The identification of a Clonorchis sinensis gene encoding an antigenic egg protein

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-β 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.

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.

Identification and characterization of microRNAs in Clonorchis sinensis of human health significance

Background

Clonorchis sinensis is a zoonotic parasite causing clonorchiasis-associated human disease such as biliary calculi, cholecystitis, liver cirrhosis, and it is currently classified as carcinogenic to humans for cholangiocarcinoma. MicroRNAs (miRNAs) are non-coding, regulating small RNA molecules which are essential for the complex life cycles of parasites and are involved in parasitic infections. To identify and characterize miRNAs expressed in adult C. sinensis residing chronically in the biliary tract, we developed an integrative approach combining deep sequencing and bioinformatic predictions with stem-loop real-time PCR analysis.

Results

Here we report the use of this approach to identify and clone 6 new and 62,512 conserved C. sinensis miRNAs which belonged to 284 families. There was strong bias on families, family members and sequence nucleotides in C. sinensis. Uracil was the dominant nucleotide, particularly at positions 1, 14 and 22, which were located approximately at the beginning, middle and end of conserved miRNAs. There was no significant "seed region" at the first and ninth positions which were commonly found in human, animals and plants. Categorization of conserved miRNAs indicated that miRNAs of C. sinensis were still innovated and concentrated along three branches of the phylogenetic tree leading to bilaterians, insects and coelomates. There were two miRNA strategies in C. sinensis for its parasitic life: keeping a large category of miRNA families of different animals and keeping stringent conserved seed regions with high active innovation in other places of miRNAs mainly in the middle and the end, which were perfect for the parasite to perform its complex life style and for host changes.

Conclusions

The present study represented the first large scale characterization of C. sinensis miRNAs, which have implications for understanding the complex biology of this zoonotic parasite, as well as miRNA studies of other related species such as Opisthorchis viverrini and Opisthorchis felineus of human and animal health significance.

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.

Differential expression of Paragonimus westermani eggshell proteins during the developmental stages

Eggs of trematode parasites are comprised of numerous vitelline cells and one fertilized ovum, and are encapsulated within a protein shell provided by the vitellocytes. In this study, we isolated two full-length cDNA clones that showed substantial levels of sequence identity with trematode-specific eggshell precursor proteins from the human lung fluke, Paragonimus westermani. These cDNAs, designated Pw-Vit20 (868-bp-long) and Pw-Vit36 (883-bp-long), shared a 76% identity with one another at the nucleotide level, and each encoded a 261-amino acid (aa) polypeptide. The deduced aa sequences contained a N-terminal hydrophobic segment, as well as a sequence motif of Gly-Gly-Gly-Tyr-Asp-Asn/Thr-Tyr-Gly-Lys/Gln, which is highly homologous with the eggshell proteins of Fasciola hepatica. With the high frequencies of tyrosine, glycine and lysine, the positions occupied by tyrosine, which has been proved to be converted into dihydroxyphenylalanine, were well preserved. Pw-Vit20 and Pw-Vit36 were found to be monoexonic genes with variably diverged variants scattered into multiple genomic loci. Their protein products were localized in the vitelline follicles and eggshells. Expression of Pw-Vit20 was restricted to the egg and adult stages, thus suggesting a critical involvement of Pw-Vit20 in the parasite's fecundity activity. Conversely, Pw-Vit36 was constitutively expressed in the metacercariae and juvenile stages in the vitelline follicles and ducts, which suggested that the prepositioning of stem or primordial vitelline cells within the juveniles prior to sexual maturation. Pw-Vit36 might acquire a unique or additional function relevant to the maturation and/or development of the vitelline cells/follicles during the evolutionary period of P. westermani. Differential biological implications of multiple eggshell precursor proteins may provide insight into the molecular mechanism of eggshell formation and the developmental process of the vitelline follicles in the parasitic trematode.

Opisthorchis viverrini: identification of a glycine-tyrosine rich eggshell protein and its potential as a diagnostic tool for human opisthorchiasis

A cDNA encoding a novel eggshell protein (OvESP) with high-glycine (49.2%) and -tyrosine (27.8%) content was cloned from the human liver fluke Opisthorchis viverrini. In the adult parasite, the RNA products of the OvESP gene are limited to the vitelline follicles. They have a size of 800 nucleotides and are already present in 2-week-old juveniles. Immune sera of hamsters, experimentally infected, and humans, naturally infected with O. viverrini, detect bacterially expressed recombinant OvESP (rOvESP). A rabbit anti-rOvESP antiserum only reacts with the shells of intrauterine eggs in tissue sections of the parasite. Comparison of rOvESP with the parasite's excretion/secretion products as diagnostic tools for human opisthorchiasis shows a higher sensitivity (0.82-0.48) and specificity (0.97-0.91) of the recombinant protein in the ELISA technique. But the observed weak cross-reactivity of immune sera from mice infected with Schistosoma mansoni, Schistosoma mekongi, and Fasciola gigantica in Western blots of rOvESP indicates that the diagnostic quality of this protein might be compromised if infections by other trematodes are present.

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.