Molecular characterization and serodiagnosis analysis of a novel lysophospholipase from Clonorchis sinensis

Serodiagnostic antigens of Clonorchis sinensis identified and evaluated by high-throughput proteogenomics

Clonorchiasis caused by Clonorchis sinensis is endemic in East Asia; approximately 15 million people have been infected thus far. To diagnose the infection, serodiagnostic tests with excellent functionality should be performed. First, 607 expressed sequence tags encoding polypeptides with a secretory signal were expressed into recombinant proteins using an in vitro translation system. By protein array-based screening using C. sinensis-infected sera, 18 antigen candidate proteins were selected and assayed for cross-reactivity against Opisthorchis viverrini-infected sera. Of the six antigenic proteins selected, four were synthesized on large scale in vitro and evaluated for antigenicity against the flukes-infected human sera using ELISA. CsAg17 antigen showed the highest sensitivity (77.1%) and specificity (71.2%). The sensitivity and specificity of the bacterially produced CsAg17-28GST fusion antigen was similar to those of CsAg17 antigen. CsAg17 antigen can be used to develop point-of-care serodiagnostic tests for clonorchiasis.

Human clonorchiasis is a parasitic disease caused by the Chinese liver fluke, Clonorchis sinensis. Humans are infected through eating raw freshwater fishes carrying C. sinensis metacercariae, the encysted larvae. They excyst in the duodenum, move into the liver via bile duct and grow to adult worms. Excretory-secretory products of the worm damage the liver causing various inflammatory pathological changes and may lead to bile duct cancer. Although there exists an anthelmintic choice praziquantel to kill the fluke, emphasis is placed on early diagnosis and prevention before the infection becomes disease. Microscopic stool examination is the standard diagnostic method but is cumbersome and time consuming. Blood serum antibodies from clonorchiasis patients could provide a simple and fast diagnosis. However, antibody detecting diagnostics developed so far have a low specificity and sensitivity. In the present study we selected 607 antigenic candidate proteins from the genomic database and synthesized them through an integrated high-throughput proteogenomic tools. We identified several antigenic proteins and evaluated their diagnostic potential for clonorchiasis. One of them, CsAg17, showed a high sensitivity and specificity. This antigen deserves development of point-of-care serodiagnostics for C. sinensis infections.

Insight Into the Salivary Secretome of Varroa destructor and Salivary Toxicity to Apis cerana

The Varroa destructor (Acari Varroidae) mite is a serious threat to honey bee due to hemolymph feeding and virus transmission. Mite salivary proteins are involved in these interactions. However, the salivary secretome has not been previously characterized. In this paper, the saliva of V. destructor was found to be toxic to the worker larvae of Apis cerana (Hymenoptera Apidae) in the absence of deformed wing virus (DWV) and to stimulate the development of deformed wings in Apis mellifera (Hymenoptera Apidae) adults in the presence of DWV. The salivary secretome was analyzed by nano-liquid chromatography coupled to tandem mass spectrometry (nano-LC-MS/MS). A search of the resulting data against peptide databases using the software Mascot yielded 356, 53, and 9 matched proteins from V. destructor, A. mellifera, and DWV, respectively. The saliva contained Varroa mite proteins identified as important for potential virulence to A. cerana larvae, for the inhibition of harmful microorganisms, for the utilization of bee nutrients, and for antioxidant, oxidation-reduction and detoxification functions as well as A. mellifera proteins identified as nutrients important for mite reproduction. The saliva proteins also contained viral proteins from one virus, DWV. These results provide a strong foundation for understanding the interactions among the Varroa mite, honeybee, and DWV.

The Role of Stroma in Cholangiocarcinoma: The Intriguing Interplay between Fibroblastic Component, Immune Cell Subsets and Tumor Epithelium

Cholangiocarcinoma (CCA) is a severe and mostly intractable adenocarcinoma of biliary epithelial cells. A typical feature of CCA is its highly desmoplastic microenvironment containing fibrogenic connective tissue and an abundance of immune cells (T lymphocytes, Natural Killer (NK) cells, and macrophages) infiltrating tumor epithelium. This strong desmoplasia is orchestrated by various soluble factors and signals, suggesting a critical role in shaping a tumor growth-permissive microenvironment that is responsible for CCA poor clinical outcome. Indeed stroma not only provides an abundance of factors that facilitate CCA initiation, growth and progression, but also a prejudicial impact on therapeutic outcome. This review will give an overview of tumor-stroma signaling in a microenvironment critically regulating CCA development and progression. Identification of CCA secreted factors by both the fibroblast component and immune cell subsets might provide ample opportunities for pharmacological targeting of this type of cancer.

Clonorchis sinensis lysophospholipase A upregulates IL-25 expression in macrophages as a potential pathway to liver fibrosis

Background

Liver fibrosis is an excessive wound-healing reaction that requires the participation of inflammatory cells and hepatic stellate cells (HSCs). The pathogenesis of liver fibrosis caused by viruses and alcohol has been well characterized, but the molecular mechanisms underlying liver fibrosis induced by the liver fluke Clonorchis sinensis are poorly understood. Lysophospholipase A (LysoPLA), which deacylates lysophospholipids, plays a critical role in mediating the virulence and pathogenesis of parasites and fungi; however, the roles of C. sinensis lysophospholipase A (CsLysoPLA) in C. sinensis-induced liver fibrosis remain unknown.

Methods

A mouse macrophage cell line (RAW264.7) was cultured and treated with CsLysoPLA. IL-25 and members of its associated signaling pathway were detected by performing quantitative real-time PCR, Western blotting and immunofluorescent staining. A human hepatic stellate cell line (LX-2) was cultured and exposed to IL-25. LX-2 cell activation markers were examined via quantitative real-time PCR, Western blotting and immunofluorescent staining. Migration was analyzed in transwell plates.

Results

Treating RAW264.7 cells with CsLysoPLA significantly induced IL-25 expression. Elevated PKA, B-Raf, and ERK1/2 mRNA levels and phosphorylated B-Raf and ERK1/2 were detected in CsLysoPLA-stimulated RAW264.7 cells. The PKA inhibitor H-89 weakened B-Raf and ERK1/2 phosphorylation whereas the AKT activator SC79 attenuated ERK1/2 phosphorylation in RAW264.7 cells. Both H-89 and SC79 inhibited CsLysoPLA-induced IL-25 upregulation. In addition, stimulation of LX-2 cells with IL-25 upregulated the expression of mesenchymal cell markers, including α-smooth muscle actin (α-SMA) and collagen type I (Collagen-I), and promoted cell migration.

Conclusions

CsLysoPLA activates HSCs by upregulating IL-25 in macrophages through the PKA-dependent B-Raf/ERK1/2 pathway and potentially promotes hepatic fibrosis during C. sinensis infection.

Clonorchis sinensis lysophospholipase inhibits TGF-β1-induced expression of pro-fibrogenic genes through attenuating the activations of Smad3, JNK2, and ERK1/2 in hepatic stellate cell line LX-2

Liver fibrosis is a wound healing response associated with chronic liver injury. Hepatic stellate cells (HSCs) activation is a key event in the development of liver fibrosis. Since helminths have the ability to live for decades in the host by establishing an adaptive relationship in the interplay with its hosts, we hypothesize that whether Clonochis sinensis LysophospholipaseA (CsLysoPLA), a component of excretory/secretory proteins, can attenuate the fibrogenic response by inhibiting activation of LX-2 cells, thereby balancing the pro-fibrotic and anti-fibrotic response during the Clonochis sinensis (C. sinensis) infection. In the present study, LX-2 cells were stimulated with CsLysoPLA in the presence of TGF-β1, and the expressions of collagen type I (COL1A1), α-smooth muscle actin (α-SMA), and matrix metalloproteinase 2 (MMP2) were decreased. In addition, CsLysoPLA significantly inhibited the proliferation and migration of LX-2 cells stimulated by TGF-β1. Pretreatment of LX-2 cells with CsLysoPLA attenuated the phosphorylation of Smad3 as well as JNK2 and ERK1/2 in response to the stimulation of TGF-β1. For the first time, our results showed an anti-fibrogenic effect of CsLysoPLA by attenuating the response of LX-2 cells to TGF-β1 through inhibiting the activations of Smad3, ERK1/2, and JNK2.

Clonorchis sinensis acetoacetyl-CoA thiolase: identification and characterization of its potential role in surviving in the bile duct

BACKGROUND

Clonorchis sinensis (C. sinensis) inhabits in bile duct of the host. However, the mechanisms involved in why C. sinensis can survive in the bile environment containing lipids have not yet been explored. In this study, C. sinensis acetoacetyl-CoA thiolase (CsACAT), a member of the thiolase family which has a key role in the beta oxidation pathway of fatty acid production, was identified and characterized to understand its potential role in adapting to the bile environment.

METHODS

The encoding sequence, conserved domains and spatial structure of CsACAT were identified and analyzed by bioinformatic tools. Recombinant CsACAT (rCsACAT) was obtained using a procaryotic expression system. The expression pattern of CsACAT was confirmed by quantitative real-time PCR, western blotting, and immunofluorescence. Gradients of lecithin were then set to culture C. sinensis adults in vitro and the survival rate of C. sinensis was analyzed, as well as the expression level and enzymatic activity of CsACAT in different lipid environments. Hypercholesteremia rabbit models were established by feeding with a hyperlipidemic diet and then infected intragastrically with C. sinensis. One and a half months later, the worm burdens and the expression level of CsACAT was detected.

RESULTS

CsACAT was confirmed to be a member of the thiolase family and present in the excretory/secretory proteins of C. sinensis. CsACAT was specifically localized at the vitellarium and sub-tegumental muscle layer in adult worms. The mRNA level of CsACAT in eggs was higher than those in adult worms and metacercariae. When adult worms were cultured with higher concentration of lecithin, the expression level and enzyme activity of CsACAT were up-regulated. The survival rate of adult worms was higher than control group. More adult worms were recovered from hypercholesteremia rabbit models. The expression level of CsACAT in these worms was higher than control group.

CONCLUSIONS

Our results implied that C. sinensis might sense lipid levels and survive better in the bile environment with higher lipid levels. C. sinensis might modulate the expression and enzymatic activity of CsACAT, an enzyme involved in fatty acid metabolism, for energy or physical requirements to adapt to the host.

Clonorchis sinensis ferritin heavy chain triggers free radicals and mediates inflammation signaling in human hepatic stellate cells

Clonorchiasis, caused by direct and continuous contact with Clonorchis sinensis, is associated with hepatobiliary damage, inflammation, periductal fibrosis, and the development of cholangiocarcinoma. Hepatic stellate cells respond to liver injury through production of proinflammatory mediators which drive fibrogenesis; however, their endogenous sources and pathophysiological roles in host cells were not determined. C. sinensis ferritin heavy chain (CsFHC) was previously confirmed as a component of excretory/secretory products and exhibited a number of extrahepatic immunomodulatory properties in various diseases. In this study, we investigated the expression pattern and biological role of CsFHC in C. sinensis. CsFHC was expressed throughout life stages of C. sinensis. More importantly, we found that treatment of human hepatic stellate cell line LX-2 with CsFHC triggered the production of free radicals via time-dependent activation of NADPH oxidase, xanthine oxidase, and inducible nitric oxide synthase. The increase in free radicals substantially promoted the degradation of cytosolic IκBα and nuclear translocation of NF-κB subunits (p65 and p50). CsFHC-induced NF-κB activation was markedly attenuated by preincubation with specific inhibitors of corresponding free radical-producing enzyme or the antioxidant. In addition, CsFHC induced an increased expression level of proinflammatory cytokines, IL-1β and IL-6, in NF-κB-dependent manner. Our results indicate that CsFHC-triggered free radical-mediated NF-κB signaling is an important factor in the chronic inflammation caused by C. sinensis infection.

Development of a polymerase chain reaction applicable to rapid and sensitive detection of Clonorchis sinensis eggs in human stool samples

Microscopic examination of eggs of parasitic helminths in stool samples has been the most widely used classical diagnostic method for infections, but tiny and low numbers of eggs in stool samples often hamper diagnosis of helminthic infections with classical microscopic examination. Moreover, it is also difficult to differentiate parasite eggs by the classical method, if they have similar morphological characteristics. In this study, we developed a rapid and sensitive polymerase chain reaction (PCR)-based molecular diagnostic method for detection of Clonorchis sinensis eggs in stool samples. Nine primers were designed based on the long-terminal repeat (LTR) of C. sinensis retrotransposon1 (CsRn1) gene, and seven PCR primer sets were paired. Polymerase chain reaction with each primer pair produced specific amplicons for C. sinensis, but not for other trematodes including Metagonimus yokogawai and Paragonimus westermani. Particularly, three primer sets were able to detect 10 C. sinensis eggs and were applicable to amplify specific amplicons from DNA samples purified from stool of C. sinensis-infected patients. This PCR method could be useful for diagnosis of C. sinensis infections in human stool samples with a high level of specificity and sensitivity.

Biochemical characterization and functional analysis of fructose-1,6-bisphosphatase from Clonorchis sinensis

Fructose-1,6-bisphosphatase (FBPase), a key regulatory enzyme of gluconeogenesis, plays an essential role in metabolism and development of most organisms. To the wealth of available knowledge about FBPase from Clonorchis sinensis (CsFBPase), in this study, the characteristics of CsFBPase and its potential role in pathogenesis of clonorchiasis were investigated. The Km value of CsFBPase was calculated to be 41.9 uM. The optimal temperature and pH of CsFBPase were 37 °C and pH 7.5-8.0, respectively. In addition, Mg(2+) or K(+) played a regulatory role in enzyme activity of CsFBPase. Both transcriptional and translational level of CsFBPase were higher in metacercariae (one of larva stages) than those in adult worm (P < 0.05). CsFBPase were observed to extensively express in the intestine, vitellaria and tegument of adult worms and ubiquitously in metacercariae. Moreover, CsFBPase was confirmed as a component of excretory/secretory products. Consequently, the translocation of CsFBPase could be detected on epithelial cells of bile duct in liver of C. sinensis infected rat. Recombinant CsFBPase can specifically bind to the membrane of human hepatic stellate cell line LX-2 by immunofluorescence analysis and stimulated proliferation and activation of LX-2 which demonstrated by Cell Counting Kit-8 and upregulation of key fibrosis-related factors, such as α-smooth muscle actin, collagen I and collagen III using qRT-PCR. Thus, we predicated that CsFBPase might be a multifunctional enzyme which played as both regulatory enzyme and virulence factor in pathogenesis of C. sinensis infection.

Stage-specific expression, immunolocalization of Clonorchis sinensis lysophospholipase and its potential role in hepatic fibrosis

Lysophospholipase, belonging to the complex family of phospholipases, is supposed to play a vital role in virulence and pathogenesis of parasites and fungi. In the current study, the potential role of Clonorchis sinensis lysophospholipase (CslysoPLA) in hepatic fibrosis induced by C. sinensis was explored for the first time. In the liver of the cat infected with C. sinensis, CslysoPLA was recognized in the lumen between adult worms and surrounding bile duct epithelia together with some inside the cells by means of immunolocalization. Both Cell Counting Kit-8 (CCK-8 assay) and cell cycle analysis of human hepatic stellate cell line LX-2 showed that a higher percentage of cells were at proliferation phase after incubation with lower concentrations of recombinant CslysoPLA (rCslysoPLA). Quantitative real-time polymerase chain reaction (RT-PCR) demonstrated an upregulation in fibrogenic genes of smooth muscle α-actin, collagen III, matrix metalloproteinase 2 and tissue inhibitors of metalloproteinase II in LX-2 treated with rCslysoPLA. Moreover, human biliary epithelial cell line 5100 proliferated significantly in response to rCslysoPLA. Notably, CslysoPLA was localized in the adenomatoid hyperplastic tissue within the intrahepatic bile duct of experimentally infected rats by immunolocalization analysis. In addition, quantitative RT-PCR implied that CslysoPLA was differentially expressed at the developmental stages of C. sinensis (metacercariae, adult worms and eggs), with the highest level at metacercariae stage. Immunolocalization analysis showed that CslysoPLA was distributed in the intestine, vitelline gland, tegument and eggs in the adult worms and in the tegument and vitelline gland in the metacercariae, respectively. Collectively, it suggests that CslysoPLA might be involved in the initiation and promotion of C. sinensis-related human hepatic fibrosis and advance future studies on its promotion to C. sinensis-induced cholangiocarcinogenesis.

Molecular cloning, expression, and immunolocalization of protein disulfide isomerase in excretory-secretory products from Clonorchis sinensis

Protein disulfide isomerase (PDI) is an essential catalyst of the endoplasmic reticulum with folding and chaperone activities in different biological systems. Here, PDI of Clonorchis sinensis (CsPDI) was isolated from the cDNA library of adult C. sinensis. The open reading frame contains 1,317 bp encoding 438 amino acids and shares 53 %, 49 %, and 43 % identity with PDI from Bos taurus, Homo sapiens, and Schistosoma mansoni, respectively. Two catalytic thioredoxin motifs CxxC were found in this sequence, which were characteristic domains of thioredoxin superfamily. The CsPDI protein was expressed and purified from Escherichia coli BL21 (DE3). According to western blotting analysis, the recombinant CsPDI could be recognized by anti-CsPDI rat serum, anti-excretory/secretory products rat serum, and serum of rat infected with C. sinensis, respectively. Quantitative real-time polymerase chain reaction showed that transcription level of CsPDI in the metacercaria stage was six and four times higher than that in the adult worm and egg stage, respectively. Immunolocalization analysis showed CsPDI could be detected in the intestine, vitellarium, and intrauterine eggs of adult worm, as well as in the cyst wall and vitellarium of metacercaria. In addition, the strong fluorescence signal was observed both on the wall of bile duct and in the lumen of liver tissue of C. sinensis-infected cat. Those results demonstrated that CsPDI was a component of C. sinensis excretory-secretory products. The present study will enhance our understanding of biological functions of CsPDI and pave the way for further studies on host-parasite interaction during C. sinensis infection.

Cloning and characterization of a novel cathepsin B-like cysteine proteinase from Angiostrongylus cantonensis

Cysteine protease plays a key role in host-parasite interactions. In this study, we identified a novel gene encoding a cathepsin B-like cysteine protease (AcCBL1) from the cDNA library of Angiostrongysus cantonensis fourth-stage larvae (L4) and characterized its biological role in the parasite. Sequence and phylogeny analysis showed that AcCBL1 is related to other cathepsin B family members with the conserved catalytic triad (Cys, His, Asn) and diagnostic occluding loop. In addition, the sequence contains a specific "hemoglobinase motif" and might have a hemoglobinase (Hb)-degrading function. The recombinant AcCBL1 (rAcCBL1) exhibited the protease activity by gelation SDS/PAGE assay; rAcCBL1 can cleave the fluorogenic substrate Z-Arg-Arg-AMC, and the optimum pH was 5.5. The enzyme can hydrolyse several host proteins including Hb and human IgG in acidic pH, but low levels of hydrolysis were observed in neutral pH. Reverse transcription polymerase chain reaction revealed that AcCBL1 expression was detected throughout various developmental stages, L3, L4, adult male and female worms. Western blotting analysis indicated that AcCBL1 was an excretory/secretory product of L4 in mature form of protease. Immunolocalization demonstrated that AcCBL1 was mainly localized in the intestine of L4. These results suggest that rAcCBL1 may play an important role in the parasite nutrition uptake.

The draft genome of the carcinogenic human liver fluke Clonorchis sinensis

Background

Clonorchis sinensis is a carcinogenic human liver fluke that is widespread in Asian countries. Increasing infection rates of this neglected tropical disease are leading to negative economic and public health consequences in affected regions. Experimental and epidemiological studies have shown a strong association between the incidence of cholangiocarcinoma and the infection rate of C. sinensis. To aid research into this organism, we have sequenced its genome.

Results

We combined de novo sequencing with computational techniques to provide new information about the biology of this liver fluke. The assembled genome has a total size of 516 Mb with a scaffold N50 length of 42 kb. Approximately 16,000 reliable protein-coding gene models were predicted. Genes for the complete pathways for glycolysis, the Krebs cycle and fatty acid metabolism were found, but key genes involved in fatty acid biosynthesis are missing from the genome, reflecting the parasitic lifestyle of a liver fluke that receives lipids from the bile of its host. We also identified pathogenic molecules that may contribute to liver fluke-induced hepatobiliary diseases. Large proteins such as multifunctional secreted proteases and tegumental proteins were identified as potential targets for the development of drugs and vaccines.

Conclusions

This study provides valuable genomic information about the human liver fluke C. sinensis and adds to our knowledge on the biology of the parasite. The draft genome will serve as a platform to develop new strategies for parasite control.

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.

Molecular characterization of cathepsin B from Clonorchis sinensis excretory/secretory products and assessment of its potential for serodiagnosis of clonorchiasis

Background

Cathepsin cysteine proteases play multiple roles in the life cycle of parasites such as food uptake, immune invasion and pathogenesis, making them valuable targets for diagnostic assays, vaccines and drugs. The purpose of this study was to identify a cathepsin B of Clonorchis sinensis (CsCB) and to investigate its diagnostic value for human helminthiases.

Results

The predicted amino acid sequence of the cathepsin B of C. sinensis shared 63%, 52%, 50% identity with that of Schistosoma japonicum, Homo sapiens and Fasciola hepatica, respectively. Sequence encoding proenzyme of CsCB was overexpressed in Escherichia coli. Reverse transcription PCR experiments revealed that CsCB transcribed in both adult worm and metacercaria of C. sinensis. CsCB was identified as a C. sinensis excretory/secretory product by immunoblot assay, which was consistent with immunohistochemical localization showing that CsCB was especially expressed in the intestine of C. sinensis adults. Both ELISA and western blotting analysis showed recombinant CsCB could react with human sera from clonorchiasis and other helminthiases.

Conclusions

Our findings revealed that secreted CsCB may play an important role in the biology of C. sinensis and could be a diagnostic candidate for helminthiases.

Biliary parasites: diagnostic and therapeutic strategies

Parasitic infections of the biliary tract are a common cause of biliary obstruction in endemic areas. This article focuses on primary biliary parasites: Ascaris lumbricoides, Clonorchis sinensis, Opisthorchis viverrini, Opisthorchis felineus, Dicrocoelium dendriticum, Fasciola hepatica, and Fasciola gigantica. Tropical and subtropical countries have the highest incidence and prevalence of these infections. Diagnosis is made primarily through direct microscopic examination of eggs in the stool, duodenal, or bile contents. Radiologic imaging may show intrahepatic ductal dilatation, whereas endoscopic retrograde cholangiopancreatography can be used diagnostically and therapeutically. However, oral treatment is inexpensive and effective for most of these parasites and can prevent untoward consequences. Primary and alternative treatments are available and are reviewed in this article.

Proteomic analysis of excretory secretory products from Clonorchis sinensis adult worms: molecular characterization and serological reactivity of a excretory-secretory antigen-fructose-1,6-bisphosphatase

Clonorchis sinensis is a food-borne zoonotic parasite that resides in bile ducts and causes clonorchiasis, which may result in cholelithiasis, cholecystitis, hepatic fibrosis, and liver tumors. Although total excretory secretory products (ESP) of C. sinensis adults induce hepatic fibrosis in vivo in rats, the causative mechanism is not well understood. To study components of the ESP, C. sinensis culture medium was collected and analyzed using shotgun LC-MS/MS. We identified a total of 110 proteins, including glycometabolic enzymes (such as fructose-1,6-bisphosphatase (FBPase) and enolase), detoxification enzymes (such as glutamate dehydrogenase, dihydrolipoamide dehydrogenase and cathepsin B endopeptidase), and a number of RAB family proteins. To identify a potential causative agent for hepatic fibrosis, we expressed and purified a recombinant FBPase, a 1,041-bp gene product that encodes a 41.7-kDa protein with prototypical FBPase domains and that can form a tetramer with a molecular mass of 166.8 kDa. In addition, we found that FBPase is an antigen present in the ESP and in circulation. Immunofluorescence showed that FBPase localizes to the intestinal cecum and vitellarium in C. sinensis adults. Our results describe the components of the excretory secretory products from C. sinensis adult worms and suggest that FBPase may be an important antigen present in the ESP of C. sinensis and may lay the foundation for additional studies on the development of clonorchiasis-associated hepatic fibrosis.

Towards improved diagnosis of zoonotic trematode infections in Southeast Asia

Humans in Southeast Asia are at risk for at least 70 species of food-borne and water-borne trematodes, including blood flukes, intestinal flukes, liver flukes and lung flukes, which are shared with a great variety of animals. Co-infection with several other zoonotic trematodes is pervasive, and hence differential diagnosis represents a major challenge. Many zoonotic trematodes are commonly overlooked, leading to unreliable prevalence data, underappreciation of their veterinary and public health burden and impact, and general neglect with respect to treatment and control. Additionally, many eggs are indistinguishable by microscopy. For example, failure to address this diagnostic dilemma has resulted in overestimation of Clonorchis sinensis prevalence and underestimation of minute intestinal flukes. Test insensitivity is becoming a problem of prime interest as surveillance is gaining in importance and various control programmes now regularly register progress. Hence, the likelihood of underestimating the true burden of disease is growing in well-controlled areas when the faecal egg excretion among infected individuals approaches zero. While antibody testing has ultimate sensitivity, its use as a test of cure remains contentious. On the other hand, employing faecal egg detection as the diagnostic 'gold' standard makes many positive antibody test results (incorrectly) appear false. Polymerase chain reaction (PCR)-based diagnostics could solve this dilemma, but more experience is needed and costs must be brought down to permit large-scale use of this approach. The future development of virtual microscopy to be used for diagnosis of parasitic infections in the field could make ordinary microscopy obsolete by electronically capturing specimens at point-of-contact in remote areas.

Functional genes and proteins of Clonorchis sinensis

During the past several decades, researches on parasite genetics have progressed from biochemical and serodiagnostic studies to protein chemistry, molecular biology, and functional gene studies. Nowadays, bioinformatics, genomics, and proteomics approaches are being applied by Korean parasitology researchers. As for Clonorchis sinensis, investigations have been carried out to identify its functional genes using forward and reverse genetic approaches and to characterize the biochemical and biological properties of its gene products. The authors review the proteins of cloned genes, which include antigenic proteins, physiologic and metabolic enzymes, and the gene expression profile of Clonorchis sinensis.

Molecular characterization of a novel Clonorchis sinensis secretory phospholipase A(2) and investigation of its potential contribution to hepatic fibrosis

A gene encoding a homologue of phospholipase A(2) was identified from the Clonorchis sinensis adult cDNA plasmid library. The deduced amino acid sequence including a signal peptide that has 28-46% identity with secretory phospholipase A(2), group III (group III sPLA(2)) of other species. It also has typical features of group III sPLA(2)s including 10 cysteines, the key residues of the Ca(2+) loop and catalytic site. The recombinant protein encoded by this gene expressed in Escherichia coli showed a product of about 34kDa in SDS-PAGE. Prediction of signal peptide and Western blot analysis indicated the group III secretory phospholipase A(2) of C. sinensis (CsGIIIsPLA(2)) was an excretory-secretory product (ES product). The enzyme activity of the recombinant protein was determined using phosphatidylcholine as substrates. The result revealed that the protein was a Ca(2+)-dependent PLA(2). Both MTT test and cell cycle analysis of LX-2 showed a higher percentage of cells are in proliferation phase. Semi-quantitative RT-PCR experiments demonstrated an up-regulated expression of collagen III in these cells after incubation with the recombinant protein. We also identified that the recombinant CsGIIIsPLA(2) could bind to some membrane proteins on LX-2 cells specifically by immunofluorescence, thus there might be receptors of CsGIIIsPLA(2) on the LX-2 cell membrane. Our results suggest that CsGIIIsPLA(2) might play an important role in the initiation and development of hepatic fibrosis caused by C. sinensis.

Serodiagnostic applicability of recombinant antigens of Clonorchis sinensis expressed by wheat germ cell-free protein synthesis system

We evaluated the diagnostic applicability of recombinant proteins from Clonorchis sinensis, the human liver fluke. Four recombinant proteins, 7-kDa protein (Cs7P), 28-kDa cysteine protease (Cs28CP), and 26- and 28-kDa glutathione s-transferases (Cs26GST and Cs28GST), were expressed by wheat germ cell-free protein synthesis system. In ELISA, crude antigen showed the highest sensitivity (92.7%). However, sensitivities of r7P (47.3%), r28CP (30.9%), r26GST (21.8%), and r28GST (14.5%) were dramatically lower. The overall specificities of the crude antigen, r7P, r28CP, r26GST, and r28GST, were 100%, 94.5%, 96.7%, 94.5%, and 98.9%, respectively. Taken together, r7P and r28CP showed moderate sensitivities and high specificities, whereas r26GST and r28GST revealed low sensitivities and high specificities. We demonstrated that recombinant antigens, when used as a single antigen for ELISA, are not sensitive enough to diagnose clonorchiasis. Cocktail or chimeric antigens may be useful to increase the sensitivity of each antigen and may improve the serodiagnosis of clonorchiasis.