Synthesis of oxadiazole-2-oxide derivatives as potential drug candidates for schistosomiasis targeting SjTGR.

BACKGROUND: Schistosomiasis is a chronic parasitic disease that affects millions of people's health worldwide. Because of the increasing drug resistance to praziquantel (PZQ), which is the primary drug for schistosomiasis, developing new drugs to treat schistosomiasis is crucial. Oxadiazole-2-oxides have been identified as potential anti-schistosomiasis reagents targeting thioredoxin glutathione reductase (TGR). METHODS: In this work, one of the oxadiazole-2-oxides derivatives furoxan was used as the lead compound to exploit a series of novel furoxan derivatives for studying inhibitory activity against both recombinant Schistosoma japonicum TGR containing selenium (rSjTGR-Sec) and soluble worm antigen protein (SWAP) containing wild-type Schistosoma japonicum TGR (wtSjTGR), in order to develop a new leading compound for schistosomiasis. Thirty-nine novel derivatives were prepared to test their activity toward both enzymes. The docking method was used to detect the binding site between the active molecule and SjTGR. The structure-activity relationship (SAR) of these novel furoxan derivatives was preliminarily analyzed. RESULTS: It was found that several new derivatives, including compounds 6a-6d, 9ab, 9bd and 9be, demonstrated greater activity toward rSjTGR-Sec or SWAP containing wtSjTGR than did furoxan. Interestingly, all intermediates bearing hydroxy (6a-6d) showed excellent inhibitory activity against both enzymes. In particular, compound 6d with trifluoromethyl on a pyridine ring was found to have much higher inhibition toward both rSjTGR-Sec (half-maximal inhibitory concentration, IC50,7.5nM) and SWAP containing wtSjTGR (IC50 55.8nM) than furoxan. Additionally, the docking method identified the possible matching sites between 6d and Schistosoma japonicum TGR (SjTGR), which theoretically lends support to the inhibitory activity of 6d. CONCLUSION: The data obtained herein showed that 6d with trifluoromethyl on a pyridine ring could be a valuable leading compound for further study.

Therapeutic potential of fucoidan in the reduction of hepatic pathology in murine schistosomiasis japonica.

BACKGROUND: Hepatic granuloma formation and fibrosis as the consequence of tissue entrapped eggs produced by female schistosomes characterize the pathology of Schistosoma japonicum infection. It has been proposed that fucoidan, a sulfated polysaccharide existing naturally in brown seaweed Fucus vesiculosus, plays a diversified role to perform immunomodulatory activities. However, whether fucoidan functions in the host hepatic pathology is unknown and identifying the potential mechanism that is responsible for hepatic improvement is still necessary. METHODS: We evaluated the hepatic pathology from S. japonicum-infected mice after treatment with fucoidan. qRT-PCR and immunofluorescence were used to detect the pro- or anti-inflammatory factors and the phosphorylated p65 in the livers. In addition, flow cytometry was also performed to investigate the T cell subsets in the S. japonicum-infected mice after treatment with fucoidan, and functional molecules relatively specific to Treg cells were detected in vitro. Furthermore, macrophages were treated with fucoidan in vitro and to detect the inflammatory cytokines. RESULTS: Treatment with fucoidan significantly reduced the hepatic granuloma size and fibrosis response during S. japonicum infection. The attenuated phospho-p65 protein levels and the mRNA levels of pro-inflammatory cytokines (IL-6, IL-12 and TNF-α) were observed in the livers from fucoidan-treated S. japonicum-infected mice; however, the mRNA levels of anti-inflammatory cytokines (IL-4 and IL-13) were increased. In addition, the infiltration of Treg cells was significantly enhanced both in the livers and spleens from fucoidan-treated S. japonicum-infected mice. Consistent with this, the mRNA levels of IL-10 and TGF-ß were dramatically increased in the livers from S. japonicum-infected mice after fucoidan treatment. Furthermore, in vitro stimulated splenocytes with fucoidan resulted in increasing Treg cells in splenocytes as well as the functional expression of CC chemokine receptor type 4 (CCR4) and CXC chemokine receptor type 5 (CXCR5) in Treg cells. Additionally, fucoidan promoted the mRNA levels of IL-4 and IL-13 in macrophages. CONCLUSIONS: These findings suggest an important role of natural fucoidan in reducing hepatic pathology in the progress of S. japonicum infection with a stronger Treg response, which may reveal a new potential therapeutic strategy for hepatic disease caused by parasitic chronic infection.

Sorafenib and praziquantel synergistically attenuate Schistosoma japonicum-induced liver fibrosis in mice.

Liver fibrosis is an important process that occurs in most types of chronic liver diseases and often results in the end stage of liver diseases, such as cirrhosis, portal hypertension, and hepatocellular carcinoma. Sorafenib, a multiple tyrosine kinase inhibitor, has been shown to inhibit liver fibrosis in multiple experimental fibrosis mouse and rat models. The aim of this study was to test the therapeutic effect of sorafenib on liver fibrosis induced by infection with a parasite, Schistosoma japonicum, in mice. Mice were percutaneously infected through the abdomen with Schistosoma cercariae to develop a schistosomula liver fibrosis model. Eight weeks after infection, infected mice were treated with the anti-parasitic agent praziquantel for 2 days and sorafenib for 2 weeks. Hepatic histopathological changes were assessed using hematoxylin and eosin (HE) and Masson's trichome staining. The hepatic expression levels of collagen I, collagen III, alpha-smooth muscle actin (α-SMA), platelet-derived growth factor (PDGF), and PDGF receptor-beta (PDGFR-ß) were analyzed by immunohistochemistry and western blot. Praziquantel administration alone but not sorafenib reduced liver fibrosis, and the combination of praziquantel and sorafenib significantly attenuated liver fibrosis in S. japonicum-infected mice. Moreover, sorafenib plus praziquantel markedly decreased the hepatic deposition of collagen and expression of fibrogenic genes in these mice. In conclusion, the use of sorafenib following praziquantel treatment may represent a potential therapeutic strategy for liver fibrosis induced by S. japonicum in patients.

Antischistosomal Properties of Hederacolchiside A1 Isolated from Pulsatilla chinensis.

Background: Schistosomiasis is a major neglected disease for which the current control strategy involves mass treatment with praziquantel, the only available drug. Hence, there is an urgent need to develop new antischistosomal compounds. Methods: The antischistosomal activity of hederacolchiside A1 (HSA) were determined by total or female worm burden reductions in mice harboring Schistosoma japonicum or S. mansoni. Pathology parameters were detected on HSA against 1-day-old S. japonicum-harboring mice. Moreover, we confirmed the antischistosomal effect of HSA on newly transformed schistosomula (NTS) of S. japonicum in vitro. Results: HSA, a natural product isolated from Pulsatilla chinensis (Bunge) Regel, was initially corroborated to possess promising antischistosomal properties. We demonstrated that HSA had high activity against S. japonicum and S. mansoni less in 11 days old parasites harbored in mice. The antischistosomal effect was even more than the currently used drugs, praziquantel, and artesunate. Furthermore, HSA could ameliorate the pathology parameters in mice harboring 1-day-old juvenile S. japonicum. We also confirmed that HSA-mediated antischistosomal activity is partly due to the morphological changes in the tegument system when NTS are exposed to HSA. Conclusions: HSA may have great potential to be an antischistosomal agent for further research.

In vivo and in vitro activity of oil extract of garlic (Allium sativum Linnaeus) against Schistosoma japonicum cercariae.

INTRODUCTION:: The activity of garlic oil extract against Schistosoma japonicum cercariae was evaluated. METHODS:: The in vitro and in vivo cercaricidal activities against S. japonicum larvae were determined. RESULTS:: Exposure to ≥ 10-6 (v/v) garlic emulsions for 30 min led to 100% cercariae mortality; pre-exposure treatment with ≥ 10-4 (v/v) garlic emulsions showed 100% preventive efficacy against S. japonicum infection, while pre-treatment with 10-5 and 10-6 (v/v) emulsions achieved 20%-40% preventive efficacy and 35.2%-63.6% worm burden reduction. CONCLUSIONS:: Garlic oil extract has activity against S. japonicum larvae and a promising preventive efficacy against S. japonicum infection.

In vivo and in vitro activity of oil extract of garlic (Allium sativum Linnaeus) against Schistosoma japonicum cercariae

Abstract: INTRODUCTION: The activity of garlic oil extract against Schistosoma japonicum cercariae was evaluated. METHODS: The in vitro and in vivo cercaricidal activities against S. japonicum larvae were determined. RESULTS: Exposure to ≥ 10-6 (v/v) garlic emulsions for 30 min led to 100% cercariae mortality; pre-exposure treatment with ≥ 10-4 (v/v) garlic emulsions showed 100% preventive efficacy against S. japonicum infection, while pre-treatment with 10-5 and 10-6 (v/v) emulsions achieved 20%-40% preventive efficacy and 35.2%-63.6% worm burden reduction. CONCLUSIONS: Garlic oil extract has activity against S. japonicum larvae and a promising preventive efficacy against S. japonicum infection.

Taurine drinking ameliorates hepatic granuloma and fibrosis in mice infected with Schistosoma japonicum.

In schistosomiasis, egg-induced hepatic granuloma formation is a cytokine-mediated, predominantly CD4(+) Th2 immune response that can give rise to hepatic fibrosis. Hepatic fibrosis is the main cause of increased morbidity and mortality in humans with schistosome infection. Taurine has various physiological functions and hepatoprotective properties as well as anti-inflammatory and immunomodulatory activity. However, little is known about the role of taurine in schistosome egg-induced granuloma formation and fibrosis. We aimed to evaluate the therapeutic potential of taurine as preventative treatment for Schistosoma japonicum infection. Mice infected with S. japonicum cercariae were supplied with taurine drinking water (1% w/v) for 4 weeks starting at 4 weeks post-infection. Taurine supplementation significantly improved the liver pathologic findings, reduced the serum levels of aminotransferases and area of hepatic granuloma, and prevented fibrosis progression. In addition, taurine decreased the expression of the granulomatous and fibrogenic mediators transforming growth factor ß1, tumor necrosis factor α, monocyte chemotactic protein 1α and macrophage inflammatory protein 1α as well as the endoplasmic reticulum stress marker glucose-regulated protein 78. Thus, taurine can significantly attenuate S. japonicum egg-induced hepatic granuloma and fibrosis, which may depend in part on the downregulation of some relevant cytokine/chemokines and reducing the endoplasmic reticulum stress response.

Transdermal praziquantel administration attenuates hepatic granulomatosis in mice infected with Schistosoma japonicum.

Liver granuloma is a major pathogenic factor responsible for schistosomiasis, and no effective drugs or therapy methods to treat it have been found so far. Praziquantel (PZQ) has shown some anti-schistosomal effect, but little information is available about the effect of PZQ-prolonged administration on granuloma formation around schistosome eggs. Herein, we investigated the effect of PZQ on hepatic granuloma formation by treating the mice infected with Schistosoma japonicum using a long-term PZQ transdermal delivery. The results showed that the mean area of granulomas in the group treated with PZQ transdermal agent was (175.47 ± 116.73) × 10(3) µm(2) at the 49th day postinfection and (71.96 ± 45.99) × 10(3) µm(2) at the 56th day, while that in the control group was (304.51 ± 140.55) × 10(3) µm(2) and (526.44 ± 268.06) × 10(3) µm(2), respectively. The content of hydroxyproline in the livers of mice approached to the normal level on the 154th day in the treatment group, but it continued to increase from the 28th day to the 154th day after infection in the control group and nontreatment group. The ALT activity in serum of mice in the treatment group was also significantly lower than that in the control group (*P ≤ 0.05). Our results suggest that the long-term PZQ transdermal delivery is critical in the therapeutic approach to control the progress of hepatic schistosomiasis induced by egg granulomas.

Research and control of advanced schistosomiasis japonica in China.

Among the three main schistosomes (Schistosoma japonicum, Schistosoma mansoni, and Schistosoma haematobium) known to infect humans, S. japonicum causes the most serious pathological lesions. In China, only schistosomiasis japonica is transmitted. From the 1950s, massive epidemiological investigations and active control measures for schistosomiasis japonica have been carried out. At the early stage of schistosomiasis control program, there were about 12 million schistosomiasis patients, and about 5% of schistosomiasis patients belong to advanced patients, which was 600,000. After more than a half century of active schistosomiasis control work, the schistosomiasis situation has been reduced markedly. The nearest epidemiological investigation showed that, by the end of 2012, there were still 240,000 schistosomiasis patients with the descent rate of 98% and 30,000 advanced patients with the descent rate of 95%. This paper reviews the rich experiences of advanced schistosomiasis research and control in China, including that the epidemiology researches confirm there is a family aggregation of advanced schistosomiasis and advanced schistosomiasis patients have no significance to the schistosomiasis transmission in transmission-interrupted areas but still are an infection source in endemic areas; pathogenic mechanism researches verify that genetic factors and immunoregulation play important roles in the disease developing process; ultrasound image examinations are used not only in the diagnosis and differential diagnosis of advanced schistosomiasis but also in the guidance of treatment and evaluation of therapeutic effects and, furthermore, in the risk predictions of portal hypertension and upper gastrointestinal hemorrhage; clinical practices demonstrate that praziquantel can be used in most of advanced schistosomiasis patients, and the therapy not only can interrupt the schistosomiasis transmission somewhat but also is favorable for liver fibrosis improvement; the ascetic fluid concentration afflux is used in the therapy for obstinate ascites, and endoscopic varices ligation is used in the treatment of upper gastrointestinal bleeding, and both have good effects; hundreds and thousands of severe splenomegaly advanced schistosomiasis patients received splenectomy, and the long-term survival rate is more than 90%, most of them are basically cured from the disease and their labor force recovers, some dwarf patients begin growing and developing again, and some sterile women became fertile; the researches of traditional Chinese medicine in the treatment of liver fibrosis have made progress, such as Cordyceps sinensis showing some anti-fibrosis effect in the animal experiments and primary clinical trials; the animal experiments and epidemiological investigations indicate that schistosome infection is one of the carcinogenesis risk factors, especially for liver cancer. In conclusion, these experiences and lessons are plentiful and worth sharing with the peers of other endemic countries for reference.

[Jatropha seed oils extracted by different methods and their effect on killing cercaria of Schistosoma japonicum].

OBJECTIVE: To evaluate the effect of Jatropha seed oils extracted by different methods on killing cercaria of Schistosomajaponicum so as to screen the optimum process and formulations. METHODS: The cercaria directly contacting tests with Jatropha seed oils extracted by 6 different extraction processes were carried out, and the mouse immediate contacting cercaria infection trials with different formulations of Jatropha seed oil and various additives were performed. RESULTS: With 95% ethanol, the ratio of material to liquid being 1:8, and 2 h extraction, the oil extraction rate was 30.7%. The cercaria directly contacting tests showed that 6 kinds of Jatropha seed oil killed all cercaria within 30 min. In the mouse immediate contacting cercaria infection trials, the worm declined rate of Jatropha seed oil liquid was 70.97%, and the worm declined rate of the sample added with benzyl benzoate was 58.87%, and the worm declined rate of the sample added with laurocapram was 77.42%. The worm declined rate of the samples added with benzyl benzoate, dibutyl phthalate and laurocapram was 100%. CONCLUSION: The process with 95% ethanol, the ratio of material to liquid being 1:8, and 2 h extraction is the optimum, and the Jatropha seed oil has a good killing schistosome cercaria effect.

A boswellic acid-containing extract ameliorates schistosomiasis liver granuloma and fibrosis through regulating NF-κB signaling in mice.

Boswellic acid (BA)-containing extracts such as BSE have anti-inflammatory and immunomodulatory activity. In chronic schistosomiasis, the hepatic granuloma and fibrosis induced by egg deposition in the liver is the most serious pathological manifestations. However, little is known regarding the role of BAs in Schistosoma japonicum (S. japonicum) egg-induced liver granuloma and fibrosis. In order to investigate the effect of a water-soluble complex preparation of BSE, BSE-CD, on S. japonicum egg-induced liver pathology, liver granuloma and fibrosis were induced by infecting C57BL/6 mice with 18-22 cercariae of S. japonicum. S. japonicum cercariae infected mice were injected with BSE-CD at the onset of egg granuloma formation (early phase BSE-CD treatment after 4 weeks infection) or after the formation of liver fibrosis (late phase BSE-CD treatment after 7 weeks infection). Our data show that treatment of infected mice with BSE-CD significantly reduced both the extent of hepatic granuloma and fibrosis. Consistent with an inhibition of NF-κB signaling as evidenced by reduced IκB kinase (IKK) activation, the mRNA expression of VEGF (vascular endothelial growth factor, VEGF), TNF-α (tumor necrosis factor-alpha TNF-α) and MCP-1 (monocyte chemotactic protein 1, MCP-1) was decreased. Moreover, immunohistochemical analysis (IHC) revealed that the content of α-SMA in liver tissue of BSE-CD treated mice was dramatically decreased. Our findings suggest that BSE-CD treatment attenuates S. japonicum egg-induced hepatic granulomas and fibrosis, at least partly due to reduced NF-κB signaling and the subsequently decreased expression of VEGF, TNF-α, and MCP-1. Suppression of the activation of hepatic stellate cells (HSC) may also be involved in the therapeutic efficacy of BSE-CD.

3-oxoacyl-ACP reductase from Schistosoma japonicum: integrated in silico-in vitro strategy for discovering antischistosomal lead compounds.

BACKGROUND: Schistosomiasis is a disease caused by parasitic worms and more than 200 million people are infected worldwide. The emergence of resistance to the most commonly used drug, praziquantel (PZQ), makes the development of novel drugs an urgent task. 3-oxoacyl-ACP reductase (OAR), a key enzyme involved in the fatty acid synthesis pathway, has been identified as a potential drug target against many pathogenic organisms. However, no research on Schistosoma japonicum OAR (SjOAR) has been reported. The characterization of the SjOAR protein will provide new strategies for screening antischistosomal drugs that target SjOAR. METHODOLOGY/PRINCIPAL FINDINGS: After cloning the SjOAR gene, recombinant SjOAR protein was purified and assayed for enzymatic activity. The tertiary structure of SjOAR was obtained by homology modeling and 27 inhibitor candidates were identified from 14,400 compounds through molecular docking based on the structure. All of these compounds were confirmed to be able to bind to the SjOAR protein by BIAcore analysis. Two compounds exhibited strong antischistosomal activity and inhibitory effects on the enzymatic activity of SjOAR. In contrast, these two compounds showed relatively low toxicity towards host cells. CONCLUSIONS/SIGNIFICANCE: The work presented here shows the feasibility of isolation of new antischistosomal compounds using a combination of virtual screening and experimental validation. Based on this strategy, we successfully identified 2 compounds that target SjOAR with strong antischistosomal activity but relatively low cytotoxicity to host cells.

Aldose reductase from Schistosoma japonicum: crystallization and structure-based inhibitor screening for discovering antischistosomal lead compounds.

BACKGROUND: Schistosomiasis is a neglected tropical disease with high morbidity and mortality in the world. Currently, the treatment of this disease depends almost exclusively on praziquantel (PZQ); however, the emergence of drug resistance to PZQ in schistosomes makes the development of novel drugs an urgent task. Aldose reductase (AR), an important component that may be involved in the schistosome antioxidant defense system, is predicted as a potential drug target. METHODS: The tertiary structure of Schistosoma japonicum AR (SjAR) was obtained through X-ray diffraction method and then its potential inhibitors were identified from the Maybridge HitFinder library by virtual screening based on this structural model. The effects of these identified compounds on cultured adult worms were evaluated by observing mobility, morphological changes and mortality. To verify that SjAR was indeed the target of these identified compounds, their effects on recombinant SjAR (rSjAR) enzymatic activity were assessed. The cytotoxicity analysis was performed with three types of human cell lines using a Cell Counting Kit-8. RESULTS: We firstly resolved the SjAR structure and identified 10 potential inhibitors based on this structural model. Further in vitro experiments showed that one of the compounds, renamed as AR9, exhibited significant inhibition in the activity of cultured worms as well as inhibition of enzymatic activity of rSjAR protein. Cytotoxicity analysis revealed that AR9 had relatively low toxicity towards host cells. CONCLUSIONS: The work presented here bridges the gap between virtual screening and experimental validation, providing an effective and economical strategy for the development of new anti-parasitic drugs. Additionally, this study also found that AR9 may become a new potential lead compound for developing novel antischistosomal drugs against parasite AR.

A boswellic acid-containing extract attenuates hepatic granuloma in C57BL/6 mice infected with Schistosoma japonicum.

Granuloma formation has been shown to be induced and elicited by schistosome egg antigens, and it finally develops into fibrosis in intestine and the liver. Hepatic fibrosis is the main cause of increased morbidity and mortality in humans infected with schistosomes. Boswellic acid (BA)-containing extracts such as extracts of the oleogum resin from Boswellia serrata (BSE) have anti-inflammatory and immunomodulatory activity. However, little is known about the role of such extracts in schistosome egg-induced granulomatous inflammation. In order to investigate the effect of a watersoluble cyclodextrin complex preparation of BSE (BSE-CD) on Schistosoma japonicum (S. japonicum) egg-induced liver granuloma, mice infected with S. japonicum cercariae were injected with BSE-CD during egg granuloma formation. The data showed that BSE-CD significantly reduced the size of liver granuloma and levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST); however, BSE-CD treatment had no effect on worm load and egg burden. The data also showed that BSE-CD significantly decreased the expression of leukotriene B(4) (LTB(4)) and prostaglandin E(2) (PGE(2)), as well as the expression of matrix metallopeptidase 9 (MMP-9) in liver both on the mRNA and protein level. Thus, BSE-CD can significantly attenuate S. japonicum egg-induced hepatic granuloma, which may be partly dependent on the downregulation of some biochemical mediators.

Effect of Mirazid in Schistosoma japonicum-infected mice: parasitological and pathological assessment.

Conflicting reports are found in the literature about the antischistosomal efficacy of Mirazid (MZ), which is a special formulation of myrrh obtained from the stem of the plant Commiphora molmol. This initiated the present study to assess this drug for the first time in experimental schistosomiasis japonicum. Mice were divided into four groups: infected untreated control (I); infected treated with MZ, 500 mg/kg (II); infected treated with MZ, 250 mg/kg (III); and infected treated with praziquantel (PZQ), 200 mg/kg (IV). The drugs were given 7 weeks post-infection for five successive days. All animals were killed 3 weeks posttreatment. Results showed no signs of antibilharzial activity of MZ. Total worms, total tissue egg load, egg developmental stages, and granuloma area were not affected by any of the MZ treatment regimens as compared to the infected untreated group (P > 0.05 for all variables). These results were in contrast to those obtained in PZQ-treated animals in which 82.82 % total worm reduction, 94.62 % egg reduction, and 86.35 % granuloma area reduction were observed. Also, it significantly increased the percentage of dead ova and decreased the percentage of mature ova with complete absence of immature ones in comparison with the control group (P < 0.01 for all variables). In conclusion, the results of the current study raise serious doubts about the antischistosomal activity of MZ.

[Killing effect of garlic extract on Schistosoma japonicum cercariae and Oncomelania snails].

The killing effect of different concentrations of garlic extract solution on Schistosoma japonicum cercariae and Oncomelania snails was observed under dissecting microscope. Mice were infected by cercariae through the abdominal skin daubed by garlic solution or by deionized water as control. The results showed that the cercariae were killed in (77.33 +/- 25.01) s in average, it needed (73.00 +/- 1.73)- (299.67 +/- 18.96) s under the garlic solution concentrations of 50.00%-0.79% respectively, while the cercariae kept alive in 600 s in the control. The snails were killed in 1 d by 100% garlic solution but no death in the control in 2 d. No mouse daubed with different concentrations of garlic solution was found infected by schistosomes while 100% of the control mice got infected. It is concluded that the garlic shows satisfactory effect in killing cercariae and Oncomelania snails, and may prevent schistosome infection by daubing the skin.

Schistosoma japonicum calcium-binding tegumental protein SjTP22.4 immunization confers praziquantel schistosomulumicide and antifecundity effect in mice.

A family of platyhelminth tegument-specific proteins comprising of one or two calcium ion binding EF-hand and a dynein light chain-like domain, termed tegumental proteins, are considered as candidates of vaccine. In this study, we cloned and characterized SjTP22.4, a novel membrane-anchored tegumental protein in Schistosoma japonicum with theoretic MW of 22.4. The recombinant SjTP22.4 could be recognized by S. japonicum infected sera. Immunofluorescence revealed that this protein is not only located on the surface of tegument of adult and schistosomulum and cercaria, but also in the parenchymatous tissues and intestinal epithelium. Circular dichroism (CD) measurement demonstrated rSjTP22.4 had Ca(2+)-binding ability. The rSjTP22.4 vaccination without adjuvants produced comparable high level of antibody with that of immunization with adjuvants together indicated it was an antigen of strong antigenicity. The level of IgG1 is much higher than that of IgG2a and IgE is nearly negative in S. japonicum-infected and rSjTP22.4 immunized mice. In cercaria challenge experiment, mice vaccinated with SjTP22.4 showed no reduction in adult burden and egg production, comparing with the control mice, but 41% decrease in egg mature rate and 32% reduction in liver egg granuloma area. However, the SjTP22.4 immunized mice that received praziquantel treatment at 10d post infection caused 26% reduction in adult burden and 53% decrease in egg mature rate, comparing with the control mice only received praziquantel treatment. In conclusion, SjTP22.4 is a valuable vaccine candidate for S. japonicum of anti-pathogenesis and anti-transmission effect and plays a synergetic role in praziquantel to kill schistosomulum.

Research and development of antischistosomal drugs in the People's Republic of China a 60-year review.

A comprehensive 60-year review of antischistosomal drug discovery and development research in the People's Republic of China (P.R. China) is presented. In the 1950s, three antimonials were developed, which, compared to potassium antimony tartrate-the treatment of choice against schistosomiasis at the time-showed equal efficacy but lower toxicity when administered orally or intramuscularly. Activity of furapromidum against Schistosoma japonicum was reported in the early 1960s, and this drug became the first non-antimonial used in clinical treatment of schistosomiasis japonica. Subsequently, two additional nitrofuran derivatives (furadiamine and fuvinazole) were investigated in the laboratory and clinically. In the late 1960s, niridazole and amoscanate were developed by western scientists, which encouraged Chinese researchers to synthesise and further modify the chemical structures of these compounds. However, the modified compounds were less efficacious but similarly toxic, which impeded their further development. The advent of the safe, highly efficacious broad-spectrum antischistosomal drug praziquantel, in the mid-1970s, eventually resulted in a change of the global schistosomiasis control strategy from a multi-pronged transmission control approach to drug-based morbidity control. Numerous studies were carried out in P.R. China to further the understanding of efficacy, mechanism of action and safety of praziquantel against S. japonicum. Efforts have also been made to develop antischistosomal drugs from Chinese traditional medicine, and research with cucurbitin (an amino acid isolated from pumpkin seeds), among other products, showed interesting in vitro and in vivo activities against S. japonicum. In the 1990s, the artemisinins-originally reserved for malaria treatment-were developed as 'chemoprophylactic' agents against S. japonicum, which in turn led to a series of new developments of artemisinins and related compounds as broad-spectrum antischistosomal and anthelminthic therapies.

Paeoniflorin ameliorates schistosomiasis liver fibrosis through regulating IL-13 and its signalling molecules in mice.

Treatment of liver fibrosis associated with Schistosoma japonicum ova-induced granulomas remains a challenging proposition. Paeoniflorin (PAE, C23H28O11) has anti-inflammatory, anti-allergic, and immunoregulatory effects and it is commonly used in Chinese Herbal prescriptions to treat hepatic disorders. The present study was carried out to investigate the effects of PAE on hepatic fibrosis of mice infected with S. japonicum and to explore its possible mechanism. Upon pathological examination of PAE-treated mice, the size of egg granuloma, fibrosis scores, the concentration of IL-13 and hydroxyproline in liver were significantly reduced compared with the model mice. In the primary culture of hepatic stellate cells (HSCs), PAE inhibited IL-13-induced collagen synthesis. These results suggested that PAE might alleviate the hepatic granulomas and fibrosis caused by S. japonicum and the inhibitory effect of PAE on hepatic fibrosis might be associated with its ability to decrease the level of IL-13 and to interfere with the IL-13 signalling molecule in HSCs.