Schistosomes, blood flukes, are an important global public health concern. Paired adult female schistosomes produce large numbers of eggs that are primarily responsible for the disease pathology and critical for dissemination. Consequently, understanding schistosome sexual maturation and egg production may open novel perspectives for intervening with these processes to prevent clinical symptoms and to interrupt the life-cycle of these blood-flukes. microRNAs (miRNAs) are key regulators of many biological processes including development, cell proliferation, metabolism, and signal transduction. Here, we report on the identification of Schistosoma japonicum miRNAs using small RNA deep sequencing in the key stages of male-female pairing, gametogenesis, and egg production. We identified 38 miRNAs, including 10 previously unknown miRNAs. Eighteen of the miRNAs were differentially expressed between male and female schistosomes and during different stages of sexual maturation. We identified 30 potential target genes for 16 of the S. japonicum miRNAs using antibody-based pull-down assays and bioinformatic analyses. We further validated some of these target genes using either in vitro luciferase assays or in vivo miRNA suppression experiments. Notably, suppression of the female enriched miRNAs bantam and miR-31 led to morphological alteration of ovaries in female schistosomes. These findings uncover key roles for specific miRNAs in schistosome sexual maturation and egg production.

More than 40 kinds of mammals in China are known to be naturally infected with Schistosoma japonicum (S. japonicum); Microtus fortis (M. fortis), a species of vole, is the only mammal in which the schistosomes cannot mature or cause significant pathogenic changes. In the current study, we compared the differences in pathology by Hematoxylin-eosin staining and in changes in the T cell subsets with flow cytometry as well as gene expression using genome oligonucleotide microarrays in the lung and liver, before challenge and 10 days post-infection with schistosomes in a S. japonicum-susceptible mouse model of infection, a non-susceptible rat model and the non-permissive host, M. fortis. The results demonstrated that S. japonicum promoted a more intensive immune response and more pathological lesions in M. fortis and rats than in mice. Hematoxylin-eosin staining revealed that the immune effector cells involved were mainly eosinophilic granulocytes supplemented with heterophilic granulocytes and macrophages. The analysis of splenic T cell subsets showed that CD4+ T cell subsets and the CD4+/CD8+ ratio were increased, while the CD8+ T cell subsets decreased remarkably in rats; whereas the CD8+ T cell subsets were increased, but the CD4+/CD8+ ratio was decreased significantly in mice. The analysis of the pattern of gene expression suggested that some immune-associated genes and apoptosis-inducing genes up-regulated, while some development-associated genes were down-regulated in the infected M. fortis compared to the uninfected controls; the three different hosts have different response mechanisms to schistosome infection. The results of this study will be helpful for identifying the key molecules in the immune response to S. japonicum in M. fortis and for understanding more about the underlying mechanism of the response, as well as for elucidating the interaction between S. japonicum and its hosts.

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The interplay between sexes is a prerequisite for female growth, reproductive maturation, and egg production, and the basis of schistosome pathopoiesis and propagation. The tegument is in direct contact with the host environment and its surface membranes are particularly crucial for schistosome survival in the definitive host. In this study, a streptavidin-biotin affinity purification technique combined with LC-MS/MS was used to analyze putative tegument-exposed proteins in female and male adult Schistosoma japonicum worms. In total, 179 proteins were identified in females and 300 in males, including 119 proteins common to both sexes, and 60 female biased and 181 male biased proteins. Some (e.g., serpin and CD36-like class B scavenger receptor) were involved in host-schistosome interactions, while some (e.g., gynecophoral canal protein) were important in the interplay between sexes. Gene Ontology analysis revealed that proteins involved in protein glycosylation and lysosome were highly expressed in females, while proteins involved in intracellular signal transduction, regulation of actin filament polymerization, and proteasome core complex were highly expressed in males. These results might elucidate physiological differences between the sexes. Our study provides new insights into schistosome growth and sexual maturity in the final host and permits the screening of vaccine candidates or drug targets for schistosomiasis.

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

Schistosomiasis is a tropical, parasitic disease affecting humans and several animal species. The aim of this study was to identify proteins involved in the growth and survival of the parasitic forms inside a host. Schistosomula of Schistosoma japonicum were isolated from three different hosts: the susceptible BALB/c mice; the Wistar rats, which have a considerably lower susceptibility; and the resistant reed vole, Microtus fortis. Soluble proteins of the schistosomula collected from the above three hosts 10 days postinfection were subjected to two-dimensional difference gel electrophoresis. Comparative proteomic analyses revealed that 39, 21, and 25 protein spots were significantly differentially expressed between schistosomula from mice and rats, mice and reed voles, or rats and reed voles, respectively (ANCOVA, p < 0.05). Further, the protein spots were identified by liquid chromatographytandem MS. Bioinformatics analysis showed that the differentially expressed proteins were essentially those involved in the metabolism of proteins, ribonucleotides, or carbohydrates, or in stress response or cellular movement. This study represents the first attempt at profiling S.

Small non-coding RNAs including microRNAs and small interfering RNAs play important roles in many biological processes of many organisms. Argonaute proteins serve as a key component of the RNA-induced silencing complex for mediating miRNA/siRNA functions. In the present study, we systematically investigated Argonaute proteins in Schistosoma japonicum by using bioinformatics in combination with 5'- and 3'-Rapid Amplification of cDNA ends techniques and thus obtained three full-length cDNAs encoding Argonaute proteins, named as SjAgo1, SjAgo2, and SjAgo3, respectively. Additionally, SjAgo1/2/3 were differentially expressed in different developmental stages of schistosomes as determined by real-time RT-PCR and Western blot. Taken together, our preliminary results suggested that SjAgo1/2/3 may control gene expression during the life cycle of S. japonicum and therefore may regulate schistosome development and other biological processes.

BackgroundWhen compared to the murine permissive host of Schistosoma japonicum, Wistar rats are less susceptible to Schistosoma japonicum infection, and are considered to provide a less suitable microenvironment for parasite growth and development. MicroRNAs (miRNAs), are a class of endogenous, non-coding small RNAs, that impose an additional, highly significant, level of gene regulation within eukaryotes.MethodsTo investigate the regulatory mechanisms provided by miRNA in the schistosome-infected rat model, we utilized a miRNA microarray to compare the progression of miRNA expression within different host tissues both before and 10 days after cercarial infection, in order to identify potential miRNAs with roles in responding to a schistosome infection.ResultsAmong the analysed miRNAs, 16 within the liver, 61 within the spleen and 10 within the lung, were differentially expressed in infected Wistar rats. Further analysis of the differentially expressed miRNAs revealed that many important signal pathways are triggered after infection with S. japonicum in Wistar rats. These include the signal transduction mechanisms associated with the Wnt and MAPK signaling pathways, cellular differentiation, with a particular emphasis on adipocyte and erythroid differentiation.ConclusionsThe results presented here include the identification of specific differentially expressed miRNAs within the liver, lungs and spleen of Wistar rats. These results highlighted the function of host miRNA regulation during an active schistosome infection. Our study provides a better understanding of the regulatory role of miRNA in schistosome infection, and host–parasite interactions in a non-permissive host environment.