Proteomic and deep sequencing analysis of extracellular vesicles isolated from adult male and female Schistosoma japonicum

Schistosomes are the causative agent of schistosomiasis, which affects more than 200 million people worldwide. Unlike other trematode parasites, schistosomes (along with the Didymozoidae) have evolved separate sexes. Pairing of males and females is a prerequisite for female sexual development and subsequent egg production. However, the mechanisms underlying these processes remain poorly understood. Extracellular vesicles (EVs) have been shown to play important roles in many biological processes. In the present study, we characterized EVs isolated from adult male and female Schistosoma japonicum. Proteomic analyses of the isolated EVs revealed that some proteins are significantly enriched in male or female EVs. RNA-sequencing analysis of a small RNA population associated with EVs identified 18 miRNAs enriched in male and female S. japonicum EVs. Among these, miR-750 was specifically enriched in female EVs. Additionally, the inhibition of miR-750 by a miRNA inhibitor led to decreased egg production in female schistosomes cultured in vitro. Collectively, our results suggest that miR-750 within female EV cargo may be involved in regulating ovary development and egg production in S. japonicum females.

Schistosomiasis is a neglected tropical disease caused by the genus Schistosoma and affects more than 200 million people worldwide. Previously, we and other groups found that Schistosoma japonicum can secrete extracellular vesicles (EVs) that are taken up by mammalian cells. Here, we characterized EVs isolated from adult male and female S. japonicum and found that some proteins and microRNAs (miRNAs) were significantly enriched in male or female EVs. More importantly, the inhibition of miR-750, which is specifically enriched in female EVs, resulted in decreased egg production. Overall, our study suggests that female EV miRNA cargo may play important roles in regulating female ovary development and egg production during male-female pairing in S. japonicum.

Prohibitin 1 (PHB1) controls growth and development and regulates proliferation and apoptosis in Schistosoma japonicum

Schistosomiasis is a zoonotic parasitic disease caused by the trematode blood flukes of the genus Schistosoma. The prodigious egg output of females is the main cause of the disease in definitive hosts, while the female worm relies on continuous pairing with the male worm to fuel the growth and maturation of the reproductive organs and egg production. Prohibitin, which contains the functionally interdependent PHB1 and PHB2 subunits in human and some other species, has been proposed to participate in the cell proliferation and apoptosis regulation in mammals. However, little is known about the function of PHB homolog in the growth and reproductive development of schistosomes. Here, we reported the Phb1 gene that was structurally and evolutionarily conserved in Schistosoma japonicum when compared with that of other species from Caenorhabditis elegans to human. Real-time PCR detected that SjPhb1 was highly transcribed in the vitellaria of female worms. SjPhb1 knockdown achieved through the dsRNA-mediated RNAi in vivo resulted in retarded growth, decreased pairing, and fecundity in adult worms, as well as attenuated pathogenicity or virulence of worms to their hosts. Cell proliferation and apoptosis examination found decreased cell proliferation and increased cell apoptosis in SjPhb1 dsRNA-treated worms. Therefore, our study provides the first characterization of S. japonicum PHB1 and reveals its fundamental role in the regulation of growth and development of S. japonicum by specific dsRNA-mediated RNAi in vivo. Our findings prompt for a promising molecular of schistosomes that can be targeted to effectively retard the growth and development of the schistosomes.

Function of the lesswright (lwr) gene in the growth, development, and reproduction of Schistosoma japonicum

The lesswright (lwr) gene and its products are essential molecules in mitosis, DNA repair, and embryo formation in many eukaryotes. In this study, immunohistochemical analysis revealed that the Lwr protein was located in the internal tissues and the surface layer of the adult Schistosoma japonicum (Sj) worms. The mRNA expression levels of SjLwr at different points were evaluated by quantitative real-time RT-PCR. The expression of SjLwr peaked at 14 days and then decreased thereafter. SjLwr expression was relatively more stable in male worms than in female worms. The functions of SjLwr were explored by siRNA-based gene silencing with a simple soaking method. The results showed that knockdown of the SjLwr gene impaired the growth and development of S. japonicum in mice, as well as survival, morphology, reproductive capacity, and egg vitality. These observations imply that SjLwr presents a novel target for the development of immuno- and/or small molecule-based therapeutics for the control and treatment of schistosome infections.

A meta-analysis of infection rates of Schistosoma japonicum in sentinel mice associated with infectious waters in mainland China over last 40 years

BACKGROUND

Schistosomiasis japonica is a zoonotic parasitic disease. After nearly 70 years of control efforts in China, Schistosomiasis transmission has been reduced to a much lower level. The absence or near absence of infections in humans or livestock, based on traditional fecal and serological tests, has made the targets and priorities of future control efforts difficult to determine. However, detection of schistosome cercariae in waters using sentinel mice could be an alternative way of identifying remaining foci of infection, or even serve as a tool for evaluation of control efficacy. This method has been employed in China over last forty years. We therefore performed a meta-analysis of the relevant research to investigate if infections in sentinel mice mirror the ongoing trend of schistosomiasis transmission in China.

METHODS

We conducted a meta-analysis of studies reporting infection rates of S. japonicum in sentinel mice in China before Sep 1, 2018 in accordance with the PRISMA guidelines. We retrieved all relative studies based on five databases (CNKI, WanFang, VIP, PubMed and Web of Science) and the reference lists of resulting articles. For each individual study, the infection rate in sentinel mice is presented together with its 95% confidence interval (CI). Point estimates of the overall infection rates and their 95% CIs were calculated. Subgroup analyses were performed according to study periods, seasons or regions.

RESULTS

We identified 90 articles, including 290 studies covering eight endemic provinces. The overall rate in sentinel mice was 12.31% (95% CI: 10.14-14.65%) from 1980 to 2018. The value of 3.66% (95% CI: 2.62-4.85%) estimated in 2004 to 2018 was significantly lower than in 1980 to 2003 (22.96%, 95% CI: 19.25-26.89%). The estimate was significantly higher in the middle and lower reaches than in the upper reaches of the Yangtze River. The highest estimates were obtained in Hunan (30.11%, 95% CI: 25.64-34.77%) followed by Anhui (26.34%, 95% CI: 12.88-42.44%) and then Jiangxi (13.73%, 95% CI: 6.71-22.56%). Unlike the other provinces in the middle and lower reaches, no significant reduction was seen in Hubei after 2003. Even in Hubei two studies carried out after 2014 reported infections in sentinel mice, although no infected snails were reported across the province. Infections were most found in April (17.40%, 95% CI: 1.13-45.49%), July (24.98%, 95% CI: 15.64-35.62%) and October (17.08%, 95% CI 5.94-32.05%). High degrees of heterogeneity were observed.

CONCLUSION

This meta-analysis provides a comprehensive analysis of schistosome infection in sentinel mice across China. The estimates largely mirror the ongoing trends of transmission in terms of periods and regions. Infections were most likely to occur in April, July and October. In areas where no infected snails were reported infections in sentinel mice were still observed. Due to the presence of snails and infected wildlife, detection of schistosomes in waters using such a highly sensitive method as the deployment of sentinel mice, remains of importance in schistosomiasis monitoring. We would suggest the current criteria for transmission interruption or elimination of schistosomiasis in China be adjusted by integrating the results of sentinel mice based surveys.

Comparative analysis of microRNA expression profiles of adult Schistosoma japonicum isolated from water buffalo and yellow cattle

BACKGROUND

Yellow cattle and water buffalo are important natural reservoir hosts and the main transmission sources of Schistosoma japonicum in endemic areas of China. The worms from the two hosts have marked differences in general worm morphology and ultrastructure, gene transcription and protein expression profiles.

RESULTS

To investigate microRNAs (miRNAs) involved in the regulation of schistosome development and survival, we compared miRNA expression profiles of adult schistosomes derived from yellow cattle and water buffalo by using high-throughput sequencing with Illumina Hiseq Xten. Schistosoma japonicum from water buffalo and yellow cattle yielded 63.78 million and 63.21 million reads, respectively, of which nearly 50% and 49% could be mapped to selected miRNAs in miRbase. A total of 206 miRNAs were identified, namely 79 previously annotated miRNAs of S. japonicum and 127 miRNAs that matched with the S. japonicum genome and were highly similar to the annotated miRNAs from other organisms. Among the 79 miRNAs, five (sja-miR-124-3p, sja-miR-219-5p, sja-miR-2e-3p, sja-miR-7-3p and sja-miR-3490) were significantly upregulated in the schistosomes from water buffalo compared with those from yellow cattle. A total of 268 potential target genes were predicted for these five differentially expressed miRNAs. Eleven differentially expressed targets were confirmed by qRT-PCR among 15 tested targets, one of which was further validated through dual-luciferase reporter assay. Among the 127 'possible' S. japonicum miRNAs, ten were significantly differentially expressed in the schistosomes from these two hosts.

CONCLUSIONS

These results highlight the important roles of miRNAs in regulating the development and survival of schistosomes in water buffalo and yellow cattle and facilitate understanding of the miRNA regulatory mechanisms in schistosomes derived from different susceptible hosts.

Gene Expression in Developmental Stages of Schistosoma japonicum Provides Further Insight into the Importance of the Schistosome Insulin-Like Peptide

We showed previously that the Schistosoma japonicum insulin-like peptide (SjILP) binds the worm insulin receptors, thereby, activating the parasite’s insulin pathway and emphasizing its important role in regulating uptake of glucose, a nutrient essential for parasite survival. Here we show that SjILP is differentially expressed in the schistosome life cycle and is especially highly transcribed in eggs, miracidia, and adult female worms. RNA inference was employed to knockdown SjILP in adults in vitro, with suppression confirmed by significantly reduced protein production, declined adenosine diphosphate levels, and reduction in glucose consumption. Immunolocalization showed that SjILP is located to lateral gland cells of mature intra-ovular miracidia in the schistosome egg, and is distributed on the ciliated epithelium and internal cell masses of newly transformed miracidia. In schistosomula, SjILP is present on the tegument in two antero-lateral points, indicating highly polarized expression during cercarial transformation. Analysis of serum from S. japonicum-infected mice by ELISA using a recombinant form of SjILP as an antigen revealed IgG immunoreactivity to this molecule at 7 weeks post-infection indicating it is likely secreted from mature eggs into the host circulation. These findings provide further insights on ILP function in schistosomes and its essential roles in parasite survival and growth in different development stages.

Preliminary evaluation of neoblast-like stem cell factor and transcript expression profiles in Schistosoma japonicum

Neoblast-like stem cell factors and transcripts are essential for cell proliferation, self-renewal, and differentiation. Recent studies have demonstrated that nanos, sox, and vasa-like transcription factors are associated with neoblast-like stem cells in Schistosoma mansoni and play crucial roles in the regulation of worm development. However, these neoblast-like stem cell factors and transcripts and their expression profiles remain unknown in Schistosoma japonicum. In this study, we identified orthologs of 11 neoblast-like stem cell factors and transcripts in S. japonicum using bioinformatics and confirmed them by PCR. The expression profiles of neoblast-like stem cell factors and transcripts revealed that some of them were highly expressed in certain stages. Sex-based expression analysis revealed that nanos, polo-like kinase, PCNA, cyclin B, and H2A showed significantly higher expression in female worms, whereas ago and bruli showed higher expression in male worms. In addition, we noted that ago, bruli, and pp32 exhibited higher expression in the testes, while nanos, polo-like kinase, cyclin B, H2A, and H2B showed notable higher expression in both isolated ovaries and testes. Our preliminary results are expected to provide important information about the regulatory roles of these stem cell factors in parasite development and sexual maturation.

The ratio of the seroprevalence to the egg-positive prevalence of Schistosoma japonicum in China: a meta-analysis

BACKGROUND

Schistosomiasis, caused by Schistosoma japonicum, remains one of the most important parasitic diseases, and detection of S. japonicum infections in humans plays a crucial role in control and treatment. However, comparisons between the parasitological and the immunological examinations in the fields of China are lacking. Therefore we performed a meta-analysis to compare the seroprevalence of Schistosoma japonicum, as determined by IHA or ELISA, with coprological prevalence, as determined by Kato-Katz, and estimate the ratio of the serological to the egg-positive prevalence in order to evaluate the potential threat of egg-negative but worm-positive schistosomiasis.

METHODS

Studies published up to July 2018 on the parasitological and immunological examinations of schistosomiasis in the fields of China were searched in five databases including CNKI, WanFang, VIP, PubMed and Web of Science. The ratio of the serological to the egg-positive prevalence and its 95%CI for each study were calculated, and then point estimates and their 95%CIs of pooled prevalence ratio were meta-analyzed. Subgroup meta-analyses were also performed according to potential influential factors.

RESULTS

A total of 23 articles were included. The prevalence ratio varied from 0.57 to 48.83 for IHA to Kato-Katz and ranged from 0.38 to 13.97 for ELISA to Kato-Katz. The pooled ratio was 4.72 (95%CI: 3.87~ 5.76) for IHA to KK and 4.65 (95%CI: 3.50~ 6.17) for ELISA to KK. Subgroup analyses implied that the ratio of the serological to the egg-positive prevalence may decrease with the endemic levels. The highest prevalence ratio was observed when Kato-Katz was performed with three slides per stool or in hilly and mountainous regions.

CONCLUSIONS

The worm-determined prevalence by IHA or ELISA is 4- to 5-fold higher than the egg-determined prevalence by Kato-Katz, which implied Kato-Katz may largely underestimate the prevalence of S. japonicum in China. The degree of underestimation was greater when Kato-Katz with three slides per stool was carried out, especially in low endemic areas or in hilly and mountainous regions. Therefore, more attention should be paid to those egg-negative but worm-positive patients with the aim of final elimination of S. japonicum in China.

Cross-species prophylactic efficacy of Sm-p80-based vaccine and intracellular localization of Sm-p80/Sm-p80 ortholog proteins during development in Schistosoma mansoni, Schistosoma japonicum, and Schistosoma haematobium

Schistosomiasis remains a major global health problem. Despite large-scale schistosomiasis control efforts, clear limitations such as possible emergence of drug resistance and reinfection rates highlight the need for an effective schistosomiasis vaccine. Schistosoma mansoni large subunit of calpain (Sm-p80)-based vaccine formulations have shown remarkable efficacy in protecting against S. mansoni challenge infections in mice and baboons. In this study, we evaluated the cross-species protective efficacy of Sm-p80 vaccine against S. japonicum and S. haematobium challenge infections in rodent models. We also elucidated the expression of Sm-p80 and Sm-p80 ortholog proteins in different developmental stages of S. mansoni, S. haematobium, and S. japonicum. Immunization with Sm-p80 vaccine reduced worm burden by 46.75% against S. japonicum challenge infection in mice. DNA prime/protein boost (1 + 1 dose administered on a single day) resulted in 26.95% reduction in worm burden in S. haematobium-hamster infection/challenge model. A balanced Th1 (IFN-γ, TNF-α, IL-2, and IL-12) and Th2 (IL-4, IgG1) type of responses were observed following vaccination in both S. japonicum and S. haematobium challenge trials and these are associated with the prophylactic efficacy of Sm-p80 vaccine. Immunohistochemistry demonstrated that Sm-p80/Sm-p80 ortholog proteins are expressed in different life cycle stages of the three major human species of schistosomes studied. The data presented in this study reinforce the potential of Sm-p80-based vaccine for both hepatic/intestinal and urogenital schistosomiasis occurring in different geographical areas of the world. Differential expression of Sm-p80/Sm-p80 protein orthologs in different life cycle makes this vaccine potentially useful in targeting different levels of infection, disease, and transmission.

Protective effects of hydrogen sulfide on portal hypertensive vasculopathy in rabbits by activating AKT-NF-κB pathway

The role of hydrogen sulfide (H₂S) in portal hypertension (PH)-induced esophagus-gastric junction vascular lesions in rabbits was observed. The rabbit PH models were established. The animals were randomly divided into the following groups: normal, PH, PH+sodium hydrosulfide (PH+S), PH+propargylglycine (PH+PPG). The plasma H₂S levels, apoptosis of esophageal-gastric junction vascular smooth muscle cells, and the expression of nuclear transcription factor-κB (NF-κB), p-AKT, IκBa and Bcl-2 were detected. The cystathionine γ lyase (cystathionine-gamma-splitting enzyme, CSE) in the junction vascular tissue was measured. The results showed that the plasma H₂S levels and the CSE expression levels had statistically significant difference among different groups (P<0.05). As compared with PH group, plasma H₂S levels were declined obviously (11.9±4.2 vs. 20.6±4.5, P<0.05), and CSE expression levels in the junction vascular tissue were notably reduced (1.7±0.6 vs. 2.8±0.8, P<0.05), apoptosis rate of vascular smooth muscle cells per unit area was significantly decreased (0.10±0.15 vs. 0.24±0.07, P<0.05), and the expression levels of p-AKT and NF-κB were significantly decreased (2.31±0.33 vs. 3.04±0.38, P<0.05; 0.33±0.17 vs. 0.51±0.23, P<0.05), however, IκBa and Bcl-2 expression increased obviously (5.57±0.17 vs. 3.67±0.13, P<0.05; 0.79±0.29 vs. 0.44±0.36, P<0.05) in PH+PPG group. As compared with PH group, H₂S levels were notably increased (32.7±7.3 vs. 20.6±4.5, P<0.05), the CSE levels in the junction vascular tissue were significantly increased (6.3±0.7 vs. 2.8±0.8, P<0.05), apoptosis rate of vascular smooth muscle cells per unit area was significantly increased (0.35±0.14 vs. 0.24±0.07, P<0.05), and the expression levels of p-AKT and NF-κB were significantly increased (4.29±0.49 vs. 3.04±0.38, P<0.05; 0.77±0.27 vs. 0.51±0.23, P<0.05), yet IκBa and Bcl-2 expression decreased significantly (3.23±0.24 vs. 3.67±0.13, P<0.05; 0.31±0.23 vs. 0.48±0.34, P<0.05) in PH+S group. It is concluded that esophagus-gastric junction vascular lesions happen under PH, and apoptosis of smooth muscle cells is declined. H₂S can activate NF-κB by the p-AKT pathway, leading to the down-regulation of Bcl-2, eventually stimulating apoptosis of vascular smooth muscle cells, easing PH. H₂S/CSE system may play an important role in remission of PH via the AKT-NF-κB pathway.

Optimisation of a droplet digital PCR assay for the diagnosis of Schistosoma japonicum infection: A duplex approach with DNA binding dye chemistry

Schistosomiasis is a chronically debilitating helminth infection with a significant socio-economic and public health impact. Accurate diagnostics play a pivotal role in achieving current schistosomiasis control and elimination goals. However, many of the current diagnostic procedures, which rely on detection of schistosome eggs, have major limitations including lack of accuracy and the inability to detect pre-patent infections. DNA-based detection methods provide a viable alternative to the current tests commonly used for schistosomiasis diagnosis. Here we describe the optimisation of a novel droplet digital PCR (ddPCR) duplex assay for the diagnosis of Schistosoma japonicum infection which provides improved detection sensitivity and specificity. The assay involves the amplification of two specific and abundant target gene sequences in S. japonicum; a retrotransposon (SjR2) and a portion of a mitochondrial gene (nad1). The assay detected target sequences in different sources of schistosome DNA isolated from adult worms, schistosomules and eggs, and exhibits a high level of specificity, thereby representing an ideal tool for the detection of low levels of parasite DNA in different clinical samples including parasite cell free DNA in the host circulation and other bodily fluids. Moreover, being quantitative, the assay can be used to determine parasite infection intensity and, could provide an important tool for the detection of low intensity infections in low prevalence schistosomiasis-endemic areas.

GdCl3 Attenuates Schistosomiasis japonicum Egg-Induced Granulomatosis Accompanied by Decreased Macrophage Infiltration in Murine Liver

Early-stage hepatic granuloma and advanced-stage fibrosis are important characteristics of schistosomiasis. The direct consequences of gadolinium chloride (GdCl₃) in egg-induced granuloma formation have not been reported, although GdCl₃ is known to block the macrophages. In present study, mice were infected with 15 Schistosoma japonicum (S. japonicum) cercariae and treated with GdCl₃ (10 mg/kg body weight) twice weekly from day 21 to day 42 post-infection during the onset of egg-laying towards early granuloma formation. Histochemical staining showed that repeated injection of GdCl₃ decreased macrophages infiltration in liver of mice infected with S. japonicum. Macrophage depletion by GdCl₃ during the initial phase attenuated liver pathological injury characterized by smaller granuloma size and decreased immune inflammation as well as less fibrogenesis. In addition, IL-13Rα2 expression was reduced by GdCl₃ in liver of mice infected with S. japonicum. The results suggest that GdCl₃ depleted macrophages, which attenuated helminth infected immune responses involving with IL-13Rα2 signal. These findings would highlight a therapeutic potential via manipulating IL-13Rα2+ macrophage in schistosomiasis.

[Recombinant expression of Schistosoma japonicum fructose-1, 6-bisphos- phate aldolase and its expression in different developmental stages of S. japonicum]

OBJECTIVE

To clone, express and purify Schistosoma japonicum fructose-1, 6-bisphosphate aldolase (SjFBPA) in E. coli and observe its expression in different developmental stages of S. japonicum.

METHODS

FBPA gene was amplified from S. japonicum adult worm cDNA by using PCR. The amplified product was recombined into pET28a plasmid, and inducibly expressed with IPTG in E. coli BL21. SDS-PAGE and Western blotting were employed to analyze and identify the recombinant protein SjFBPA (rSjFBPA). Then, rSjFBPA was purified by chromatographic purification and its purity was analyzed by SDS- PAGE. The protein concentration of rSjFBPA purified was measured by the BCA method. Furthermore, SjFBPA mRNA was ana- lyzed in different developmental stages of S. japonicum by RT-PCR.

RESULTS

SjFBPA was successfully amplified by using PCR and identified by restriction enzyme digestion and sequencing. The Western blotting analysis confirmed that the recombinant pro- tein could specifically reactive to the anti-His-tag monoclonal antibody. The concentration of the purified recombinant protein was about 4 mg/ml. The result of RT-PCR showed that SjFBPA mRNA was expressed in cercaria, schistosomulum, adult worm and egg of S. japonicum.

CONCLUSION

SjFBPA is successfully recombined and expressed in a prokaryotic system, and SjFBPA mRNA is expressed in cercaria, schistosomulum, adult worm and egg of S. japonicum.

Intake of Erythrocytes Required for Reproductive Development of Female Schistosoma japonicum

The reproductive development and maturation of female schistosomes are crucial since their released eggs are responsible for the host immunopathology and transmission of schistosomiasis. However, little is known about the nutrients required by female Schistosoma japonicum during its sexual maturation. We evaluated the promoting effect of several nutrients (calf serum, red blood cells (RBCs), ATP and hypoxanthine) on the reproductive development of pre-adult females at 18 days post infection (dpi) from mixed infections and at 50 dpi from unisexual infections of laboratory mice in basic medium RPMI-1640. We found RBCs, rather than other nutrients, promoted the female sexual maturation and egg production with significant morphological changes. In 27% of females (18 dpi) from mixed infections that paired with males in vitro on day 14, vitelline glands could be positively stained by Fast Blue B; and in 35% of females (50 dpi) from unisexual infections on day 21, mature vitelline cells were observed. Infertile eggs were detected among both groups. To analyze which component of mouse RBCs possesses the stimulating effect, RBCs were fractionated and included in media. However, the RBC fractions failed to stimulate development of the female reproductive organs. In addition, bovine hemoglobin hydrolysate, digested by neutral protease, was found to exhibit the promoting activity instead of untreated bovine hemoglobin. The other protein hydrolysate, lactalbumin hydrolysate, exhibited a similar effect with bovine hemoglobin hydrolysate. Using quantitative RT-PCR, we found the expression levels of four reproduction-related genes were significantly stimulated by RBCs. These data indicate that RBCs provide essential nutrients for the sexual maturation of female S. japonicum and that the protein component of RBCs appeared to constitute the key nutrient. These findings would improve laboratory culture of pre-adult schistosomes to adult worms in medium with well-defined components, which is important to investigate the function of genes related to female sexual maturation.

Suppression of the Insulin Receptors in Adult Schistosoma japonicum Impacts on Parasite Growth and Development: Further Evidence of Vaccine Potential

To further investigate the importance of insulin signaling in the growth, development, sexual maturation and egg production of adult schistosomes, we have focused attention on the insulin receptors (SjIRs) of Schistosoma japonicum, which we have previously cloned and partially characterised. We now show, by Biolayer Interferometry, that human insulin can bind the L1 subdomain (insulin binding domain) of recombinant (r)SjIR1 and rSjIR2 (designated SjLD1 and SjLD2) produced using the Drosophila S2 protein expression system. We have then used RNA interference (RNAi) to knock down the expression of the SjIRs in adult S. japonicum in vitro and show that, in addition to their reduced transcription, the transcript levels of other important downstream genes within the insulin pathway, associated with glucose metabolism and schistosome fecundity, were also impacted substantially. Further, a significant decrease in glucose uptake was observed in the SjIR-knockdown worms compared with luciferase controls. In vaccine/challenge experiments, we found that rSjLD1 and rSjLD2 depressed female growth, intestinal granuloma density and faecal egg production in S. japonicum in mice presented with a low dose challenge infection. These data re-emphasize the potential of the SjIRs as veterinary transmission blocking vaccine candidates against zoonotic schistosomiasis japonica in China and the Philippines.

Schistosomiasis affects over 200 million people globally. An anti-schistosome vaccine is not currently available. Schistosome eggs play a critical role in host pathology and the transmission of schistosomiasis; thus a vaccine targeting parasite fecundity and/or egg viability represents a realistic strategy for blocking transmission, promoting disease control in endemic areas. Based on our previous studies on the insulin receptors (SjIRs) of Schistosoma japonicum, as potential vaccine candidates, we have now further investigated the impact of insulin signaling on the growth, development, sexual maturation and egg production of adult schistosomes. Protein binding assays and RNAi strongly support our hypothesis that the insulin pathway in schistosomes is activated by the binding between host insulin and the parasite IRs, regulating the transcription of downstream genes integrally involved in glucose uptake and fecundity in these parasites. This feature was reflected in the striking decreased glucose levels of worms when the SjIRs were knocked down. Furthermore, the importance of the SjIRs in the growth and fecundity of adult S. japonicum was further demonstrated in murine vaccine trials using a low dose cercarial challenge which resulted in depressed female growth and faecal egg production in mice vaccinated with the recombinant L1 subdomains of SjIR1 and SjIR2.

[Application effect of Oncomelania hupensis snail crushers in batch detection]

OBJECTIVE

To evaluate the application effect of Oncomelania hupensis snail crusher in batch detection.

METHODS

The O. hupensis snail crushers and triangular flasks for cercariae shedding were made. The uninfected snails were divided into 4 groups with the snail number of 50, 100, 200, 300, respectively, and then they were put in 40 triangular flasks, 10 flasks each group. Three flasks in each group were randomly selected, and 12 schistosome infected O. hupensis snails were put into the flasks (1 snail per flask). The 12 flasks with infected O. hupensis snails were put back to each group and were numbered uniformly. The O. hupensis snails in each group were crushed by the O. hupensis snail crushers, and the crushing rate of snails, and average crushing time and duration were recorded. When all the O. hupensis snails were crushed, water was added into the flasks, and water films from each flask were taken and observed under microscopes, the number of cercariae was recorded and the detection rates of each group were calculated. Meanwhile, the O. hupensis snails in the field were collected and detected by the crushing method and crushing and shedding method with O. hupensis snail crushers, and the coincidence rate of the two methods was calculated.

RESULTS

The crushing rate of snails in all the 4 groups were 100% , the average crushing times of groups with 50, 100, 200, 300 snails were 15.70, 23.20, 32.20, 39.20, respectively, and the average duration was 1.01, 1.70, 2.00, 3.00 min, respectively. Both the crushing time and duration were positively correlated with the number of snails detected (r = 0.68, 0.73, both P <0.01). The detection rates of cercariae in all the 4 groups were 100%. In the field application, 109 snails were detected by the crushing method, 620 ones were detected by the crushing and shedding method with O. hupensis snail crushers, and no infected snails were found, the coincidence rate of the two methods were 100%.

CONCLUSION

The O. hupensis snail crusher with the advances of easy operation and labor-saving is valuable of field promotion.

[Effect of calcium cyanamid synthetic drug on Schistosoma japonicum egg morphology]

OBJECTIVE

To study the morphological change of Schistosoma japonicum eggs processed by calcium cyanamide synthetic drug, so as to provide the basis for further study of the mechanism that calcium cyanamide synthetic drug to schistosome eggs.

METHODS

The calcium cyanamide synthetic drug was added to the cattle feces containing schistosome eggs and mixed up, and then the cattle feces was stacked as original shape on the marshland. Blank controls were set at the same time. The cattle feces samples were collected and.the schistosome eggs were observed under a microscope on the 1st, 2nd, 3rd, 7th day after the experiment.

RESULTS

By the effect of calcium cyanamide synthetic drug, the color of eggs was deepening gradually, the miracidia were atrophied, and the shells of eggs were thickened. The embryonic membrane of miracidia was no longer completed 3 days later, and the miracidia were deformed severely 7 days later. The atrophy of miracidia was not obvious in the blank controls.

CONCLUSION

The schistosome miracidia and embryonic membrane can be damaged by the calcium cyanamide synthetic drug, and worse damaged with time extending.

[Experimental study on determination of viability of Schistosoma japonicum cercariae by staining]

OBJECTIVE

To determine the viability of Schistosoma japonicum cercariae by staining.

METHODS

Schistosoma japonicum cercariae were stained by 0.4% trypan blue, 0.5% methylene blue-eosin-borax (M.E.B), 0.5% eosin, 0.5% methylene blue and 0.05% neutral red, respectively, for 5 min, then they were observed under a stereoscopic microscope.

RESULTS

The dead cercariae were stained in the trypan blue, M.E.B, eosin and neutral red, but unstained in the methylene blue. The vital cercariae were unstained in all the five kinds of dyes.

CONCLUSION

The staining methods by using 0.4% trypan blue, 0.5%M.E.B, 0.5% eosin and 0.05% neutral red can be used to determine the viability of S. japonicum cercariae.

[Distribution characteristics of deposited eggs and pathological changes in viscera of New Zealand white rabbits infected with Schistosoma japonicum at different time]

OBJECTIVE

To study the distribution characteristics of deposited eggs and pathological changes in the viscera of animal infected with Schistosoma japonicum at different time.

METHODS

New Zealand white rabbits were infected artificially with quantitative S. japonicum miracidia, then the distribution characteristics and the hatchability of schistosome eggs as well as the pathological changes of the corresponding viscera of the rabbits 42 and 60 d post-infection were observed and compared.

RESULTS

On the 42nd day post-infection, among all the viscera observed, the percentage of eggs deposited, the number of eggs per gram and the hatchability were the highest in the liver, while on the 60th day post-infection, the tissues and organs with the highest values of the above 3 indexes were the liver, rectum and upper section of the small intestine, respectively. From 42 day to 60 day post-infection, the liver of infected rabbits became swelling, hardening and lost elasticity, the color changed from black to dark grey, and egg nodules gradually appeared in the different sections of the small intestine, and also the mucosal hyperemia, edema and egg nodules were seen in the colon, cecum and rectum. The lesion levels tended to be correlated with the deposition of eggs.

CONCLUSION

The amount and the density as well as the hatching rate of deposited eggs of S. japonicum in the viscera of infected rabbits at different time are different, and the lesion level in the host is correlated with the deposition of eggs.

[Surveillance and forecast system of schistosomiasis in Jiangsu Province. VI. Detection technology of water infectivity based on enrichment of Schistosoma japonicum cercariae on water surface]

OBJECTIVE

To explore the enrichment technique of Schistosoma japonicum cercariae on the water surface, so as to establish a new method combined with the existing technology to detect the cercarial infested water body quickly and sensitively.

METHODS

Soybean oil, gasoline, kerosene and isophorone were screened as expanding agents. The cercariae were enriched by the thrust of the expanding agents when diffusing on the water surface, and PE adsorption film and C-6 film were applied to seize them so as to determine the infectivity of the water quickly. The relationship between the dose of expanding agents and diffusion radius were explored.

RESULTS

Gasoline, kerosene and isophorone were suitable expanding agents, and the diffusion effect of isophorone was the best. After the enrichment by the expanding agents, the detection rate of cercariae of the method seizing cercariae with the film significantly improved in the water.

CONCLUSION

This new method could effectively improve the detection rate of the cercarial infested water and is suitable for the low-degree infested water.

[Cloning and function analysis of high mobility group box 1 (HMGB1) protein of Schistosoma japonicum (Mainland strain)]

OBJECTIVE

To clone and express a high mobility group box 1(HMGB1) protein of Schistosomajaponicum (Mainland strain) and analyze its function.

METHODS

The DNA fragment of open reading frame encoding Sj HMGB 1 protein was amplified by RT-PCR from the mRNA of S. japonicum worms, then it was subcloned into the expression vector pET28a(+) to form the recombinant expression plasmid SjHMGB1-pET28a. The recombinant expression plasmid was transformed into the component E. coli BL21(DE3), and the tranformant containing recombinant expression plasmid was induced with IPTG to express the recombinant protein SjHMGB1. The recombinant SjHMGB1 protein was purified by affinity chromatography with nickel chelating affinity chromatography agarose gel. The Gel retard experiment and animal immunization were performed to analyze the DNA binding capacity and the immunologic property of recombinant SjHMGB1. The expression levels of HMGB1 in different life cycle stages of S. japonicum were analyzed by Western bloting and RT-PCR. Female ICR mice were immunized with the recombinant SjHMGB1 protein and infected with 45 +/- 2 cercariae of S. japonicum after three immunizations. Forty-two days post-infection, the worms and eggs of S. japonicum were recovered from the portal vein and liver tissue, respectively. The worm and egg reduction rates were calculated respectively.

RESULTS

A 530 bp of specific DNA fragment was amplified from mRNA of S. japonicum by RT-PCR, which was the open reading frame (ORF) encoding SjHMGBlprotein confirmed by DNA sequencing analysis. The recombinant expression plasmid SjHMGB1-pET28a was constructed by cloning the ORF of SjHMGB1 into a expression vector pET28a(+). The bacterium transformants containing the recombinant plasmid expressed a soluble recombinant protein about 28 kDa after induced by IPTG, and the recombinant SjHMGB1 protein was purified by nickel chelating affinity chromatography. The gel retard experiment showed that the recombinant SjHMGB1 protein could bind to both supercoiled DNA and linear DNA, and the recombinant protein immunized mice produced high titers of antiserum IgG. Western bloting indicated that the recombinant SjHMGB1 protein was recognized specifically by the S. japonicum-infected mice serum. Above results showed that the recombinant SjHMGB1 protein possessed both functional activity and immunogenicity as the natural protein. RT-PCR and Western blot results showed that SjHMGB1 was abundantly expressed in the adult and egg stages whereas barely detectable in the cercaria stage. The immune protection experiment showed that the recombinant SjHMGB1 induced mice to produce high titers of specific antibody IgG but failed to conduct an effective immune protection against S. japonicum.

CONCLUSION

The gene encoding HMGB1 from S. japonicum and the soluble recombinant SjHMGB1 protein with natural functional activity are obtained, and the recombinant SjHMGB1 has a high immunogenicity but is not able to induce an effective immune protection against S. japonicum.

[Cloning and expression of Schistosoma japonicum VCP gene and its mRNA expression levels in different stages]

OBJECTIVE

To prokaryotically express the valosin-containing protein (VCP) of Schistosoma japonicum, and analyze its VCP mRNA expressions in the cercaria, schistosomulum, adult worm (female and male worms) and egg.

METHODS

RNA of S. japonicum eggs were extracted, and reversely transcribed into cDNA. The VCP gene of S. japonicum was amplified by using polymerase chain reaction (PCR), and subcloned into the prokaryotically expressed vector pET15b. The recombined plasmid was transformed into BL21 cells, and the expression of the target gene was induced with isopropyl-beta-D-thiogalactopyranoside (IPTG). The recombinant protein was yielded through the purification of inclusion body, and identified by using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The RNA (s) of cercaria, schistosomulum, female adult worm, male adult worm, and egg of S. japonicum were extracted, digested with DNase, purified, and reversely transcribed into cDNA. The mRNA expressions of the VCP gene in various developmental stages of S. japonicum were determined by using fluorescence-based quantitative real-time PCR.

RESULTS

The VCP gene of S. japonicum was yielded by PCR amplification, and the recombinant protein was obtained through recombinant plasmid expression and purification of inclusion body. The highest VCP mRNA expression in S. japonicum cercaria was detected by the fluorescence-based quantitative real-time PCR, while low expressions were found in the schistosomulum, egg, female and male adult worms.

CONCLUSION

The recombinant protein encoded by the VCP gene of S. japonicum is successfully obtained, and the VCP mRNA expression is determined in various developmental stages of S. japonicum.

[Optimization of time of artificial population schistosome infected Oncomelania hupensis snails]

OBJECTIVE

To explore the optimizational time of artificial population schistosome infected Oncomelania hupensis snails.

METHODS

Under laboratory conditions, the snails were infected with the miracidia of Schistosoma japonicum for 2 h, 3 h and 4 h respectively, and the death rates and the infection rates of the snails, and the quantities of cercariae of each group were observed 60-120 d after the infection, and all the data observed were analyzed to get the optimizational time of artificial population schistosome infected snails.

RESULTS

Of the 3 h group, the snail infection rate was the highest and the mortality was the lowest among the 3 groups (P<0.05). The average number of cercariae of the 3 h group was higher than that of the 2 h group (P<0.05), while there was no statistical difference between the 3 h group and the 4h group (P>0.05).

CONCLUSION

Under laboratory conditions, the optimizational time is 3 h in artificial population schistosome infected O. hupensis snails.

A circular analysis of chronobiology of Schistosoma japonicum cercarial emergence from hilly areas of Anhui, China

About 46 mammal species have been suspected as reservoir hosts for Schistosoma japonicum and therefore the track of the target parasites, in relation to definitive host species, may be of great importance in terms of theoretical and practical implications. The circadian rhythm of cercariae emergence, a genetically controlled behavior for parasites to adapt to their definitive hosts, may seem to be a perfect biological marker for S. japonicum. In this study, a late (or nocturnal) cercarial emergence pattern was observed on the parasites from one hilly region in Anhui of China, where rodents serve as reservoirs, and on the first generation of the parasites. Moreover, by using the circular statistics, the homogeneity of parasites in such trait was also demonstrated. All these provide evidence for the genetically controlled biological trait, which seems essential in the investigation of macro- or micro-dynamics of parasite transmission of interest. This is particularly true in the case of S. japonicum when multiple parasite isolates or strains are more likely to exist.

[Study of closed colony of Microtus fortis infected with Schistosoma japonicum]

OBJECTIVE

To understand the pathological changes of tissues and organs in Microtus fortis infected with Schistosoma japonicum for further insight into the biological dynamic variation and explore immune mechanisms of M. fortis against S. japonicum infection.

METHODS

The healthy M. fortis and mouse were infected with cercariae of S. japonicum through abdominal skin. On the day 12, 20 and 40, the M. fortis and mouse were sacrificed by cervical dislocation and dissected. The liver and kidney slices of M. fortis and mouse of the different groups were prepared and stained with hematoxylin eosin stain (HE) by conventional techniques, respectively.

RESULTS

We did not find obvious lesions on the internal organs of mouse 12 d and 20 d after the infection and the lesions of M. fortis 40 d after the infection. However, white nodules appeared on the liver, kidney and spleen of the M. fortis 12 d and 20 d after the infection, and there were a lot of S. japonicum worms on pathological sections of inflamed liver and kidney tissues, and the boundary between worms and normal organization was clear. There were no parasites on pathological section of liver and kidney of mouse 12 d and 20 d after the infection.

CONCLUSION

Among M. fortis, there are severe immune responses and the immune responses have an individual difference 12 days after S. japonicum infection.

[Parasitological characteristics, epidemiological and clinical features, and current control approaches for three major kinds of human schistosomiasis]

Schistosomiasis is a tropical disease, which could do serious damage to the people's health, and it hinders the development of the social economy but may be neglected. After a positive control, some countries and regions have blocked the spread of schistosomiasis. However, in the past few years, with the development of social economy, due to the global movement of people, schistosomiasis not only poses a threat to control areas, but also may cause new endemic areas. This article reviews the parasitological characteristics, clinical manifestations, epidemiological situation, and control approaches of three major kinds of human schistosomiasis, schistosomiasis japonica, schistosomiasis haematobia, and schistosomiasis mansoni.

Schistosoma japonicum egg antigen up-regulates fibrogenesis and inhibits proliferation in primary hepatic stellate cells in a concentration-dependent manner

AIM: To investigate the effects of different concentrations of Schistosoma japonicum (S. japonicum) egg antigen on fibrogenesis and apoptosis in primary hepatic stellate cells (HSCs).

METHODS: A mouse model of schistosomiasis-associated liver fibrosis (SSLF) was established by infecting mice with schistosomal cercaria via the abdomen. HSCs were isolated from SSLF mice by discontinuous density gradient centrifugation, and their identity was confirmed by immunofluorescence double staining of α-smooth muscle actin (α-SMA) and desmin. The growth inhibitory effect and 50% inhibitory concentration (IC50) of S. japonicum egg antigen for primary HSCs (24 h) were determined using a cell counting kit-8 (CCK-8) assay. The expression levels of α-SMA, matrix metalloproteinase-9 (MMOL/LP-9) and tissue inhibitor of metalloproteinases-1 (TIMP-1) in HSCs in response to different concentrations of S. japonicum egg antigen were detected by Western blotting and real-time reverse transcription-polymerase chain reaction. The levels of phospho-P38 (P-P38), phospho-Jun N-terminal kinase (P-JNK) and phospho-Akt (P-AKT) in HSCs were detected by Western blotting.

RESULTS: An SSLF mouse model was established, and primary HSCs were successfully isolated and cultured. S. japonicum egg antigen inhibited HSC proliferation in a concentration-dependent manner. The IC50 of the S. japonicum egg antigen was 244.53 ± 35.26 μg/mL. S. japonicum egg antigen enhanced α-SMA expression at both the mRNA and protein levels and enhanced TIMP-1 expression at the mRNA level in HSCs (P < 0.05), whereas the expression of MMOL/LP-9 was attenuated at both the mRNA and protein levels in a concentration-dependent manner (P < 0.05). A high concentration of S. japonicum egg antigen enhanced P-P38, P-JNK and P-AKT activation (P < 0.05). The changes in α-SMA and MMOL/LP-9 expression induced by S. japonicum egg antigen were closely correlated with P-P38 and P-JNK activation (P < 0.05). The attenuation of MMOL/LP-9 was also correlated with P-AKT activation (P < 0.05), but the increase in α-SMA expression was not. TIMP-1 expression was not correlated with P-P38, P-JNK or P-AKT activation.

CONCLUSION: S. japonicum egg antigen promotes fibrogenesis, activates the P38/JNK mitogen-activated protein kinase and AKT/PI3K signaling pathways and inhibits proliferation in primary HSCs isolated from SSLF mice in a concentration-dependent manner.

[Effect of Pulsatilla chinensis (Bunge) Regel saponins on eggs, miracidia and cercariae of Schistosoma japonicum]

OBJECTIVE

To investigate the effect of Pulsatilla chinensis (Bunge) Regel saponins (PRS) against the eggs, miracidia, cercariae of Schistosoma japonicum in vitro and compare its efficacy with praziquantel.

METHODS

ICR mice were infected with the cercariae of S. japonicum by the patching abdominal method. The livers of the mice were grinded, screened, and then the eggs of S. japonicum were obtained 42 days post-infection. The miracidia were hatched by using the eggs, and the cercariae were obtained by using the infected Oncomelania snails on the light. The eggs, miracidia and cercariae of S. japonicum were incubated with 0, 1, 2, 3, 4, 5, 6, 7, 8 microg/ml PRS for different time, and praziquantel (PZQ) was used as the control.

RESULTS

PRS suppressed the hatching rates of eggs for 24 h slightly superior to that of the control drug PZQ at different concentrations, especially in the 4 microg/ml concentration. After the miracidia were incubated with 1, 2, 3, 4, 5, 6, 7, 8 microg/ml PRS for 30 min, the dead rates of miracidia were 13.47, 26.05, 60.99, 90.84, 100, 100, 100, 100%, respectively. After the cercariae were incubated with 1, 2, 3, 4, 5, 6, 7, 8 microg/ml PRS for 30 min, the dead rates of cercariae were 5.32, 18.81, 44.7, 76.87, 98.28, 100, 100, 100%, respectively. PRS showed time- and dose-dependent mortality effects on the miracidia and cercariae of S. japonicum.

CONCLUSION

PRS has the effects against eggs, miracidia, cercariae of S. japonicum in vitro, and it may become a new anti-schistosome agent.

Development of adult worms and granulomatous pathology are collectively regulated by T- and B-cells in mice infected with Schistosoma japonicum

Schistosoma blood flukes, which cause schistosomiasis affecting 200 million people in the world, are dependent on signals from host CD4⁺ T cells to facilitate parasite growth and development in the mammalian host and to induce Th2-biased inflammatory granulomas. B cells, however, are reported to down-regulate granulomatous pathology in schistosomiasis, but not to affect the development of blood flukes together with CD4⁺ T lymphocytes. Thus it is not clear whether B cells mediate parasite development, reproduction and egg granuloma formation of schistosomes without the help of CD4⁺ T lymphocytes. Using mice that have severe combined immunodeficiency (scid) and mice lacking T cells (nude), we found that the absence of B cells can more seriously hamper the development and paring of adult worms, but granuloma formation of Schistosoma japonicum in scid mice was not down-regulated comparing with that in nude mice. The level of IL-10 in the sera of nude mice was significantly higher than of scid mice at 43 days post infection (p.i.). Thus multiple mechanisms of immune modulation seem to be involved in parasite development and reproduction by helminth-induced regulatory B cells. Our findings have significance for understanding the molecular connections between schistosomes and T- and B-cells, indicating that more research is needed to develop efficient vaccine-based therapies for schistosomiasis.

[Infectivity difference between mice challenged by the laboratory-cultivated and field collected Schistosoma japonicum-infected Oncomelania hupensis]

OBJECTIVE

To explore the infectivity difference between the mice challenged by laboratory-cultivated and field collected Schistosomajaponicum-infected Oncomelania hupensis snails.

METHODS

A total of 120 Kunming mice were randomly divided into two groups. S. japonicum-infected O. hupensis releasing cercariae was according to routine cercaria shedding method. Each mouse was challenged by 40 cercariae. The worm-load, the development rate, EPG of liver and EPG of feces in the mice were calculated.

RESULTS

The mean worm-load, adult worm development rate, EPG of liver and EPG of feces in the group of mice infected by field collected S. japonicum-infected snails were 27.43 +/- 3.78, 68.53 +/- 9.44, 19 800.97 +/- 6 752.59 and 196.37 +/- 11.56, respectively, which were significantly higher than those in the group challenged by cercariae from laboratory-cultivated S. japonicum-infected snails (23.93 +/- 4.93, 59.83 +/- 12.32, 5 803.69 +/-1 560.49 and 107.73 +/- 10.32) (P < 0.05). The mean worm-load, adult worm development rate and EPG of liver in the male mouse group were higher than those in the female mouse group (P < 0.05).

CONCLUSION

The cercariae released from field collected S. japonicum-infected snails have more aggressive infection ability, compared with the cercariae released from the laboratory-cultivated S. japonicum-infected snails and the results also show male mice are more susceptibility to the schistosome infection than female mice.

[Effect of agroforestry model on inhibition of Oncomelania snails in plateau mountainous area of Yunnan Province]

OBJECTIVE

To evaluate the effect of agroforestry models on the inhibition of Oncomelania snails in the plateau mountainous area of Yunnan Province.

METHODS

The experimental field was established at Sanying Village of Eryuan County, Yunnan Province, where the "Flourishing Forest and Controlling Snails Project" was implemented. Different drought crops (alfalfa, vegetables, broad bean, garlic, lettuce, celery, green onions, and wheat) were intercropped under walnut forest in experimental groups, and the crops were not intercropped under walnut forest in a control group. The growth of forest, the change of snails and short-term income of residents were investigated.

RESULTS

Agroforestry models promoted the forestry growth and effectively inhibited the growth of snails. There was a little snail in one of the experimental group that forest was intercropped with alfalfa (the occurrence rate of frames with living snails was 3.33%, the average density of living snails was 0.004/0.1 m2, and the declining rates were both 50.00%). The snails were not found in other intercropped models. The income of residents in the experimental groups increased (900-6 800 Yuan per year) compared with that in the control group.

CONCLUSION

The model of walnut forest intercropped with crops not only has the obvious effect on inhibition of snails, but also has good economic and ecological benefits in the plateau mountainous area of Yunnan Province.

[Schistosomicidal effect of BTW5 on adult and juvenile Schistosoma japonicum in vitro]

OBJECTIVE

To evaluate the killing effect of BTW5 on both juvenile and adult worms of Schistosoma japonicum in vitro.

METHODS

The mice were infected with cercariae of Schistosoma japonicum obtained from infected Oncomelania hupensis. The juvenile worms were obtained from the liver and mesenteric veins of the mice by perfusion 18 d after the infection, and the adult worms were obtained from the liver and mesenteric veins of the mice by perfusion 5 weeks after the infection. The adult and juvenile worms were cultivated in DMEM medium containing different concentrations of BTW5 and were observed for 3 d. After the observation, the worms were stained by hydrochloric acid carmine to observe the injuries.

RESULTS

The death rates and motility reducing rates of adult and juvenile worms in DMEM medium containing different concentrations of BTW5 were significantly higher than those in the controls. The staining suggested that BTW5 had a damage effect on the tegument and the intestinal canal of the male and female worms, in addition to the ovaries of the female worms.

CONCLUSION

BTW5 has an antischistosomal effect on adult and juvenile worms of Oncomelania hupensis.

Schistosoma japonicum UDP-glucose 4-epimerase protein is located on the tegument and induces moderate protection against challenge infection

Schistosomiasis is an important global public health problem, as millions of people are at risk of acquiring this infection. An ideal method for sustainable control of schistosomiasis is using a vaccine alone or in combination with drugs. In the present study, we cloned the SjGALE gene and generated the expression product in E. coli. The expression level of SjGALE during different developmental stages of S. japonicum was evaluated by real-time RT-PCR and western blotting. Immunolocalization indicated that the protein was mainly located on the tegument of the parasite. Infection of rSjGALE-immunized mice demonstrated a 34% and 49% reduction of the mean worm burden and liver egg burden, respectively, in two independent experiments, indicating immune protection. The liver egg count from each female adult worm was significantly reduced by 63% in the two trials. The cytokine profile and IgG isotype analysis demonstrated the induction of a Th1 immune profile in response to immunization with this protein, further suggesting protection against infection. In conclusion, these findings indicated that SjGALE is a potential vaccine against S. japonicum.

[Studies on resistance of Schistosoma to praziquantel XIV experimental comparison of susceptibility to praziquantel between PZQ-resistant isolates and PZQ-susceptible isolates of Schistosoma japonicum in stages of adult worms, miracidia and cercariae]

OBJECTIVE

To investigate the changes of sensitivity to praziquantel (PZQ) about PZQ-resistant isolates of Schistosoma japonicum established in laboratory by means of the resistance-inducement method during the stages of adult worms, cercariae and miracidia, so as to provide the basis for establishing the sensitivity-detecting technique to praziquantel.

METHODS

A Jiangsu laboratory-maintaining isolate and a Hunan field-collecting isolate of S. japonicum that were never treated with PZQ were as PZQ-susceptible isolates, and two PZQ-induced isolates that were established via drug-treated passage in laboratory were as PZQ-resistant isolates. Mice were infected with S. japonicum cercariae collected from above four isolates each. Thirty-five days after the infection, the mice were divided into 6 groups and administered orally with PZQ at dosages of 0, 37.5, 75, 150, 300 mg/kg and 600 mg/kg, respectively. All the mice were sacrificed two weeks after the treatment, and all the adult worms in the hepatic and portomesenteric veins were recovered and counted. The mean worm burden and reductions were calculated and input into Graphpad Prism 5.0 software, and the PZQ ED50 values of four isolates were calculated by the software. The cercariae of above four isolates were exposed to 10(-5), 5 x 10(-6), 10(-6), 5 x 10(-7), 10(-7) mol/L PZQ solutions for 20, 40, 60, 80, 100 min and the changes of tail shedding were observed under a dissecting microscope, then the tail shedding rates of cercariae were calculated. The miracidia of above four isolates were exposed to 5 x 10(-6), 10(-6), 5 x 10(-7), 10(-7) mol/L PZQ solutions for 1, 3 and 5 min and the morphological changes were observed under a dissecting microscope, then the morphological change rates of miracidia were calculated.

RESULTS

The PZQ ED50 values of PZQ-susceptible and PZQ-resistant isolates of Jiangsu were 147.7 mg/kg and 565.5 mg/kg, respectively, and the PZQ ED50 values of PZQ-susceptible and PZQ-resistant isolates of Hunan were 151.8 mg/kg and 467.2 mg/kg, respectively. When the cercariae were exposed to 10(-5) mol/L PZQ solution over 20 min, the tail shedding rate of cercariae from PZQ-susceptible isolate of Jiangsu was 68.8%, and the tail shedding rate of cercariae from PZQ-resistant isolate of Jiangsu was 38.2% (P < 0.01). When the cercariae were exposed to 10(-7) mol/L PZQ solution over 100 min, the tail shedding rate of cercariae from PZQ-susceptible isolate of Jiangsu was 15.9%, and the tail shedding rate of cercariae from PZQ-resistant isolate of Jiangsu was 6.7% (P < 0.01). When the cercariae were exposed to 10(-5) mol/L PZQ solution over 20 min, the tail shedding rates of cercariae from PZQ-susceptible isolate of Hunan was 59.4%, and the tail shedding rates of cercariae from PZQ-resistant isolate of Hunan was 54.6% (P < 0.05). When the cercariae were exposed to 5 x 10(-7) mol/L PZQ solution over 40 min, the tail shedding rates of cercariae from PZQ-susceptible isolate of Jiangsu was 34.3%, and the tail shedding rates of cercariae from PZQ-resistant isolate of Jiangsu was 18.4% (P < 0.01). When the miracidia were exposed to 5 x 10(-7) mol/L and 10(-7) mol/L PZQ solutions for 1, 3 and 5 min respectively, the morphological change rates of miracidia from PZQ-susceptible isolates of Jiangsu and Hunan were significantly higher than those of PZQ-resistant isolates (P < 0.01).

CONCLUSIONS

PZQ-resistant isolates of S. japonicum has been established in mice with sub-curative doses of PZQ by artificial selection in laboratory, and their sensitivities to PZQ are significantly lower than those of the isolates never treated with PZQ. The drug-resistance could exhibit in the stages of adult worms, cercariae and miracidia. The PZQ ED50 value of adult worms, the tail shedding rates of cercariae and the morphological change rates of miracidia as quantitative indicators can be used for monitoring the S. japonicum sensitivity to PZQ.

[Studies on resistance of Schistosoma to praziquantel XIII resistance of Schistosoma japonicum to praziquantel is experimentally induced in laboratory]

OBJECTIVE

To investigate the possibility of the emergence of praziquantel resistance in Schistosoma japonicum in Mainland China under drug pressure.

METHODS

S. japonicum cercaria were released from the infected Oncomelania hupensis snails collected from the marshland in Hunan Province that was endemic for schistosomiasis japonica and raised in the laboratory of Jiangsu Institute of Parasitic Diseases, and mice were infected. O. hupensis snails were infected with miracidia hatched from the schistosome mature eggs that were isolated from the liver of the infected mice. The life cycles of a field isolate and a laboratory passage isolate of S. japonicum were established in laboratory via the cycle of mouse-snail. The mice were infected with 40 cercariae each, 35 days later post-infection, were grouped randomly into control and resistance-induced groups. All the mice in the control group were sacrificed on day 45 post-infection, and any adult S. japonicum worms in the hepatic and portomesenteric veins were recovered and counted, and the worm burdens were calculated. The mice in the resistance-induced group were administered orally with the sub-curative dose of praziquantel, and were sacrificed 22 days post-treatment. Any adult S. japonicum worms in the hepatic and portomesenteric veins were recovered and counted, and the worm burdens and reduction in the worms recovered which were obviously caused by the praziquantel treatment were calculated. The eggs in the liver of the mice in the resistance-induced group were isolated and hatched to yield miracidia, and then the snails were again infected with the newly hatched miracidia to complete the first-passage inducement. After raising in laboratory at 25 degrees C for 60-70 days post-infection, the infected snails were isolated and shed cercaria, and the mice were infected with the newly released cercaria to start a new passage of resistance-inducement. The oral dose of praziquantel for the first-passage inducement was 100 mg/kg, and an additional 100 mg/kg was given every 2-3 passages. The mice were infected with cercariae of the parasite with 8-passge resistance-inducement and the isolate that was not induced, and 35 days post-infection, were administered with praziquantel at a single oral doses of 300 mg/kg and 600 mg/kg respectively. All the mice were sacrificed 14 days post - treatment, and any adult S. japonicum worms in the hepatic and portomesenteric veins were recovered and counted, and the reductions in the worm burdens were calculated to assess the sensitivity of praziquantel in the parasites after 8-passage resistance-inducement.

RESULTS

Two isolates of Jiangsu laboratory passage of Jiangsu and field isolate of Hunan were established in the laboratory, and a total 8-passage resistance -inducement was completed. For the laboratory passage isolate, the worm burden reduction was 22.3% post-treatment with 100 mg/kg praziquantel during the first-passage inducement, and 53.7% post-treatment with 300 mg/kg praziquantel during the 8-passage inducement, appearing that the worm burden reduction increased with the increasing dose of praziquantel. For the field-collected isolate, the worm burden reduction was 66.8% post-treatment with 100 mg/kg praziquantel during the first-passage inducement, and 20.6% post-treatment with 300 mg/kg praziquantel during the 8-passage inducement, indicating that the worm burden reduction markedly decreased with the increasing dose of praziquantel. The worm burden reductions were 71.5% and 97.4% respectively for the mice infected with the non-induced laboratory passage isolate, while administered with praziquantel at doses of 300 mg/kg and 600 mg/kg respectively. After 8-passage treatment with sub-curative praziquantel, the corresponding worm burden reductions decreased to 32.6% and 68.1%, respectively. For the field-collected isolate without inducement, the worm burden reductions in the mice were 70.8% and 97.5% respectively post-treatment with praziquantel at doses of 300 mg/kg and 600 mg/ kg respectively, and the corresponding worm burden reductions decreased to 45.7% and 61.9%, respectively after 8-passage treatment. COCLUSIONS: S. japonicum (strain of Mainland China) is able to develop resistance to praziquantel under continuous drug pressure. However, there are variations in the potential of the emergence of resistance due to various susceptibility of praziquantel among different isolates. The successful establishment of praziquantel-resistant strain of S. japonicum (Mainland China) will provide the basis for exploring the mechanism of praziquantel resistance in S. japonicum, and developing related techniques to detect and monitor praziquantel resistance.

[Experiment of praziquantel rectal administration in treatment of schistosomiasis in mice]

OBJECTIVE

To evaluate the efficiency of rectal administration of praziquantel in the treatment of schistosomiasis in mice.

METHODS

Forty mice were divided into 4 groups. Each mouse was infected with Schistosoma japonicum cercariae 40 +/- 2. Forty-two days after the infection, the mouse was rectally administered with different doses of praziquantel. In the first, second and third group, each mouse was given 100, 200 mg/kg, and 400 mg/kg single dose of praziquantel, and the fourth group was a blank control group. One week after the administration, all the mice were sacrificed and the worm reduction rate, reduction rate of liver eggs, and matching reduction rate were calculated. RESULTS The worm reduction rate and matching reduction rate were 57.63% and 76.60% respectively in the 200 mg/kg group, and 49.15% and 51.06% respectively in the 400 mg/kg group, which were better than those in the 100 mg/kg group.

CONCLUSION

Rectal administration of praziquantel has good efficiency in the treatment of schistosomiasis in mice; therefore, it provides a new option for the prevention and control of animal schistosomiasis.

Identification of in vivo protein phosphorylation sites in human pathogen Schistosoma japonicum by a phosphoproteomic approach

Schistosome is the causative agent of human schistosomiasis and related animal disease. Reversible protein phosphorylation plays a key role in signaling processing that are vital for a cell and organism. However, it remains to be undercharacterized in schistosomes. In the present study, we characterized in vivo protein phosphorylation events in different developmental stages (schistosomula and adult worms) of Schistosoma japonicum by using microvolume immobilized metal-ion affinity chromatography (IMAC) pipette tips coupled to nanoLC-ESI-MS/MS. In total, 127 distinct phosphorylation sites were identified in 92 proteins in S. japonicum. A comparison of the phosphopeptides identified between the schistosomula and the adult worms revealed 30 phosphoproteins co-detected in both of the two worms. These proteins included several signal molecules and enzymes such as 14-3-3 protein, cysteine string protein, heat shock protein 90, epidermal growth factor receptor pathway substrate 8, proliferation-associated protein 2G4, peptidyl-prolyl isomerase G, phosphofructokinase and thymidylate kinase. Additionally, the phosphorylation sites were examined for phosphorylation specific motif and evolutionarily conservation. The study represents the first attempt to determine in vivo protein phosphorylation in S. japonicum by using a phosphoproteomic approach. The results by providing an inventory of phosphorylated proteins may facilitate to further understand the mechanisms involved in schistosome development and growth, and then may result in the development of novel vaccine candidates and drug targets for schistosomiasis control.

Identification of phage display peptides with affinity for the tegument of Schistosoma japonicum schistosomula

Peptides, bound to the tegument of live Schistosoma japonicum schistosomula, were differentially screened by phage display in vitro using three rounds of reverse absorption and bio-panning. Three M13 phage peptides were isolated and identified by determination of their recovery rate, immunohistochemical localization, immunoblot analysis, and their anti-schistosomal effects in vivo and in vitro. Of the three, M13 phage peptide ZL4 (MppZL4, YSGLQDSSLRLR, 1.4kDa, pI 8.8) bound to the tegument of mechanically transformed schistosomula and to other developmental stages of S. japonicum from the mammalian host. By contrast, MppZL4 did not bind to the surface of cercariae. To further examine its binding properties, MppZL4 was conjugated to Rhodamine B (RhB-YSGLQDSSLRLR, RhB-ZL4) and a peptide control (RhB-AIPYFSGILQWR, RhB-12P) was similarly synthesized. The binding capacities of RhB-ZL4 to the surface membrane of S. japonicum schistosomula in vitro and of S. japonicum adult worms in vivo were examined and revealed specificity for binding. When examined for anti-parasite activity, both MppZL4 and RhB-ZL4 exhibited a potent schistosomicidal effect in vitro. Further MppZL4 also affected the growth and development of schistosomula in vivo. These findings extend previous studies showing that phage display techniques can recover polypeptides that bind specifically to living schistosomes and, moreover, that these bound peptides have the potential to inhibit key physiological processes in these parasites. Our findings suggest further that ectogenic polypeptides, which can bind to the tegument of S. japonicum, might be adapted as vectors to deliver experimental probes and/or pharmacologically relevant compounds to the schistosome tegument, including drugs and immunological mediators.

Further studies on mefloquine and praziquantel alone or interaction of both drugs against Schistosoma japonicum in vitro

The aim of the present study is to further understand and analyze the interaction of mefloquine with praziquantel against adult Schistosoma japonicum in vitro. Mice infected with S. japonicum cercariae for 35-37 days were sacrificed, and adult schistosomes were collected by perfusion. Schistosomes were placed to each of 12 wells of a Falcon plate and maintained in RPMI 1640 supplemented by 10% calf serum. For determination of 50% and 95% lethal concentration (LC50 and LC95) of the two drugs in vitro, schistosomes were exposed to mefloquine at concentrations of 1, 2, 3, 4, 5, 6, 7, and 10 μg/mL or praziquantel at concentrations of 0.001, 0.01, 0.05, 0.1, 0.2, 0.5, 1, 10, and 30 μg/mL. The plate was incubated at 37°C in 95% air + 5% CO₂ for 72 h. According to the half-life of oral mefloquine and praziquantel in mice, mefloquine combined with praziquantel simultaneously, mefloquine administered within 1 h after praziquantel and praziquantel administered within 17 h after mefloquine were used to evaluate the effect of mefloquine in combination with praziquantel against S. japonicum in vitro. The results showed that the LC50 and LC95 of mefloquine calculated by the Bliss method were 6.17 μg/mL (95% confidence limits, 5.84-6.517 μg/mL) and 8.703 μg/mL (95% confidence limits, 7.632-9.797 μg/mL), respectively. As to praziquantel, no worm death was seen when schistosomes were exposed to praziquantel at concentrations of 0.005-0.2 μg/mL for 72 h. While in the worms exposed to praziquantel 1, 10, and 30 μg/mL, strong spasmodic contractions of the worm body and vesiculation along the worm surface were observed, but 48-75% of the schistosomes survived the exposure in 72-h incubation. Meanwhile, the number of dead worms that emerged in each group was not proportion to the increasing concentrations. Therefore, it is not appropriate to calculate the LC50 and LC95 of praziquantel. For evaluation of the interaction with the two drugs, praziquantel 0.1 or 0.2 μg/mL, which may induce moderate or strong spasmodic contractions of the worm body and vesiculation along the worm surface, was combined with mefloquine 5, 6, or 7 μg/mL. It was found that when mefloquine combined with praziquantel simultaneously or administered 1 h after addition of praziquantel, the spasmodic contraction of the male worm body was antagonized by mefloquine in various degrees according to the concentrations of mefloquine used. Meanwhile, praziquantel-induced weakened motor activity could be reversed by mefloquine. In female worms, morphological alterations and stimulated motor activity induced by mefloquine still developed. Interestingly, using these two regimens to combine mefloquine with praziquantel resulted in no impact or a decrease in worm mortality. On the other hand, praziquantel 0.2 μg/mL administered within 17 h after mefloquine 5 or 6 μg/mL promoted the damage to the tegument of the worms, which led to enhance the worm mortality compared with that of worms exposed to mefloquine alone. The results indicate that in vitro higher concentrations of praziquantel administered within 17 h after mefloquine may increase the effect against adult schistosomes, while praziquantel combined with mefloquine simultaneously or administered 1 h before addition of mefloquine exhibits no impact or decrease in the effect against schistosomes.

Profiles of small non-coding RNAs in Schistosoma japonicum during development

Background

The gene regulation mechanism along the life cycle of the genus Schistosoma is complex. Small non-coding RNAs (sncRNAs) are essential post transcriptional gene regulation elements that affect gene expression and mRNA stability. Preliminary studies indicated that sncRNAs in schistosomal parasites are generated through different pathways, which are developmentally regulated. However, the data of sncRNAs of schistosomal parasites are still fragmental and a complete expression profile of sncRNAs during the parasite development requires a deep investigation.

Methodology/Principal Findings

We employed high-throughput genome-wide transcriptome analytic techniques to explore the dynamic expression of microRNAs (miRNAs) and endogenous siRNAs (endo-siRNAs) of Schistosoma japonicum covering the free-living cercarial stage and all stages in the definitive host. This led us to analyze over 70 million clean reads represented both high and low abundance of the small RNA population. Patterns of differential expression of miRNAs and endo-siRNAs were observed. MiRNAs was twice more than endo-siRNAs in cercariae, but gradually decreased along with the development of the parasite. Both small RNA types were presented in equal aboudance in lung-stage schistosomula, while endo-siRNAs accumulated to 6 times more than miRNAs in adult female worms and hepatic eggs. Further, miRNAs were found mainly derived from genes located in the intergenic regions, while endo-siRNAs were mainly generated from transposable elements (TEs). The expression pattern of TE-siRNAs, as well as the pseudogene-derived siRNAs clustered in mRNAs of cytoskeletal proteins, stress proteins, enzymes related to energy metabolism also revealed distinction throughout different developmental stages. Natural antisense transcripts (NATs)-related siRNAs accounted for minor proportion of the endo-siRNAs which were dominantly expressed in cercariae.

Conclusions/Significance

Our results represented a comprehensive expression profile of sncRNAs in various developmental stages of S. japonicum with high accuracy and coverage. The data would facilitate a deep understanding of the parasite biology and potential discovery of novel targets for the design of anti-parasite drugs.

Schistosomiasis, a debilitating disease, caused by agents of the genus Schistosoma afflicts more than 200 million people worldwide. Schistosomes could serve as an interesting model to explore gene regulation due to its evolutional position, complex life cycle and sexual dimorphism. We previously indicated that sncRNA profile in the parasite S. japonicum was developmentally regulated in hepatic and adult stages. In this study, we systematically investigated mircoRNA (miRNA) and endogenous siRNA (endo-siRNA) profile in this parasite in more detailed developmental stages (cercariae, lung-stage schistosomula, separated adult worms, and liver tissue-trapped eggs) using high-throughput RNA sequencing technology. We observed that the ratio of miRNAs to endo-siRNAs was dynamically changed throughout different developmental stages of the parasite. MiRNAs were expressed dominantly in cercariae, while endo-siRNAs accumulated in adult female worms and hepatic eggs. We demonstrated that miRNAs were mostly derived from intergenic regions whereas siRNAs were mostly derived from transposable elements. We also annotated miRNAs and siRNAs with stage- and gender- biased expression. Our findings would facilitate to understand the gene regulation mechanism of this parasite and discover novel targets for anti-parasite drugs.

[Dynamic changes of early immune responses to attenuated Schistosoma japonicum cercariae induced in BALB/c mice]

OBJECTIVE

To study the early immune activation and its dynamic changes between the attenuated cercariae immunized mice and the normal infected mice.

METHODS

The dendritic cell surface molecules CD11c and T cell surface molecule CD25 expression differences and CD3+CD25+/CD3+ T ratio of the early spleen and/or lung of the attenuated cercariae immunized mice and normal mice were assayed and compared by FCM and IHC, and the immune activation and dynamics of T cells were analyzed.

RESULTS

CD3+CD25+CD3+ T ratio in the spleen cells 7 days post-infection in the immunized group and the normal infected group were (19.52 +/- 3.65)% and (22.12 +/- 3.24)%, respectively; the rates of 14 days and 21 days post-infection were (28.73 +/- 3.94)%, (13.68 +/- 3.64)% and(26.43 +/- 0.40)%, (14.42 +/- 2.24)%, respectively. The expressions of CD11c+DC in the lung of the two groups were (1.05 +/- 0.16)%, (0.96 +/- 0.15)%, (1.34 +/- 0.15)%, (1.09 +/- 0.17)%, (1.49 +/- 0.14)%, (0.97 +/- 0.16)%, respectively; the expressions in the spleen were (2.05 +/- 0.26)%, (1.95 +/- 0.18)%, (2.24 +/- 0.25)%, (2.17 +/- 0.25)%, and (2.18 +/- 0.26)%, (2.06 +/- 0.18)%, respectively, on the 7, 14 and 21 days post-infection. The expressions of CD25+T cells in the lung of the two groups were (1.24 +/- 0.13)%, (1.17 +/- 0.16)%, (1.48 +/- 0.11)%, (1.25 +/- 0.13)%, and (1.55 +/- 0.14)%, (0.97 +/- 0.12)%, respectively; the expressions in the spleen were (3.25 +/- 0.22)%, (2.93 +/- 0.20)%, (4.57 +/- 0.23)%, (3.69 +/- 0.24)% and (4.28 +/- 0.24)%, (3.86 +/- 0.26)%, respectively, on the 7, 14 and 21 days post-infection. The CD3+CD25+/CD3+T rate in the infection control group was significantly higher than that in the cercariae attenuated group, while 14, 21 days post-infection the rates of the attenuated group were significantly higher than those in the normal control group. On the 7, 14 and 21 days post-infection, the lung tissue of the attenuated cercariae immunized mice raised more CD11c+ DC and CD25+ T cells than that of the normal infected mice did.

CONCLUSIONS

The activation of T cells of the immune group and the activation of pulmonary dendritic cells are higher than those in the control group 7 and 14 days post-infection, suggesting that attenuated cercariae in the lungs can raise more antigen presenting cells and their activation.

[Susceptibilities of Oncomelania hupensis snails to Schistosoma japonicum miracidia from different hosts]

OBJECTIVE

To understand the susceptibilities of Oncomelania hupensis snails to Schistosoma japonicum miracidia from different hosts.

METHODS

The Schistosoma japonicum eggs from different hosts, such as rabbits, cattle and mice were collected. These eggs were incubated for miracidia, respectively. Each snail from the same site was exposed to 5 miracidia of Schistosoma japonicum from different hosts. The infected snails were fed in the laboratory for two months. Then all the snails were dissected and observed under the dissecting microscope in order to know the infection rate of snails.

RESULTS

In the experiment group, the infection rates of snails infected with miracidia from rabbits, cattle and mice were 1.42%, 8.67% and 19.87%, respectively, the mortality rates were 29.5%, 13.5% and 24.5%, respectively. However, the infection rates of snails in the control group were 2.63%, 2.02% and 11.66%, respectively, and the mortality rates were 24.0%, 49.5% and 18.5%, respectively.

CONCLUSION

The susceptibilities of Oncomelania snails to Schistosoma japonicum miracidia from 3 kinds of hosts are significantly different.

[Cloning, expression and identification of Toll like receptor interacting protein gene of Schistosoma japonicum]

OBJECTIVE

To clone and express Schistosoma japonicum Toll like receptor interacting protein (SjTollip) in prokaryotic expression system and analyze its stage-specific transcription and expression.

METHODS

The encoding sequence selected from S. japonicum cDNA library was amplified by PCR. The SjTollip gene obtained was subcloned into pET-28a, then transformed into E.coli BL21 and induced with IPTG for expression. The expressed protein was purified with Ni-NTA resin. Total RNA were extracted from different stages of S. japonicum. The immune rabbit sera were prepared by immunizing New Zealand white rabbits with purified recombinant SjTollip protein. RT-PCR and Western blotting were used to analyze the transcription and expression level at the different stages and the immunogenicity.

RESULTS

The expression vector of SjTollip/pET-28a was constructed and expressed as inclusion bodies (Mr 24 000). The recombinant protein rSjTollip was specifically recognized by the S. japonicum-infected rabbit serum. SjTollip showed lower transcription level in stages including cercariae and male worms. Western blotting analysis showed that the target protein was detected in all stages. The expression level in stages including schistosomulum and female worm was much higher.

CONCLUSIONS

The SjTollip transcription and expression level at the different stages of S. japonicum is different, and this gene might be a potential candidate for target of vaccine, drug and diagnosis.

Apoptosis governs the elimination of Schistosoma japonicum from the non-permissive host Microtus fortis

The reed vole, Microtus fortis, is the only known mammalian host in which schistosomes of Schistosoma japonicum are unable to mature and cause significant pathogenesis. However, little is known about how Schistosoma japonicum maturation (and, therefore, the development of schistosomiasis) is prevented in M. fortis. In the present study, the ultrastructure of 10 days post infection schistosomula from BALB/c mice and M. fortis were first compared using scanning electron microscopy and transmission electron microscopy. Electron microscopic investigations showed growth retardation and ultrastructural differences in the tegument and sub-tegumental tissues as well as in the parenchymal cells of schistosomula from M. fortis compared with those in BALB/c mice. Then, microarray analysis revealed significant differential expression between the schistosomula from the two rodents, with 3,293 down-regulated (by ≥ 2-fold) and 71 up-regulated (≥ 2 fold) genes in schistosomula from the former. The up-regulated genes included a proliferation-related gene encoding granulin (Grn) and tropomyosin. Genes that were down-regulated in schistosomula from M. fortis included apoptosis-inhibited genes encoding a baculoviral IAP repeat-containing protein (SjIAP) and cytokine-induced apoptosis inhibitor (SjCIAP), genes encoding molecules involved in insulin metabolism, long-chain fatty acid metabolism, signal transduction, the transforming growth factor (TGF) pathway, the Wnt pathway and in development. TUNEL (terminal deoxynucleotidyl transferase dUTP nick end labeling) and PI/Annexin V-FITC assays, caspase 3/7 activity analysis, and flow cytometry revealed that the percentages of early apoptotic and late apoptotic and/or necrotic cells, as well as the level of caspase activity, in schistosomula from M. fortis were all significantly higher than in those from BALB/c mice.

[Mathematical modeling as an aid in understanding transmission and control of Schistosoma japonicum in hilly and mountainous regions of China]

Over the past years there has been an increasing trend in the application of mathematical models in the studies and control of infectious disease. With development of computing technologies and increasing access to them, it becomes appealing for public health professionals to use mathematical models in their work. In this paper based on our previous experience working on environmental determinants and control of schistosomiasis in the hilly and mountainous regions of Sichuan Province, we introduce principles and basic procedures in building a mathematical model for schistosomiasis transmission; we then illustrate the use of a mathematical model to integrate data from diverse sources and to aid in designing control strategies, assessing progress, and evaluating surveillance programs.

[Evaluation of Kato-Katz technique combined with stool hatching test in diagnosis of schistosomiasis japonica]

OBJECTIVE

To develop an aetiology detection method with higher sensitivity and accuracy for schistosomiasis japonica.

METHODS

The fresh fecal samples were collected from residents of a schistosomiasis japonica endemic village in Laozi County of Hubei Province. Two samples per person were collected in two consecutive days. Each sample was examined three times with Kato-Katz technique, then the negative cases were re-examined by the stool hatching test after the egg concentration with nylon-tissue bags. The detective rates and the relation with egg per gram (EPG) of different methods were analyzed and compared. The epidemiology data were collected as well.

RESULTS

A total of 562 residents were examined by Kato-Katz technique, and 67 of them were positive. The samples of 495 negative persons were re-examined by using the hatching test after the egg concentration with nylon-tissue bags. Six persons were positive. The total number of positive cases was 73. The rates of Kato-Katz technique with three slides of one sample and six slides of two samples were 65.8% and 91.8%, respectively. The detective rate was increased with the increase of examining slides. The geometrical averages of EPG from one slide to six slides were 61.12, 31.92, 23.71, 20.88, 19.35 and 8.83, respectively. The accuracy of EPG increased with the increase of numbers of slides.

CONCLUSION

Kato-Katz technique with six slides of two samples is applicable in diagnosis of schistosomiasis japonica in order to achieve higher detective rate and more accurate EPG.

[Destructive effect of eggs of Schistosoma japonicum on spleens in C57BL/6 mice]

OBJECTIVE

To observe the destructive effect of eggs of Schistosomajaponicum on the splenic structure in C57BL/6 mice.

METHODS

The C57BL/6 mice were injected intravenously with eggs of S. japonicum or soluble egg antigen (SEA), or the eggs were injected surgically into the spleens of the mice. Four weeks later, the mice were sacrificed, the splenic paraffin sections were stained with H & E and the splenic structures were observed. Other two groups of mice were infected with single-sex and both sexes of schistosome cercariae, respectively. Nine weeks after the infection, the mice were sacrificed, and the splenic structures were observed and compared among the groups aforementioned.

RESULTS

The splenic structure of mice injected intravenously with eggs were destroyed, and characterized with decreased number of lymphoid follicles and blurred marginal zone. Lymphoid follicles around the eggs injected into the spleen were also seriously depauperated. The splenic weight (0.15 +/- 0.01) g of the mice infected with single-sex cercariae significantly less than that (0.41 +/- 0.03) g of the mice infected with both sexes cercariae (P < 0.01). However, the splenic structure of the mice infected with single-sex cercariae kept integrated.

CONCLUSION

Eggs of S. japonicum have a destructive effect on the splenic structure in C57BL/6 mice.

[Antibody responses to leucine aminopeptidase in Schistosoma japonicum infection]

OBJECTIVE

To investigate the antibody response to leucine aminopeptidase in the different stages of Schistosoma japonicum infection.

METHODS

The expression product of SjLAP was identified by Western blot and further purified by using nickel column. The IgG levels in the response to SjLAP in murine and porcine sera were detected by ELISA at different time points after the infection of S. japonicum.

RESULTS

SjLAP expressed by E. coli was recognized by anti-his monoclonal antibody and S. japonicum-infected mice sera by Western blot. The results of ELISA showed that IgG responses to SjLAP rose gradually and reached the peak at 4 weeks post-infection for pigs (P1) and 6 weeks post-infection for mice (P2). With the appearance of a large number of eggs in the tissue, SjLAP-specific IgG levels were significantly down-regulated ( P1 = 0. 0004, P2 = 0. 0001).

CONCLUSION

SjLAP originated from the adult worm might become a potential target for early diagnosis of schistosomiasis japonica.

[Surveillance and forecast system of schistosomiasis in Jiangsu Province V monitoring of infectivity of Schistosoma japonicum miracidia of Yangtze River]

OBJECTIVE

To establish an approach to monitor the Schistosoma japonicum miracidia in waterbody of the Yangtze River, and monitor the infectivity of water body, so as to provide the evidence for tracing and controlling infection source and interrupting the transmission of schistosomiasis, and Oncomelania snail control.

METHODS

The floating bottle-nylon bag sentinel snails method was employed. A total of 45 surveillance sites were selected along the Jiangsu section of the Yangtze River, 500 snails were placed into each site from May to September, once every month. Twenty-eight hours later, all the snails were transferred and raised in an incubator at 25 degrees C. Two months after the first recovery, the snail infection was detected each month by using the cercaria-shedding test. Three months after the final placement, all the snails were dissected for observation of the infection. The activities of humans and domestic animals were surveyed in the settings where infected snails were found. The database of surveillance results of sentinel snails in the Yangtze River, Jiangsu Province was established, and the geographical distribution map of site with infected snails was drawn, and the probability that snails were infected with S. japonicum was estimated.

RESULTS

A total of 44 717 sentinel snails were placed in 45 sites during the period of 5 months, and 43 477 recovered, with a recovery rate of 97.23%. A total of 81 410 snails were detected by the cercaria-shedding test, no infections were found. A total of 13 033 snails were dissected, and 5 were infected, with an infection rate of 0.038%. The probability of snail infection in water was 4.11 out of a million. Five sites with infected snails were found in 45 sites, with an occurrence rate of 11.11%. The sites with infected sentinel snails were distributed in south bank (3, 21.43%), north bank (1, 5.56%) and river center (1, 7.69%), respectively. The occurrence rate of sites with infected snails in south bank was 3.8 times more than that in north bank. Among the 5 sites, 3 were anchor points of boat fishermen.

CONCLUSIONS

The contamination of S. japonicum eggs in south bank of the Yangtze River is higher than that in north bank in Jiangsu Province, and the anchor point of boat fisherman is one of the important contamination regions. The floating bottle-nylon bag sentinel snails testing method is an effective approach to monitor the contamination of S. japonicum eggs in water.

[Effects of signal transducers and activators of transcription 4 and 6 on development of worms and granuloma formation in mice infected with Schistosoma japonicum]

OBJECTIVE

To explore the effects of STAT4 and STAT6 on the development of worms and granuloma formation in mice infected with Schistosoma japonicum.

METHODS

All the intact BALB/cJ mice and STAT4(-/-), STAT6(-/-) mice with the same genetic background were infected with 25 S. japonicum cercariae. All the mice were sacrificed on the 42nd day after infection and the worms were collected. The total number of worms and the mean number of worm pairs were counted. The liver of each mouse was removed for the count of eggs, the histological examination and the determination of the size of single-egg granulomas in the liver.

RESULTS

No significant differences were found in the total number of worms, the number of worm pairs and the number of eggs per pair of worms in the liver among STAT4(-/-), STAT6(-/-) and BALB/cJ mice. The size of single-egg granulomas in the liver of STAT6(-/-) mice (213.3 +/- 68.6) microm was significantly smaller than that in the liver of normal BALB/cJ mice (319.5 +/- 71.9) microm (P < 0.05). The liver granulomas were not well formed and the liver fibrosis decreased in STAT6(-/-) mice.

CONCLUSIONS

STAT4 or STAT6 deficiency has no conspicuous effect on the development and fecundity of S. japonicum. STAT6 plays an important role for the granuloma formation and liver fibrosis.