Evaluation of the TLR3 involvement during Schistosoma japonicum-induced pathology

BACKGROUND

Despite the functions of TLRs in the parasitic infections have been extensively reported, few studies have addressed the role of TLR3 in the immune response to Schistosoma japonicum infections. The aim of this study was to investigate the properties of TLR3 in the liver of C57BL/6 mice infected by S. japonicum.

METHODS

The production of TLR3+ cells in CD4+T cells (CD4+CD3+), CD8+T cells (CD8+CD3+), γδT cells (γδTCR+CD3+), NKT cells (NK1.1+CD3+), B cells (CD19+CD3-), NK (NK1.1-CD3+) cells, MDSC (CD11b+Gr1+), macrophages (CD11b+F4/80+), DCs (CD11c+CD11b+) and neutrophils (CD11b+ Ly6g+) were assessed by flow cytometry. Sections of the liver were examined by haematoxylin and eosin staining in order to measure the area of granulomas. Hematological parameters including white blood cell (WBC), red blood cell (RBC), platelet (PLT) and hemoglobin (HGB) were analyzed. The levels of ALT and AST in the serum were measured using biochemical kits. The relative titers of anti-SEA IgG and anti-SEA IgM in the serum were measured by enzyme-linked immunosorbent assay (ELISA). CD25, CD69, CD314 and CD94 molecules were detected by flow cytometry.

RESULTS

Flow cytometry results showed that the expression of TLR3 increased significantly after S. japonicum infection (P < 0.05). Hepatic myeloid and lymphoid cells could express TLR3, and the percentages of TLR3-expressing MDSC, macrophages and neutrophils were increased after infection. Knocking out TLR3 ameliorated the damage and decreased infiltration of inflammatory cells in infected C57BL/6 mouse livers.,The number of WBC was significantly reduced in TLR3 KO-infected mice compared to WT-infected mice (P < 0.01), but the levels of RBC, platelet and HGB were significantly increased in KO infected mice. Moreover, the relative titers of anti-SEA IgG and anti-SEA IgM in the serum of infected KO mice were statistically decreased compared with the infected WT mice. We also compared the activation-associated molecules expression between S.japonicum-infected WT and TLR3 KO mice.

CONCLUSIONS

Taken together, our data indicated that TLR3 played potential roles in the context of S. japonicum infection and it may accelerate the progression of S. japonicum-associated liver pathology.

Vaccination against the HDL receptor of S. japonicum inhibits egg embryonation and prevents fatal hepatic complication in rabbit model

BACKGROUND

Schistosomiasis is one of the most important neglected tropical infectious diseases to overcome and the primary cause of its pathogenesis is ectopic maturation of the parasite eggs. Uptake of cholesteryl ester from the host high-density lipoprotein (HDL) is a key in this process in Schistosoma japonicum and CD36-related protein (CD36RP) has been identified as the receptor for this reaction. Antibody against the extracellular domain of CD36RP (Ex160) efficiently blocked the HDL cholesteryl ester uptake and the egg embryonation in vitro. However, whether Ex160 immunization could efficiently raise proper antibody responses to sufficiently block HDL cholesteryl ester uptake and the egg embryonation to protect host in vivo is very interesting but unknown.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, rabbits were immunized with the recombinant Ex160 peptide (rEx160) to evaluate its anti-pathogenic vaccine potential. Immunization with rEx160 induced consistent anti-Ex160 IgG antibody and significant reduction in development of the liver granulomatosis lesions associated with suppressed intrahepatic maturation of the schistosome eggs. The immunization with rEx160 rescued reduction of serum HDL by the infection without changing its size distribution, being consistent with interference of the HDL lipid uptake by the parasites or their eggs by antibody against Ex160 in in vitro culture.

CONCLUSIONS/SIGNIFICANCE

The results demonstrated that vaccination strategy against nutritional supply pathway of the parasite is effective for reducing its pathogenesis.

[Protective effect of recombinant Schistosoma japonicum cystatin against acute kidney injury associated with acute liver failure in mice]

OBJECTIVE

To evaluate the protective effect of recombinant Schistosoma japonicum cystatin (rSj-Cys) against acute kidney injury induced by acute liver failure and unravel the underlying mechanism, so as to provide insights into the clinical therapy of acute kidney injury.

METHODS

Twenty-four male C57BL/6J mice at ages of 6 to 8 weeks were randomly divided into the normal control group, rSj-Cys control group, lipopolysaccharide (LPS)/D-galactosamine (D-GaIN) model group and LPS/D-GaIN + rSj-Cys treatment group, of 6 mice each group. Mice in the LPS/D-GaIN group and LPS/D-GaIN + rSj-Cys group were intraperitoneally injected with LPS (10 μg/kg) and D-GaIN (700 mg/kg), and mice in the LPS/D-GaIN + rSj-Cys group were additionally administered with rSj-Cys (1.25 mg/kg) by intraperitoneal injection 30 min post-modeling, while mice in the rSj-Cys group were intraperitoneally injected with rSj-Cys (1.25 mg/kg), and mice in the normal control group were injected with the normal volume of PBS. All mice were sacrificed 6 h post-modeling, and mouse serum and kidney samples were collected. Serum creatinine (Cr) and urea nitrogen (BUN) levels were measured, and the pathological changes of mouse kidney specimens were examined using hematoxylin-eosin (HE) staining. Serum tumor necrosis factor (TNF)-α and interleukin (IL)-6 levels were detected using enzyme-linked immunosorbent assay (ELISA), and the expression of inflammatory factors and pyroptosis-related proteins was quantified in mouse kidney specimens using immunohistochemistry. In addition, the expression of pyroptosis-related proteins and nuclear factor-kappa B (NF-κB) signaling pathway-associated proteins was determined in mouse kidney specimens using Western blotting assay.

RESULTS

HE staining showed no remarkable abnormality in the mouse kidney structure in the normal control group and the rSj-Cys control group, and renal tubular injury was found in LPS/D-GaIN group, while the renal tubular injury was alleviated in LPS/D-GaIN+rSj-Cys treatment group. There were significant differences in serum levels of Cr (F = 46.33, P < 0.001), BUN (F = 128.60, P < 0.001), TNF-α (F = 102.00, P < 0.001) and IL-6 (F = 202.10, P < 0.001) among the four groups, and lower serum Cr [(85.35 ± 32.05) μmol/L], BUN [(11.90 ± 2.76) mmol/L], TNF-α [(158.27 ± 15.83) pg/mL] and IL-6 levels [(56.72 ± 4.37) pg/mL] were detected in the in LPS/D-GaIN + rSj-Cys group than in the LPS/D-GaIN group (all P values < 0.01). Immunohistochemical staining detected significant differences in TNF-α (F = 24.16, P < 0.001) and IL-10 (F = 15.07, P < 0.01) expression among the four groups, and lower TNF-α [(106.50 ± 16.57)%] and higher IL-10 expression [(91.83 ± 5.23)%] was detected in the LPS/D-GaIN + rSj-Cys group than in the LPS/D-GaIN group (both P values < 0.01). Western blotting and immunohistochemistry detected significant differences in the protein expression of pyroptosis-related proteins NOD-like receptor thermal protein domain associated protein 3 (NLRP3) (F = 24.57 and 30.72, both P values < 0.001), IL-1β (F = 19.24 and 22.59, both P values < 0.001) and IL-18 (F = 16.60 and 19.30, both P values < 0.001) in kidney samples among the four groups, and lower NLRP3, IL-1β and IL-18 expression was quantified in the LPS/D-GaIN + rSj-Cys treatment group than in the LPS/D-GaIN group (P values < 0.05). In addition, there were significant differences in the protein expression of NF-κB signaling pathway-associated proteins p-NF-κB p-P65/NF-κB p65 (F = 71.88, P < 0.001), Toll-like receptor (TLR)-4 (F = 45.49, P < 0.001) and p-IκB/IκB (F = 60.87, P < 0.001) in mouse kidney samples among the four groups, and lower expression of three NF-κB signaling pathway-associated proteins was determined in the LPS/D-GaIN + rSj-Cys treatment group than in the LPS/D-GaIN group (all P values < 0.01).

CONCLUSIONS

rSj-Cys may present a protective effect against acute kidney injury caused by acute liver failure through inhibiting inflammation and pyroptosis and downregulating the NF-κB signaling pathway.

[Imbalance of Th17/Tregs promotes egg granuloma formation of liver with Schistosomiasis japonicum in mice]

Objectives To investigate the effect of the imbalance of Th17/Treg on egg granuloma formation of liver with Schistosomiasis japonicum. Methods The BALB/c mice were infected with Schistosoma japonicum cercariae to establish a model of Schistosomiasis japonica. The blood samples, liver tissues and spleen tissue were harvested at the 2nd, 4th, 6th, 8th week, respectively. HE staining and Masson staining were performed to assess the pathological characteristics of the liver. Flow cytometry (FCM) was conducted to evaluate the proportion of CD4⁺ T cell subsets including Th17 cells and Tregs in liver and spleen tissue. The quantitative real-time PCR (qRT-PCR) was carried out to investigate the mRNA level of cytokines including RORγt, FOXP3, IL-6, IL-17, IL-23 and IL-10 in liver tissues. Finally, ELISA was performed to assess the serum level of cytokines including IL-6, IL-17, IL-23 and TGF-β. Schistosoma japonicium soluble egg antigen (SjSEA) were prepared to stimulate mouse spleen cells in vitro. qRT-PCR was carried out to investigate the mRNA level of cytokine including RORγt and FOXP3 and ELISA was performed to assess the expression level of cytokines including IL-6, IL-17, IL-23 and TGF-β at different time points. Results HE and Masson staining demonstrated that inflammatory cell infiltration, schistosome egg granuloma formation and the collagen deposition increased in the liver tissue after the 4th week. The longer the infection, the more severe the liver pathology. In the liver and spleen tissues, the percentage of Th17 cells of infection group (2nd, 4th and 6th weeks) were significantly higher than the healthy group. The percentage of Tregs in the liver tissues of infection group (4th, 6th and 8th weeks) were significantly higher than the healthy group, and the percentage of Tregs in the spleen of infection group (2nd and 4th weeks) were significantly higher than the healthy group. Th17/Treg ratios in the liver of infection group were lower than the healthy group. Th17/Treg ratios in the spleen of infection group (2nd and 4th weeks) were lower than the healthy group, while it increased in the 6th week. At the same time, the levels of Th17 cells and Tregs related nuclear transcription factors and cytokines showed similar dynamic changes as the percentages of T cell subsets. SjSEA can induce the differentiation of Th17 and Tregs and the expression of related cytokines and transcription factors. Conclusion Th17 cells may play a major role in liver pathology, and the imbalance of Th17 cells/Tregs was closely related to the schistosome egg granuloma formation.

Comparative transcriptome profiles of Schistosoma japonicum larval stages: Implications for parasite biology and host invasion

Schistosoma japonicum is prevalent in Asia with a wide mammalian host range, which leads to highly harmful zoonotic parasitic diseases. Most previous transcriptomic studies have been performed on this parasite, but mainly focus on stages inside the mammalian host. Moreover, few larval transcriptomic data are available in public databases. Here we mapped the detailed transcriptome profiles of four S. japonicum larval stages including eggs, miracidia, sporocysts and cercariae, providing a comprehensive development picture outside of the mammalian host. By analyzing the stage-specific/enriched genes, we identified functional genes associated with the biological characteristic at each stage: e.g. we observed enrichment of genes necessary for DNA replication only in sporocysts, while those involved in proteolysis were upregulated in sporocysts and/or cercariae. This data indicated that miracidia might use leishmanolysin and neprilysin to penetrate the snail, while elastase (SjCE2b) and leishmanolysin might contribute to the cercariae invasion. The expression profile of stem cell markers revealed potential germinal cell conversion during larval development. Additionally, our analysis indicated that tandem duplications had driven the expansion of the papain family in S. japonicum. Notably, all the duplicated cathepsin B-like proteases were highly expressed in cercariae. Utilizing our 3rd version of S. japonicum genome, we further characterized the alternative splicing profiles throughout these four stages. Taken together, the present study provides compressive gene expression profiles of S. japonicum larval stages and identifies a set of genes that might be involved in intermediate and definitive host invasion.

Schistosoma japonicum SjE16.7 Protein Promotes Tumor Development via the Receptor for Advanced Glycation End Products (RAGE)

Schistosome infection contributes to cancer development, but the mechanisms are still not well-understood. SjE16.7 is an EF-hand calcium-binding protein secreted from Schistosoma japonicum eggs. It is a neutrophil attractant and macrophage activator and, as such, plays an important role in the inflammatory granuloma response in schistosomiasis. Here, we show that SjE16.7 binds to host cells by interacting with receptors for advanced glycation end products (RAGE). This ligation leads to activation of the NF-κB signaling pathway, an increase in the generation of reactive oxygen species, and production of the pro-inflammatory cytokines IL-6 and TNF-α. Using a mouse model of colorectal cancer, we demonstrate that intraperitoneal injection of SjE16.7 promotes colorectal cancer progression along with systemic myeloid cell accumulation. Thus, our results identify a new helminth antigen contributing to tumor development in the mammalian host.

Why does oxamniquine kill Schistosoma mansoni and not S. haematobium and S. japonicum?

Human schistosomiasis is a disease which globally affects over 229 million people. Three major species affecting humans are Schistosoma mansoni, S. haematobium and S. japonicum. Previous treatment of S. mansoni includes the use of oxamniquine (OXA), a prodrug that is enzymatically activated in S. mansoni but is ineffective against S. haematobium and S. japonicum. The OXA activating enzyme was identified and crystallized, as being a S. mansoni sulfotransferase (SmSULT). S. haematobium and S. japonicum possess homologs of SmSULT (ShSULT and SjSULT) begging the question; why does oxamniquine fail to kill S. haematobium and S. japonicum adult worms? Investigation of the molecular structures of the sulfotransferases indicates that structural differences, specifically in OXA contact residues, do not abrogate OXA binding in the active sites as previously hypothesized. Data presented argue that the ability of SULTs to sulfate and thus activate OXA and its derivatives is linked to the ability of OXA to fit in the binding pocket to allow the transfer of a sulfur group.

Identification of Schistosoma japonicum GSK3β interacting partners by yeast two-hybrid screening and its role in parasite survival

Schistosoma is the causative agent of schistosomiasis, a common infectious disease distributed worldwide. Our previous phosphoproteomic analysis suggested that glycogen synthase kinase 3 (GSK3), a conserved protein kinase in eukaryotes, is likely involved in protein phosphorylation of Schistosoma japonicum. Here, we aimed to identify the interacting partners of S. japonicum GSK3β (SjGSK3β) and to evaluate its role in parasite survival. Toward these ends, we determined the transcription levels of SjGSK3β at different developmental stages and identified its interacting partners of SjGSK3β by screening a yeast two-hybrid S. japonicum cDNA library. We further used RNA interference (RNAi) to inhibit the expression of SjGSK3β in adult worms in vitro and examined the resultant changes in transcription of its putative interacting proteins and in worm viability compared with those of control worms. Reverse transcription-quantitative polymerase chain analysis indicated that SjGSK3β is expressed throughout the life cycle of S. japonicum, with higher expression levels detected in the eggs and relatively higher expression level found in male worms than in female worms. By screening the yeast two-hybrid library, eight proteins were identified as potentially interacting with SjGSK3β including cell division cycle 37 homolog (Cdc37), 14-3-3 protein, tegument antigen (I(H)A), V-ATPase proteolipid subunit, myosin alkali light chain 1, and three proteins without recognized functional domains. In addition, SjGSK3β RNAi reduced the SjGSK3β gene transcript level, leading to a significant decrease in kinase activity, cell viability, and worm survival. Collectively, these findings suggested that SjGSK3β may interact with its partner proteins to influence worm survival by regulating kinase activity.

Spatiotemporal expression pattern of Sjfz7 and its expression comparison with other frizzled family genes in developmental stages of Schistosoma japonicum

Wnts are secreted signaling molecules that are implicated in a variety of growth-related processes. Frizzled proteins have been identified as receptors for Wnt ligands in vertebrates and invertebrates, but a functional role for dioecious flatworm Frizzleds has not been determined. To evaluate the endogenous role of Frizzled proteins during development, we have identified and characterized a Schistosoma japonicum frizzled gene (Sjfz7). We found that Sjfz7 encodes a 698 amino acid protein with typical characteristics of Frizzled proteins. The immunohistochemical localization pattern showed that Sjfz7 protein was extensively distributed in almost all tissues of S. japonicum, including subtegumental muscle cells, parenchymal cells, intestinal epithelial cells and male and female germ cells. This indicated that Sjfz7-mediated Wnt signaling might be associated with the development of musculature, intestinal tract and reproductive organs in schistosome. Comparing mRNA levels between frizzled family members showed that Sjfz7 mRNA was consistently higher in the developmental stages analyzed, suggesting that Sjfz7 may be responsible for more functional tasks than other frizzled family members. Comparing frizzled mRNA levels between not fully developed and normal worms suggested that Wnt signaling might be abnormal in not fully developed worms.

Toll-like receptor-2 regulates macrophage polarization induced by excretory-secretory antigens from Schistosoma japonicum eggs and promotes liver pathology in murine schistosomiasis

Schistosomiasis is endemic to many regions of the world and affects approximately 200 million people. Conventional adaptive T cell responses are considered to be the primary contributors to the pathogenesis of Schistosoma japonicum infection, leading to liver granuloma and fibrosis. However, the functional polarization of macrophages and the associated underlying molecular mechanisms during the pathogenesis of schistosomiasis remains unknown. In the present study, we found that excretory-secretory (ES) antigens derived from S. japonicum eggs can activate macrophages, which exhibit an M2b polarization. Furthermore, ES antigen-induced M2b polarization was found to be dependent on enhanced NF-κB signaling mediated by the MyD88/MAPK pathway in a TLR2-dependent manner. In addition, the cytokine profile of the liver macrophages from wild-type-infected mice are quite distinct from those found in TLR2 knockout-infected mice by quantitative PCR analysis. More importantly, the size of granuloma and the severity of the fibrosis in the livers of TLR2^-/- mice were significantly reduced compared to that in WT mice. Our findings reveal a novel role for M2b polarization in the pathogenesis of schistosome infection.

Schistosomiasis is a global health concern that affects primarily tropical and subtropical areas. During a schistosome infection, the eggs are trapped in the host liver and products derived from eggs induce a polarized Th2 response, resulting in granuloma formation and eventually fibrosis. Thus, it is important to elucidate the mechanism of granuloma formation and fibrosis development. Here, we show that activated macrophages play a novel role in the promotion of hepatic granuloma formation and liver fibrosis in a Schistosoma japonicum-infected mouse model. In addition, M2b polarization induced by egg products was dependent on enhanced NF-κB signaling mediated by the MyD88/MAPK pathway in a TLR2-dependent manner. Our findings reveal a novel role and mechanism of M2b polarization in the liver pathogenesis in S. japonicum-infected mice.

Schistosoma japonicum IAP and Teg20 safeguard tegumental integrity by inhibiting cellular apoptosis

Schistosomes are causative agents of human schistosomiasis, which is endemic in tropical and subtropical areas of the world. Adult schistosomes can survive in their final hosts for several decades, and they have evolved various strategies to overcome the host immune response. Consequently, understanding the mechanisms that regulate parasitic cell survival will open avenues for developing novel strategies against schistosomiasis. Our previous study suggested that an inhibitor of apoptosis protein in Schistosoma japonicum (SjIAP) may play important roles in parasitic survival and development. Here, we demonstrated that SjIAP can negatively regulate cellular apoptosis in S. japonicum by suppressing caspase activity. Immunohistochemistry analysis indicated that SjIAP ubiquitously expressed within the worm body including the tegument. Silencing of SjIAP expression via small interfering RNA led to destruction of the tegument integrity in schistosomes. We further used co-immunoprecipitation to identify interaction partners of SjIAP and revealed the tegument protein SjTeg-20 as a putative interacting partner of SjIAP. The interaction between SjIAP and SjTeg-20 was confirmed by a yeast two-hybrid (Y2H) assay. Moreover, results of a TUNEL assay, RNA interference, scanning and transmission electron microscopy, caspase assays, transcript profiling, and protein localization of both interacting molecules provided first evidence for an essential role of SjIAP and SjTeg-20 to maintain the structural integrity of the tegument by negatively regulating apoptosis. Taken together, our findings suggest that the cooperative activities of SjIAP and SjTeg-20 belong to the strategic inventory of S. japonicum ensuring survival in the hostile environment within the vasculature of the final host.

Schistosomiasis is a worldwide public health concern particularly in developing countries. The causative agents, schistosomes, can survive within the vascular system of their final hosts for several decades despite facing the host’s immune response. Therefore, elucidating the mechanism of cell survival will contribute to the understanding of host-parasite interaction and may lead to the identification of suitable targets for developing novel strategies against schistosomiasis. Inhibitor of apoptosis proteins are highly conserved proteins functioning as endogenous inhibitors of apoptotic cell death. Here, we demonstrated that an inhibitor of apoptosis protein of Schistosoma japonicum (SjIAP) governs the integrity of the tegument of schistosomes by inhibiting cellular apoptosis of the parasite. Further studies revealed that SjTeg-20, an S. japonicum tegumental protein, cooperates with SjIAP to inhibit apoptosis in schistosomes. Our findings provide new insights into the role of SjIAP and SjTeg-20 in maintaining the integrity of the worm tegument by negatively regulating apoptosis.

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

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

Comparative analysis of codon usage pattern and its influencing factors in Schistosoma japonicum and Ascaris suum

Schistosoma japonicum and Ascaris suum are considered as the major parasites of human which cause various life threatening diseases such as schistomiasis and ascariasis. The codon usage bias (CUB) is known as the phenomenon of more usage of a specific codon than the other synonymous codons for an amino acid. The factors that influence the codon usage bias are mutation pressure, natural selection, gene expression, gene length, GC content, RNA stability, recombination rates, codon position etc. Here we had used various bioinformatic tools and statistical analyses to understand the compositional features, expression level and codon usage bias in the genes of these two species.After estimating the effective number of codon (ENC) in both the species, codon usage bias was found to be low and gene expression was high. The nucleobase A and T were used most often than C and G. From neutrality plot and correspondence analysis it was found that both natural selection and mutation pressure played an important role in shaping the codon usage pattern of both species. Moreover, natural selection played a major role while mutation pressure played a minor role in shaping the codon usage bias in S. japonicum and A.suum. This is the first report on the codon usage biology in S. japonicum and A.suum, and the factors influencing their codon usage bias. These results are expected to be useful for genetic engineering and evolutionary studies.

A field trial of recombinant Schistosoma japonicum paramyosin as a potential vaccine in naturally-infected water buffaloes

The overall aims of this project are to assess the safety and immunogenicity of the Schistosoma japonicum vaccine paramyosin among water buffaloes residing in endemic areas. The study was conducted in four villages in Leyte, the Philippines, an area highly endemic for schistosomiasis japonica. One hundred and fifteen (N=115) animals provided baseline stool samples for coprologic examination, with preliminary results using FLOTAC showing a 10% prevalence of schistosomiasis. Forty-nine (N=49) animals consented to treatment with 25 mg/kg Praziquantel, and 40, 36 and 32 animals consented to the first, second and third dose of the paramyosin vaccine, respectively. The safety trial involved the first 20 animals and included skin testing, vaccination, anaphylaxis monitoring, as well as hematology and serum chemistry analysis. Skin tests revealed that only three out of 20 animals exhibited redness at the injection site, with none greater than 1 cm. None of the animals exhibited anaphylaxis, and all hematology and serum chemistry markers were within normal range or were similar to pre-vaccination levels. None of the 40 animals administered with the first dose exhibited anaphylaxis, nor any of the subsequent vaccine doses. Immunogenicity assessment of sera collected prior to every vaccination and one month after the last dose showed that the paramyosin vaccine induced robust antibody responses to all animals, as assessed by ELISA. The cytokine levels of whole blood culture supernatants will be further assessed. Our findings demonstrate that the S. japonicum paramyosin vaccine is a safe, well-tolerated and immunogenic treatment among water buffalos residing in endemic areas.

Specific anti-glycan antibodies are sustained during and after parasite clearance in Schistosoma japonicum-infected rhesus macaques

Background

Human immunity to Schistosoma infection requires many years of exposure, and multiple infections and treatments to develop. Unlike humans, rhesus macaques clear an established schistosome infection naturally at the same time acquiring immunity towards re-infection. In macaques, schistosome egg production decreases after 8 weeks post-infection and by week 22, physiological impairment of the worm caused by unclarified antibody-mediated processes is observed. Since strong antibody responses have been observed against schistosome glycan antigens in human and animal infections, we here investigate if anti-glycan antibodies are associated with immunity against schistosome infections in macaques.

Methods

We used a microarray containing a large repertoire of glycoprotein- and glycolipid-derived glycans from different schistosome life stages to analyse anti-glycan serum IgG and IgM from S. japonicum-infected macaques during the course of infection and self-cure. We also used an in vitro schistosomula assay to investigate whether macaque sera containing anti-glycan antibodies can kill schistosomula.

Conclusions/significance

Antibody responses towards schistosome glycans at week 4 post-infection were dominated by IgM while IgG was high at week 8. The profound increase in IgG was observed mainly for antibodies towards a large subset of glycans that contain (multi-)fucosylated terminal GalNAcβ1-4GlcNAc (LDN), and Galβ1-4(Fucα1–3)GlcNAc (LeX) motifs. In general, glycans with a higher degree of fucosylation gave rise to stronger antibody responses than non-fucosylated glycans. Interestingly, even though many IgG and IgM responses had declined by week 22 post-infection, IgG towards O-glycans with highly fucosylated LDN motifs remained. When incubating macaque serum with schistosomula in vitro, schistosomula death was positively correlated with the duration of infection of macaques; macaque serum taken 22 weeks post-infection caused most schistosomula to die, suggesting the presence of potentially protective antibodies. We hypothesize that IgGs against highly fucosylated LDN motifs that remain when the worms deteriorate are associated with infection clearance and the resistance to re-infection in macaques.

Schistosomes express many glycan antigens to which antibodies are raised by the infected host. These glycans may therefore form potential vaccine targets. Unlike humans where the disease persists chronically if not treated, schistosome-infected rhesus macaques are able to elicit a self-cure process naturally. To find out if anti-glycan responses could contribute to the natural clearance process, we followed the dynamics of anti-glycan serum antibodies in Schistosoma-infected macaques in a longitudinal study starting from the onset of infection until 22 weeks post-infection, when the macaques had eliminated most of the parasites. We found that sera of macaques taken after 22 weeks of infection contained high IgG titres towards specific schistosome glycan epitopes highly abundant on schistosome larvae. Moreover, infected macaque serum at week 22 was able to kill schistosomula in vitro. Our results suggest that anti-glycan antibodies play an important role in the self-cure process and the acquired resistance to re-infection in Schistosoma infected macaques.

Cloning and in vitro characterization of a Schistosoma japonicum aquaglyceroporin that functions in osmoregulation

As one of the three major human pathogens that cause schistosomiasis, Schistosoma japonicum is the only one that is endemic in China. Despite great progress on schistosomiasis control over the past 50 years in China, S. japonicum transmission still occurs in certain endemic regions, which causes significant public health problems and enormous economic losses. During different life stages, parasites are able to survive dramatic osmolality changes between its vector, fresh water, and mammal host. However, the molecular mechanism of parasite osmoregulation remains unknown. To address this challenging question, we report the first cloning of an S. japonicum aquaglyceroporin (SjAQP) from an isolate from Jiangsu province, China. Expressing SjAQP in Xenopus oocytes facilitated the permeation of water, glycerol, and urea. The water permeability of SjAQP was inhibited by 1 mM HgCl2, 3 mM tetraethylammonium, 1 mM ZnCl2, and 1 mM CuSO4. SjAQP was constitutively expressed throughout the S. japonicum life cycle, including in the egg, miracidia, cercaria, and adult stages. The highest expression was detected during the infective cercaria stage. Our results suggest that SjAQP plays a role in osmoregulation throughout the S. japonicum life cycle, especially during cercariae transformation, which enables parasites to survive osmotic challenges.

[Prokaryotic expression and identification of secretory proteins and peripheral membrane proteins of Schistosoma japonicum]

OBJECTIVE

To prokaryotic express and identify the recombinant plasmids containing the genes or gene segments which coding secreted or peripheral membrane protein of Schistosoma japonicum.

METHODS

A number of 28 pET32 (+) previous constructed recombinant plasmids containing these genes or segments were transferred into E. coli BL21 (DE3) strain for culture via the CaCl₂ transformation method, and then induced by IPTG for prokaryotic expression. Then, the bacteria were treated by broking the wall with ultrasonic, and the bacterial suspension, supernatant and precipitation were detected with 12% SDS-PAGE. The size and distribution of these target proteins were determined. Finally, the expression of the recombinant fusion protein was further identified by the protein microarray combined with anti-His tag fluorescent antibody.

RESULTS

Under the inducing conditions of 0.1 mmol/L IPTG, 37 ℃, 200 r/min and 4 h, these fusion proteins were highly expressed in E. coli BL21 (DE3). The SDS-PAGE results showed all the 28 recombinant fusion proteins were expressed in different degrees, among which 2 were distributed in the supernatant, and the other 26 were distributed in precipitation, and the sizes of the fusion proteins were the same as that of prediction. The fluorescent signals of His antibody were successfully detected by confocal laser scanner.

CONCLUSIONS

A series of recombinant plasmids containing genes or gene segments that coding secreted protein and peripheral membrane protein of S. japonicum have been successfully expressed by using an efficient prokaryotic expression system of E. coli. It has established a foundation for the high throughput immunoscreening of the vaccine candidates or diagnostic antigens of S.japonicum.

Comparative Analysis of Transcriptional Profiles of Adult Schistosoma japonicum from Different Laboratory Animals and the Natural Host, Water Buffalo

Background

Schistosomiasis is one of the most widely distributed parasitic diseases in the world. Schistosoma japonicum, a zoonotic parasite with a wide range of mammalian hosts, is one of the major pathogens of this disease. Although numerous studies on schistosomiasis japonica have been performed using laboratory animal models, systematic comparative analysis of whole-genome expression profiles in parasites from different laboratory animals and nature mammalian hosts is lacking to date.

Methodology/Principal Findings

Adult schistosomes were obtained from laboratory animals BALB/c mice, C57BL/6 mice, New Zealand white rabbits and the natural host, water buffaloes. The gene expression profiles of schistosomes from these animals were obtained and compared by genome-wide oligonucleotide microarray analysis. The results revealed that the gene expression profiles of schistosomes from different laboratory animals and buffaloes were highly consistent (r>0.98) genome-wide. Meanwhile, a total of 450 genes were identified to be differentially expressed in schistosomes which can be clustered into six groups. Pathway analysis revealed that these genes were mainly involved in multiple signal transduction pathways, amino acid, energy, nucleotide and lipid metabolism. We also identified a group of 1,540 abundantly and stably expressed gene products in adult worms, including a panel of 179 Schistosoma- or Platyhelminthes-specific genes that may be essential for parasitism and may be regarded as novel potential anti-parasite intervention targets for future research.

Conclusions/Significance

This study provides a comprehensive database of gene expression profiles of schistosomes derived from different laboratory animals and water buffaloes. An expanded number of genes potentially affecting the development of schistosomes in different animals were identified. These findings lay the foundation for schistosomiasis research in different laboratory animals and natural hosts at the transcriptional level and provide a valuable resource for screening anti-schistosomal intervention targets.

The zoonotic parasite Schistosoma japonicum is one of the major pathogens of schistosomiasis and can parasitize a wide range of mammals. Although numerous schistosome transcriptional profiling studies have been performed using laboratory animal models, the differences in the global gene expression profiles of worms from different laboratory animals and natural mammalian hosts have not been characterized. Therefore, we studied the gene expression profiles of adult worms from BALB/c mice, C57BL/6 mice, rabbits and buffaloes using a transcriptomics approach. Our results indicate that, although the expression profiles of adult worms from different mammals are generally similar, hundreds of genes are differentially expressed, which were mainly involved in various signal transduction pathways, amino acid, energy, nucleotide and lipid metabolism. Numerous abundantly and stably expressed genes in adults were identified, including some genes that are only found in blood flukes or expanded within the phylum Platyhelminthes and may be important for parasitism. Our data provide a basis for schistosomiasis research in different mammalian hosts at the transcriptional level as well as a valuable resource for the screening of anti-schistosomal intervention targets.

M13 phage peptide ZL4 exerts its targeted binding effect on schistosoma japonicum via alkaline phosphatase

The present study was to determine the targeting effect of M13 phage peptide ZL4 (MppZL4) on Schistosoma japonicum (S.j). Mice infected with S.j were injected with MppZL4. Real-time PCR was used to detect the distribution and metabolism of MppZL4 in the livers and lungs of mice. In vivo refusion test was performed to detect the targeting of MppZL4. Western blotting was employed to determine the expression of MppZL4. Live imaging was used to detect the distribution of oligopeptide MppZL4. Immunohistochemistry was employed to determine MppZL4 location on adult S.j body surface. Gomori method was employed to detect the influence of oligopeptide MppZL4 on alkaline phosphatase activity. The distribution and metabolism of MppZL4 and M13KE are not significantly different from each other at each time point. The abundance of MppZL4 is changed as S.j migrates in mice. The targeted binding effect of MppZL4 varies at different stages. ZL4 oligopeptide targets S.j in mice. The specific binding sites of MppZL4 on S.j body are mainly located in syncytial cells. The binding sites of MppZL4 on S.j body surface might be ALP or ALP-related proteins. MppZL4 had targeted binding effect on S.j with its binding site being associated with proteins related to S.j alkaline phosphatase. S.j tegument had a specifically binding site with exogenous peptides, offering new means to explore the interactions between hosts and parasites. Additionally, MppZL4 can possibly be used as targeting molecules in worm-resistant drugs or as tracing molecules in imaging diagnosis technologies.

[Cloning, expression and protective efficacy evaluation of radiation sensitive protein 23 (RAD23) from Schistosoma japonicum]

Radiation sensitive protein 23 (RAD23) is a nucleotide excision repair (NER) protein that plays an important role in Ubiquitin-proteasome pathway (UPP). Schistosoma japonicum radiation sensitive protein23 (SjRAD23) cDNA sequences were amplified by PCR and cloned into pET28a (+) vector to construct recombinant expression plasmid pET28a(+)-SjRAD23. The recombinant protein was expressed as both inclusion bodies and the supernatant in Escherichia coli BL21 (DE3) cell. Immunofluorescence observation shows that SjRAD23 was mainly distributed on the tegument surface of the worms. ELISA assay reveals that specific IgG, IgG1 and IgG2a antibodies could be detected in the sera of rSjRAD23 immunized mice. Western blotting analysis shows that the recombinant SjRAD23 could be recognized by serum specific to soluble adult worm antigen of S. japonicum. BALB/c mice vaccinated with rSjRAD23 combined with 206 adjuvant revealed 35.94% worm reduction and 40.59% liver egg reduction when compared with that of the adjuvant control

The affinity of magnetic microspheres for Schistosoma eggs

Schistosomiasis is a chronic parasitic disease of humans, with two species primarily causing the intestinal infection: Schistosoma mansoni and Schistosoma japonicum. Traditionally, diagnosis of schistosomiasis is achieved through direct visualisation of eggs in faeces using techniques that lack the sensitivity required to detect all infections, especially in areas of low endemicity. A recently developed method termed Helmintex™ is a very sensitive technique for detection of Schistosoma eggs and exhibits 100% sensitivity at 1.3 eggs per gram of faeces, enough to detect even low-level infections. The Helminthex™ method is based on the interaction of magnetic microspheres and schistosome eggs. Further understanding the underlying egg-microsphere interactions would enable a targeted optimisation of egg-particle binding and may thus enable a significant improvement of the Helmintex™ method and diagnostic sensitivity in areas with low infection rates. We investigated the magnetic properties of S. mansoni and S. japonicum eggs and their interactions with microspheres with different magnetic properties and surface functionalization. Eggs of both species exhibited higher binding affinity to the magnetic microspheres than the non-magnetic microspheres. Binding efficiency was further enhanced if the particles were coated with streptavidin. Schistosoma japonicum eggs bound more microspheres compared with S. mansoni. However, distinct differences within eggs of each species were also observed when the distribution of the number of microspheres bound per egg was modelled with double Poisson distributions. Using this approach, both S. japonicum and S. mansoni eggs fell into two groups, one having greater affinity for magnetic microspheres than the other, indicating that not all eggs of a species exhibit the same binding affinity. Our observations suggest that interaction between the microspheres and eggs is more likely to be related to surface charge-based electrostatic interactions between eggs and magnetic iron oxide rather than through a direct magnetic interaction.

Expression profile of the Schistosoma japonicum degradome reveals differential protease expression patterns and potential anti-schistosomal intervention targets

Blood fluke proteases play pivotal roles in the processes of invasion, nutrition acquisition, immune evasion, and other host-parasite interactions. Hundreds of genes encoding putative proteases have been identified in the recently published schistosome genomes. However, the expression profiles of these proteases in Schistosoma species have not yet been systematically analyzed. We retrieved and culled the redundant protease sequences of Schistosoma japonicum, Schistosoma mansoni, Echinococcus multilocularis, and Clonorchis sinensis from public databases utilizing bioinformatic approaches. The degradomes of the four parasitic organisms and Homo sapiens were then comparatively analyzed. A total of 262 S. japonicum protease sequences were obtained and the expression profiles generated using whole-genome microarray. Four main clusters of protease genes with different expression patterns were identified: proteases up-regulated in hepatic schistosomula and adult worms, egg-specific or predominantly expressed proteases, cercaria-specific or predominantly expressed proteases, and constantly expressed proteases. A subset of protease genes with different expression patterns were further validated using real-time quantitative PCR. The present study represents the most comprehensive analysis of a degradome in Schistosoma species to date. These results provide a firm foundation for future research on the specific function(s) of individual proteases and may help to refine anti-proteolytic strategies in blood flukes.

Parasite proteases play critical roles in host-parasite interactions and thus are considered to be potential anti-schistosomal targets. Although numerous schistosome proteases have been predicted based on recently published genomes, no systematic analysis of their expression in Schistosoma species has been performed. Thus, we comparatively analyzed the degradomes of four parasitic organisms and human host, and performed whole-genome microarray analysis to analyze the expression profile of the Schistosoma japonicum degradome at four developmental stages. The expression profile generated for the S. japonicum degradome was divided into four main clusters with different expression patterns, and a subset of selected proteases were further validated using real-time quantitative PCR. Our work is the most comprehensive analysis of a degradome in Schistosoma species to date. Many protease genes were first characterized in blood flukes, and some could be treated as potential anti-schistosomal targets for intensive research in the future. The results provide a firm foundation for deep study on the specific function(s) of individual proteases or protease families in schistosomes.

[Prokaryotic expression and function analysis of Schistosoma japonicum calpain]

OBJECTIVE

To clone and express recombinant calpain of Schistosoma japonicum (Sjcalpain), observe the distribution of Sjcalpain in S. japonicum cercariae and analyze its role in skin invasion.

METHODS

The primers were designed according to the full-length sequence of calpain (GenBank accession No. AB016726). The genes encoding catalytic domain and Ca2+ binding domain of Sjcalpain were amplified by PCR, and the target fragments were subcloned into pET-28a. The recombinant proteins were expressed in E. coli BL21 (DE3) and purified by Ni-NTA resin. The rabbit polyclonal antibodies were prepared with the two purified recombinant proteins by immunizing New Zealand white rabbits. ELISA was used to detect the titer of rabbit antiserum. Immunolocalization was used to investigate the distribution of Sjcalpain in S. japonicum cercariae. Cercariae were incubated with specific inhibitor before infection of mice and the worm reduction rate was calculated.

RESULTS

The recombinant expression vector Sjcalpain catalytic domain/pET28a and Sjcalpain Ca2+ binding domain/pET28a were constructed and the recombinant proteins were successfully expressed in E. coli BL21 (DE3) (about M(r) 43 000 and M(r) 39 000, respectively). The two target proteins were expressed as inclusion bodies. The purified target proteins were obtained through Ni-NTA affinity purification. ELISA result showed that the titer of prepared rabbit polyclonal antibodies was higher than 1 : 80 000. Immunolocalization study demonstrated that Sjcalpain protein was mainly expressed in the head of cercariae. Inhibition assays suggested that the average number of adult worms in calpain inhibitor-incubation group and control group was 19 and 23, respectively, with a worm reduction rate of 17.4%.

CONCLUSION

Sjcalpain is mainly expressed in the head of S. japonicum cercariae. Inhibition of Sjcalpain could reduce the number of invading cercariae in infected mice, which suggest that Sjcalpain may play a role in skin invasion by cercariae.

[Cloning, expression and transcription specificity analysis of two tyrosinases from Schistosoma japonicum]

OBJECTIVE

To clone and express the recombinant proteins based on the whole open reading frame of two tyrosinases (tyrosinase 1 and tyrosinase 2) from Schistosoma japonicum, and study the transcription specificity of the two tyrosinases in different sex and developmental stages of S. japonicum.

METHODS

The full-length of SjTYR1 and SjTYR2 were amplified with specific primers and subcloned into pSJ2. The recombinant plasmids were transformed into E. coli Rosetta Gami strains and induced with IPTG for expression. The recombinant proteins were purified by Ni-NTA agarose. The recombinant proteins SjTYR1 and SjTYR2 were used to produce the specific antibodies by immunizing the rabbits. The immunogenicity of the recombinant proteins SjTYR1 and SjTYR2 were detected by Western blotting using sera of recombinant proteins-immunized rabbits and S. japonicum-infected rabbit serum as the primary antibody, respectively. The reactivity of sera from recombinant proteins-immunized rabbits was analyzed by Western blotting against the native protein of S. japonicum worm. Total RNA was extracted from 14, 16, 18, 20, 22, 24, 26, and 28-day male and female worms. Transcription levels of the two tyrosinases in different sex and different stage were determined via RT-PCR method.

RESULTS

The expression vector of SjTYR1/pSJ2 and SjTYR2/pSJ2 were constructed and the recombinant pro teins SjTYR1 and SjTYR2 were expressed in inclusion body in E. coli (about M(r) 55 000 and M(r) 56 800). The sera of S. japonicum-infected rabbits reacted positively with the purified recombinant protein SjTYR1, but not with recombinant protein SjTYR2. The native protein of S. japonicum worm could be recognized by sera of rSjTYR1-immunized rabbits (M(r) 100 000), but not by sera of rSjTYR2-immunized rabbits. Transcription levels of the two tyrosinases in male worms were nearly zero. In female worms, the transcription levels of the two tyrosinases increased sharply from the 24th day post-in- fection and reached maximum on the 28th day.

CONCLUSION

The recombinant proteins of SjTYR1 and SjTYR2 show immunogenicity and immunoreactivity. SjTYR1 and SjTYR2 are both expressed specifically in female worms and the transcription levels increase in 24-28 days after infection.

Recombinant production, crystallization and preliminary structural characterization of Schistosoma japonicum profilin

Helminthic parasites of the genus Schistosoma contain a tegumental membrane, which is of crucial importance for modulation of the host immune response and parasite survival. The actin cytoskeleton plays an important role in the function of the tegument. Profilins are among the most important proteins regulating actin dynamics. Schistosoma japonicum possesses one profilin-like protein, which has been characterized as a potential vaccine candidate. Notably, profilins are highly immunogenic molecules in many organisms. Here, the profilin from S. japonicum was expressed, purified and crystallized. A native data set to 1.91 Å resolution and a single-wavelength anomalous diffraction (SAD) data set to a resolution of 2.2 Å were collected. The crystals belonged to space group P2(1)2(1)2(1), with unit-cell parameters a = 31.82, b = 52.17, c = 59.79 Å and a = 35.29, b = 52.15, c = 59.82 Å, respectively.

[Characterization and immunoprotective effect of SjIrV1, a 66 kDa calcium-binding protein from Schistosoma japonicum]

Calcium-binding protein is an indispensable protein which performs extensive and important functions in the growth of Schistosoma japonicum. Based on our primary study on tegument surface proteins of S. japonicun, a cDNA encoding a 66 kDa calcium-binding protein of S. japonicum (Chinese strain) was cloned, sequence analysis revealed that it was identical with that of SjIrV1 of Philippines strains S. japonicum. The expression of SjIrV1 were detected by Real-time PCR, using cDNA templates isolated from 7, 14, 21, 28, 35 and 42 days worms and the results revealed that the gene was expressed in all investigated stages, and the mRNA level of SjIrV1 is much higher in 42 d female worms than that in 42 d male worms. The cDNA containing the open reading frame of IrV1 was subcloned into a pET28a (+) vector and transformed into competent Escherichia coli BL21 for expression. The recombinant protein was purified using a Ni-NTA purification system, and confirmed by high performance liquid chromatography (RP-HPLC) and tandem mass spectrometry (MS/MS). Western blotting analysis showed that recombinant SjIrV1 (rSjIrV1) could be recognized by the S. japonicum infected mouse serum and the mouse serum specific to rSjIrV1, respectively. Immunofluorescence observation exhibited that SjIrV1 was mainly distributed on the tegument of the 35-day adult worms. ELISA test revealed that IgG, IgG1 and IgG2a antibodies are significantly increased in the serum of rSjIrV1 vaccinated mice. The study suggested that rSjIrV1 might play an important role in the development of S. japonicum.

Combined TLR7/8 and TLR9 ligands potentiate the activity of a Schistosoma japonicum DNA vaccine

Background

Toll-like receptor (TLR) ligands have been explored as vaccine adjuvants for tumor and virus immunotherapy, but few TLR ligands affecting schistosoma vaccines have been characterized. Previously, we developed a partially protective DNA vaccine encoding the 26-kDa glutathione S-transferase of Schistosoma japonicum (pVAX1-Sj26GST).

Methodology/Principal Findings

In this study, we evaluated a TLR7/8 ligand (R848) and a TLR9 ligand (CpG oligodeoxynucleotides, or CpG) as adjuvants for pVAX1-Sj26GST and assessed their effects on the immune system and protection against S. japonicum. We show that combining CpG and R848 with pVAX1-Sj26GST immunization significantly increases splenocyte proliferation and IgG and IgG2a levels, decreases CD4⁺CD25⁺Foxp3⁺ regulatory T cells (Treg) frequency in vivo, and enhances protection against S. japonicum. CpG and R848 inhibited Treg-mediated immunosuppression, upregulated the production of interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-4, IL-10, IL-2, and IL-6, and decreased Foxp3 expression in vitro, which may contribute to prevent Treg suppression and conversion during vaccination and allow expansion of antigen-specific T cells against pathogens.

Conclusions

Our data shows that selective TLR ligands can increase the protective efficacy of DNA vaccines against schistosomiasis, potentially through combined antagonism of Treg-mediated immunosuppression and conversion.

There is evidence that TLR activation can block Treg cell responses and thereby break tolerance to self-antigens. It is expected that the use of TLR ligands as vaccine adjuvants will induce potent anti-pathogen immune responses and simultaneously overcome immune inhibition mediated by Tregs. However, the impact of TLR ligands on schistosomiasis vaccines is unclear. Here, we demonstrate that the use of a TLR7/8 ligand (R848) and a TLR9 ligand (CpG) as adjuvants in combination with the S. japonicum vaccine pVAX1-Sj26GST improves disease protection. The combination of CpG and R848 administered after vaccination causes an immune response marked by an upregulation of splenocyte proliferation and IgG and IgG2a levels that also coincides with a decreased proportion of CD4⁺CD25⁺ Tregs in mice. We also show that combined adjuvant use of CpG and R848 may impair Treg development and function by promoting the secretion of proinflammatory cytokines and reducing Foxp3 expression. Our findings suggest that in combination with the vaccine, TLR ligands may protect the effector response from Treg-mediated suppression, thereby eliciting the appropriate immune response to improve vaccine efficacy. Immunization combined with the TLR ligands CpG and R848 thus represents a promising new approach for the design of schistosoma vaccines.

[Identification of glycosylphosphatidylinositol-anchored protein from Schistosoma japonicum]

OBJECTIVE

To identify glycosylphosphatidylinositol (GPI) anchored protein of Schistosoma japonicum.

METHODS

Based on the gene sequence of Schistosoma mansoni GPI anchored protein Sm200 (GenBank Assess No: XM_002569560.1), bioinformatics analysis was performed to find out its homologous gene sequence in S. japonicum, then a selected partial coding sequence (SjGPIs, about 933 bp) from the homologous gene sequence were amplified, and cloned into PET-28a(+) vector. The recombinant plasmid pET-28a(+)SjGPIs were transformed into E. coli Top10 cells and induced with IPTG for protein expression. The recombinant protein SjGPIs was purified with Ni-NTA resin, and the purified recombinant SjGPIs protein was used as antigen to prepare antiserum in New Zealand rabbit. The antiserum was used to detect S. japonicum GPI-anchored protein. To identify a GPI-anchored protein, the detected protein were identified by phosphatidylinositol-specific phospholipase C (PI-PLC) digestion. White blood cells from S. japonicum-infected mice was examined whether they endocytosed GPI-anchored proteins by Western blotting.

RESULTS

The homologous gene sequence of S. mansoni GPI Sm200 gene was found in S. japonicum genome. A 3 495 bp coding sequence was obtained, containing the complete C-terminal sequence. The selected gene sequence (SjGPIs) were amplified and the recombinant plasmid pET-28a(+)-SjGPIs was established. According to the analysis of C-terminal sequence, Western blotting and enzyme digestion of PI-PLC, a GPI-anchored protein was present in S. japonicum tegument (about 1M(r)200000), named SjGPI200. The protein was detected in white blood cells of infected mice.

CONCLUSION

SjGPI200 protein exists in S. japonicum, and anchored to parasite tegument via GPI.

Ultrastructural observation and gene expression profiling of Schistosoma japonicum derived from two natural reservoir hosts, water buffalo and yellow cattle

Water buffalo and yellow cattle are the two of the most important natural reservoir hosts for Schistosoma japonicum in endemic areas of China, although their susceptibility differs, with water buffalo being less conducive to the growth and development of S. japonicum. Results from the current study show that the general morphology and ultrastructure of adult schistosomes derived from the two hosts also differed. Using high-throughput microarray technology, we also compared the gene expression profiles of adult schistosomes derived from the two hosts. We identified genes that were differentially expressed in worms from the two natural hosts. Further analysis revealed that genes associated with protein kinase and phosphatase, the stimulus response, and lipid and nucleotide metabolism were overexpressed, whereas genes associated with reproduction, anatomical structure morphogenesis and multifunctional motif were underexpressed in schistosomes from water buffalo. These differentially expressed genes were mainly involved in nucleotide, energy, lipid metabolism, energy metabolism, transcription, transport and signaling pathway. This suggests that they are key molecules affecting the survival and development of schistosomes in different natural host species. The results of this study add to current understanding of the interplay between parasites and their natural hosts, and provide valuable information for the screening of vaccine candidates or new drug targets against schistosomiasis in the natural reservoir hosts in endemic areas.

Gene profile of chemokines on hepatic stellate cells of schistosome-infected mice and antifibrotic roles of CXCL9/10 on liver non-parenchymal cells

Hepatic stellate cells (HSCs) play a key role in the development of liver fibrosis caused by schistosomiasis. Chemokines were widely expressed and involved in cellular activation, proliferation and migration in inflammatory and infectious diseases. However, little is known about the expressions of chemokines on HSCs in the schistosoma infection. In addition, the roles of chemokines in pathogenesis of liver fibrosis are not totally clear. In our study, we used microarray to analyze the temporal gene expressions of primary HSCs isolated from mice with both acute and chronic schistosomiasis. Our microarray data showed that most of the chemokines expressed on HSCs were upregulated at 3 weeks post-infection (p.i) when the egg granulomatous response was not obviously evoked in the liver. However, some of them like CXCL9, CXCL10 and CXCL11 were subsequently decreased at 6 weeks p.i when the granulomatous response reached the peak. In the chronic stage, most of the differentially expressed chemokines maintained persistent high-abundances. Furthermore, several chemokines including CCR2, CCR5, CCR7, CXCR3, CXCR4, CCL2, CCL5, CCL21, CXCL9 and CXCL10 were expressed by HCSs and the abundances of them were changed following the praziquantel treatment in the chronic stage, indicating that chemokines were possibly necessary for the persistence of the chronic stage. In vitro experiments, hepatic non-parenchymal cells, primary HSCs and human HSCs line LX-2 were stimulated by chemokines. The results showed that CXCL9 and CXCL10, but not CXCL11 or CXCL4, significantly inhibited the gene expressions of Col1α1, Col3α1 and α-SMA, indicating the potential anti-fibrosis effect of CXCL9 and CXCL10 in schistosomiasis. More interestingly, soluble egg antigen (SEA) of Schistosoma japonicum was able to inhibit transcriptional expressions of some chemokines by LX-2 cells, suggesting that SEA was capable of regulating the expression pattern of chemokine family and modulating the hepatic immune microenvironment in schistosomiasis.

Integrated refolding techniques for Schistosoma japonicum MTH1 overexpressed as inclusion bodies in Escherichia coli

The full-length cDNA of MTH1in Schistosoma japonicum was previously isolated. However, insoluble protein expression in Escherichia coli is the biggest bottleneck limiting biological and biophysical studies. Protein aggregation could not be significantly prevented using solubilization or refolding techniques, and denatured MTH1 protein could not be refolded to the native monomer form. Hence, integrating several refolding techniques within the protein refolding process of MTH1, a large amount of active MTH1 was obtained for protein crystallization. We primarily utilized the two-step-denaturing and refolding method and the protein refolding screening technique, as well as the continuous dialysis method. First, we identified the refolding buffer composition that allowed for successful refolding to overcome protein precipitation. Next, we used the two-step-denaturing and refolding method and the continuous dialysis method to suppress protein aggregation. In the end, we obtained 15 mg of active MTH1 monomer with 95% purity from 0.5l medium. Integrated refolding techniques proved to be excellent for obtaining the native monomer of S. japonicum MTH1 from inclusion bodies, paving the way for future biological and biophysical studies.

[Cloning, expression and immunodiagnostic analysis of Schistosoma japonicum calcium-binding EF-hand domain containing protein]

OBJECTIVE

To clone and expression Schistosoma japonicum calcium-binding EF-hand domain containing protein (SjEFCAB), purify the expressed protein, and evaluate its antigenicity and diagnostic value.

METHODS

The positive clone screened from egg cDNA library was used as template to amplify the SjEFCAB gene by PCR. The target fragment was cloned into prokaryotic expression vector pGEX-4T-1. The positive recombinant plasmids were transformed into E.coli BL21 and induced by IPTG for expression of the protein. The recombinant protein was purified with GST-tag affinity chromatography. Western blotting was used to analyze the antigenicity. The purified protein was used as coating antigen for indirect ELISA to evaluate its diagnostic effect. Serum samples from patients with schistosomiasis japonica (78 cases), clonorchiasis sinensis (5 cases), cysticercosis (10 cases), paragonimiasis westermani (6 cases), trichinosis (9 cases) and healthy persons (50 cases) were examined.

RESULTS

The recombinant plasmid pGEX-4T-1-SjEFCAB was constructed and the SjEFCAB recombinant protein (Mr 8 200) was expressed in E. coli. The soluble fusion protein was purified with affinity chromatography. Western blotting analysis showed that the recombinant protein was recognized by sera of infected rabbits and pooled sera of schistosomiasis japonica patients. The sensitivity and specificity of ELISA for diagnosis of schistosomiasis japonica were 82.1% (64/78) and 95.0% (76/80), respectively. The cross reaction with sera of clonorchiasis sinensis, cysticercosis, and trichinosis patients were 1/5, 1/10, and 1/9, respectively. There was no cross reaction with sera of paragonimiasis westermani patients.

CONCLUSION

The recombinant SjEFCAB antigen has potential diagnostic value for schistosomiasis japonica.

[Effects of Schistosoma japonicum heat-shock protein 40 on macrophage activation]

OBJECTIVE

To clone and express heat-shock protein 40 gene of Schistosoma japonicum (SjHSP40) and analyze its effect on macrophage activation.

METHODS

The fragment of gene encoding SjHSP40 was amplified by PCR. The gene was sub-cloned into the prokaryotic expression vector pGEX-6P-1. The recombinant plasmid pGEX-6P-1-SjHSP40 was transformed into E. coli BL21 (DE3) and induced with IPTG. The recombinant protein was purified with Glutathione-Sepharose 4B resin and analyzed by SDS-PAGE and Western-blot. The fusion protein of GST-SjHSP40 was loaded to the macrophage cell-line RAW264.7 for 48 h. Following that, the surface molecules of the macrophages were analyzed by flow cytometry.

RESULTS

DNA sequencing showed that the recombinant plasmid, pGEX-6P-1-SjHSP40, was successfully constructed. The fusion protein of GST-SjHSP40 was induced, purified and specifically recognized by anti-GST antibody. Compared to GST and medium control groups, this fusion protein significantly induced the expression of co-stimulatory molecules (CD40, CD80, and CD86) and MHC-II on the surface of the macrophages.

CONCLUSIONS

SjHSP40 significantly up-regulates the expression of co-stimulatory molecules and MHC-II on the surface of the macrophages. These data indicate that SjHSP40 may initiate macrophage activation.

[Function analysis of Sj34.9 gene based on RNAi and microarray]

OBJECTIVE

To analyze the function of Sj34.9 gene, so as to provide the reference for future studies.

METHODS

The Sj34.9 gene was knocked down in Schistosoma japonicum by RNA interference (RNAi), and the microarray was used to analyze the genes'expression of S. japonicum after Sj34.9 knocked down.

RESULTS

A total of 378 genes expressed differently including 202 up-regulated genes and 176 down-regulated genes. The pathway analysis indicated that the genes expressed differently were mainly related to organelles, metabolism and signal transduction. The gene ontology category analysis showed that most of these genes might be involved in binding, membrane fomulation and cellular process.

CONCLUSION

The gene Sj34.9 might play important roles in the process of growth, development, reproduction and metabolism of S. japonicum.

Correlation between hammerhead ribozyme-mediated eggshell protein gene cleavage and reproduction inhibition of Schistosoma japonicum

Schistosoma japonicum (S. japonicum) is an extremely harmful pathogen, which infects humans and causes severe public health problems. To date, no effective therapeutic drugs for this pathogen are available. In this study, we designed and constructed three hammerhead ribozymes targeting the eggshell protein gene of S. japonicum (SjESG). The cleavage activities of these three ribozymes were determined using cleavage experiments. The in vitro cleavage results showed that among the three synthesized ribozymes (Rz1, Rz2 and Rz3), Rz1 and Rz3 cleaved their target RNAs effectively. However, Rz2 did not cleave its target RNA detectably. The putative therapeutic roles of these three ribozymes to inhibit the reproduction of S. japonicum in mice were studied in vivo. Compared with the negative controls, Rz1 and Rz3 treatments resulted in increased levels of IFN-γ but decreased levels of IL-4 in mice. Rz2 affected levels of IFN-γ and IL-4 to degrees similar with those caused by the vector controls. In addition, Rz1 and Rz3 reduced the amounts of adult worms and eggs in the livers of mice more extensively than Rz2 and the vector controls. Altogether, these results suggest a correlation between the in vitro cleavage abilities of Rz1 and Rz3 and their roles in reproduction inhibition of S. japonicum.

Thioredoxin glutathione reductase as a novel drug target: evidence from Schistosoma japonicum

Background

Schistosomiasis remains a major public health concern affecting billions of people around the world. Currently, praziquantel is the only drug of choice for treatment of human schistosomiasis. The emergence of drug resistance to praziquantel in schistosomes makes the development of novel drugs an urgent task. Thioredoxin glutathione reductase (TGR) enzymes in Schistosoma mansoni and some other platyhelminths have been identified as alternative targets. The present study was designed to confirm the existense and the potential value of TGR as a target for development of novel antischistosomal agents in Schistosoma japonicum, a platyhelminth endemic in Asia.

Methods and Findings

After cloning the S. japonicum TGR (SjTGR) gene, the recombinant SjTGR selenoprotein was purified and characterized in enzymatic assays as a multifunctional enzyme with thioredoxin reductase (TrxR), glutathione reductase (GR) and glutaredoxin (Grx) activities. Immunological and bioinformatic analyses confirmed that instead of having separate TrxR and GR proteins in mammalian, S. japonicum only encodes TGR, which performs the functions of both enzymes and plays a critical role in maintaining the redox balance in this parasite. These results were in good agreement with previous findings in Schistosoma mansoni and some other platyhelminths. Auranofin, a known inhibitor against TGR, caused fatal toxicity in S. japonicum adult worms in vitro and reduced worm and egg burdens in S. japonicum infected mice.

Conclusions

Collectively, our study confirms that a multifunctional enzyme SjTGR selenoprotein, instead of separate TrxR and GR enzymes, exists in S. japonicum. Furthermore, TGR may be a potential target for development of novel agents against schistosomes. This assumption is strengthened by our demonstration that the SjTGR is an essential enzyme for maintaining the thiol-disulfide redox homeostasis of S. japonicum.

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.

Clinics in diagnostic imaging (136). Chronic Schistosoma japonica infection of the liver

A 37-year-old man from China was initially seen at the urology clinic for symptoms of urinary colic. Plain computed tomography (CT) imaging of the kidneys, ureters and bladder was performed, which (in addition to demonstrating renal calculi) revealed incidental findings of 'turtleback' septal and capsular calcifications, features pathognomonic for schistosomiasis japonica. Other classical features were demonstrated on the triphasic hepatic CT imaging that was subsequently performed. The clinical course, radiological features and complications of schistosomiasis japonica are discussed.

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.

[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.

[Screening interaction protein of Schistosoma japonicum gynecophoral canal protein by phage display]

OBJECTIVE

To search the interaction protein of Schistosoma japonicum gynecophoral canal protein (SjGCP).

METHODS

The recombinant rSjGCP was used as a target to search the T7 phage display cDNA library from 44-day adult Schistosoma japonicum.

RESULTS

A total of 70 ESTs were obtained. The bioinformatics analyses to the screening results revealed that 5 interaction proteins or peptides of SjGCP were found. CONCLUSION; Interaction proteins or peptides of SjGCP are successfully obtained through screening the T7 phage display library.

[Cloning and expression of metalloprotease gene from Schistosoma japonicum and its immunoprotective efficiency]

OBJECTIVE

To clone and express a metalloprotease gene of Schistosoma japonicum, purify the expressed protein, and investigate the induced immune response in mice and its localization in the parasite.

METHODS

Specific primers were designed according to the EST sequence and used for amplification of the encoding sequence from the S. japonicum cDNA clone containing S. japonicum metalloprotease. The gene was subcloned into pET-28a plasmid and expressed, and the recombinant protein was purified with HisoTag affinity chromatography. Western blotting was used to analyze the immunogenicity. Eighteen C57BC/6 mice were divided into two groups. Mice in group A were immunized each with 25 microg purified recombinant SjB04 at every 2 weeks for 3 times. Mice in group B received only adjuvant as control. Each mouse was challenged by (40 +/- 2) cercariae at the third week after the last immunization. Fecal samples were collected for 6 days from 37th days after challenge. Eggs per gram feces and rate of egg reduction were calculated. S. japonicum adult worms were collected from infected mice, and used for preparing frozen sections and indirect immunofluorescence staining with specific polyclone antibody to S. japonicum metalloprotease.

RESULTS

The metalloprotease gene SjB04 was cloned, sequenced and expressed. The immuno-fluorescence localization showed that SjBO4 protein distributed mainly in the intestinal epithelium of the adult worm. The recombinant protein was specifically recognized by the S. japonicum-infected rabbit sera, showing that the expressed product possessed antigenicity. Mice immunized with the recombinant protein revealed a reduction in number of adult worms, eggs in feces by 27.1% and 57.8%, respectively.

CONCLUSION

The recombinant protein of S. japonicum metalloprotease has been obtained with Mr 36,500. The protein locates in the intestinal epithelium of adult worm. Immunization with the SjB04 protein induces significant reduction of fecal eggs.

Mapping the binding between the tetraspanin molecule (Sjc23) of Schistosoma japonicum and human non-immune IgG

Background

Schistosomal parasites can establish parasitization in a human host for decades; evasion of host immunorecognition including surface masking by acquisition of host serum components is one of the strategies explored by the parasites. Parasite molecules anchored on the membrane are the main elements in the interaction. Sjc23, a member of the tetraspanin (TSP) family of Schistosoma japonicum, was previously found to be highly immunogenic and regarded as a vaccine candidate against schistosomiasis. However, studies indicated that immunization with Sjc23 generated rapid antibody responses which were less protective than that with other antigens. The biological function of this membrane-anchored molecule has not been defined after decades of vaccination studies.

Methodology and Principal Findings

In this study, we explored affinity pull-down and peptide competition assays to investigate the potential binding between Sjc23 molecule and human non-immune IgG. We determined that Sjc23 could bind human non-immune IgG and the binding was through the interaction of the large extra-cellular domain (LED) of Sjc23 (named Sjc23-LED) with the Fc domain of human IgG. Sjc23 had no affinity to other immunoglobulin types. Affinity precipitation (pull-down assay) in the presence of overlapping peptides further pinpointed to a 9-amino acid motif within Sjc23-LED that mediated the binding to human IgG.

Conclusion and Significance

S. japonicum parasites cloak themselves through interaction with human non-immune IgG, and a member of the tetraspanin family, Sjc23, mediated the acquisition of human IgG via the interaction of a motif of 9 amino acids with the Fc domain of the IgG molecule. The consequence of this interaction will likely benefit parasitism of S. japonicum by evasion of host immune recognition or immunoresponses. This is the first report that an epitope of schistosomal ligand and its immunoglobulin receptor are defined, which provides further evidence of immune evasion strategy adopted by S. japonicum.

[Recombinant plasmid ZLW/pEGFP-C2 transfection into schistosomula of Schistosoma japonicum]

OBJECTIVE

To study the efficiency of ZLW/pEGFP-C2 plasmid transfection into Schistosoma japonicum schistosomula and observe its in vitro effect of anti-schistosomula.

METHODS

Recombinant plasmid ZLW/pEGFP-C2 was transfected into mechanically transformed schistosomula by immersion in 0.75% DMSO and high concentration of plasmid. Enhanced green fluorescent protein (EGFP) transfected cells were observed under inverted fluorescence microscope. At 48 hours after culture, total RNA and proteins from transfected schistosomula were extracted, and the presence of the transgenes (ZLW and EGFP) in schistosomula were confirmed by RT-PCR and Western blotting. At 24, 48, 72, and 96 hours after transfection, the schistosomula were counted by light microscope with methylene blue staining. pEGFP-C2 empty plasmid group and TBS group served as controls.

RESULTS

The transfection rate was about 10%. The fluorescence of ZLW/EGFP protein was mainly localized in the tegument of the worms, especially abundant around oral sucker and ventral sucker. The expected size of 259 bp fragment was successfully amplified by RT-PCR and confirmed by DNA sequencing. Western blotting analysis showed that ZLW/EGFP was expressed in schistosomula. No statistically significant difference was established for schistosomula mortality among ZLW/pEGFP-C2 group (14.0%, 48.8%), pEGFP-C2 group (15.9%, 45.7%) and TBS group (16.9%, 50.3%) at 24 and 48 hours after transfection (P > 0.05). At 72 hours after transfection the mortality rate of ZLW/pEGFP-C2 group (92.7%) was significantly higher than that of pEGFP-C2 group (73.2%) (P < 0.01), and after 96 h the mortality in ZLW/pEGFP-C2 group increased to 100%.

CONCLUSION

ZLW/pEGFP-C2 plasmid has been introduced into juvenile S. japonicum by immersion in 0.75% DMSO and high concentration of plasmid, and was expressed in the parasite.

[Cloning, expression and identification of endothelial differentiation-related factor-1 gene of Schistosoma japonicum]

OBJECTIVE

To clone and express endothelial differentiation-related factor (SjEDF)-1 gene of Schistosoma japonicum, analyze its immunogenicity and the stage-specific expression at different developmental stages of S. japonicum.

METHODS

Total RNA were extracted from eggs, cercariae, schistosomula and adult worms. The housekeeping gene SjActin was selected as the internal reference. According to the open reading frame for SjEDF-1 gene (GenBank accession number: AY336498), a pair of primers were designed to amplify the SjEDF-1 gene which was subcloned into pET-28a vector. The recombinant plasmid SjEDF-1/pET-28a was transformed into E. coli BL21 and induced with IPTG for expression. The recombinant protein was purified with Ni-NTA resin. The immune rabbit sera was prepared by immunizing New Zealand white rabbits with purified recombinant SjEDF-1 protein. Western blotting was used to analyze the immunogenicity and the expression level of SjEDF-1 at the different developmental stages.

RESULTS

The SjEDF-1 gene was detected with a band of 405 bp in eggs, schistosomula, female and male worms. The recombinant protein (rSjEDF-I) was expressed as inclusion bodies (M, 20 000). Western blotting analysis showed that the purified rSjEDF-1 protein was recognized by pooled sera of infected rabbits. The target protein was detected only in schistosomulum and adult worms.

CONCLUSION

The recombinant protein (rSjEDF-I) shows certain immunogenicity, and is detected only in schistosomula and adult worms.

[Cloning, expression and characterization of a gene encoding alpha2 subunit of the proteasome in Schistosoma japonicum]

The 26S proteasome is a proteolytic complex responsible for the degradation of the vast majority of eukaryotic proteins. Regulated proteolysis by the proteasome is thought to influence cell cycle progression, transcriptional control, and other critical cellular processes. A novel Schistosoma japonicum gene (GenBank Accession No. AY813725) proteasome alpha2 subunit (SjPSMA2) was cloned. Sequence analysis revealed that the ORF of SjPSMA2 gene contains 708 nucleotides encoding 235 amino acids, and the molecular weight was estimated to be 25.84 kDa. Real-time PCR analysis showed that this gene expressed in 7 d, 13 d, 18 d, 23 d, 32 d and 42 d schistosoma. The mRNA level of SjPSMA2 was lower in 7 d and 23 d schistosomulum than that in other stages. The SjPSMA2 cDNA fragment was subcloned into an expression vector pET28a(+) and transformed into E. coli BL21 (DE3) cells. After induction with IPTCQ the 30 kDa fusion protein was produced as included bodies. Western-blotting revealed that the fusion protein could be recognized by the rabbit serum anti-Schistosoma japonicum adult worm antigen preparation, and the protein in native could be detected. After immunization of BALB/c mice with the fusion protein, the reduction rates of worm counts and liver egg counts were 12.33% and 35.23%. ELISA results revealed that the vaccinated group showed a significant increase in the level of IgG antibody. This study provided an important basis for investigating the regulation mechanism of the proteasome during the development of Schistosoma japonicum.

Cloning and characterisation of Schistosoma japonicum insulin receptors

Background

Schistosomes depend for growth and development on host hormonal signals, which may include the insulin signalling pathway. We cloned and assessed the function of two insulin receptors from Schistosoma japonicum in order to shed light on their role in schistosome biology.

Methodology/Principal Findings

We isolated, from S. japonicum, insulin receptors 1 (SjIR-1) and 2 (SjIR-2) sharing close sequence identity to their S. mansoni homologues (SmIR-1 and SmIR-2). SjIR-1 is located on the tegument basal membrane and the internal epithelium of adult worms, whereas SjIR-2 is located in the parenchyma of males and the vitelline tissue of females. Phylogenetic analysis showed that SjIR-2 and SmIR-2 are close to Echinococcus multilocularis insulin receptor (EmIR), suggesting that SjIR-2, SmIR-2 and EmIR share similar roles in growth and development in the three taxa. Structure homology modelling recovered the conserved structure between the SjIRs and Homo sapiens IR (HIR) implying a common predicted binding mechanism in the ligand domain and the same downstream signal transduction processing in the tyrosine kinase domain as in HIR. Two-hybrid analysis was used to confirm that the ligand domains of SjIR-1 and SjIR-2 contain the insulin binding site. Incubation of adult worms in vitro, both with a specific insulin receptor inhibitor and anti-SjIRs antibodies, resulted in a significant decrease in worm glucose levels, suggesting again the same function for SjIRs in regulating glucose uptake as described for mammalian cells.

Conclusions

Adult worms of S. japonicum possess insulin receptors that can specifically bind to insulin, indicating that the parasite can utilize host insulin for development and growth by sharing the same pathway as mammalian cells in regulating glucose uptake. A complete understanding of the role of SjIRs in the biology of S. japonicum may result in their use as new targets for drug and vaccine development against schistosomiasis.

[Cloning and expression of SjMRLC and analysis of its stage-specific transcription]

OBJECTIVE

To clone and express Schistosoma japonicum myosin regulatory light chain (SjMRLC) in prokaryotic expression system and analyze its stage-specific transcription.

METHODS

The recombinant plasmid was constructed with pGEX 4T-3 vector and expressed in BL21. The recombinant SjMRLC was identified through Western blotting assay. Total RNA from different stages of Schistosoma japonicum was extracted and used to detect the stage-specific transcription of SjMRLC.

RESULTS

The recombinant plasmid of pGEX 4T-3/SjMRLC was constructed correctly. The recombinant protein (rSjMRLC) with GST tag was soluble. SjMRLC showed similar transcription level in all stages including sporocyst, miracidium, egg, cercaria, schistosomulum, female worm, male worm, and paired adults.

CONCLUSION

The soluble recombinant protein SjMRLC with GST tag was obtained. SjMRLC is a house-keeping gene.

Spatial distribution of human Schistosoma japonicum infections in the Dongting Lake Region, China

Background

The aim of this study was to spatially model the effect of demographic, reservoir hosts and environmental factors on human Schistosoma japonicum infection prevalence in the Dongting Lake area of Hunan Province, China and to determine the potential of each indicator in targeting schistosomiasis control.

Methodology/Principal Findings

Cross-sectional serological, coprological and demographic data were obtained from the 2004 nationwide periodic epidemiologic survey for Hunan Province. Environmental data were downloaded from the USGS EROS data centre. Bayesian geostatistical models were employed for spatial analysis of the infection prevalence among study participants. A total of 47,139 participants from 47 administrative villages were selected. Age, sex and occupation of residents and the presence of infected buffaloes and environmental factors, i.e. NDVI, distance to the lake and endemic type of setting, were significantly associated with S. japonicum infection prevalence. After taking into account spatial correlation, however, only demographic factors (age, sex and occupation) and the presence of infected buffaloes remained significant indicators.

Conclusions/Significance

Long established demographic factors, as well presence of host reservoirs rather than environmental factors are driving human transmission. Findings of this work can be used for epidemiologic surveillance and for the future planning of interventions in the Dongting Lake area of Hunan Province.