Route of entry of Clonorchis sinensis to the mammalian liver

Tracing of the Bile-chemotactic migration of juvenile Clonorchis sinensis in rabbits by PET-CT

Background

Adult Clonorchis sinensis live in the bile duct and cause clonorchiasis. It is known that the C. sinensis metacercariae excyst in the duodenum and migrate up to the bile duct through the common bile duct. However, no direct evidence is available on the in vivo migration of newly excysted C. sinensis juveniles (CsNEJs). Advanced imaging technologies now allow the in vivo migration and localization to be visualized. In the present study, we sought to determine how sensitively CsNEJs respond to bile and how fast they migrate to the intrahepatic bile duct using PET-CT.

Methodology/Principal Findings

CsNEJs were radiolabeled with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG). Rabbits with a gallbladder contraction response to cholecystokinin-8 (CCK-8) injection were pre-screened using cholescintigraphy. In these rabbits, gallbladders contracted by 50% in volume at an average of 11.5 min post-injection. The four rabbits examined were kept anesthetized and a catheter inserted into the mid duodenum. Gallbladder contraction was stimulated by injecting CCK-8 (20 ng/kg every minute) over the experiment. Anatomical images were acquired by CT initially and dynamic PET was then carried out for 90 min with a 3-min acquisition per frame. Twelve minutes after CCK-8 injection, about 3,000 ¹⁸F-FDG-labeled CsNEJs were inoculated into the mid duodenum through the catheter. Photon signals were detected in the liver 7–9 min after CsNEJs inoculation, and these then increased in the whole liver with stronger intensity in the central area, presenting that the CsNEJs were arriving at the intrahepatic bile ducts.

Conclusion

In the duodenum, CsNEJs immediately sense bile and migrate quickly with bile-chemotaxis to reach the intrahepatic bile ducts by way of the ampulla of Vater.

Clonorchis sinensis adults habituating in the bile duct cause clonorchiasis endemic in East Asian countries, in which about 15–20 million people are supposedly infected. It has previously been reported that C. sinensis metacercariae excyst in the duodenum and that the juvenile flukes migrate to the bile duct through the ampulla of Vater in 4–7 hours. Recently advanced imaging technologies have enabled visualization of movements and localizations of parasites in mammalian hosts. From present study, we found the following: newly excysted C. sinensis juveniles (CsNEJs) were efficiently in vitro radiolabeled with ¹⁸F-FDG since CsNEJs have glucose transporters; CCK-8-induced gallbladder contraction was various rabbit to rabbit; CsNEJs promptly recognized bile and migrated up the duodenum to reach the intrahepatic bile ducts by way of the ampulla of Vater and the common bile duct as early as 7–9 minutes after inoculation. Some CsNEJs responding slowly to the bile delayed arriving at the distal bile capillaries. It was visualized for the first time that the CsNEJs migrate quickly within 10–20 minutes from the duodenum to the intrahepatic bile duct. These findings provide fundamental information on the migration of parasites living in the biliary passages of mammals.

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.

Studies On Intestinal Trematodes In Korea: IX. Recovery Rate And Development Of Fibricola Seoulensis In Experimental Animals

An experimental study was carried out to observe the susceptibility of several kinds of laboratory animals to Fibricola seoulensis infection, a diplostomatid fluke of mammals. The metacercariae were obtained from the viscera of the snakes, Natrix tigrina lateralis and 50-2,000 in number each was artificially fed to a total of 127 animals; albino rats, mice, dogs, cats, rabbits and chickens. After 3 days to 8 weeks the animals were sacrificed and the recovery rate of worms as well as their maturity was observed. The results are as follows: The overall wom recovery rates throughout the experimental period was highest in albino rats(40.0 %) followed by mice(33.9%), cats(20.9 %), dogs(11.4 %), rabbits(0.05 %) and chickens(0 %). However, the recovery rates in the same host decreased as infection progressed longer and variable by the amount of metacercariae given. From albino rats and mice, the highest recovery rates were obtained in 1,000 and 200 metacercariae infection groups repectively, and it is considerd that such amount should be the optimum dose for experimental infection of these animals. The main location of F. seoulensis in experimental animals was small intestine especially the duodenum. The maturity index (No. mature worms/No. examined) was 100% in albino rats and mice, while only 22.7% or 0% in dogs or cats respectively. From the results, it is concluded that albino rats and mice are the most susceptible hosts for F. seoulensis infection among six kinds of laboratory animals examined.

Liver-fluke infection as an aetiological factor in bile-duct carcinoma of man

This paper reviews, with particular reference to Opisthorchis viverrini, the evidence that opisthorchiasis and clonorchiasis are aetiological factors in the causation of human bile-duct cancer, especially cholangiocarcinoma, and considers the other aetiological factors which may be operating. The epidemiology, pathology in man and experimental animals, and histogenesis of cholangiocarcinoma associated wtih liver-fluke infection are also considered.

Opisthorchis viverrini: partial success in adoptively transferring immunity with spleen cells and serum in the hamster

Three groups of golden Syrian hamsters received intraperitoneally either, (1) 1 x 10(7) spleen cells, (2) 0.5 ml. serum or, (3) 1 x 10(7) spleen cells plus 0.5 ml. serum, from donors infected 6 weeks previously with 25 Opisthorchis viverrini metacercariae, one day before and at the same time as challenge with 25 metacercariae. Three groups of control animals received the same quantities of spleen cells, serum or an admixture of both from normal non-infected donors in the same manner followed by challenge with 25 metacercariae. Animals were killed six weeks after challenge, livers and extrahepatic biliary systems carefully removed, and liver worm burdens estimated. Additionally, parasitic egg counts were performed on pooled faeces samples collected one hour prior to death. Animals receiving spleen cells, serum, or an admixture of both, from normal non-infected donors had mean worm burdens of 11.44, 12.00 and 12.66, respectively. Animals receiving spleen cells, serum, or both, from infected donors had mean worm burdens of 9.88, 7.77 and 12.00, respectively. There were no significant differences in mean worm burdens between control and experimental groups. However, a substantial reduction in parasitic faecal egg counts and subsequently mean egg production per worm was observed in all 3 groups of animals receiving spleen cells, serum, or both, from infected donors when compared to their respective control groups. These findings are discussed in relation to adoptive transfer studies performed with other helminths and their possible relevance to naturally acquired immunity is commented on.

[Ultrastructural Changes Of The Hepatocytes And Biliary Epithelia Due To Clonorchis Sinensis In Guinea Pigs]

The present study was undertaken to observe the changes of hepatocyte and biliary epithelium in the liver of guinea pigs infected with C. sinensis. Ten guinea pigs infected with 500 metacercariae of C. sinensis each were reared for 11 weeks. After sacrifice, the liver tissues were processed both for conventional light microscopy and for electronmicroscopy. The following results were obtained by light and electronmicroscopic observation of these tissue preparations. 1. The dilatation of bile ducts with chronic inflammatory cell infiltration and fibrosis, and flattening of lining epithelium were observed by light microscopy. Bile duct showed a single low columnar or cuboidal epithelium and subepithelial small round cell infiltration. Papillary proliferation, adenomatous hyperplasia and increase of goblet cells in the subepithelial glands were also noted in some areas of bile ducts. Occasionally, small fibrous nodules in the portal tract replacing bile ducts, surrounded by a heavy infiltrate of small round cells and neutrophils were observed. 2. On light microscopic examination, no cellular damages were seen in the liver cells except mild fatty degeneration. 3. Electronmicroscopic examination of the biliary epithelium revealed increased mucin granules, cytoplasmic projection into lumen, decreased microvilli and obstruction of bile canaliculi. Indistinct and/or irregular appearances of intercellular lateral interdigitation were observed in most of biliary epithelium. 4. On the electronmicrographs of hepatocytes, dilation of endoplasmic reticulum(ER) and destruction of cristae in some mitochondriae were prominent features. Disappearance of cytoplasmic organells and dilatation of bile canaliculi were also monitored. 5. Endothelial cells in the sinusoids were remained intact.

[Effects Of Prednisolone Injection On The Liver Of The Mouse Inoculated With The Adult Worms Of Clonorchis Sinensis Intraperitoneally]

In order to understand the effect of prednisolone injection on the histopathological changes of the mouse liver and the chronological changes of the worm structure of Clonorchis sinensis, when this fluke was inoculated to the mouse intraperitoneally. The recovery rate, survival rate, location and size of the inoculated worms as well as the histopathological changes of the liver were investigated for the comparison among the groups of mice, which were classified by number of worms and the duration of observation period. The result obtained were summarized as follows. 1. The recovery rate and survival rate of the worms decreased especially 28 days after the inoculation. 2. Most of worms (45.5%) were collected from the peritoneal cavity, and some of worms were found tightly adherent to the capsules of the liver, spleen, intestine and diaphragm. 3. The mean worm size after inoculation was constantly smaller than that before inoculation. 4. Remarkable atrophy in the reproductive organs of the worm, such as spermatheca, testes, vitelline gland and ovary was frequently observed at the 10th day of inoculation. 5. Histopathologically the liver failed to show any parasitic worm inside the intrahepatic biliary system. However, multiple well formed egg-containing granulomas were present along the liver capsule. These necrotic granulomas were occasionally found under the fibrotic liver capsule. Focal necrosis and focal phlebitis together with vascular dilatation were prominent features of the liver. 6. The worms recovered in the capsule of the liver were degenerated and necrotized. Usually, there were remarkable capsulitis and granuloma formation around the eggs.

[An Experimental Study On The Mouse Intraperitoneal Inoculation Of The Adult Worm Of Clonorchis Sinensis]

The present experimental study was undertaken to observe the chronological change of the worm structure of Clonorchis sinensis and the pathological findings of the liver when this fluke was inoculated to the mouse intraperitoneally. The recovery rate, survival rate, location and size of the inoculated worms as well as the pathological changes of the liver were investigated for the comparison among the groups of mice, classified by number of worms and the duration of experiment. The results obtained were summarized as follows: 1. The recovery and survival rates of the worms decreased especially 28 days after the inoculation. 2. Most of worms (90.l percent) were collected from the peritoneal cavity and some of worms were found tightly adherent to the capsules of the liver, spleen, stomach, intestine and diaphragm. There were no worms recovered penetrated in the parenchymes of these organs. 3. The mean worm size after inoculation was smaller than that before inoculation. At the 10th day after the inoculation, the shrinkage of posterior portion of the worm body was observed. 4. Remarkable atrophy in the reproductive organs of the worm, such as spermatheca, testes, vitelline glands and ovary was frequently observed at the 10th day of inoculation. 5. Histopathologically the liver failed to show any parasitic worm inside the intrahepatic biliary system. However, multiple well formed egg-containing granulomas were present along the liver capsule. These necrotic granulomas were occasionally found under the fibrotic liver capsule. Focal necrosis and focal phlebitis together with vascular dilatation were prominent features seen in the liver. The bile duct in the liver showed mild dilation of the lumen, flattening of epithelial cells and periductal small round cell infiltration. Neither adenomatous hyperplasia nor portal fibrosis was seen in the whole experimental groups. Foci of intralobular micro-granulomas were found in some experimental animals. 6. The worms recovered in the capsule of the liver were degenerated and necrotized. Usually, there were remarkable capsulitis and granuloma formation around the eggs.

Metabolic products of adult Clonorchis sinensis: their composition and antigenic potential

AdultClonorchis sinensiswere taken from the bile ducts of infected rabbits and incubated in Ringer's fluid. The soluble metabolic products secreted by the living flukes during incubation were found to include carbohydrate and protein. Enzyme activities of protease, carbohydrases and esterase, but not of lipase, were detected in the samples.

Samples with a nitrogen content of 3 μg/ml or more reacted as antigen in immunodiffusion tests in gel against sera of rabbits infected withC. sinensisor immunised against whole fluke extract.

The demonstration of enzymes in the metabolic products, the reactions of the samples as antigen and the correlation of antigenic activity with the nitrogen content of the samples suggests that the enzymes detected are effective antigens in clonorchiasis, although complete identity was not demonstrated in this study.

The enzymes investigated were those associated with digestion; intracellular enzymes which have less opportunity to elicit antibody production were not investigated.