable fecal concentration method for clinical use.

Characterization of a gut-associated asparaginyl endopeptidase of Clonorchis sinensis.

Asparaginyl endopeptidases (AEP: EC 3.4.22.34) are a family of cysteine proteases classified into the MEROPS clan CD, family C13. In this study, we characterized the biochemical and antigenic properties of an AEP of Clonorchis sinensis (CsAEP). The recombinant CsAEP showed hydrolytic activity at pH values ranging from acidic to neutral with optimum activity at pH 6.0. While the recombinant CsAEP was stable at neutral pHs, it was unstable at acidic pHs and resulted in loss of enzymatic activity. The recombinant enzyme was effectively inhibited by iodoacetic acid and N-ethylmaleimide, but not by E-64. The partially purified native CsAEP showed biochemical properties similar to the recombinant enzyme. Native CsAEP is likely to be cleaved into an N-terminal mature enzyme and a C-terminal fragment via autocatalytic activation at acidic pHs. Polyclonal antibody raised against the recombinant CsAEP recognized three forms of CsAEP, proenzyme, the N-terminal mature enzyme and the C-terminal fragment, in the worm extract (WE) of C. sinensis. However, only the C-terminal fragment was mainly found in the excretory and secretory (ES) products of the parasite. Strong CsAEP activity was found in the WE, but only a trace level of CsAEP activity was detected in the ES products of the parasite. CsAEP was expressed in various developmental stages of C. sinensis, from metacercariae to adults, and was found to be localized in the intestine of the parasite as well as in intestinal contents. Sera from rats experimentally infected with C. sinensis reacted with CsAEP beginning 4 weeks after infection. These results suggest that CsAEP is a gut-associated enzyme synthesized in the intestine of C. sinensis and subsequently secreted into the intestinal lumen of the parasite.

Inducible nitric oxide synthase response and associated cytokine gene expression in the spleen of mice infected with Clonorchis sinensis.

Clonorchis sinensis is a food-borne parasite that induces a permanent increase of nitrosation in the body upon infection. The spleen is an important secondary lymphoid organ for the regulation of immune responses locally and in the whole body. However, the functions and mechanisms of the spleen in nitric oxide (NO) responses after C. sinensis infection remain unknown. In this study, BALB/c mice were infected with 20, 40, and 80 C. sinensis metacercariae to simulate mild, moderate, and severe infections, respectively. We examined the expression of inducible nitric oxide synthase (iNOS) in the spleen and the relevant cytokine transcription in splenocytes from the mice infected with different amounts of metacercariae. The iNOS of the mice infected with 80 metacercariae was expressed in the spleen as early as 10 days post-infection (dpi) and gradually increased until 90 dpi. The iNOS expression in the mice infected with 40 metacercariae was detected only at 45 and 90 dpi, but not in the mice infected with 20 metacercariae. The level of interferon (IFN)-γ messenger RNA (mRNA) transcription in splenocytes significantly increased at 10 and 20 dpi (P < 0.05) in response to mild/moderate infection but gradually decreased to normal levels after 45 dpi. The level of IL-12p35 mRNA transcription did not change at 10 and 20 dpi but significantly decreased after 45 dpi under moderate/severe infection (P < 0.05/0.01/0.001). The level of IL-18 mRNA transcription significantly increased at 10 dpi (P < 0.05/0.01) but significantly decreased after 20 dpi (P < 0.05/0.01/0.001). These results suggest that spleen is an important organ for iNOS/NO responses, which correspond to the severity of C. sinensis infection, but cannot be attributed to the expression of the Th1 cytokines.

[A man in his thirties with icterus and itching]. / En mann i 30-årene med icterus og kløe.

BACKGROUND: We present a patient from South-East Asia who has been living in Norway for five years. He was referred to our department with jaundice caused by opisthorchiasis/clonorchiasis. This reason for jaundice is highly unusual in Europe. Worldwide, however about 35,000,000 people are infected. CASE PRESENTATION: A male in his thirties, originally from South-East Asia, experienced diffuse itching for five weeks and painless jaundice for two weeks. Blood samples showed increasing cholestasis. Abdominal ultrasound, MRCP and computed tomography showed no sign of bile duct obstruction or liver tumour. Serological tests and liver biopsy revealed no infectious or autoimmune liver disease. ERCP showed normal bile ducts, but large quantities of typical hookworms in the duodenum. Stool samples showed at least one egg typical of Opisthorchis/Clonorchis and a large quantity of hookworm eggs. We interpreted these findings as parasite-induced obstruction of some of the small bile ducts. The patient recovered completely after treatment with Praziquantel. INTERPRETATION: Jaundice due to bile duct obstruction by opisthorchiasis/clonorchiasis is a well-known problem in South-East Asia. It may become more common in Europe as well as a result of increasing migration. Treatment with Praziquantel is simple and effective.

ClonorESTdb: a comprehensive database for Clonorchis sinensis EST sequences.

BACKGROUND: Clonorchiasis, which is primarily caused by liver fluke (Platyhelminthes), is a fatal infectious disease that is mainly associated with bile duct malignancy and the subsequent development of cholangiocarcinoma. Thus, a genomic approach now represents an important step to further our knowledge of biology and the pathology of these parasites. The results of expressed sequence tags (ESTs) sequencing need to be well organized into databases to provide an integrated set of tools and functional information. FINDINGS: Here, the ClonorESTdb database represents a collection of Clonorchis sinensis ESTs that is intended as a resource for parasite functional genomics. A total of 55,736 successful EST sequences, which are cleaned and clustered into non-redundant 13,305 C. sinensis assembled EST sequences (6,497 clusters and 6,808 singletons), were obtained from three in-house prepared cDNA libraries of C. sinensis at different developmental stages. The assembled consensus sequences were annotated using the BLAST algorithm or/and hmm against NCBI NR, UniProt, KEGG and InterProScan. The ClonorESTdb database provides functional annotation, their expression profiles, tandem repeats and putative single nucleotide polymorphisms with utility tools such as local BLAST search and text retrieval. CONCLUSIONS: This resource enables the researcher to identify and compare expression signatures under different biological stages and promotes ongoing parasite drug and vaccine development and biological research.Database URL:http://pathod.cdc.go.kr/clonorestdb/.

The biochemical and immunological characterization of two serpins from Clonorchis sinensis.

Serpins (serine proteinase inhibitors) are evidenced to regulate numerous biological processes such as immunoregulation in parasitic helminths. The functions of serpins from Clonorchis sinensis remain unclear to date. In this study, two serpin genes, respectively denominated as CsproSERPIN and CsSERPIN2, had been selected from metacercaria cDNA library of C. sinensis. The biochemical activities of both recombinant proteins (rCsproSERPIN and rCsSERPIN2) were analyzed by assays of inhibition on some serine or cysteine proteases, the results showed that rCsproSERPIN significantly inhibited trypsin, chymotrypsin and thrombin, while rCsSERPIN2 inhibited only chymotrypsin. Moreover, cytokine and antibody measurements indicated that rats subcutaneously immunized with rCsproSERPIN and rCsSERPIN2 respectively developed a strong IFN-γ production and IgG2a levers of sera were higher than IgG1. Besides, immunoblot assays revealed that the rCsproSERPIN and rCsSERPIN2 could be recognized by the sera of rats infected with C. sinensis and the sera of rabbits immunized by excretory/secretory products. Furthermore, immunofluorescence assays illuminated the two were similarly localized in the reproductive organs such as vitelline glands, testis and eggs in adult stage. In short, all the results collectively indicated that CsproSERPIN and CsSERPIN2 might play important role in the parasite development by preventing the parasite from digestion by exogenous serine proteases, as well as CsproSERPIN and CsSERPIN2 probably involved in immunoregulation of host by inducing Th1-biased type cytokines in rats.

Identification, sequence analysis and characterization of Clonorchis sinensis ubiquitin.

Ubiquitin is a functionally important protein expressed in eukaryotic cells usually encoded by multigenic families containing two types of genes, ubiquitin extension genes and polyubiquitin genes. One independent monomeric locus and two independent polyubiquitin loci were firstly identified from the genome of carcinogenic liver fluke, Clonorchis sinensis (C. sinensis). The nucleotide and amino acid sequence of C. sinensis polyubiquitin, especially polyubiquitin with five tandem ubiquitin repeats (CsPUB5), were analyzed. We obtained recombinant CsPUB5 (rCsPUB5) and anti-rCsPUB5 IgG. The ubiquitin transcripts in life cycle of C. sinensis were investigated. In addition, we found that ubiquitin or ubiquitination was ubiquitous in adult worm of C. sinensis and significantly observed in the content of biliary tract and intrahepatic biliary epithelium of liver from C. sinensis infected rat. We confirmed that rCsPUB5 could bind to human intrahepatic biliary epithelial cell by immunofluorescence in vitro. It was considered that ubiquitin family constitutively expressed in C. sinensis for variety of cellular processes and might be implicated in the genesis and progression of cholangiocarcinoma induced by the infection of C. sinensis.

In vitro maintenance of Clonorchis sinensis adult worms.

Clonorchis sinensis is a biological carcinogen inducing human cholangiocarcinoma, and clonorchiasis is one of the important endemic infectious diseases in East Asia. The present study investigated survival longevity of C. sinensis adult worms in various in vitro conditions to find the best way of keeping the worms longer. The worms were maintained in 0.85% NaCl, 1×PBS, 1×Locke's solution, RPMI-1640, DMEM, and IMDM media, and in 1×Locke's solution with different supplements. All of the worms died within 3 and 7 days in 0.85% NaCl and 1×PBS, respectively, but survived up to 57 days in 1×Locke's solution. The worms lived for 106 days in DMEM, and 114 days in both RPMI-1640 and IMDM media. The survival rate in RPMI-1640 medium was the highest (50%) compared to that in DMEM (20±10%) and in IMDM (33.3±25.2%) after 3 months. The 1×Locke's solution with 0.005% bovine bile supplement showed increased duration of maximum survival from 42 days to 70 days. Higher concentration of bile supplements than 0.005% or addition of glucose were disadvantageous for the worm survival. The worms died rapidly in solutions containing L-aspartic acid, L-glutamic acid, and adenine compared to L-arginine, L-serine, and L-tryptophan. In conclusion, the 1×Locke's solution best supports the worms alive among inorganic solutions for 57 days, and the RPMI-1640 medium maintains living C. sinensis adults better and longer up to 114 days in vitro than other media.

Strain variation in the susceptibility and immune response to Clonorchis sinensis infection in mice.

Mice have shown various susceptibility to infection by Clonorchis sinensis. To compare the intra-specific variation in the host-parasite relationship of C. sinensis, 6 strains of mice (ICR, BALB/c, C57BL/6, DDY, CBA/N, and C3H/HeN) with 3 different haplotypes were evaluated on their susceptibility. The worm recovery rate and immunological responses were observed after 4 and 8 weeks of infection with 30 metacercariae. The highest worm recovery rate was observed as 20.7% in the C3H/HeN strain after 4 weeks of infection along with histopathological changes. The rate was 10.0% in C57BL/6 mice after 8 weeks. ICR, BALB/c, and CBA/N showed elevated levels of IgE at both time points when compared to the rest of the strains. The serum IgG1 and IgG2a levels were elevated in most of the strains; however, the C57BL/6 strain showed a lower level of IgG2a that indicated the IgG1 predominance over IgG2a. The production of IL-4 after concanavalin-A stimulation of splenocytes slightly increased among the mouse strains except C3H/HeN after 4 or 8 weeks of infection, but each strain produced high levels of IFN-γ after 8 weeks, which implied mixed Th1/Th2 responses. ICR, DDY, CBA/N, and C3H/HeN strains showed a significantly increased level of IL-10 after 8 weeks as compared to C57BL/6. All of the strains showed an increased level of IL-13 and suggested fibrotic changes in the mice. In conclusion, mice are insusceptible to infection with C. sinensis; however, the C57BL/6, BALB/c and ICR strains are relatively susceptible after 8 weeks of infection among the six strains. Worm expulsion may be one of the causes of low susceptibility of C3H/HeN mice strain at the 8th week. Elevated IgE, IFN-γ, and IL-13 of infected mice suggest both Th1 and Th2 responses that may be related to the low host susceptibility.

The current status of opisthorchiasis and clonorchiasis in the Mekong Basin.

This review highlights the current status and control of liver fluke infections in the Mekong Basin countries where Opisthorchis and Clonorchis are highly endemic. Updated data on prevalence and distribution have been summarized from presentations in the "96 Years of Opisthorchiasis. International Congress of Liver Flukes". It is disturbing that despite treatment and control programs have been in place for decades, all countries of the Lower Mekong Basin are still highly endemic with O. viverrini and/or C. sinensis as well as alarmingly high levels of CCA incidence. A common pattern that is emerging in each country is the difference in transmission of O. viverrini between lowlands which have high prevalence versus highlands which have low prevalence. This seems to be associated with wetlands, flooding patterns and human movement and settlement. A more concerted effort from all community, educational, public health and government sectors is necessary to successfully combat this fatal liver disease of the poor.

Coproantigen capture ELISA for detection of Clonorchis sinensis infection in experimentally infected rats.

The present study investigated the diagnostic value of an ELISA for the detection of Clonorchis sinensis antigen in the feces of experimentally infected rats. A mouse polyclonal IgG antibody against adult C. sinensis crude antigen (CsAg) was used to capture the C. sinensis coproantigen. The detection limit for pure CsAg was 20 ng/ml in sample buffer and 40 ng/ml in uninfected fecal extract. The test was evaluated using a follow-up of five groups of rats experimentally infected with 100, 50, 10, 5 and 1 metacercariae of C. sinensis and an uninfected control group. Coproantigen was detected in all infected groups of rats from 2 weeks of infection, whereas fecal eggs were not observed until 3 weeks of infection. As the infection period progressed, the fecal CsAg concentration increased in all groups of infected rats, even those infected with a single metacercaria. The fecal CsAg concentration was correlated positively with fecal egg counts and worm burden. This coproantigen capture ELISA is highly sensitive for the detection of CsAg in rat feces, and with further development, should be useful for mass screening of human subjects in clonorchiasis-endemic areas.

Development of a TaqMan based real-time PCR assay for detection of Clonorchis sinensis DNA in human stool samples and fishes.

Clonorchiasis caused by the oriental liver fluke Clonorchis sinensis is a fish-borne zoonosis endemic in a number of countries. This article describes the development of a TaqMan based real-time PCR assay for detection of C. sinensis DNA in human feces and in fishes. Primers targeting the first internal transcribed spacer (ITS-1) sequence of the fluke were highly specific for C. sinensis, as evidenced by the negative amplification of closely related trematodes in the test with the exception of Opisthorchis viverrini. The detection limit of the assay was 1pg of purified genomic DNA, 5EPG (eggs per gram feces) or one metacercaria per gram fish filet. The assay was evaluated by testing 22 human fecal samples and 37 fish tissues microscopically determined beforehand, and the PCR results were highly in agreement with the microscopic results. This real-time PCR assay provides a useful tool for the sensitive detection of C. sinensis DNA in human stool and aquatic samples in China and other endemic countries where O. viverrini and Opisthorchis felineus are absent.

Cyst formation, increased anti-inflammatory cytokines and expression of chemokines support for Clonorchis sinensis infection in FVB mice.

To verify the hypothesis that different pathology of Clonorchis sinensis infection by mouse strains is determined by different responses of cytokines and chemokines, we compared those responses of FVB with those of BALB/c mice. All of FVB mice infected with 30 metacercariae of C. sinensis showed cystic dilatation in the liver, whereas infected BALB/c mice did not. Mature worms were recovered from 19 of 20 liver sections of FVB mice while only one of 20 sections of BALB/c mice revealed a mature worm. In both strains the proportion of CD4(+) T cells was lower in C. sinensis-infected than in the uninfected group. However, the proportion of CD8(+) T cells was elevated in C. sinensis-infected from both strains compared to uninfected mice. The Th2-associated anti-inflammatory cytokines such as IL-4, IL-5 and IL-13, IL-10 and TGF-ß, were significantly more produced by the lymphocytes of FVB than by those of BALB/c mice. Especially, the 2 anti-inflammatory cytokines, IL-10 and TGF-ß, were presumably related with susceptibility and the development of worms in the liver. C. sinensis infected FVB mice also produced more chemokines such as RANTES and MIP-1α in the liver lymphocytes than BALB/c mice. In conclusion, the FVB mice provide the favorable niche for C. sinensis by cyst formation in the bile duct, increased production of Th2-associated anti-inflammatory cytokines and upregulation of chemokines.