Comparative real-time PCR and enzyme analysis of selected gender-associated molecules in Schistosoma japonicum

Use of kinase inhibitors against schistosomes to improve and broaden praziquantel efficacy

Praziquantel (PZQ) is the drug of choice for schistosomiasis. The potential drug resistance necessitates the search for adjunct or alternative therapies to PZQ. Previous functional genomics has shown that RNAi inhibition of Ca2+/calmodulin-dependent protein kinase II (CaMKII) gene in Schistosoma adult worms significantly improved the effectiveness of PZQ. Here we tested the in vitro efficacy of 15 selective and non-selective CaMK inhibitors against Schistosoma mansoni and showed that PZQ efficacy was improved against refractory juvenile parasites when combined with these CaMK inhibitors. By measuring CaMK activity and the mobility of adult S. mansoni, we identified two non-selective CaMK inhibitors, Staurosporine (STSP) and 1Naphthyl PP1 (1NAPP1), as promising candidates for further study. The impact of STSP and 1NAPP1 was investigated in mice infected with S. mansoni in the presence or absence of a sub-lethal dose of PZQ against 2- and 7-day-old schistosomula and adults. Treatment with STSP/PZQ induced a significant (47-68%) liver egg burden reduction compared with mice treated with PZQ alone. The findings indicate that the combination of STSP and PZQ dosages significantly improved anti-schistosomal activity compared to PZQ alone, demonstrating the potential of selective and non-selective CaMK/kinase inhibitors as a combination therapy with PZQ in treating schistosomiasis.

Molecular characterization of Schistosoma mansoni tegument annexins and comparative analysis of antibody responses following parasite infection

Schistosomes are parasitic blood flukes that infect approximately 250 million people worldwide. The disease known as schistosomiasis, is the second most significant tropical parasitic disease after malaria. Praziquantel is the only effective drug currently licensed for schistosomiasis and there are concerns about resistance to the drug. There has been much effort to develop vaccines against schistosomiasis to produce long-term protection in endemic regions. Surface-associated proteins, and in particular, those expressed in the body wall, or tegument, have been proposed as potential vaccine targets. Of these, annexins are thought to be of integral importance for the stability of this apical membrane system. Here, we present the structural and immunobiochemical characterization of four homologous annexins namely annexin B30, annexin B5a, annexin B7a and annexin B5b from S. mansoni. Bioinformatics analysis showed that there was no signal peptide predicted for any annexin in this study. Further analysis showed that each of all four annexin protein possesses a primary structure consisting of a short but variable N-terminal region and a long C-terminal core containing four homologous annexin repeats (I-IV), which contain five alpha-helices. The life cycle expression profile of each annexin was assessed using quantitative PCR. The results showed that the overall transcript levels of the each of four homologous annexins were relatively low in the egg stage, but increased gradually after the transition of cercariae (the invasive schistosome larvae) to schistosomula (the post-invasive larvae). Circular dichroism (CD) demonstrated that rAnnexin B30, rAnnexin B5a and rAnnexin 7a were folded, showing a secondary structure content rich in alpha-helices. The membrane binding affinity was enhanced when rAnnexin B30, rAnnexin B5a and rAnnexin 7a was incubated in the presence of Ca²⁺. All annexin members evaluated in this study were immunolocalized to the tegument, with immunoreactivity also occurring in cells and in muscle of adult parasites. All four recombinant annexins were immunoreactive and they were recognized by the sera of mice infected with S. mansoni. In conclusion, the overall results present the molecular characterization of annexin B30, annexin B5a, annexin B7a and annexin B5b from S. mansoni in host-parasite interactions and strongly suggest that the molecules could be useful candidates for vaccine or diagnostic development.

Lysosome-associated membrane glycoprotein (LAMP)--preliminary study on a hidden antigen target for vaccination against schistosomiasis

Our previously reported gene atlasing of schistosome tissues revealed transcripts that were highly enriched in the digestive tract of Schistosoma mansoni. From these, we selected two candidates, Sm-LAMP and Sm-NPC2 for testing as vaccine targets. The two molecules were selected on the basis of relatively high expression in the gastrodermis, their potentially important biological function, divergence from homologous molecules of the host and possible apical membrane expression in the gastrodermis. Bacterially expressed recombinant peptides corresponding to regions excluding trans-membrane domains of the selected vaccine targets were used in blinded vaccine trials in CBA mice using alum-CpG as adjuvant. Vaccine trials using the recombinant insoluble Sm-LAMP protein showed 16-25% significant reduction in total worm burden. Faecal egg count reduction was 52% and 60% in two trials, respectively, with similar results for the solubly expressed protein. Liver egg burden was reduced significantly (20% and 38%) with an insoluble recombinant Sm-LAMP in two trials, but not with the soluble recombinant form. Parasite fecundity was not affected by either Sm-LAMP protein preparations in the trials. It is concluded that Sm-LAMP may provide limited protection towards S. mansoni infections but could be used in combination with other vaccine candidates, to provide more comprehensive protection.

Transcriptional profiling of the oesophageal gland region of male worms of Schistosoma mansoni

The intestinal tract of schistosomes opens at the mouth and leads into the foregut or oesophageal region that is lined with syncytium continuous with the apical cytoplasm of the tegument. The oesophagus is surrounded by a specialised gland, the oesophageal gland. This gland releases materials into the lumen of the oesophagus and the region is thought to initiate the lysis of erythrocytes and neutralisation of immune effectors of the host. The oesophageal region is present in the early invasive schistosomulum, a stage potentially targetable by anti-schistosome vaccines. We used a 44k oligonucleotide microarray to identify highly up-regulated genes in microdissected frozen sections of the oesophageal gland of male worms of S. mansoni. We show that 122 genes were up-regulated 2-fold or higher in the oesophageal gland compared with a whole male worm tissue control. The enriched genes included several associated with lipid metabolism and transmembrane transport as well as some micro-exon genes. Since the oesophageal gland is important in the initiation of digestion and the fact that it develops early after invasion of the mammalian host, further study of selected highly up-regulated functionally important genes in this tissue may reveal new anti-schistosome intervention targets for schistosomiasis control.

Novel expression profiles of microRNAs suggest that specific miRNAs regulate gene expression for the sexual maturation of female Schistosoma japonicum after pairing

Background

Schistosoma japonicum is one of the major causative agents of schistosomiasis. The pairing of males and females leads to female sexual maturation and maintains this mature state. However, the mechanisms by which pairing facilitates sexual maturation are yet to be investigated.

Methods

Parasites isolated from single- and double-sex cercariae-infected mice were analyzed by Solexa to uncover pair-regulated miRNA profiles. To reveal the biological functions of differentially expressed miRNAs among the samples, we predicted the target genes of these differentially expressed miRNAs and compared the gene expression between 23-d-old female schistosomula from double-sex infections (23DSI) and 23-d-old female schistosomula from single-sex infections (23SSI) by analyzing digital gene expression profiling (DGE). KEGG pathway analysis was used to investigate the relevant biological processes of these target genes to understand the significance of differentially expressed miRNAs after pairing.

Results

The differentially expressed miRNA profiles of female 18- and 23-d post-single- and double-sex infections were analysed by Solexa. Similar miRNA profiles were observed in 18SSI and 18DSI, with the presence of identically expressed high-abundance miRNA, such as miRNA-1, miRNA-71b-5p and let-7. By contrast, in 23DSI and 23SSI, most of these high-abundance miRNAs were down-regulated. Furthermore, among all samples, bantam was distinctly up-regulated in 23 DSI, and miR-1, miR-71, miR-7-5p, and miR-7 were distinctly up-regulated in 23SSI. The transcriptomes of 23DSI and 23SSI revealed that the predicted target genes of miRNA-1, miRNA-71, miRNA-7, and miR-7-5p were associated with the ribonucleoprotein complex assembly and microtubule-based process. Conversely, the predicted target genes of bantam were related to the embryo development, development of primary sexual characteristics and regulation of transcription. KEGG pathway analysis revealed that in unpaired females, the highly-expressed miRNA-1, miRNA-71, miRNA-7, and miR-7-5p only inhibited the limited pathways, such as proteasome and ribosome assembly. Meanwhile, in paired mature females, highly-expressed bantam inhibited more biological pathways, such as the citrate cycle, glycolysis, fatty acid biosynthesis and RNA degradation.

Conclusions

The differentially expressed miRNAs between 23SSI and 23DSI and their different functions indicated that more genes or metabolic pathways in paired mature females were inhibited than those in unpaired ones. The results suggested that after pairing, specific miRNAs regulated gene expression to lead to female sexual maturation.

Transcriptome profilings of female Schistosoma japonicum reveal significant differential expression of genes after pairing

Pairing of Schistosoma japonicum initiates female development, leads to female sexual maturation, and maintains this mature state. To understand the mechanism involved in these processes, we studied parasites isolated from single- and double-sex cercariae-infected mice using deep-sequencing analysis, Solexa, to uncover pair-regulated transcriptional profiles. In this study, we report the results of high-throughput tag-sequencing (Tag-seq) analysis of the transcriptome of female worms 18 and 23 days postsingle- and double-sex infections. We sequenced over 3 million tags, obtained a total of 14,034, 27,251, 22,755, and 22,555 distinct tags corresponding to 5,773, 9,794, 8,885, and 8,870 tag-mapped genes for 23-day-old female schistosomula from double-sex infections (23DSI), 23-day-old female schistosomula from single-sex infections (23SSI), 18-day-old female schistosomula from double-sex infections (18DSI), and 18-day-old female schistosomula from single-sex infections (18SSI), respectively. Analyses of differentially expressed genes revealed similarities in the gene expression profiles between 18SSI and 18DSI as well as rational differential gene expression between 18SSI and 23SSI. However, fewer upregulated genes were found in 23DSI compared with 18DSI. Of the 3,446 differentially expressed genes between 23DSI and 23SSI, 2,913 genes were upregulated in 23SSI, whereas only 533 genes were upregulated in 23DSI. In these upregulated genes in 23DSI, phosphoglycerate mutase, superoxide dismutase, egg antigen, ribosomal proteins, ferritin-1 heavy chain, and eukaryotic translation initiation factor 2 were detected. Detection of these genes suggests that gene expression in 23DSI is specialized for functions such as promotion and maintenance of female sexual maturation and egg production. Quantitative real-time (RT)-PCR analysis confirmed the Solexa results, thereby supporting the reliability of the system. Our results offer new insights into the biological significance of pairing, which directs the expression of genes specific for sexual maturation and egg production.

Gene Atlasing of digestive and reproductive tissues in Schistosoma mansoni

Background

While considerable genomic and transcriptomic data are available for Schistosoma mansoni, many of its genes lack significant annotation. A transcriptomic study of individual tissues and organs of schistosomes could play an important role in functional annotation of the unknown genes, particularly by providing rapid localisation data and thus giving insight into the potential roles of these molecules in parasite development, reproduction and homeostasis, and in the complex host-parasite interaction.

Methodology/Principal Findings

Quantification of gene expression in tissues of S. mansoni was achieved by a combination of laser microdissection microscopy (LMM) and oligonucleotide microarray analysis. We compared the gene expression profile of the adult female gastrodermis and male and female reproductive tissues with whole worm controls. The results revealed a total of 393 genes (contigs) that were up-regulated two-fold or more in the gastrodermis, 4,450 in the ovary, 384 in the vitelline tissues of female parasites, and 2,171 in the testes. We have also supplemented these data with the identification of highly expressed genes in different regions of manually dissected male and female S. mansoni. Though relatively crude, this dissection strategy provides low resolution localisation data for critical regions of the adult parasites that are not amenable to LMM isolation.

Conclusions

This is the first detailed transcriptomic study of the reproductive tissues and gastrodermis of S. mansoni. The results obtained will help direct future research on the functional aspects of these tissues, expediting the characterisation of currently unannotated gene products of S. mansoni and the discovery of new drug and vaccine targets.

There is currently only one drug available for treatment of schistosomiasis mansoni and no vaccine. The searches for possible new drug and vaccine candidates remain two major areas of current research in schistosomiasis. There are considerable amounts of data available on the genomics, transcriptomics and proteomics of Schistosoma mansoni from which useful candidates for future drug and vaccine development can be identified. Arranging these data into a biologically relevant context through the characterisation of gene expression profiles of the different tissues of this complex metazoan parasite, is an essential step in identifying molecules with potential therapeutic value. We have used laser microdissection microscopy and microarray analysis to show that many tissue-specific genes are up-regulated in the digestive and reproductive tissues of S. mansoni. This new knowledge provides an avenue to investigate the molecular components associated with fundamental aspects of schistosome biology.

Our wormy world genomics, proteomics and transcriptomics in East and southeast Asia

Helminths are the cause of some of the major infectious diseases of humanity in what is still a "wormy" world. There is, in East and Southeast Asia, a high prevalence of several helminthiases which occur primarily in rural, impoverished areas of low-income and developing countries throughout the tropics and subtropics. Subsequent to various parasite genome projects that commenced in the early 1990s, under the aegis of the World Health Organization (WHO), the draft genomes of three major helminth species (Schistosoma japonicum, S. mansoni and Brugia malayi) have been sequenced, and many other helminth parasites have now been targeted for intensive genomics investigation. The continuing release of genome sequences has catalyzed the emergence of transcriptomics, proteomics and related "-omics" analyses of helminth parasites, which provide unprecedented approaches to understanding their biology that will result in new clues for the development of novel control interventions. In this review, we present a summary of current approaches employed in helminth "-omics" studies and review recent advances in helminth genomics and post-genomics in the Southeast Asian setting.

Developmental gene expression profiles of the human pathogen Schistosoma japonicum

BACKGROUND

The schistosome blood flukes are complex trematodes and cause a chronic parasitic disease of significant public health importance worldwide, schistosomiasis. Their life cycle is characterised by distinct parasitic and free-living phases involving mammalian and snail hosts and freshwater. Microarray analysis was used to profile developmental gene expression in the Asian species, Schistosoma japonicum. Total RNAs were isolated from the three distinct environmental phases of the lifecycle -- aquatic/snail (eggs, miracidia, sporocysts, cercariae), juvenile (lung schistosomula and paired but pre-egg laying adults) and adult (paired, mature males and egg-producing females, both examined separately). Advanced analyses including ANOVA, principal component analysis, and hierarchal clustering provided a global synopsis of gene expression relationships among the different developmental stages of the schistosome parasite.

RESULTS

Gene expression profiles were linked to the major environmental settings through which the developmental stages of the fluke have to adapt during the course of its life cycle. Gene ontologies of the differentially expressed genes revealed a wide range of functions and processes. In addition, stage-specific, differentially expressed genes were identified that were involved in numerous biological pathways and functions including calcium signalling, sphingolipid metabolism and parasite defence.

CONCLUSION

The findings provide a comprehensive database of gene expression in an important human pathogen, including transcriptional changes in genes involved in evasion of the host immune response, nutrient acquisition, energy production, calcium signalling, sphingolipid metabolism, egg production and tegumental function during development. This resource should help facilitate the identification and prioritization of new anti-schistosome drug and vaccine targets for the control of schistosomiasis.