A carbohydrate antigen of Clonorchis sinensis recognized by a species-specific monoclonal antibody

Parasitic infestations of the biliary tract

Parasitic infestations of the biliary tract are a common cause of biliary obstruction in tropical countries and can lead to such serious complications as cholangitis and cholangiocarcinoma. Endoscopic therapy has helped in the management of biliary complications caused by these parasites. Ascaris lumbricoides organisms, which normally reside in the jejunum, are actively motile and can invade the papilla, thus migrating into the bile duct and causing biliary obstruction. Endoscopic retrograde cholangiopancreatography is a useful diagnostic tool with potential for therapeutic management of biliary ascariasis. Infestation with Clonorchis sinensis organisms can cause such complications as intrahepatic stones, recurrent pyogenic cholangitis, cirrhosis, cholelithiasis, pancreatitis, and cholangiocarcinoma. Opisthorchis viverrini, Opisthorchis felineus, and Dicrocoelium dendriticum are closely related to C. sinensis and can also cause serious biliary complications. Fascioliasis, caused by Fasciola hepatica and F. gigantica, is a zoonotic helminthiasis that can present as acute hepatic or chronic biliary tract infection. CT, MRI, and ultrasound guidance are useful imaging tools for identifying these parasites and their complications.

Clonorchiasis: an update

Clonorchis sinensis, the Chinese or oriental liver fluke, is an important human parasite and is widely distributed in southern Korea, China (including Taiwan), Japan, northern Vietnam and the far eastern part of Russia. Clonorchiasis occurs in all parts of the world where there are Asian immigrants from endemic areas. The human and animal reservoir hosts (dogs, pigs, cats and rats) acquire the infection from the ingestion of raw fish containing infectious metacercariae. The first intermediate snail hosts are mainly species of Parafossarulus and Bithynia. Numerous species of freshwater fish serve as the second intermediate hosts of C. sinensis. Extensive studies of clonorchiasis during several decades in Japan, Korea, China and other countries have shown much progress in proving its morphological features including ultrastructure, biology, pathogenesis, epidemiology, clinical manifestations and chemotherapy. The present review deals with mainly current results obtained on the epidemiological, pathological and clinical aspects, as well as control measures in endemic areas. As for the complications of clonorchiasis, formation of calculi in the intrahepatic biliary passages is one of the most characteristic pathological features. It is sometimes accompanied by suppurative cholangitis, cholecystitis, cholangiohepatitis and ultimately can cause cholangiocarcinoma. Experimental results on the relationship to the occurrence of cholangiocarcinoma are presented. Clinical diagnosis by radiological findings including cholangiography, sonography and computerized tomography as well as magnetic resonance imaging for biliary or pancreatic ducts are outlined. Current studies on immunology and molecular biology of C. sinensis were introduced. Praziquantel is the drug of choice for clonorchiasis. The most effective regimen is 25 mg kg(-1) three times daily (total dose, 75 mg kg(-1)) administered orally at 5- to 6-h intervals over a single day. Prevention and control measures are also discussed.

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.

Molecular cloning and characterization of an antigenic protein with a repeating region from Clonorchis sinensis

In the course of immunoscreening of Clonorchis sinensis cDNA library, a cDNA CsRP12 containing a tandem repeat was isolated. The cDNA CsRP12 encodes two putative peptides of open reading frames (ORFs) 1 and 2 (CsRP12-1 and -2). The repetitive region is composed of 15 repeats of 10 amino acids. Of the two putative peptides, CsRP12-1 was proline-rich and found to have homologues in several organisms. Recombinant proteins of the putative peptides were bacterially produced and purified by an affinity chromatography. Recombinant CsRP12-1 protein was recognized by sera of clonorchiasis patients and experimental rabbits, but recombinant CsRP12-2 was not. One of the putative peptide, CsRP12-1, is designated CsPRA, proline-rich antigen of C. sinensis. Both the C-termini of CsRP12-1 and -2 were bacterially produced and analysed to show no antigenicity. Recombinant CsPRA protein showed high sensitivity and specificity. In experimental rabbits, IgG antibodies to CsPRA was produced between 4 and 8 weeks after the infection and decreased thereafter over one year. These results indicate that CsPRA is equivalent to a natural protein and a useful antigenic protein for serodiagnosis of human clonorchiasis.

Immunoblot patterns of clonorchiasis

Clonorchis sinensis is a liver fluke which is the most prevalent helminth of humans in Korea. The better diagnostic measure of clonorchiasis is required for its nationwide control program. The present study observed antigenic bands of C. sinensis and reacting immunoglobulins in serum of infected residents. Adult C. sinensis were recovered from experimentally infected rabbits and soluble crude extract of the worms was used as the antigen after supplementation of E-64, a cysteine proteinase inhibitor. SDS-PAGE of the crude antigen resolved more than 20 protein bands between 200 and 14 kDa. The sera of infected humans collected at an endemic village showed specific IgG and IgE antibodies but little IgM and IgA antibodies. The protein bands of 94, 80, 72, 68, 52, 47, 43, 37, 34, and 28-25 kDa strongly reacted with serum Ig(GMA) or IgG antibody and 64, 62, 52, 47, 44, 34, 28, and 26 kDa bands reacted with serum IgE antibody. However, the 94, 80, 72, 68, 64, 62, 52, 47, and 40 kDa bands of C. sinensis antigen were found non-specific. The protein bands of 43, 34, and 28-25 kDa of C. sinesis are primary target molecules of further analysis.