Functional Genes and Proteins of Clonorchis sinensis

Abstract

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. CHROMOSOMES AND GEOGRAPHICAL ISOLATESC. sinensis has 2n = 56 chromosomes, where n consists of 8 large and 20 small chromosomes. C. sinensis geographical isolates collected in Korea and northeastern China (Liaoning Province) have all demonstrated the same chromosome number, but different karyotypes. Specifically, Korean isolates have 3 metacentric and 1 meta-/submetacentric pairs, whereas Chinese isolates have 2 and 2 pairs, respectively. The 2 isolates have same number, 16 and 8, of submetacentric and subtelomeric pairs [13].Genetic relationships between geographical isolates have been studied by employing sequence analyses of nuclear ribosomal DNA (18S, internal transcribed spacer 1 and 2; ITS1 and ITS2) and mitochondrial DNA (cytochrome c oxidase subunit 1 [CO-1]). C. sinensis Korean isolates collected in Kimhae city were compared with Chinese isolates collected in Shenyang, Liaoning and Nanning, and Guangxi provinces. The geographical isolates were nearly identical in terms of nuclear ribosomal and mitochondrial DNA sequences, and revealed no more than a 1% sequence difference between Korean and Chinese isolates [14][15][16][17]. Isozyme electrophoresis had been used to study trematode systematics, and isozymes of the Korean and Chinese isolates show homozygous monomorphic banding patterns. Furthermore, alpha-glycerophosphate dehydrogenase produced a unique band pattern and was found to differentiate geographical isolates of C. sinensis [14]. However, in C. sinensis, intraspecific genetic variations among geographical isolates in the SinoKorea region appear minimal.As compared with O. viverrini, C. sinensis ITS2 revealed 95% identity and differences at 28 nucleotide points. Furthermore, the mitochondrial CO1 gene of O. viverrrini was found to be 96% identical with that of C. sinensis. Even a different genus in the same family Opisthorchidae, namely, O viverrrini appears to be genetically close to C. sinensis [17].

Current status and perspectives of Clonorchis sinensis and clonorchiasis: epidemiology, pathogenesis, omics, prevention and control

“…The detection of a specific antibody is more often applied than the detection of an antigen due to the trace amount of antigen present and sensitivity limitations, although Nie et al showed that an IgY (egg yolk immunoglobulin)-based immunomagnetic bead enzyme linked immunosorbent assay (ELISA) system (IgY-IMB-ELISA) appears to be a sensitive and specific assay for the detection of circulating antigen in human clonorchiasis and a significant correlation has been found between ELISA optical density and egg counts (EPG) [ 31 ]. Crude extracts of C. sinensis are considered sufficiently sensitive for the serodiagnosis of clonorchiasis, but cross-react with other trematodes [ 13 , 32 ]. Regarding the source and standardization of crude extracts, many purified recombinant proteins from the tegument or excretory/secretory proteins (ESPs) of the worm such as the 21.1-kDa tegumental protein, cathepsin L proteinase, cysteine protease, and a fragment of paramyosin ( Cs PmyC-2) [ 33 – 36 ] have been evaluated regarding their potential role in diagnosis.…”

Molecular characterization of Clonorchis sinensis tetraspanin 2 extracellular loop 2

“…Serologic method using soluble crude lysate and excretory-secretory products of adult worm or specific single antigens is an alternative and complementary diagnostic method. As reviewed by Kim et al (2009), glycinerich protein, proline-reach antigen, myoglobin, lysophosphatidic acid phosphatase, lysophospholipase, fatty acid binding protein, and cysteine proteinases have been studied as putative serodiagnostic single antigens. However, some of them have limited sensitivities and specificities.…”

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

“…It is difficult to produce a sufficient amount of CsESPs for serodiagnostic testing. Several recombinant proteins such as 7-kDa protein, CsEF-1α, 28-kDa cysteine protease, and 26-kDa and 28-kDa glutathione S-transferases of C. sinensis have shown relatively PLOS NEGLECTED TROPICAL DISEASES higher specificity than the C. sinensis crude extracts or ESPs for the serodiagnosis of clonorchiasis, but not sufficient sensitivity [17,33]. As alternatives, cocktails of multiple recombinant antigens and recombinant chimeric multi-epitope antigens were applied to enhance the antigenicity/sensitivity over single molecules [17][18][19].…”

“…These diagnostics, however, have low specificity and low sensitivity. Antigenic proteins have been identified from the excretory-secretory products (ESP) of C. sinensis [17]. The enzyme-linked immunosorbent assay (ELISA) using ESP as the antigen are more sensitive and specific than those using crude antigen.…”

“…As single antigens for serodiagnosis of human clonorchiasis, the defined antigenic proteins have high specificity, but low sensitivity, especially toward the patients with low worm burden PLOS NEGLECTED TROPICAL DISEASES [17]. Hence, researches have been focused to identify effective serodiagnostic antigens for clonorchiasis.…”