Cystatin capture enzyme-linked immunosorbent assay for serodiagnosis of human clonorchiasis and profile of captured antigenic protein of Clonorchis sinensis

Novel recombinant proteins and peptides from Clonorchis sinensis and Opisthorchis viverrini for liver fluke exposure ELISA

Human serum samples from individuals living in Vietnam and Taiwan suspected of past Clonorchis sinensis or Opisthorchis viverrini infection were screened using several novel peptides and recombinant liver fluke proteins to determine if any consistent patterns could be discerned and used as the basis for future liver fluke ELISA development. Absorbance values at 405 nm were compared to those of pooled unexposed normal human serum and analyzed for statistical significance. The data exhibited some interesting patterns consistent with egg antigen sequestration in the gut possibly leading to lower serum antibody levels and potential regional exposure differences between Vietnamese and Taiwanese subjects. In particular, antibodies against Cathepsin B and B2 peptides, as well as a partial Cahedrin Domain peptide may be elevated in some Taiwanese serum samples while antibodies against recombinant Clonorchis egg protein and Hepatocellular Carcinoma Peptide Antigen 59 may be elevated in some samples from both Taiwan and Vietnam. The data appear to suggest that some of the novel recombinant protein and peptide antigens selected and tested herein warrant further study with larger sample sizes as possible targets for detecting anti-liver fluke antibodies by ELISA from humans suspected of liver fluke infections.

Microscopic examination of gallbladder stones improves rate of detection of Clonorchis sinensis infection

To improve the rate of detection of Clonorchis sinensis infection, we compared different specimens from patients with cholecystolithiasis. Feces, gallbladder bile, and gallbladder stones collected from 179 consecutive patients with cholecystolithiasis underwent microscopic examination, and according to the results, 30 egg-positive and 30 egg-negative fecal, gallbladder bile, and gallbladder stone specimens, respectively, underwent real-time fluorescent PCR. The detection rates of eggs in feces, bile, and gallbladder stones were 30.7%, 44.7%, and 69.8%, respectively, and the differences were statistically significant (P<0.01). The PCR results confirmed that the eggs in the specimens were C. sinensis eggs. Eggs in the feces were "fresh" and in the gallbladder stones were "old." Microscopic examination of gallbladder stones may improve the detection rates of C. sinensis infection, which is important for developing individualized treatments to prevent the recurrence of gallbladder stones and to prevent the occurrence of severe liver damage and cholangiocarcinoma.

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.

Antigenic properties of cystatin-binding cysteine proteinases from Neodiplostomum seoulense

The antigenic properties of cysteine proteinases binding to cystatin were analyzed in Neodiplostomum seoulense, an intestinal trematode that infects humans and rodents in the Republic of Korea. Cystatin was found to effectively capture cysteine proteinases present in the crude extract of N. seoulense. The IgG levels against cystatin-binding cysteine proteinases in sera of mice infected with N. seoulense were higher than those in sera of mice immunized with the crude extract of N. seoulense. The production of IgG antibodies against cystatin-binding cysteine proteinases increased according to the length of infection period. In immunoblots of purified cystatin-binding proteinases, 2 molecules, approximately 50 kDa and 60 kDa, reacted with N. seoulense-infected mouse sera. Of the sera from patients infected with various helminths, those of sparganum-infected patients showed the strongest affinities for cystatin-binding cysteine proteinases of N. seoulense. Cystatin-binding cysteine proteinases of N. seoulense are suggested to be putative antigens for serodiagnosis of human N. seoulense infection.

Characterization of cysteine proteases from the carcinogenic liver fluke, Opisthorchis viverrini

Protease activities in extracts of Opisthorchis viverrini were investigated using gelatin zymography and fluorogenic peptide substrates. Using gelatin-impregnated X-ray film, 2 microg of O. viverrini excretory-secretory products (Ov-ES) and adult somatic extract (Ov-SE) showed proteolytic activity. Zymography of both O. viverrini extracts revealed bands at approximately 30 kDa. Using fluorogenic peptide substrates, the majority of O. viverrini activity was determined to be cathepsin L-like cysteine protease (cleaved Z-Phe-Arg-aminomethylcoumarin (AMC)) whereas little or no activity was ascribable to other classes of proteases. The O. viverrini cysteine protease activity was greatest at pH 6.0 and the activity was inhibited by the class-specific inhibitors, E-64 and Z-Ala-CHN2. Chromatographic purification of O. viverrini cysteine proteases on thiol-sepharose enriched for protein(s) of approximately 30 kDa from Ov-ES and Ov-SE. The activity profile of the purified enzyme was similar to that of the cathepsin L-like activity characterized in Ov-SE and Ov-ES. Furthermore, determination of cysteine protease activity in several developmental stages of the parasite revealed the highest protease activity in metacercariae soluble extract, followed by Ov-ES, egg soluble extract, and Ov-SE. These findings demonstrated that O. viverrini has a cathepsin L-like cysteine protease(s) and suggested that abundant cysteine protease activity was present in metacercariae where the hydrolase might be involved in cyst excystation during mammalian infection.

Vaccination with DNA encoding cysteine proteinase confers protective immune response to rats infected with Clonorchis sinensis

Cysteine proteinases of C. sinensis are important virulence factors that induce pathological changes associated with larval migration and localized biliary epithelial destruction. This study investigated the immunogenicity and protective efficacy of a DNA vaccine encoding Clonorchis sinensis cysteine proteinase (CsCP). The CsCP cDNA sequence displays significant homology to the mammalian or trematode cathepsin L. Plasmid DNA carrying the CsCP gene (pcDNA3.1-CsCP) was injected into Sprague-Dawley (SD) rats intradermally. Animals injected with pcDNA3.1-CsCP developed CsCP-specific antibodies, which exhibited an IgG2a dominance in sera. In addition, the DNA vaccine elicited the production of IFN-gamma, but not IL-4 in splenocytes, suggesting the induction of a typical Th-1 dominated immune response in rats. The pcDNA3.1-CsCP induced a significant level of protection (31.5%, p<0.05) in SD rats challenged with C. sinensis metacercariae. These results indicate that pcDNA3.1-CsCP induces both humoral and cellular immune responses. The CsCP gene may be a good candidate for use in future studies of vaccination against clonorchiasis.

Clonorchis sinensis: molecular cloning and localization of myosin regulatory light chain

One cDNA clone was purified from an adult Clonorchis sinensis cDNA library, and its deduced polypeptide sequence was found to be homologous with myosin regulatory light chain (MRLC) of invertebrates and vertebrates. Two amino-acid residues, Thr and Ser, were conserved at the phosphorylation sites that regulate the function of MRLCs. Recombinant C. sinensis MRLC (rCsMRLC) protein was produced and purified from Escherichia coli, and mouse anti-CsMRLC immune sera recognized a protein of molecular weight 24 kDa from a soluble protein preparation of C. sinensis. The CsMRLC protein was immunohistochemically localized to the muscle fibers of the subtegumental muscle layer and to the muscles of oral and ventral suckers. However, the rCsMRLC protein proved to be less useful antigen for the serodiagnosis of human clonorchiasis.

Immunology and molecular biology of Opisthorchis viverrini infection

Opisthorchiasis is the major public health problems in Laos PDR and Thailand. The disease becomes chronic and persists for many years, leading to hepatobiliary disease and cholangiocarcinoma. Less severe manifestations include cholangitis, chronic cholecystitis and cholelithiasis. A significant degree of humoral and cell mediated immune responses to the parasite can be detected both in patients and animal models. The patients IgG levels appear to correlate with gall bladder size and dysfunction and correlated significantly with opisthorchis egg count and decrease after treatment. However, the possible significance of these immune responses to protective immunity is presently unknown. The development of immunodiagnostic method for Opisthorchis viverrini detection has been attempted. The components with molecular weight >116, 89, 78 and 20 kDa appear to be specifically associated with the somatic extract of adult fluke. The 89 kDa protein is the most prominent component found in the in vitro culture fluid of adult worms and the metacercarial extract that can be a candidate with significant immunodiagnostic potential. Highly specific and sensitive monoclonal antibodies for O. viverrini antigens were prepared to detect parasite antigens in stool and antibody in serum. Information regarding the molecular approaches of O. viverrini is very limited. The genome of O. viverrini has neither CpG nor A methylated as found in other parasites. The total length O. viverrini ribosomal DNA is approximately 13 kb. and the presence of a highly repeated DNA specific for the parasite was demonstrated. A O. viverrini specific DNA probe was constructed and PCR based detection with high specificity for amplification of the repeated sequences is performed to detect the presence of eggs' DNA in stool samples in comparison with classical methods.

Use of a recombinant Clonorchis sinensis pore-forming peptide, clonorin, for serological diagnosis of clonorchiasis

A recombinant pore-forming peptide of Clonorchis sinensis, clonorin, was evaluated for serodiagnostic reagent of clonorchiasis by enzyme-linked immunosorbent assay detecting IgG antibody. Recombinant clonorin showed 100% specificity and low sensitivity for sera of human clonorchiasis. In contrast, C. sinensis crude antigen revealed lower specificity and higher sensitivity than recombinant clonorin did. In sera of experimental rabbits, clonorin-specific IgG antibody was increased remarkably 8 weeks after the infection and retained around level of OD(490)=0.2 for 1 year. With excellent antigenic specificity, it is suggested that the recombinant clonorin can be used as an ingredient of the cocktail antigen for serodiagnosis of clonorchiasis from early stages of the infection.