Organ-specific antigens of Clonorchis sinensis

This study was carried out to find out specific proteins from different organs of Clonorchis sinensis. Crude extract, organ-specific and excretory-secretory (ES) proteins were analyzed by immunoblot with infected human sera. The bands of 7- and 17-kDa were main component of intestinal fluid and ES protein and commonly found in all organspecific proteins. The 17-kDa protein was observed from ES antigen, intestinal fluid, eggs and sperms, 26- and 28-kDa proteins were from the uterus, vitellaria, and ovary, and 34-, 37-, 43- and 50-kDa proteins were mainly from the testis and sperms. Serum of mice immunized with sperms reacted to the 50-kDa protein by immunoblotting and immunohistochemical staining showed a positive reaction at the seminal receptacle and seminiferous tubule. The present results show that the 7-kDa protein is a common antigen of every part or organ of C. sinensis, but different organs express their specific antigenic protein bands.     

Chromosomes of the liver fluke, Clonorchis sinensis

A karyological study was carried out in order to compared the chromosome numbers, chromosome morphologies and karyotypes of the oriental liver fluke, Clonorchis sinensis (Trematoda: Opisthorchiidae), collected from Korea and China. Chromosome preparations were made by means of air-drying method. The chromosome number was 2n = 56 in both Korean and Chinese flukes, and chromosomes were divided into two groups based on this size; consisting of 8 pairs of large and 20 pairs of small chromosomes. However, the karyotypes showed some differences between Korean and Chinese flukes. The karyotype of liver flukes from Korea consisted of three metacentric pairs, one meta-/submetacentric pair, 16 submetacentric pairs and eight subtelocentric pairs of chromosomes. On the other hand, liver flukes from China consisted of two metacentric pairs, two meta-/submetacentric pairs, 16 submetacentric pairs and eight subtelocentric pairs of chromosomes.     

Clonorchis sinensis and clonorchiasis, an update

Clonorchis sinensis is the most common human liver fluke in East Asia. Several studies proved its carcinogenesis in humans and it was reclassified as a group 1 biological carcinogen in 2009. It is still actively transmitted in endemic areas of Korea, China, Russia, and Vietnam. Currently it is estimated that more than 200 million people are at risk of infection, 15-20 million people are infected and 1.5-2 million show symptoms or complications. Several molecules and genes of the fluke have been identified and characterized. Studies on its oncogenesis and omics-based findings have been especially encouraging. Diagnosis of its infection depends mainly on detection of eggs in feces but other methods have been developed. ELISA using crude extract antigen is now popular for its diagnosis. Diagnosis by detecting DNAs from eggs in feces has been developed using PCR, real-time PCR, and LAMP, which have been found sensitive and specific. Imaging diagnosis has been studied in depth and is widely used. Any evidence of clonorchiasis, such as eggs, DNAs, or images, may lead to recommendations of chemotherapy in endemic areas. Praziquantel is the major chemotherapeutic agent for clonorchiasis and recently tribendimidine was found effective and is now under investigation as a promising chemotherapeutic alternative. Sustainable control programs which include mass chemotherapy with praziquantel and education for prevention of re-infection may reduce its morbidity and eliminate its infections in endemic areas.     

Identification and Molecular Characterization of Parkin in Clonorchis sinensis

Clonorchis sinensis habitating in the bile duct of mammals causes clonorchiasis endemic in East Asian countries. Parkin is a RING-between-RING protein and has E3-ubiquitin ligase activity catalyzing ubiquitination and degradation of substrate proteins. A cDNA clone of C. sinensis was predicted to encode a polypeptide homologous to parkin (CsParkin) including 5 domains (Ubl, RING0, RING1, IBR, and RING2). The cysteine and histidine residues binding to Zn²⁺ were all conserved and participated in formation of tertiary structural RINGs. Conserved residues were also an E2-binding site in RING1 domain and a catalytic cysteine residue in the RING2 domain. Native CsParkin was determined to have an estimated molecular weight of 45.7 kDa from C. sinensis adults by immunoblotting. CsParkin revealed E3-ubiquitin ligase activity and higher expression in metacercariae than in adults. CsParkin was localized in the locomotive and male reproductive organs of C. sinensis adults, and extensively in metacercariae. Parkin has been found to participate in regulating mitochondrial function and energy metabolism in mammalian cells. From these results, it is suggested that CsParkin play roles in energy metabolism of the locomotive organs, and possibly in protein metabolism of the reproductive organs of C. sinensis.     

Antigenic profile and localization of Clonorchis sinensis proteins in the course of infection.

In the course of Clonorchis sinensis infection, antigens presented to the hosts may be in a close relation to growth of the fluke. The antigenic proteins stimulating IgG antibody production were chronologically identified by immunoblot and localized by immunohistochemical staining. In the early stage of infection until 12 weeks post-infection (PI), antigens were proteins with molecular mass larger than 34 kDa which were derived from the tegument, testes and intrauterine eggs. After 20 weeks PI, antigens recognized were 29, 27 and 26 kDa proteins from the intestine, excretory bladder and reproductive organs. It is suggested that the tegumental proteins are the most potent antigens and the excretory-secretory proteins with middle molecular mass of 26-45 kDa contribute to the high level production of antibodies after 20 weeks of the C. sinensis infection.     

Characterization of partially purified 8 kDa antigenic protein of Clonorchis sinensis

The 8 kDa antigenic protein of Clonorchis sinensis was partially purified by ammonium sulfate precipitation and subsequently by a column chromatographic steps. The purified protein was separated into 7 and 8 kDa protein bands through SDS-tricine gel electrophoresis, while the protein was found to migrate to a 8 kDa band in 7.5-15% SDS-PAGE. The molecular weight of the antigen was estimated to be 110 kDa by Superose 6 HR 10/30 gel filtration. The purified antigen strongly reacted with the human sera of clonorchiasis. The hyperimmune sera of BALB/c mice immunized against the 8 kDa protein were reacted with both the crude extract and the excretory-secretory product of adult worms, but not with the metacercarial extract. Immunohistochemical staining demonstrated that the protein was distributed to the tegument and subtegumental cells and also to the seminal receptacle. The present findings suggest that the 8 kDa protein is a partition of the multicomplex protein originating from various organs of adult C. sinensis, and that it is composed of several 7 and 8 kDa proteins.     

Partial characterization of a 17 kDa protein of Clonorchis sinensis

A 17 kDa protein from Clonorchis sinensis adults was purified by a procedure including Sephacryl S-200 HR gel filtration and Q-Sepharose anion exchange chromatography. The protein was proved to be a cysteine protease as it showed hydrolytic activity toward Cbz-Phe-Arg-AMC in the presence of dithiothreitol and was inhibited by specific inhibitors such as iodoacetic acid or trans epoxy-succinly-L-leucyl-amido(4-guanidino) butane. The polyclonal antibody raised against the protein reacted to 17 kDa proteins of trematodes such as Paragonimus westermani, Fasciola hepatica, Opisthorchis viverrini, Gymnophalloides seoi, and Metagonimus yokogawai. The antibody recognized the 17 kDa and 16 kDa cysteine proteases purified from C. sinensis, P. westermani, and G. seoi as well. These results suggest that the 17 kDa protein may be a cysteine protease commonly present in trematodes.     

Cloning of a pore-forming subunit of ATP-sensitive potassium channel from Clonorchis sinensis

A complete cDNA sequence encoding a pore-forming subunit (Kir6.2) of ATP-sensitive potassium channel in the adult worm, Clonorchis sinensis, termed CsKir6.2, was isolated from an adult cDNA library. The cDNA contained a single open-reading frame of 333 amino acids, which has a structural motif (a GFG-motif) of the putative pore-forming loop of the Kir6.2. Peculiarly, the CsKir6.2 shows a lack-sequence structure, which deleted 57 amino acids were deleted from its N-terminus. The predicted amino acid sequence revealed a highly conserved sequence as other known other Kir6.2 subunits. The mRNA was weekly expressed in the adult worm.     

Infection Status of Freshwater Fish with Metacercariae of Clonorchis sinensis in Korea

This study investigated freshwater fish for their current infection status with metacercariae of Clonorchis sinensis in Korea. Twenty-one species of freshwater fish (n = 677) were collected from 34 regions nationwidely from February 2007 to June 2008. They were individually examined by digestion technique. Eight species of freshwater fish from 17 different regions were recognized positive for the metacercariae of C. sinensis. The positive rates (range of metacercariae number per fish) of fish by the species were as follows: 48% (1-1,142) in Pseudorasbora parva, 60% (1-412) in Pungtungia herzi, 15.7% (1-23) in Pseudogobio esocinus, 29% (1-7) in Acheilognathus intermedia, 21% (1-4) in Odontobutis interrupta, 33% (1-6) in Zacco temmincki, 3.6% (1-4) in Zacco platypus, and 26.3% (1) in Hemibarbus labeo. The two species, P. parva and P. herzi, are able to be the index fish for estimation of C. sinensis transmission in a certain locality. Still several species of freshwater fish are briskly transmitting C. sinensis infection in many riverside areas of southern Korea.     

Molecular Cloning and Characterization of a Paramyosin from Clonorchis sinensis

Paramyosin is a myofibrillar protein present in helminth parasites and plays multifunctional roles in host-parasite interactions. In this study, we identified the gene encoding paramyosin of Clonorchis sinensis (CsPmy) and characterized biochemical and immunological properties of its recombinant protein. CsPmy showed a high level of sequence identity with paramyosin from other helminth parasites. Recombinant CsPmy (rCsPmy) expressed in bacteria had an approximate molecular weight of 100 kDa and bound both human collagen and complement 9. The protein was constitutively expressed in various developmental stages of the parasite. Imunofluorescence analysis revealed that CsPmy was mainly localized in the tegument, subtegumental muscles, and the muscle layer surrounding the intestine of the parasite. The rCsPmy showed high levels of positive reactions (74.6%, 56/75) against sera from patients with clonorchiasis. Immunization of experimental rats with rCsPmy evoked high levels of IgG production. These results collectively suggest that CsPmy is a multifunctional protein that not only contributes to the muscle layer structure but also to non-muscular functions in host-parasite interactions. Successful induction of host IgG production also suggests that CsPmy can be applied as a diagnostic antigen and/or vaccine candidate for clonorchiasis.     

Development of resistance to reinfection by Clonorchis sinensis in rats

We investigated the induction of resistance to Clonorchis sinensis infection by prior infection in rat and hamster models. Animals were challenged with C. sinensis metacercariae, then treated with praziquantel and reinfected. Worm recovery rate in reinfected animals was used to estimate resistance to reinfection. The determined resistance rates to reinfection in rats and hamsters were 97.7% and 10.3%, respectively. In rats, cure from the primary infection of C. sinensis increased resistant to reinfection, and the greater the worm burden and the longer the duration of primary infection, the higher was the resistance rate. For primary infection doses of 10, 40 and 100 metacercariae per rat, the resistance rates were 87.4%, 93.8% and 98.4%, respectively. The resistance rates in rats after 2 or 8-week primary infection were 78.7% and 95.3%, respectively. All worms recovered from reinfected rats were immature. When cured rats were administered with methylprednisolone, resistance to reinfection became impaired. These findings indicate that rats develop a high degree of resistance to reinfection by C. sinensis after cure. The growths and maturations of reinfected worms were also impaired.     

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.     

Ultrastructural localization of 28 kDa glutathione S-transferase in adult Clonorchis sinensis

Glutathione S-transferase (28GST) with molecular mass of 28 kDa is an antioxidant enzyme abundant in Clonorchis sinensis. In adult C. sinensis, 28GST was localized in tegumental syncytium, cytons, parenchyma, and sperm tails examined by immunoelectron microscopy. C. sinensis 28GST was earlier found to neutralize bioreactive compounds and to be rich in eggs. Accordingly, it is suggested that 28GST plays important roles in phase II defense system and physiological roles in worm fecundity of C. sinensis.     

Bile duct changes in rats reinfected with Clonorchis sinensis

This study describes an evaluation of the sonographic, cholangiographic, pathological, and immunological findings, and the protective effect shown by rats reinfected with Clonorchis sinensis. Eight experimental rat groups were, namely, a normal control, a primary infection control, a reinfection I (reinfection 7 week after treatment following 3-week infection), a reinfection II (reinfection 2 week after treatment following 8-week infection), a reinfection III (exploration of the intrahepatic bile ducts 1 week after reinfection 4 week after treatment following 4-week infection), a superinfection, a secondary infection control, and an infection following immunization group. Sonographic and cholangiographic findings showed moderate or marked dilatation of the bile duct confluence in the primary infection control, reinfection II, and secondary infection control groups. Juvenile worms survived in the intrahepatic bile ducts 1 week after reinfection following treatment in the reinfection III group. It was concluded that reinfecting juvenile worms found during the first week following reinfection failed to survive or grow further. Anatomical, pathophysiological, or immunological changes may induce protection from reinfection in rats.     

Metacercarial proteins interacting with WD40-repeat protein of Clonorchis sinensis

The WD40-repeat proteins serve as a platform coordinating partner proteins and are involved in a range of regulatory cellular functions. A WD40-repeat protein (CsWD1) of Clonorchis sinensis previously cloned is expressed stage-specifically in the tegumental syncytium of C. sinensis metacercariae. In the present study, interacting proteins with the CsWD1 protein was purified by immunoprecipitation and 2 dimension gel electrophoresis from the C. sinensis metacercaria soluble extract, and tryptic peptides were analyzed by LC/ESI-MS. Putative partner proteins were annotated to be actin-2, glyceraldehyde-3-phosphate dehydrogenase, and hypothetical and unmanned proteins. The CsWD1 protein was predicted to contain 3 conserved actin-interacting residues on its functional surface. With these results, the CsWD1 protein is suggested to be an actin-interacting protein of C. sinensis.     

Susceptibility of experimental animals to reinfection with Clonorchis sinensis

The present study observed the resistance to reinfection with Clonorchis sinensis in various experimental animals including mice, guinea pigs, rabbits, and dogs, as well as rats and hamsters. The resistance rates to reinfection in rats, mice, hamsters, guinea pigs, rabbits, and dogs were 79.7%, 58.0%, -12.6%, 54.8%, 62.6%, and 6.0%, respectively. Worms recovered from reinfected rats and mice were immature, and significantly smaller than those from the primarily infected (P < 0.01), whereas those from other animals were fully matured to adults. These findings indicate that the protective response against reinfection with C. sinensis is prominent in rats and mice, and that they may be a good animal model to investigate the mechanism of resistance to reinfection with C. sinensis.     

Collection of Clonorchis sinensis adult worms from infected humans after praziquantel treatment

A cohort was established for evaluation of cancer risk factors in Sancheong-gun, Gyeongsangnam-do, Korea. As one of the cohort studies, stools of 947 residents (403 males and 544 females, age range: 29-86 years) were screened for Clonorchis sinensis eggs using both Kato-Katz method and formalin-ether sedimentation technique. The overall egg positive rate of C. sinensis was 37.7% and individual EPG (eggs per gram of feces) counts ranged from 24 to 28,800. Eight egg positive residents voluntarily joined a process of collection of the passed worms after praziquantel treatment. A total of 158 worms were recovered from 5 of the 8 treated persons, ranged from 3 to 108 in each individual. The worms were 15-20 mm x 2-3 mm in size, and showed brown-pigmented, red, or white body colors. This is the first collection record of C. sinensis adult worms from humans through anthelmintic treatment and purgation. The adult worms of C. sinensis may be paralyzed by praziquantel and then discharged passively through bile flow in the bile duct and by peristaltic movement of the bowel.     

Infection status of Clonorchis sinensis in residents of Hamyang-gun,Gyeongsangnam-do,Korea

Oriental liver fluke (Clonorchis sinensis) infection was surveyed among residents of Hamyang-gun, Gyeongsangnam-do, Korea during the period of January 2001 to March 2002. Total 1,041 stool samples were collected from residents who visited Public Health Center and its branches in Hamyang-gun and examined using formalin-ether sedimentation method. The overall egg positive rate was 16%, male showing higher positive rate (21%) than female (10%). The age group of 30 to 50 years had the highest egg positive rate of C. sinensis from 20% to 22%. The positive examinees were treated with praziquantel and educated individually to prevent reinfection. Egg positive rate in this area was decreased when compared with results recorded in the past, however, still remained more than 10%. This study suggests that periodic examination, treatment as well as education of residents should be continued and systematized.     

Specific and common antigens of Clonorchis sinensis and Opisthorchis viverrini(Opisthorchidae,Trematoda)

The antigenic characterizations and serological reactions of human liver flukes, Clonorchis sinensis and Opisthorchis viverrini, were analyzed by immunoblot. The antigenic profiles of the crude extract of Clonorchis contained major proteins of 8, 26-28, 34-37, 43, and 70 kDa, and those of Opisthorchis 34-37, 43, 70, and 100 kDa. Of these, the 8, 26-28 and 34-37 kDa bands of Clonorchis and the 100 kDa of Opisthorchis were major components of each excretory-secretory antigen. The 8 and 26-28 kDa bands were specific to Clonorchis but the 100 kDa of Opisthorchis cross-reacted with the sera of clonorchiasis, and the 34-37, 70 and 100 kDa bands cross-reacted with sera of other helminthiases. The frequency and intensity of the immunoblot reactions were positively correlated with the intensity of the liver fluke infection.     

Variation of nuclear and mitochondrial DNAs in Korean and Chinese isolates of Clonorchis sinensis

We compared the DNA sequence difference of isolates of Clonorchis sinensis from one Korean (Kimhae) and two Chinese areas (Guangxi and Shenyang). The sequences of nuclear rDNA (18S, internal transcribed spacer 1 and 2: ITS1 and ITS2) and mitochondrial DNA (cytochrome c oxidase subunit 1: cox1) were compared. A very few intraspecific nucleotide substitution of the 18S, ITS1, ITS2 and cox1 was found among three isolates of C. sinensis and a few nucleotide insertion and deletion of ITS1 were detected. The 18S, ITS1, ITS2 and cox1 sequences were highly conserved among three isolates. These findings indicated that the Korean and two Chinese isolates are similar at the DNA sequence level.