β2-Adrenergic Receptor Enhances the Alternatively Activated Macrophages and Promotes Biliary Injuries Caused by Helminth Infection

The autonomic nervous system has been studied for its involvement in the control of macrophages; however, the mechanisms underlying the interaction between the adrenergic receptors and alternatively activated macrophages (M2) remain obscure. Using FVB wild-type and beta 2 adrenergic receptors knockout, we found that β2-AR deficiency alleviates hepatobiliary damage in mice infected with C. sinensis. Moreover, β2-AR-deficient mice decrease the activation and infiltration of M2 macrophages and decrease the production of type 2 cytokines, which are associated with a significant decrease in liver fibrosis in infected mice. Our in vitro results on bone marrow-derived macrophages revealed that macrophages from Adrb2-/- mice significantly decrease M2 markers and the phosphorylation of ERK/mTORC1 induced by IL-4 compared to that observed in M2 macrophages from Adrb2+/+ . This study provides a better understanding of the mechanisms by which the β2-AR enhances type 2 immune response through the ERK/mTORC1 signaling pathway in macrophages and their role in liver fibrosis.

Recombinant CsHscB of carcinogenic liver fluke Clonorchis sinensis induces IL-10 production by binding with TLR2

BACKGROUND

Clonorchis sinensis, a fluke dwelling in the intrahepatic bile ducts causes clonorchiasis, which affect about 15 million people wide-distributed in eastern Asia. During C. sinensis infection, worm-host interaction results in activation of patterns recognition receptors (PRRs) such as Toll-like receptors (TLRs) and further triggers immune responses, which determines the outcome of the infection. However, the mechanisms by which pathogen-associated molecules patterns from C. sinensis interact with TLRs were poorly understood. In the present study, we assumed that the molecules from C. sinensis may regulate host immune responses via TLR2 signaling pathway.

METHODOLOGY/PRINCIPAL FINDINGS

In the present study, we have identified a ~34 kDa CsHscB from C. sinensis which physically bound with TLR2 as demonstrated by molecular docking and pull-down assay. We also found that recombinant CsHscB (rCsHscB) potently activates macrophage to express various proteins including TLR2, CD80, MHCII, and cytokines like IL-6, TNF-α, and IL-10, but rCsHscB failed to induce IL-10 in macrophages from Tlr2-/- mice. Moreover, ERK1/2 activation was required for rCsHscB-induced IL-10 production in macrophages. In vivo study revealed that rCsHscB triggered a high production of IL-10 in the wild-type (WT) but not in Tlr2-/- mice. Consistently, the phosphorylation of ERK1/2 was also attenuated in Tlr2-/- mice compared to the WT mice, after the treatment with rCsHscB.

CONCLUSIONS/SIGNIFICANCE

Our data thus demonstrate that rCsHscB from C. sinensis interacts with TLR2 to be endowed with immune regulatory activities, and may have some therapeutic implications in future beyond parasitology.

Oral delivery of Bacillus subtilis spores expressing Clonorchis sinensis paramyosin protects grass carp from cercaria infection

Clonorchis sinensis (C. sinensis), an important fishborne zoonotic parasite threatening public health, is of major socioeconomic importance in epidemic areas. Effective strategies are still urgently expected to prevent against C. sinensis infection. In the present study, paramyosin of C. sinensis (CsPmy) was stably and abundantly expressed on the surface of Bacillus subtilis spores. The recombinant spores (B.s-CotC-CsPmy) were incorporated in the basal pellets diet in three different dosages (1 × 10⁵, 1 × 10⁸, 1 × 10¹¹ CFU/g pellets) and orally administrated to grass carp (Ctenopharyngodon idella). The immune responses and intestinal microbiota in the treated grass carp were investigated. Results showed that specific anti-CsPmy IgM levels in sera, skin mucus, bile, and intestinal mucus, as well as mRNA levels of IgM and IgZ in the spleen and head kidney, were significantly increased in B.s-CotC-CsPmy-10¹¹ group. Besides, transcripts levels of IL-8 and TNF-αin the spleen and head kidney were also significantly elevated than the control groups. Moreover, mRNA levels of tight junction proteins in the intestines of B.s-CotC-CsPmy-10¹¹ group increased. Potential pathogenetic bacteria with lower abundance and higher abundances of candidate probiotics and bacteria associated with digestion in 1 × 10¹¹ CFU/g B.s-CotC-CsPmy spores administrated fishes could be detected compared with control group. The amount of metacercaria in per gram fish flesh was statistically decreased in 1 × 10¹¹ CFU/g B.s-CotC-CsPmy spores orally immunized group. Our work demonstrated that B. subtilis spores presenting CsPmy on the surface could be a promising effective, safe, and needle-free candidate vaccine against C. sinensis infection for grass carp.

Venom allergen-like protein 28 in Clonorchis sinensis: four epitopes on its surface and the potential role of Cys124 for its conformational stability

Venom allergen-like (VAL) proteins are important to host-parasite interactions. We previously demonstrated that a Clonorchis sinensis VAL (CsVAL) protein-derived synthetic peptide suppresses allergic and inflammatory responses. However, little is known regarding the physicochemical and antigenic properties of CsVAL proteins. Here, we identified a novel 194 amino acid VAL protein, named C. sinensis VAL 28 (CsVAL28), and characterized its functional motifs and structural details as a new member of the CAP superfamily. Unlike members of the Schistosoma mansoni VAL (SmVAL) family, CsVAL28 has a single CAP1 motif and six highly conserved disulfide bond-forming cysteines. Tertiary models of wild-type CsVAL28 and mutants were built using SmVAL4 as template via homology modeling. Normal mode analysis predicted that disulfide bond breaking by mutation of cysteine 124 to serine would greatly affect protein mobility. Four major immunoreactive linear epitopes were identified in the surface-exposed region or its vicinity via epitope mapping, using sera from clonorchiasis patients and healthy controls. Our findings provide in-depth knowledge on the structure-function properties of VAL proteins and may help determine highly antigenic regions for developing new diagnostic approaches.

TLR2 signal influences the iNOS/NO responses and worm development in C57BL/6J mice infected with Clonorchis sinensis

BACKGROUND

Although the responses of inducible nitric oxide synthase (iNOS) and associated cytokine after Clonorchis sinensis infection have been studied recently, their mechanisms remain incompletely understood. In this study, we investigated the effects of toll-like receptor 2 (TLR2) signals on iNOS/nitric oxide (NO) responses after C. sinensis infection. We also evaluated the correlations between iNOS responses and worm development, which are possibly regulated by TLR2 signal.

METHODS

TLR2 wild-type and mutant C57BL/6 J mice were infected with 60 C. sinensis metacercariae, and the samples were collected at 30, 60, 90 and 120 days post-infection (dpi). The total serum NO levels were detected using Griess reagent after nitrate was reduced to nitrite. Hepatic tissue samples from the infected mice were sliced and stained with hematoxylin and eosin (HE) to observe worm development in the intrahepatic bile ducts. The iNOS mRNA transcripts in the splenocytes were examined by real time reverse transcriptase polymerase chain reaction (qRT-PCR), and iNOS expression was detected by immunohistochemistry.

RESULTS

Developing C. sinensis juvenile worms were more abundant in the intrahepatic bile ducts of TLR2 mutant mice than those of TLR2 wild-type mice. However, no eggs were found in the faeces of both mice samples. The serum levels of total NO significantly increased in TLR2 mutant mice infected with C. sinensis at 30 (t (5) = 2.595, P = 0.049), 60 (t (5) = 7.838, P = 0.001) and 90 dpi (t (5) = 3.032, P = 0.029). Meanwhile, no changes occurred in TLR2 wild-type mice compared with uninfected controls during the experiment. The iNOS expression in splenocytes showed unexpected higher background levels in TLR2 mutant mice than those in TLR2 wild-type mice. Furthermore, the iNOS mRNA transcripts in splenocytes were significantly increased in the TLR2 wild-type mice infected with C. sinensis at 30 (t (5) = 5.139, P = 0.004), 60 (t (5) = 6.138, P = 0.002) and 90 dpi (t (5) = 6.332, P = 0.001). However, the rising of iNOS transcripts dropped under the uninfected control level in the TLR2 mutant mice at 120 dpi (t (5) = -9.082, P < 0.0001). Both total NO and iNOS transcripts were significantly higher in the TLR2 mutant mice than those in the TLR2 wild-type mice at 30 (t (5) = 3.091/2.933, P = 0.027/0.033) and 60 dpi (t (5) = 2.667/6.331, P = 0.044/0.001), respectively. In addition, the remarkable increase of iNOS expressions was immunohistochemically detected in the splenic serial sections of TLR2 wild-type mice at 30 and 60 dpi. However, the expressions of iNOS were remarkably decreased in the splenocytes of both TLR2 wild-type and mutant mice at 120 dpi.

CONCLUSIONS

These results demonstrate that TLR2 signal plays an important role in the regulation of iNOS expression after C. sinensis infection. TLR2 signal is also beneficial to limiting worm growth and development and contributing to the susceptibility to C. sinensis in which the iNOS/NO reactions possibly participate.

Oral delivery of Bacillus subtilis spores expressing cysteine protease of Clonorchis sinensis to grass carp (Ctenopharyngodon idellus): Induces immune responses and has no damage on liver and intestine function

Clonorchis sinensis (C. sinensis) is a fish-borne trematode. Human can be infected by ingestion of C. sinensis metacercariae parasitized in grass carp (Ctenopharyngodon idella). For induction of effective oral immune responses, spores of Bacillus subtilis (B. subtilis) WB600 were utilized as vehicle to delivery CsCP (cysteine protease of C. sinensis) cooperated with CotC (B.s-CotC-CP), one of coat proteins, to the gastrointestinal tract. After routine culture of 8-12 h in LB medium, B. subtilis containing CotC-CsCP was transferred into the sporulation culture medium. SDS-PAGE, western blotting and the growth curve indicated that the best sporulation time of recombinant WB600 was 24-30 h at 37 °C with continuous shaking (250 rpm). Grass carp were fed with three levels of B.s-CotC-CP (1 × 10⁶, 1 × 10⁷, and 1 × 10⁸ CFU g^-1) incorporated in the basal pellets diet. The commercial pellets or supplemented with spores just expressing CotC (1 × 10⁷ CFU g^-1) were served as control diet. Our results showed that grass carp orally immunized with the feed-based B.s-CotC-CP developed a strong specific immune response with significantly (P < 0.05) higher levels of IgM in samples of serum, bile, mucus of surface and intestinal compared to the control groups. Abundant colonization spores expressing CsCP were found in hindgut that is conducive to absorption and presentation of antigen. Moreover, B. subtilis spores appeared to show no sign of toxicity or damage in grass carp. Our cercariae challenge experiments suggested that oral administration of spores expressing CsCP could develop an effective protection against C. sinensis in fish body. Therefore, this study demonstrated that the feed-based recombinant spores could trigger high levels of mucosal and humoral immunity, and would be a promising candidate vaccine against C. sinensis metacercariae formation in freshwater fish.

Increased hepatic Th2 and Treg subsets are associated with biliary fibrosis in different strains of mice caused by Clonorchis sinensis

Previous studies showed that CD4⁺T cells responses might be involved in the process of biliary fibrosis. However, the underlying mechanism resulting in biliary fibrosis caused by Clonorchis sinensis remains not yet fully elucidated. The objectives of the present study were to investigate the different profiles of hepatic CD4⁺T cell subsets (Th1, Th2, Th17 and Treg cells) and their possible roles in the biliary fibrosis of different strains of mice (C57BL/6, BALB/c and FVB mice) induced by C. sinensis infection. C57BL/6, BALB/c and FVB mice were orally gavaged with 45 metacercariae. All mice were sacrificed on 28 days post infection in deep anesthesia conditions. The leukocytes in the liver were separated to examine CD4⁺T cell subsets by flow cytometry and the left lobe of liver was used to observe pathological changes, collagen depositions and the concentrations of hydroxyproline. The most serious cystic and fibrotic changes appeared in FVB infected mice indicated by gross observation, Masson’s trichrome staining and hydroxyproline content detection. In contrast to C57BL/6 infected mice, diffuse nodules and more intensive fibrosis were observed in the BALB/c infected mice. No differences of the hepatic Th1 subset and Th17 subset were found among the three strains, but the hepatic Th2 and Treg cells and their relative cytokines were dramatically increased in the BALB/c and FVB infected groups compared with the C57BL/6 infected group (P<0.01). Importantly, increased Th2 subset and Treg subset all positively correlated with hydroxyproline contents (P<0.01). This result for the first time implied that the increased hepatic Th2 and Treg cell subsets were likely to play potential roles in the formation of biliary fibrosis in C. sinensis-infected mice.

Immune response induced by oral delivery of Bacillus subtilis spores expressing enolase of Clonorchis sinensis in grass carps (Ctenopharyngodon idellus)

Clonorchiasis, caused by the consumption of raw or undercooked freshwater fish containing infective metacercariae of Clonorchis sinensisis (C.sinensis), remains a common public health problem. New effective prevention strategies are still urgent to control this food-borne infectious disease. The previous studies suggested Bacillus subtilis (B. subtilis) spores was an ideal vaccines delivery system, and the C.sinensis enolase (CsENO) was a potential vaccine candidate against clonorchiasis. In the current study, we detected CsENO-specific IgM levels by ELISA in sera, intestinal mucus and skin mucus in grass carps (Ctenopharyngodon idella) through oral administration with B. subtilis spores surface expressing CsENO. In addition, immune-related genes expression was also measured by qRT-PCR. Grass carps orally treated with B. subtilis spores or normal forages were used as controls. The results of ELISA manifested that specific IgM levels of grass carps in CsENO group in sera, intestine mucus and skin mucus almost significantly increased from week 4 post the first oral administration when compared to the two control groups. The levels of specific IgM reached its peak in intestine mucus firstly, then in sera, and last in skin mucus. qRT-PCR results showed that 5 immune-related genes expression had different degree of rising trend in CsENO group when compared to the two control groups. Our study demonstrated that orally administrated with B. subtilis spores expressing CsENO induced innate and adaptive immunity, systemic and local mucosal immunity, and humoral and cellular immunity. Our work may pave the way to clarify the exact mechanisms of protective efficacy elicited by B. subtilis spores expressing CsENO and provide new ideas for vaccine development against C. sinensis infection.

The Dynamics of Treg/Th17 and the Imbalance of Treg/Th17 in Clonorchis sinensis-Infected Mice

Clonorchiasis, caused by the liver fluke Clonorchis sinensis, is a chronic parasitic infection regulated by T cell subsets. An imbalance of CD4⁺CD25⁺ Foxp3⁺regulatory T (Treg) and interleukin (IL)-17-secreting T cells (Th17) may control inflammation and play an important role in the pathogenesis of immune evasion. In the present study, we assessed the dynamics of Treg/Th17 and determined whether the Treg/Th17 ratio is altered in C. sinensis-infected mice. The results showed that the percentages of splenic Treg cells in CD4⁺ T cells were suppressed on day 14 post-infection (PI) but increased on day 56 PI, while Th17 cells were increased on day 56 PI compared with normal control (NC) mice. The Treg/Th17 ratio steadily increased from day 28 to day 56 PI. The hepatic levels of their specific transcription factors (Foxp3 for Treg and RORγt for Th17) were increased in C. sinensis-infected mice from day 14 to 56 PI, and significantly higher than those in NC mice. Meanwhile, serum levels of IL-2 and IL-17 were profoundly increased in C. sinensis-infected mice throughout the experiment; while the concentrations of IL-6 and transforming growth factor β₁ (TGF-β₁) peaked on day 14 PI, but then decreased on day 28 and 56 PI. Our results provide the first evidence of an increased Treg/Th17 ratio in C. sinensis-infected mice, suggesting that a Treg/Th17 imbalance may play a role in disease outcomes of clonorchiasis.

[Characterization of a Clonorchis sinensis antigen, calmodulin, and its relationship with liver fibrosis]

OBJECTIVE

To characterize the biological function of calmodulin (CaM) from Clonorchis sinensis (C. sinensis, Cs) and investigate its role in clonorchiasis-associated hepatic fibrosis.

METHODS

The full-length sequence of CsCaM gene was isolated from Cs cDNA library and its homologues were searched using BLASTx for comparison. Bioinformatics analysis was performed to compare the homologues and predict the physiochemical characteristics and functional domains. The gene was cloned in a prokaryotic plasmid and expressed in E. coli, and the recombinant protein was purified by affinity chromatography for immunizing rats to produce polyclonal antibodies, whose titer was determined using ELISA analysis. Immunoblotting analysis was carried out to determine of the purity and antibody recognition of CsCaM. Immunofluorescence assay was employed to analyze the tissue location of the protein. A rat model of liver fibrosis was established by introperitoneal injection of the recombinant protein.

RESULTS

The recombinant CsCaM protein obtained contained 150 amino acids with a theoretical molecular mass of 23.4 kD. CsCaM homologue had EF hand motifs. The recombinant pET-30a-CsCaM plasmid expressed in BL21 E. coli was about 23.4 kD. The total IgG antibody titer in the immunized mice reached the peak level (over 1: 51200) 2 to 4 weeks after the first injection. Immunohistochemistry showed that CsCaM located in the testis of adult C. sinensis. The rats receiving intraperitoneal injection of CsCaM showed severe liver inflammation with mild to moderate liver fibrosis.

CONCLUSION

The pro-inflammation and pro-fibrosis effects of CsCaM in rat liver suggest its involvement in clonorchiasis- associated hepatic fibrosis.

Inducible nitric oxide synthase response and associated cytokine gene expression in the spleen of mice infected with Clonorchis sinensis

Clonorchis sinensis is a food-borne parasite that induces a permanent increase of nitrosation in the body upon infection. The spleen is an important secondary lymphoid organ for the regulation of immune responses locally and in the whole body. However, the functions and mechanisms of the spleen in nitric oxide (NO) responses after C. sinensis infection remain unknown. In this study, BALB/c mice were infected with 20, 40, and 80 C. sinensis metacercariae to simulate mild, moderate, and severe infections, respectively. We examined the expression of inducible nitric oxide synthase (iNOS) in the spleen and the relevant cytokine transcription in splenocytes from the mice infected with different amounts of metacercariae. The iNOS of the mice infected with 80 metacercariae was expressed in the spleen as early as 10 days post-infection (dpi) and gradually increased until 90 dpi. The iNOS expression in the mice infected with 40 metacercariae was detected only at 45 and 90 dpi, but not in the mice infected with 20 metacercariae. The level of interferon (IFN)-γ messenger RNA (mRNA) transcription in splenocytes significantly increased at 10 and 20 dpi (P < 0.05) in response to mild/moderate infection but gradually decreased to normal levels after 45 dpi. The level of IL-12p35 mRNA transcription did not change at 10 and 20 dpi but significantly decreased after 45 dpi under moderate/severe infection (P < 0.05/0.01/0.001). The level of IL-18 mRNA transcription significantly increased at 10 dpi (P < 0.05/0.01) but significantly decreased after 20 dpi (P < 0.05/0.01/0.001). These results suggest that spleen is an important organ for iNOS/NO responses, which correspond to the severity of C. sinensis infection, but cannot be attributed to the expression of the Th1 cytokines.

[Current treatments for clonorchiasis]

The paper briefly reviews the current techniques for treatment for human clonorchiasis, which are both widely used in medical practice and developed at experimental research laboratories. It describes specific examples of chemotherapy, including combined therapy, clonorchiasis vaccines and drug resistance. Particular emphasis is placed on the prospects of use of minor interfering RNA as a source of new-generation diagnostic and remedial agents.

Molecular cloning and characterization of growth factor receptor bound-protein in Clonorchis sinensis

Background

Clonorchis sinensis causes clonorchiasis, a potentially serious disease. Growth factor receptor-bound protein 2 (Grb2) is a cytosolic protein conserved among animals and plays roles in cellular functions such as meiosis, organogenesis and energy metabolism. In the present study, we report first molecular characters of growth factor receptor bound-protein (CsGrb2) from C. sinensis as counter part of Grb2 from animals and its possible functions in development and organogenesis of C. sinensis.

Methodology/Principal Findings

A CsGrb2 cDNA clone retrieved from the C. sinensis transcriptome encoded a polypeptide with a SH3-SH2-SH3 structure. Recombinant CsGrb2 was bacterially produced and purified to homogeneity. Native CsGrb2 with estimated molecular weight was identified from C. sinensis adult extract by western blotting using a mouse immune serum to recombinant CsGrb2. CsGrb2 transcripts was more abundant in the metacercariae than in the adults. Immunohistochemical staining showed that CsGrb2 was localized to the suckers, mesenchymal tissues, sperms in seminal receptacle and ovary in the adults, and abundantly expressed in most organs of the metacercariae. Recombinant CsGrb2 was evaluated to be little useful as a serodiagnostic reagent for C. sinesis human infections.

Conclusion

Grb2 protein found in C. sinensis was conserved among animals and suggested to play a role in the organogenesis, energy metabolism and mitotic spermatogenesis of C. sinensis. These findings from C. sinensis provide wider understanding on diverse function of Grb2 in lower animals such as platyhelminths.

41.5-kDa Cathepsin L protease from Clonorchis sinensis: expression, characterization, and serological reactivity of one excretory-secretory antigen

Cysteine proteases (CPs) were associated with the pathogenicity and excystment of Clonorchis sinensis. Most of them were potential antigens for the immunodiagnosis of clonorchiasis. More researches on CPs will let us know more about their functions, and further employ them for the development of more efficient diagnostic reagent and prevention strategies. In the current study, a full-length sequence encoding cathepsin L from C. sinensis (CsCL41.5) was identified from our adult cDNA library. Bioinformatic analysis showed that CsCL41.5 included typical motifs of cathepsin L (ERFNIN and GNFD motifs) and conserved amino acid positions which constituted the active center of the enzyme. The identity of its amino acid sequence with the cathepsin L of Schistosoma japonicum was 49.6 %. Recombinant CsCL41.5 (rCsCL41.5) was highly expressed in the form of inclusion body in Escherichia coli, and soluble rCsCL41.5 was obtained after purification and renaturation. Western blotting analysis indicated that CsCL41.5 is an excretory-secretory antigen of C. sinensis adult. Immunolocalization demonstrated that CsCL41.5 is distributed in the intestine and eggs in the uterus of adult worm, tegument of metacercaria, oral suck, and tail of cercaria. ELISA assays showed that IgG4 was the predominant IgG isotype responding to rCsCL41.5 in sera from clonorchiasis patients. The sensitivity and specificity of specific IgG4 detection with rCsCL41.5 was 62.5 % (15/24) and 81.7 % (49/60), respectively. It was concluded that there were differences in biological function, efficiency of serodiagnosis, and characterization of immune reactivity between CsCL41.5 and other CPs of C. sinensis, combining with previous studies.

[Cloning, expression and evaluation on effect in serological diagnosis of cysteine protease of Clonorchis sinensis]

OBJECTIVE

To clone and express the cysteine protease of Clonorchis sinensis and evaluate its effect on immunodiagnosis of human clonorchiasis.

METHODS

Based on a cysteine protease gene fragment of C. sinensis (CS-CP, GenBank accession: AF093242), a pair of primers were designed and amplified from total cDNA of C. sinensis, and the gene was cloned into plasmid pPIC9K and expressed in Pichia pastoris GS115. The expressed product was purified. Ten BALA/c mice were immunized with the purified CS-CP, and the anti CS-CP antibody in the sera of immunized mice was tested with ELISA. Finally, its effect on serodiagnosis was evaluated with Dot-ELISA and Western blot.

RESULTS

The CS-CP gene (approximately 927 bp) was successfully amplified, cloned and expressed in Pichia pastoris GS115. The sera of mice immunized with purified rCS-CP could be recognized by the soluble antigen of C. sinensis adult worms and its special anti CS-CP antibody titer was high (1: 64 000). The rCS-CP was probed by Dot-ELISA and Western-blot with sera from patients with clonorchiasis and other parasitic infections, and it had a sensitivity of 91.7% (55/60) in diagnosis of clonorchiasis and a specifity of 97.6% (82/84) for healthy population. The rCS-CP had no cross-reaction with the patients of schistosomiasis japonica, but had a cross-reactivity of 20.0% (2/10) with the patients with paragonimiasis westermani.

CONCLUSIONS

rCS-CP possesses a favorable diagnostic effect and it is a better serodiagnostic one among recombinant antigens.

Coproantigen capture ELISA for detection of Clonorchis sinensis infection in experimentally infected rats

The present study investigated the diagnostic value of an ELISA for the detection of Clonorchis sinensis antigen in the feces of experimentally infected rats. A mouse polyclonal IgG antibody against adult C. sinensis crude antigen (CsAg) was used to capture the C. sinensis coproantigen. The detection limit for pure CsAg was 20 ng/ml in sample buffer and 40 ng/ml in uninfected fecal extract. The test was evaluated using a follow-up of five groups of rats experimentally infected with 100, 50, 10, 5 and 1 metacercariae of C. sinensis and an uninfected control group. Coproantigen was detected in all infected groups of rats from 2 weeks of infection, whereas fecal eggs were not observed until 3 weeks of infection. As the infection period progressed, the fecal CsAg concentration increased in all groups of infected rats, even those infected with a single metacercaria. The fecal CsAg concentration was correlated positively with fecal egg counts and worm burden. This coproantigen capture ELISA is highly sensitive for the detection of CsAg in rat feces, and with further development, should be useful for mass screening of human subjects in clonorchiasis-endemic areas.

[Evaluation of Clonorchis sinensis PPMP I antigen Cs2 recombinant protein for immunodiagnosis of clonorchiasis]

OBJECTIVE

To develop and preliminarily evaluate two immunodiagnostic methods for clonorchiasis using Clonorchis sinensis PPMP I antigen Cs2 recombinant protein (rCs2).

METHODS

Using the soluble rCs2, an indirect ELISA and a colloidal-gold immuno-chromatography assay (GICA) dynamic flow strip was developed for detecting specific antibodies in serum. Serum samples from 35 egg-positive clonorchiasis patients, 33 healthy individuals, 15 schistosomiasis patients, 15 paragonimiasis westermani patients and 13 cysticercosis patients were examined by ELISA and GICA strip test. To further evaluate the diagnostic value of these two methods, eight New Zealand rabbits were randomly divided into infected group and treatment group. Each rabbit was infected with 600 C. sinensis metacercaria. Rabbits in treatment group were treated with praziquantel [150 mg/(kg x d) x 2d] individually at day 56 post-infection. ELISA and GICA strip test were used to observe the dynamic changes of specific antibodies against rCs2 in the two parallel groups during the period of 0-44 weeks.

RESULTS

The sensitivity, specificity and total coincidence rate determined by the ELISA method were 71.4% (25/35), 93.4% (71/76), and 86.5% (96/111), respectively, and the cross reaction with schistosomiasis, paragonimiasis and cysticercosis patients were 1/15, 1/15, and 1/13, respectively. The sensitivity, specificity and coincidence rate in the GICA strip test were 85.7% (30/35), 92.1% (70/76), and 90.1%(100/111), respectively. In C sinensis infected rabbits, antibodies level began to increase at 4 weeks after infection, peaked at the 6th week, and declined rapidly to a lower level in the 20th week, while the changing pattern of antibodies level in the treatment group was similar with that of infected group (P > 0.05). In the GICA strip test, antibodies in two groups could be detected in 4-16 weeks.

CONCLUSION

Indirect ELISA and the GICA dynamic flow strip developed in this study may be of value in the immunodiagnosis of clonorchiasis.

[Purification of Clonorchis sinensis native protein and their application in immunodiagnosis of clonorchiasis]

Lots of purified antigens have been obtained from crude antigens of Clonorchis sinensis. Some of them have applied to immunodiagnosis of clonorchiasis in laboratory. Here, we review purification methods, diagnostic efficacy and application prospect of purified antigens.

Relationships Between IgG, IgM, IgE and Resistance to Reinfection During the Early Phase of Infection withClonorchis sinensisin Rats

An enzyme linked immunosorbent assay (ELISA) was used to study the correlation between the levels of IgG, IgM and IgE immunoglobulin isotypes and resistance to reinfection in rats during the first month of infection with Clonorchis sinensis. Rats were infected with Clonorchis sinensis (primary infection), and then treated with praziquantel on the 1st, 3rd, 7th, 14th and 28th day post infection (p.i.). To measure resistance, rats were re-infected with C. sinensis (secondary infection), 2 weeks after the treatment and worms were recovered 4 weeks later. During the primary infection, significantly increased levels of IgG isotype were observed on days 14 and 28 p.i. (P < 0.001) and IgM levels were significantly increased on 3rd and 28th day (P < 0.001). During the secondary infection, significantly increased levels of IgG isotype were found from 3rd to 28th day and IgE isotype on 7th and 14th day (P < 0.01) while significant levels of IgM were found on the 3rd and 28th day (P < 0.05). Furthermore, significant differences of worm numbers between infected and control group was found on the 14th and 28th day (P < 0.001). An inverse correlation betwee the IgG levels and the resistance to re-infection was also observed (r = -0.948, P = 0.004), indicating that the resistance to reinfection is highly associated with the levels of IgG during the early phase of infection, and then with the IgM and IgE.

Clonorchis sinensis: expression, characterization, immunolocalization and serological reactivity of one excretory/secretory antigen-LPAP homologue

From a Clonorchis sinensis adult cDNA plasmid library, a cDNA clone encoding a novel lysophosphatidic acid phosphatase (LPAP) homologue was isolated. The predicted molecular weight of putative protein was 48.8 kDa and the deduced amino acid sequence had 45%, 32%, and 29% identity with LPAP of Schistosoma japonicum, Danio rerio, and Homo sapiens, respectively. Prediction of signal peptide and Western blot analysis indicated that the CsLPAP homologue was an excretory-secretory antigen (ES antigen) of C. sinensis. Immunostaining revealed that the CsLPAP was markedly localized in the intestinal cecum, seminal receptacle and eggs of the adult worm. The recombinant CsLPAP showed slightly higher sensitivity (82.14%) and specificity (85.86%) than the crude worm antigen by enzyme-linked immunosorbent assay (ELISA), a result which suggested that the recombinant antigen might be valuable in the serodiagnosis of human clonorchiasis.

Susceptibility of experimental animals to reinfection with Clonorchis sinensis

The present study observed the resistance to reinfection with Clonorchis sinensis in various experimental animals including mice, guinea pigs, rabbits, and dogs, as well as rats and hamsters. The resistance rates to reinfection in rats, mice, hamsters, guinea pigs, rabbits, and dogs were 79.7%, 58.0%, -12.6%, 54.8%, 62.6%, and 6.0%, respectively. Worms recovered from reinfected rats and mice were immature, and significantly smaller than those from the primarily infected (P < 0.01), whereas those from other animals were fully matured to adults. These findings indicate that the protective response against reinfection with C. sinensis is prominent in rats and mice, and that they may be a good animal model to investigate the mechanism of resistance to reinfection with C. sinensis.

MOLECULAR CLONING AND CHARACTERIZATION OF VITELLINE PRECURSOR PROTEIN B1 FROM CLONORCHIS SINENSIS

In trematodes, vitelline precursor proteins are required for eggshell formation. A cDNA clone of Clonorchis sinensis (CsVpB1) was selected from an EST pool, encoding a polypeptide of 245 amino acids. The CsVpB1 polypeptide demonstrated homology with vitelline precursor proteins from trematodes with high sequential identities. In a phylogenic tree, CsVpB1 clustered with trematode VpB proteins. The CsVpB1 polypeptide was found to be rich in tyrosine residues, including putative predihydroxyphenyl alanine (DOPA) residues, involved in cross-linking of the precursor proteins. Mouse immune sera were raised against a recombinant CsVpB1 protein. In adult C. sinensis, CsVpB1 protein was exclusively localized in vitelline follicles. Based on these results, the CsVpB1 cDNA is believed to encode a VpB of C. sinensis.

Resistance to reinfection in rats induced by irradiated metacercariae of Clonorchis sinensis

A study was made to observe the association between the resistance to reinfection induced by irradiated metacercariae (MC) of Clonorchis sinensis and antigen specific Th1- and Th2-type cytokine productions in rats. Rats were infected with 20 MC of C. sinensis, previously exposed to a single dose of gamma irradiation, which varied from 0 to 100 Gy. All of them, single dose of 12 Gy showed higher IgG antibody titer with lowest worm recovery. Thus, 50 MC were used to challenge infection in rats previously infected with 20 MC irradiated at 12 Gy and the highest resistance to challenge infection was observed. The results of lymphocyte proliferation with specific antigen, ES Ag were shown no difference of proliferative responses as compared with primary and challenge infection at 12 Gy irradiation dose. In the case of cytokines production were observed that interferon (IFN-gamma) and interlukin (IL-2) were significantly enhanced, while IL-4 and IL-10 was almost unchanged to make comparison between primary and secondary infection at 12 Gy irradiation dose. In conclusion, the single dose of 12 Gy could be adopted for induction of the highest resistance to challenge infection. Up-regulation of Th1 type cytokines, IFN-gamma and IL-2 may be affected to develop vaccine by irradiated MC.

Evaluation of Clonorchis sinensis recombinant 7-kilodalton antigen for serodiagnosis of clonorchiasis

The diagnostic applicability of the Clonorchis sinensis recombinant 7-kDa protein was evaluated. In enzyme-linked immunosorbent assays and immunoblots, the protein showed high sensitivities (81.3 and 71.9%, respectively) and specificities (92.6 and 89.7%, respectively) for sera obtained from various helminthic infections. Some paragonimiasis sera showed cross-reactions. The antigen might be valuable in the serodiagnosis of human clonorchiasis.

Development of resistance to reinfection by Clonorchis sinensis in rats

We investigated the induction of resistance to Clonorchis sinensis infection by prior infection in rat and hamster models. Animals were challenged with C. sinensis metacercariae, then treated with praziquantel and reinfected. Worm recovery rate in reinfected animals was used to estimate resistance to reinfection. The determined resistance rates to reinfection in rats and hamsters were 97.7% and 10.3%, respectively. In rats, cure from the primary infection of C. sinensis increased resistant to reinfection, and the greater the worm burden and the longer the duration of primary infection, the higher was the resistance rate. For primary infection doses of 10, 40 and 100 metacercariae per rat, the resistance rates were 87.4%, 93.8% and 98.4%, respectively. The resistance rates in rats after 2 or 8-week primary infection were 78.7% and 95.3%, respectively. All worms recovered from reinfected rats were immature. When cured rats were administered with methylprednisolone, resistance to reinfection became impaired. These findings indicate that rats develop a high degree of resistance to reinfection by C. sinensis after cure. The growths and maturations of reinfected worms were also impaired.

Proliferation and cytokine production of lymphocytes from Clonorchis sinensis-infected rats in response to stimulators in vitro

OBJECTIVE

To study the rat lymphocyte proliferation, differentiation and cytokine production in response to Clonorchis sinensis infection.

METHODS

The lymphocyte proliferation and cytokine production (IFN-gamma, IL-2, IL-4, IL-10) in response to mitogen phytohaemagglutinin (PHA), C. sinensis excretory-secretory antigen (ES Ag), C. sinensis crude antigen (crude Ag) and Anisakis larvae antigen were detected in vitro from splenic lymphocytes (SLC) and mesenteric lymph node cells (MLNC) of rats infected with C. sinensis. Statistical analysis was performed by Sigma Plot System.

RESULTS

Lymphocyte proliferations in MLNC were higher than that in SLC. At concentrations of 3 x 10(6) or 9 x 10(6) cells/well, lymphocyte proliferations were significantly higher in both SLS and MLNC than in the control with cell alone (P < 0.01). At the lymphocyte concentration of 5 x 10(6) cells/well and stimulator concentration of 5 or 10 micrograms/ml, significant lymphocyte activation was observed. Under the same culture condition (5 x 10(6) cells/ well with 10 micrograms/ml stimulator), cytokine IFN-gamma and IL-10 production in vitro increased significantly in MLNC.

CONCLUSION

Concentrations of 5 x 10(6) lymphocytes/well and 10 micrograms/ml stimulator were selected as the optimal culture condition for activation of lymphocyte proliferation and cytokine production. Since the production of Th1-type cytokine IFN-gamma and Th2-type cytokine IL-10 was much enhanced from MLNC of C. sinensis-infected rats, it is considered that C. sinensis ES Ag may stimulate lymphocyte proliferation and cytokine production in C. sinensis-infected rats in vivo.

Molecular expression of a cysteine proteinase of Clonorchis sinensis and its application to an enzyme-linked immunosorbent assay for immunodiagnosis of clonorchiasis

We produced a recombinant cysteine proteinase of Clonorchis sinensis and tested its value as an antigen for serologic diagnosis of C. sinensis infections. The predicted amino acid sequence of the cysteine proteinase of C. sinensis was 58, 48, and 40% identical to those of cathepsin L cysteine proteinases from Paragonimus westermani, Schistosoma japonicum, and Fasciola hepatica, respectively. Western blotting analysis showed that sera from patients infected with C. sinensis strongly reacted with the recombinant protein and that sera from patients infected with S. japonicum weakly reacted with the recombinant protein. Antibody against the recombinant protein stained proteins migrating at about 37 and 28 kDa in C. sinensis adult worm crude extracts. Immunostaining revealed that the cysteine proteinase of C. sinensis was located in the intestinal epithelial cells of the adult parasite and in intrauterine eggs. The specificity and sensitivity of the recombinant antigen or C. sinensis adult worm crude extracts were assessed by an enzyme-linked immunosorbent assay (ELISA) using serum samples from humans infected with different parasites, including 50 patients with clonorchiasis, and negative controls. The sensitivities of the ELISA with the recombinant antigen and C. sinensis adult worm crude extracts were 96 and 88%, respectively. The specificities of the ELISA with the recombinant antigen and C. sinensis adult worm crude extracts were 96.2 and 100%, respectively. The results suggested that the recombinant cysteine proteinase-based ELISA could provide a highly sensitive and specific assay for diagnosis of clonorchiasis.

[Studies on the relationship between the level of cytokine and liver function in patients with clonorchiasis sinensis]

OBJECTIVE

To explore the relationship between cytokine level and liver function among patients infected with Clonorchis sinensis.

METHODS

47 patients were divided into three groups according to the degree of Child-Pugh liver function grade: 20 in group A (3-4 scores), 15 in group B (5-6 scores) and 12 in group C (7-9 scores). Interleukin 2 (IL-2), soluble IL-2 receptor (sIL-2R), interleukin 8 (IL-8) and tumor necrosis factor (TNF-alpha) were examined by radioimmunoassay (RIA) and enzyme-linked immunosorbent assay (ELISA). Automatic biochemical analyzer was employed for the determination of serum level of total bilirubin (TBL), albumin (ALB) and alanine aminotransferase (ALT). Data were analyzed with SAS statistic software.

RESULTS

Serum levels of sIL-2R, IL-8 and TNF-alpha from patients were significantly higher than those obtained from healthy people (P<0.05, P<0.05, P<0.01), whereas the IL-2 level was significantly lower than the former (P<0.01). With the affected degree of the liver, serum levels of sIL-2R, IL-8 and TNF-alpha increased, in contrast to the decrease of IL-2 level. The differences were significant between groups A and C (P<0.05). The level of sIL-2R and TNF-alpha directly correlated with that of TBL (r=0.331 P<0.05, r=0.518 P<0.01) and ALT (r=0.475 P<0.01, r=0.285 P<0.05) respectively, but inversely correlated with the level of ALB (r=-0.319 P<0.05, r=-0.665 P<0.01).

CONCLUSION

The infection of Clonorchis sinensis results in the reduction of cellular immune function of the patients. Certain relationship exists between serum cytokine level and liver function. Two cytokines, sIL-2R and TNF-alpha, are involved in the process of pathology.

[Application of dot immunogold filtration assay for detecting serum antibodies in clonorchiasis patients]

OBJECTIVE

To establish a new, fast, sensitive and specific assay for detecting antibodies in clonorchiasis.

METHODS

Using Clonorchis sinensis adult worm antigen and SPA labelled with colloidal gold as color developing agent, a dot immunogold filtration assay (DIGFA) for detecting clonorchiasis antibodies was tested. Dot-ELISA was used as the parallel control.

RESULTS

The positive rate of DIGFA and dot-ELISA in testing the sera from 119 proved cases were 96.4% (115/119) and 92.4% (110/119), respectively, the difference between the two assays being in significant (P > 0.05). The negative rate of DIGFA in healthy people was 100% (40/40). The cross reaction rate in 20 cysticercosis cases and 25 schistosomiasis cases were 5% (1/20) and 4% (1/25), respectively. Both coincidence rates comparing DIGFA with dot-ELISA were 90.9% (50/55).

CONCLUSION

DIGFA is as sensitive and specific as the dot-ELISA, and has the advantages of simplicity and without specific equipment.

Chemotherapeutic efficacy of praziquantel in rats with protective immunity to Clonorchis sinensis infection

OBJECTIVE

To study the synergic effect of praziquantel (PZQ) and host acquired immunity on Clonorchis sinensis.

METHODS

Acquired immunity to C. sinensis was induced by immunization with crude adult worm antigen (AW Ag) and excretory-secretory antigen (ES Ag) or infection with C. sinensis metacercariae. The effect was assessed by the worm reduction rate compared with the control groups after challenge infection with 50 metacercariae and treated orally with a subcurative dose of praziquantel (50 mg/kg). Significant test was performed by analysis of variance (ANOVA) and Npar1 way Kruskal-Wallis test. All calculations were performed by PC-SAS system.

RESULTS

1. PZQ was more effective against C. sinensis larvae than against adult worms in the control (P < 0.001), ES Ag (P < 0.01) or crude AW Ag immunization group (P < 0.001). 2. As compared with the control, the worm reduction rate after challenge infection was significantly higher (P < 0.001) in ES Ag immunized group (35.6%) and metacercaria infection group (97.5%) and less in crude AW Ag group (23.4%). The PZQ efficacy was significantly enhanced in ES Ag immunized group.

CONCLUSION

The efficacy of PZQ against C. sinensis could be synergically enhanced in rats by inducing host acquired immunity.

Cytokine responses in mice infected with Clonorchis sinensis

FVB and BALB/c mice show different morbidity, development of Clonorchis sinensis, and pathological changes following C. sinensis infection. FVB mice are susceptible and BALB/c mice are relatively more resistant to C. sinensis infection. To investigate the relationship between cytokine reaction and susceptibility to C. sinensis infection in FVB and BALB/c mice, we described both the patterns and kinetics of Th1 cytokines and Th2 cytokines in spleen cell culture. Interleukin (IL)-4 and IL-10 cytokine production in the culture supernatants of the concanavalin-A-stimulated spleen cells increased at 2-3 weeks post-infection in both strains. IL-5 production increased between 2 and 5 weeks post-infection in both strains, and reached a peak level at 2 weeks post-infection in BALB/c mice and 4 weeks post-infection in FVB mice. In contrast, gamma interferon (IFN-gamma) production decreased between 2 and 4 weeks in both strains. IL-2 production increased slightly in BALB/c mice following infection, but was unchanged in FVB mice. IL-4 production over preinfection levels was significantly higher in FVB mice, whereas IFN-gamma, IL-2, and IL-10 production were significantly higher in BALB/c mice. The levels of serum immunoglobulin E (IgE) and blood eosinophils in both mouse strains significantly increased between 3 and 6 weeks postinfection. Serum IgE levels were significantly higher in FVB mice than in BALB/c mice. The results of this study suggest that susceptibility to C. sinensis infection is associated with Th2 cytokine production, especially IL-4 which is predominant in relatively susceptible FVB mice.

Excretory-secretory antigen is better than crude antigen for the serodiagnosis of clonorchiasis by ELISA

Although stool examination is the standard diagnostic method of clonorchiasis, serodiagnosis by ELISA using crude antigen is now widely used because of its convenience. However, ELISA diagnosis still suffers from cross-reactions, and therefore there is a need to improve the present conventional ELISA. The present study was undertaken to evaluate the diagnostic value of ELISA using excretory-secretory antigen (ESA) instead of crude antigen (CA) of Clonorchis sinensis. The diagnostic sensitivity of ELISA using excretory-secretory antigen was 92.5%, which was higher than that of ELISA using crude Clonorchis sinensis antigen (88.2%). In addition, the specificity of excretory-secretory antigen was found 93.1% while that of crude antigen was 87.8%. In summary, Clonorchis sinensis ESA was found to be a better serodiagnostic antigen than CA for ELISA.

Clonorchis sinensis: glutathione S-transferase as a serodiagnostic antigen for detecting IgG and IgE antibodies

Human Clonorchis sinensis infection is endemic in East Asian countries. Glutathione S-transferases (GSTs) are anti-oxidant enzymes found in all living creatures as well as in trematodes. In this study, we examined the recombinant 26kDa GST protein of C. sinensis (Cs26GST) for its serodiagnostic antigenicity toward IgG and IgE antibodies by ELISA and immuno-enhanced chemiluminescence, respectively. In IgG ELISA, recombinant Cs26GST showed 33.3% sensitivity and 100% specificity for trematode-infected human sera. In the case of the IgE antibody, recombinant Cs26GST showed 50.0% sensitivity and 93.2% specificity for clonorchiasis infection. We propose that the recombinant Cs26GST is a potent serodiagnostic antigen for detecting C. sinensis-specific IgG and IgE antibodies, and that it be best used as an antigenic cocktail in combination with other antigens.

Purification and characterization of a 7-kDa protein from Clonorchis sinensis adult worms

A 7-kDa protein was purified from extracts of adult Clonorchis sinensis by a combination of ammonium sulfate precipitation, anion exchange chromatography, cation exchange chromatography, gel-filtration chromatography, and reversed-phase FPLC. The 7-kDa protein exists in the excretory-secretory products of adult C. sinensis, but not in extracts of adult Paragonimus westermani. Also, the 7-kDa protein reacted with the sera of patients with clonorchiasis but not with paragonimiasis or normal human sera. To observe the localization of the 7-kDa protein in the tissue of adult C. sinensis, an immunogold labeling method was followed using anti-7-kDa antibody. The gold particles were observed in the basal layer below the tegumental syncytium, in the interstitial matrix of the parenchyma, and in the content of the uterus. The 7-kDa cDNA was obtained through reverse transcription-polymerase chain reaction using a primer designed from N-terminal sequence analysis. Rapid amplification of cDNA ends (5'-RACE) was used to obtain the complete protein coding sequence. The sequence encodes a 90-amino acid polypeptide. The deduced amino acid sequence of the 7-kDa protein revealed no homology with proteins of different organisms reported so far. These results suggest that the 7-kDa protein is a fluid antigen and may be valuable as a tool for the immunodiagnosis of clonorchiasis.

Characterization of partially purified 8 kDa antigenic protein of Clonorchis sinensis

The 8 kDa antigenic protein of Clonorchis sinensis was partially purified by ammonium sulfate precipitation and subsequently by a column chromatographic steps. The purified protein was separated into 7 and 8 kDa protein bands through SDS-tricine gel electrophoresis, while the protein was found to migrate to a 8 kDa band in 7.5-15% SDS-PAGE. The molecular weight of the antigen was estimated to be 110 kDa by Superose 6 HR 10/30 gel filtration. The purified antigen strongly reacted with the human sera of clonorchiasis. The hyperimmune sera of BALB/c mice immunized against the 8 kDa protein were reacted with both the crude extract and the excretory-secretory product of adult worms, but not with the metacercarial extract. Immunohistochemical staining demonstrated that the protein was distributed to the tegument and subtegumental cells and also to the seminal receptacle. The present findings suggest that the 8 kDa protein is a partition of the multicomplex protein originating from various organs of adult C. sinensis, and that it is composed of several 7 and 8 kDa proteins.

Antigenic profile and localization of Clonorchis sinensis proteins in the course of infection

In the course of Clonorchis sinensis infection, antigens presented to the hosts may be in a close relation to growth of the fluke. The antigenic proteins stimulating IgG antibody production were chronologically identified by immunoblot and localized by immunohistochemical staining. In the early stage of infection until 12 weeks post-infection (PI), antigens were proteins with molecular mass larger than 34 kDa which were derived from the tegument, testes and intrauterine eggs. After 20 weeks PI, antigens recognized were 29, 27 and 26 kDa proteins from the intestine, excretory bladder and reproductive organs. It is suggested that the tegumental proteins are the most potent antigens and the excretory-secretory proteins with middle molecular mass of 26-45 kDa contribute to the high level production of antibodies after 20 weeks of the C. sinensis infection.

Infectivity and pathological changes in murine clonorchiasis: comparison in immunocompetent and immunodeficient mice

The main complications of clonorchiasis are periportal inflammation, biliary hyperplasia, periductal fibrosis, and subsequently the development of biliary tumors in the liver. This study was undertaken to compare the infectivity and histopathologic changes between in immunocompetent FVB/NJ and BALB/cA strains, and immunodeficient severe combined immunodeficient (SCID) and athymic nude mice after the metacercariae of Clonorchis (C.) sinensis were infected. The experiment showed that C. sinensis was very infective in all strains studies, but the status of worm development, infectivity, recovery rate, and morphological changes of livers were very different in each strain. FVB/NJ mice showed more worm recovery than any other strain. Histopathologically the liver of FVB/NJ mice at 4 weeks postinfection showed marked cystic and fibrotic changes, in which C. sinensis was fully developed with ovum production, severe infiltration of inflammatory cells, mostly eosinophils, and high degrees of biliary hyperplasia. In SCID and nude mice, there were few foci of inflammatory cells even at 8 weeks postinfection in periportal areas of the liver, associated with no development into adult worm with ovum production. Fibrosis occurring at 4 weeks postinfection was highly correlated with inflammatory infiltration when each strain was compared. We suggest that massive infiltration of eosinophil and plasma cells caused by the infection might initiate cystic formation and fibrosis. These data demonstrate that the infection of C. sinensis might be related to pathologic consequences of inflammatory cell infiltration, cystic formation and fibrosis which might play a role in the defense mechanism against the parasitism in the liver of each strain. The FVB/NJ mouse model might be very helpful in elucidating the mechanism for human clonorchiasis.

Shared epitope for monoclonal IR162 between Anisakis simplex larvae and Clonorchis sinensis and cross-reactivity between antigens

IR162 is a rat monoclonal IgE antibody (mAb). In the investigation of rat IgE production, the antigens recognized by IR162 (IR-Ags) were found to be expressed by a variety of helminthic parasites. By western blot analysis, IR162 detected bands in crude extracts of Anisakis simplex larvae, Clonorchis sinensis, Paragonimus westermani, plerocercoids of Spirometra mansoni, and Toxocara canis. Excretory-secretory material from A. simplex larvae also contained a protein recognized by IR162. IR162 mAb obtained from both Serotec and Zymed recognized identical bands of A. simplex larvae. Sandwich enzyme-linked immunosorbent assay analysis indicated that both IR-Ags of A. simplex larvae (IR-As) and C. sinensis (IR-Cs) were important antigens with respect to induction of specific IgG in human infections with these 2 organisms. Even though minimal cross-reaction between IR-As and IR-Cs was observed using sera from infected individuals, these results indicate that IR-Ags are found in the parasites examined, that IR-As and IR-Cs are the antigens that induce specific antibody in natural infection, and that the epitope that binds IR162 is shared by A. simplex larvae and C. sinensis.

Comparative studies on detecting CAg in urine of acute schistosomiasis patients by mAb-RIHA and mAb-DotELISA

Urine was concentrated 20-fold for assay for CAg of Schistosoma japonicum. mAb-RIHA and mAb-DotELISA were positive in 78, 31% and 65.06% of cases respectively, of 83 patients with acute schistosomiasis. The false positive rates in 101 healthy controls were 14.85% and 0%, respectively. Cross-reactions (using mAb-RIHA) were seen in 16.36% and 14.28% of patients with clonorchiasis, 49 patients with ankylostomiasis, respectively. Corresponding figures for mAb-DotELISA were 0% and 0%.

Worm recovery and precipitin antibody response in guinea pigs and rats infected with Clonorchis sinensis

Guinea pigs (Hartley strain) and rats (Wistar strain) were each fed 200 and 100 Clonorchis sinensis metacercariae, respectively. Five animals from each species were sacrificed weekly between 1-8 weeks postinfection (WPI) and then at 12, 16, 20 and 30 WPI for collection of worms, bile and sera. The overall worm recovery rates for guinea pigs and rats were 18.7% and 12.4%, respectively. Only one of the five rats examined at 20 WPI still harbored one worm, while all were worm-free at 30 WPI. By a double diffusion test, no antibodies were detected against C. sinensis adult antigens in the bile juice. Serum antibodies were detected in at least 95% of the infected guinea pigs between 4-30 WPI and rats between 3-16 WPI. Precipitin antibodies seemed to be correlated with the presence of live worms in rats that had been infected for more than 12 weeks.

Antibodies in serum of patients with clonorchiasis before and after treatment

Sera of 31 patients infected with Clonorchis sinensis were examined using fraction 1 antigen by ELISA during a one-year observation. The results of ELISA with Igs, IgG and IgA demonstrated high sensitivity (100%, 100% and 90%) and specificity (100%, 100% and 87%). Sera specific Igs and IgG were significantly decreased in the 3rd month after treatment with praziquantel (25mg/kg body weight in one dose), and IgA was significantly decreased in the 1st month (paired t-test, p < 0.05). No eggs were found in the stool after treatment. Detection of sera specific Igs, IgG and IgA by ELISA was combined with stool examination to evaluate the effect of praziquantel and the completeness of the cure.

[Immune reactions between excretory-secretory antigens and specific antibodies of Clonorchis sinensis before and after praziquantel treatment in experimentally infected rabbits]

This study was designed to evaluate the humoral immune reactions in clonorchiasis before and after praziquantel treatment. Rabbits were infected with 150 or 450 metacercariae, treated on 4 and 8 1/2 months after infection, and observed for 13 months of posttreatment. Infection controls were maintained for 22 months. Antigen was the metabolic product of worms incubated in physiologic saline. The immune reactions of anti-Clonorchis IgG were observed using SDS-PAGE/immunoblot. During the infection and posttreatment, the antigenic proteins of 66, 63, 54, 52, 50, 47, 42, 40, 38, 34, 33, 30, 27, 25, 23, 20, 19, 18, 17, 16, 15, 14, 13, 12.5 and 11.5 kDa were detected. Of them, 33, 27, 13, and 12.5-kDa antigens were highly antigenic and observed predominantly in infection controls. After the treatment, 13 and 12.5-kDa antigens faded in 6 months after the second treatment, but 33 and 27-kDa antigens were detected until 13 months of posttreatment. The results clearly demonstrate that 13 and 12.5-kDa antigens represent attenuated host immune reactions by praziquantel treatment. As the 12.5-kDa antigen had a large amount of protein in SDS-PAGE, it was designated as 'K2-Ag' of C. sinensis.

The use of dot-immunogold-silver staining (dot-IGSS), dot-ELISA and dot-IGSS to detect serum antibodies from clonorchiasis patients: a comparative study

We report the use of immunogold-silver staining (IGSS), dot-ELISA and dot-IGSS methods in the study of clonorchiasis in China. These methods were employed to detect the antibody in sera from 40 clonorchiasis patients. The positive rates were 100%, 90.0% and 95.0%, respectively. When the three methods were used to examine 40 normal sera, the negative rates were 100%, 97.5% and 97.5%, respectively. These results suggest that IGSS, dot-ELISA and dot-IGSS are highly specific and sensitive in detecting anti-Clonorchis antibody in patients.

Detection of specific serum IgE in clonorchiasis cases and analysis of Clonorchis sinensis allergens

Specific serum IgE levels of Clonorchis sinensis in infected humans were measured by avidin-biotin ELISA, and allergens from C. sinensis were identified by immunoblot and autoradiography. Then, allergens fractionated by Sephadex G-200 gel filtration were analyzed, and cross-reactive allergenic components of C. sinensis reacted with paragonimiasis sera were revealed. Fourteen out of 15 C. sinensis egg-positives were found to be serum IgE positive (absorbance > 0.27). Of 14 IgE-reacting allergen bands visualized, major allergens of 66, 61.5, 45, 37, 28.5, 23.5 and 15.5 KD were recognized by more than 50% of the sera of infected humans. The considerable individual variations of IgE immune responses to C. sinensis allergenic components were also noticed. C. sinensis extract was separated into 5 fractions by Sephadex G-200 gel filtration. Seventy-four KD allergen was recognized in the first fraction, 50, 45, 37, 29.5 and 28.5 KD in the third, and 15.5 KD in the fourth. Cross-reactive allergens with sera of paragonimiasis cases were identified as 66, 45, 28.5, 13 and 7.5 KD.

Antibodies of different immunoglobulin isotypes in serum and bile of patients with clonorchiasis

Specimens of serum and bile from patients were assayed by an enzyme-linked immunosorbent assay to reveal antibodies specific to antigens from adult Clonorchis sinensis. Antibodies of the IgG isotype showed the greatest elevation during infection (Student's t-test, P < 0.001), whereas serum IgA and IgE and secretory IgA in bile were moderately elevated (P < 0.05). Major differences in the distribution of antibodies among the IgG subclasses were observed between patients who were and those who were not infected. IgG4 antibody levels were elevated in the serum and bile of infected patients, and there were significant correlations between the levels of IgG and IgG4 antibodies and the intensity of infection.

Attempts to transfer immunity against Clonorchis sinensis in nude and DS mice

The effects of peritoneal exudate cells (PEC) and sera of athymic nude and DS mice infected with Clonorchis sinensis metacercariae or sensitized by injection of metabolic products into footpad on transfer of immunity against the fluke to the syngeneic mice were studied. There was no significant difference in eggs per gram pattern between the sensitized and control groups, and between nude and DS mice. However, the worm burdens were slightly greater in nude mice than in DS mice. Also, a few plaque forming cells were found in only DS mice given PEC and serum from Group II DS mice. In the light of these results, it is likely that PEC and sera of nude or DS mice which are deficient, at least partially, in the cellular immune system are unable to transfer immunity against C. sinensis to syngeneic recipients.

Analysis of Clonorchis sinensis antigens and diagnosis of clonorchiasis using monoclonal antibodies

Clonorchis sinensis is a common parasite of man in Korea. Researches on the specific antigens of C. sinensis would be valuable not only because those elucidate the molecular characteristics of this fluke but also because it is applicable to immunodiagnosis. Although many monoclonal antibodies have been used in the field of parasite immunology, few articles on monoclonal antibodies against C. sinensis have been published so far. The aim of this study was to analyze C. sinensis antigens recognized by monoclonal antibodies, and to set up ELISA-inhibition test using C. sinensis specific monoclonal antibodies for improved specificity of immunodiagnostic tests. By fusion between spleen cells of the mice immunized with C. sinensis water-soluble crude adult worm antigens and plasmacytoma cells of mouse origin, 29 hybridoma clones secreting anti-C. sinensis monoclonal antibodies were made, and 8 clones among those were found specific. After cell cloning, isotypes of 6 selected specific monoclonal antibodies were determined to be IgG1, IgG2b and IgA. Four exposed antigenic determinants of natural infection were recognized by different specific monoclonal antibodies. By enzyme-immunoelectrotransfer blot, 10 KD, 34 KD antigenic determinants were found to be reacted with CsHyb 0714-20, CsHyb 0605-10 monoclonal antibodies, respectively. The antigenic determinant recognized by CsHyb 0714-20 monoclonal antibody was revealed to be located at the surface and parenchyme of a parasite by indirect immunofluorescent antibody technique, and those reacted with CsHyb 0605-10, CsHyb 0714-25 monoclonal antibodies were found at the parenchyme and intestine. The antigenic determinant reacted with CsHyb 0605-23 monoclonal antibody was found mainly around the uterine eggs. Four antigenic determinants recognized by specific monoclonal antibodies were all found to be present in the early eluted fractions of C. sinensis antigens separated by Sephadex G-200 gel filtration. By conventional ELISA, 75% of clonorchiasis cases were found positive, but 7.1% of normal controls and 37.5% of paragonimiasis cases showed false positives. However, by ELISA-inhibition test using C. sinensis specific monoclonal antibody (CsHyb 0605-23), 77.1% of clonorchiasis cases were found positive, and there were no false positives in normal controls or paragonimiasis cases, indicating 100% specificity.(ABSTRACT TRUNCATED AT 400 WORDS)

[Immunological screening of clonorchiasis]

Crude antigens of Clonorchis sinensis adult worms were purified by Sephadex G-200 column chromatography. A purified antigen was then applied to detect clonorchiasis patients and parasite-free subjects by an enzyme-linked immunosorbent assay (ELISA) and an intradermal test (IDT). The results of the ELISA showed that specific antibody levels of IgG, IgM, IgA, IgE and total IgE in 371 infected patients were significantly higher than those of 181 parasite-free subjects (Student's t-test, p less than 10(-6) or p less than 0.005). The sensitivity was 92.8% and the specificity was 89.0%. Significant correlations between the intensity of infection, expressed as egg per gram feces, and specific IgG, IgA and total IgE concentration were observed (linear regression, p less than 0.0005). Among the 309 subjects tested intradermally with Clonorchis antigen, 128 showed a positive reaction while all of the 60 parasite-free subjects showed negative results. By this test, the sensitivity was 49% and the specificity of IDT was 100%. The specific IgG, IgA and total IgE antibody levels of the IDT positive patients were significantly higher than those of the negative subjects (Student's t-test, p less than 0.0005). There was no correlation between the induced swelling diameter and the intensity of infection in IDT positive clonorchiasis patients. Cross reactions in ELISA were observed in patients infected with Capillaria philippinensis, Sparganum proliferum and Toxocara canis, when the antigens prepared in the present study were used.

Counterimmunoelectrophoresis test on human Clonorchis sinensis infection

A counterimmunoelectrophoresis test was used to detect antibodies against the adult worm antigen of Clonorchis sinensis in sera from 70 clonorchiasis patients, 20 uninfected healthy persons and 7 patients infected with other helminths. A constant voltage of 10 V/cm and a running time of 30 minutes was chosen in carrying out detection. Antibody titers of 1, 1:2 and 1:4 were obtained from 35, 21 and 14 clonorchiasis patients, respectively. Significant correlation was observed between worm burden in patients and antibody titer, the higher the antibody titer in patients, the more eggs per gram feces in their stool. Although cross reaction was observed with toxocariasis and angiostrongyliasis in this study, high (100%) sensitivity made it possible to screen the subjects in endemic areas to shorten the survey period.

A preliminary study of clinical staging in clonorchiasis

Antibody responses to infection with metacercaria of Clonorchis sinensis were studied in triplet cats. Elevated IgM antibody first appeared seven days after infection, followed by elevation of IgA and IgG. The peak titers of IgM and IgA antibodies were found at 3 weeks and 11 weeks, respectively. IgG antibody was elevated at 3 weeks and reached a peak, then a plateau at 13 weeks. Duration of antibody detection after infection was 1 week to 5 weeks for IgM, and 2 weeks to 28 weeks for IgA. IgM and IgA antibody titers decreased to normal level spontaneously without significant effect by the treatment. Using the animal model, the three clinical stages were classified according to the antibody patterns: i.e. acute stage, IgM(+) IgA(+) IgG(+); subacute stage, IgM(-) IgA(+) IgG(+); Chronic stage, IgM(-) IgA(-) IgG(+). Of 77 human patients with clonorchiasis, there were 3 (3.9%) patients who had subacute infection and 74 (96.1%) patients were in chronic stage.