Molecular characterization of the Schistosoma mansoni zinc finger protein SmZF1 as a transcription factor

Genetic difference between two Schistosoma japonicum isolates with contrasting cercarial shedding patterns revealed by whole genome sequencing

Schistosoma japonicum is one of the major infectious agents of human schistosomiasis, mainly endemic in China and the Philippines. We have previously reported the finding of two schistosome isolates, each with a different cercarial emergence pattern adapted to their different hosts. However, there are currently no whole-genome sequencing studies to investigate the underlining genetics of the adaptive traits. We sampled schistosomes in 2013 and 2020 from a hilly area Shitai (ST) and a marshland area Hexian (HX) of Anhui, China. Ten to 15 male or female adult worms from each site/year were sent for whole genome sequencing. Genetics were analyzed, and selection signals along genomes were detected. Gene enrichment analysis was performed for the genome regions under selection. The results revealed considerable genetic differentiation between the two isolates. The genome "windows" affected by natural selection were fewer in ST (64 windows containing 78 genes) than in HX (318 windows containing 276 genes). Twelve significantly enriched genes were identified in ST, but none in HX. These genes were mainly related to specific DNA binding and intercellular signaling transduction. Some functional region changes identified along the genome of the hilly schistosome may be related to its unique late afternoon cercarial emergence.

Advances in new target molecules against schistosomiasis: A comprehensive discussion of physiological structure and nutrient intake

Schistosomiasis, a severe parasitic disease, is primarily caused by Schistosoma mansoni, Schistosoma japonicum, or Schistosoma haematobium. Currently, praziquantel is the only recommended drug for human schistosome infection. However, the lack of efficacy of praziquantel against juvenile worms and concerns about the emergence of drug resistance are driving forces behind the research for an alternative medication. Schistosomes are obligatory parasites that survive on nutrients obtained from their host. The ability of nutrient uptake depends on their physiological structure. In short, the formation and maintenance of the structure and nutrient supply are mutually reinforcing and interdependent. In this review, we focus on the structural features of the tegument, esophagus, and intestine of schistosomes and their roles in nutrient acquisition. Moreover, we introduce the significance and modes of glucose, lipids, proteins, and amino acids intake in schistosomes. We linked the schistosome structure and nutrient supply, introduced the currently emerging targets, and analyzed the current bottlenecks in the research and development of drugs and vaccines, in the hope of providing new strategies for the prevention and control of schistosomiasis.

An insight into the functional genomics and species classification of Eudiplozoon nipponicum (Monogenea, Diplozoidae), a haematophagous parasite of the common carp Cyprinus carpio

BACKGROUND

Monogenea (Platyhelminthes, Neodermata) are the most species-rich class within the Neodermata superclass of primarily fish parasites. Despite their economic and ecological importance, monogenean research tends to focus on their morphological, phylogenetic, and population characteristics, while comprehensive omics analyses aimed at describing functionally important molecules are few and far between. We present a molecular characterisation of monogenean representative Eudiplozoon nipponicum, an obligate haematophagous parasite infecting the gills of the common carp. We report its nuclear and mitochondrial genomes, present a functional annotation of protein molecules relevant to the molecular and biochemical aspect of physiological processes involved in interactions with the fish hosts, and re-examinate the taxonomic position of Eudiplozoon species within the Diplozoidae family.

RESULTS

We have generated 50.81 Gbp of raw sequencing data (Illumina and Oxford Nanopore reads), bioinformatically processed, and de novo assembled them into a genome draft 0.94 Gbp long, consisting of 21,044 contigs (N50 = 87 kbp). The final assembly represents 57% of the estimated total genome size (~ 1.64 Gbp), whereby repetitive and low-complexity regions account for ~ 64% of the assembled length. In total, 36,626 predicted genes encode 33,031 proteins and homology-based annotation of protein-coding genes (PCGs) and proteins characterises 14,785 (44.76%) molecules. We have detected significant representation of functional proteins and known molecular functions. The numbers of peptidases and inhibitors (579 proteins), characterised GO terms (16,016 unique assigned GO terms), and identified KEGG Orthology (4,315 proteins) acting in 378 KEGG pathways demonstrate the variety of mechanisms by which the parasite interacts with hosts on a macromolecular level (immunomodulation, feeding, and development). Comparison between the newly assembled E. nipponicum mitochondrial genome (length of 17,038 bp) and other diplozoid monogeneans confirms the existence of two distinct Eudiplozoon species infecting different fish hosts: Cyprinus carpio and Carassius spp.

CONCLUSIONS

Although the amount of sequencing data and characterised molecules of monogenean parasites has recently increased, a better insight into their molecular biology is needed. The E. nipponicum nuclear genome presented here, currently the largest described genome of any monogenean parasite, represents a milestone in the study of monogeneans and their molecules but further omics research is needed to understand these parasites' biological nature.

Identification and characterization of the zinc finger protein SjZF in Schistosoma japonicum

Schistosomiasis represents one of the most prevalent parasitic infections affecting over 249 million people worldwide. The pathological damage is mainly caused by the eggs laid by female schistosomes. Zinc finger proteins (ZFPs) usually play critical roles in many biological functions. In this study, we cloned, identified and characterized the zinc finger protein SjZF of Schistosoma japonicum. SjZF ortholog proteins were also identified in S. mansoni, S. haematobium, Opisthorchis viverrini and O. sinensis. Fluorescence localization showed that SjZF was particularly expressed in the worm gut of both genders and the vitelline glands of females. In vitro RNAi assay indicated that decreased expression of SjZF could affect the survival rate of adult worms. The immune protection assay indicated that rSjZF did partially protect mice with 54.8% reduction in the worm burden and 34.1% reduction in the liver eggs. Taken in concert, our preliminary results suggest that SjZF may be a potential vaccine candidate for schistosomiasis and may further provide evidence for a possible role of SjZF in the development of schistosomes.

The molecular characterization and RNAi silencing of SjZFP1 in Schistosoma japonicum

During development, Schistosoma japonicum undergoes many morphological and physiological transformations as a result of profound changes in gene expression. Proteins containing zinc finger motifs usually play an important role in DNA recognition, RNA packaging, and transcriptional activation. In our current study, we cloned the open reading frame (ORF) of SjZFP1 of S. japonicum, which encodes a zinc finger protein. We analyzed the complementary DNA (cDNA) sequence of SjZFP1 and examined the expression of SjZFP1 messenger RNA (mRNA) at various developmental stages. We also tested the effects of RNA interference (RNAi) silencing on worm burden, spawning, and egg hatching. The ORF in the SjZFP1 cDNA was 1017 bp in length and was predicted to encode a 338-aa protein with a molecular mass of approximately 38.5 kDa and theoretical isoelectric point (pI) of 7.08. Several conserved regions, including a B-box-type zinc-binding domain, two bipartite nuclear localization signal domains, a paired amphipathic helix repeat, and overlapping RING and PHD finger domains, were identified in the predicted amino acid sequence of SjZFP1. Using real-time PCR, we showed that the SjZFP1 mRNA was expressed across all of the developmental stages of the parasite and that the level of transcription was highest in the cercariae, eggs, schistosomula, and mature adult worms. The level of SjZFP1 mRNA expression in cultured schistosomula treated with one of two SjZFP1-specific small interfering RNAs (siRNAs; AY770 and AY546) was reduced by over 80 %, compared with that in the controls. In RNAi experiments in BALB/c mice, the level of SjZFP1 mRNA increased significantly when the mice were treated with the same SjZFP1-specific siRNAs during the early stages of infection. By contrast, the level of SjZFP1 mRNA decreased significantly when the mice were treated with the SjZFP1-specific siRNAs during the middle to late stages of infection. In four independent experiments, fewer worms were recovered from mice treated with the SjZFP1-specific siRNAs, compared with the number of worms recovered from the control mice. Both the average number and hatching rates of liver eggs recovered from mice treated with the SjZFP1-specific siRNAs during the middle to late stages of infection were significantly lower than those of the liver eggs recovered from the control mice. Our results suggest that the SjZFP1 gene might be important for parasite development, spawning in the vertebrate host, and egg hatching.

Schistosome syntenin partially protects vaccinated mice against Schistosoma mansoni infection

Background

Schistosomiasis is a neglected tropical disease caused by several species of trematode of the genus Schistosoma. The disease affects more than 200 million people in the world and causes up to 280,000 deaths per year, besides having high morbidity due to chronic illness that damages internal organs. Current schistosomiasis control strategies are mainly based on chemotherapy, but many researchers believe that the best long-term strategy to control disease is a combination of drug treatment and immunization with an anti-schistosome vaccine. Among the most promising molecules as vaccine candidates are the proteins present in the tegument and digestive tract of the parasite.

Methodology/Principal Findings

In this study, we describe for the first time Schistosoma mansoni syntenin (SmSynt) and we evaluate its potential as a recombinant vaccine. We demonstrate by real-time PCR that syntenin is mainly expressed in intravascular life stages (schistosomula and adult worms) of the parasite life cycle and, by confocal microscopy, we localize it in digestive epithelia in adult worms and schistosomula. Administration of siRNAs targeting SmSynt leads to the knock-down of syntenin gene and protein levels, but this has no demonstrable impact on parasite morphology or viability, suggesting that high SmSynt gene expression is not essential for the parasites in vitro. Mice immunization with rSmSynt, formulated with Freund's adjuvant, induces a Th1-type response, as suggested by the production of IFN-γ and TNF-α by rSmSynt-stimulated cultured splenocytes. The protective effect conferred by vaccination with rSmSynt was demonstrated by 30–37% reduction of worm burden, 38–43% reduction in the number, and 35–37% reduction in the area, of liver granulomas.

Conclusions/Significance

Our report is the first characterization of syntenin in Schistosoma mansoni and our data suggest that this protein is a potential candidate for the development of a multi-antigen vaccine to control schistosomiasis.

Schistosomiasis affects more than 200 million people worldwide and causes up to 280,000 deaths per year. In terms of global mortality and morbidity, this disease is the most important human helminth infection. Current control strategies are based on chemotherapy, but recurrent re-infection of people living in endemic areas makes many researchers, and also the World Health Organization, search for an effective vaccine to provide protection against schistosomiasis. Substantial efforts have been committed to the characterization of new antigens for an anti-schistosome vaccine and, in order to find new targets for vaccine and/or drug development, we searched transcriptomics and proteomics of Schistosoma mansoni and identified the protein syntenin (SmSynt) for analysis. In this study, we characterize SmSynt and evaluate its potential as a vaccine candidate to protect mice against S. mansoni infection. We demonstrate that SmSynt is expressed in schistosomula and adult worms, the intravascular stages of S. mansoni and it is located in the intestinal tract of the worms, an important host/parasite interface. Furthermore, vaccination of mice with rSmSynt confers partial protection against S. mansoni challenge infection and ameliorates parasite-induced liver pathology. Our data suggest that SmSynt is a potential candidate in the development of a vaccine against schistosomiasis.

Sm10.3, a member of the micro-exon gene 4 (MEG-4) family, induces erythrocyte agglutination in vitro and partially protects vaccinated mice against Schistosoma mansoni infection

BACKGROUND

The parasitic flatworm Schistosoma mansoni is a blood fluke that causes schistosomiasis. Current schistosomiasis control strategies are mainly based on chemotherapy, but many researchers believe that the best long-term strategy to control disease is a combination of drug treatment and immunization with an anti-schistosome vaccine. Numerous antigens that are expressed at the interface between the parasite and the mammalian host have been assessed. Among the most promising molecules are the proteins present in the tegument and digestive tract of the parasite.

METHODOLOGY/PRINCIPAL FINDINGS

In this study, we evaluated the potential of Sm10.3, a member of the micro-exon gene 4 (MEG-4) family, for use as part of a recombinant vaccine. We confirmed by real-time PCR that Sm10.3 was expressed at all stages of the parasite life cycle. The localization of Sm10.3 on the surface and lumen of the esophageal and intestinal tract in adult worms and lung-stage schistosomula was confirmed by confocal microscopy. We also show preliminary evidence that rSm10.3 induces erythrocyte agglutination in vitro. Immunization of mice with rSm10.3 induced a mixed Th1/Th2-type response, as IFN-γ, TNF-α, and low levels of IL-5 were detected in the supernatant of cultured splenocytes. The protective effect conferred by vaccination with rSm10.3 was demonstrated by 25.5-32% reduction in the worm burden, 32.9-43.6% reduction in the number of eggs per gram of hepatic tissue, a 23.8% reduction in the number of granulomas, an 11.8% reduction in the area of the granulomas and a 39.8% reduction in granuloma fibrosis.

CONCLUSIONS/SIGNIFICANCE

Our data suggest that Sm10.3 is a potential candidate for use in developing a multi-antigen vaccine to control schistosomiasis and provide the first evidence for a possible role for Sm10.3 in the blood feeding process.

Identification of a new Schistosoma mansoni SMYB1 partner: putative roles in RNA metabolism

SMYB1 is a Schistosoma mansoni protein highly similar to members of the Y-box binding protein family. Similar to other homologues, SMYB1 is able to bind double- and single-stranded DNA, as well as RNA molecules. The characterization of proteins involved in the regulation of gene expression in S. mansoni is of great importance for the understanding of molecular events that control morphological and physiological changes in this parasite. Here we demonstrate that SMYB1 is located in the cytoplasm of cells from different life-cycle stages of S. mansoni, suggesting that this protein is probably acting in mRNA metabolism in the cytoplasm and corroborating previous findings from our group that showed its ability to bind RNA. Protein-protein interactions are important events in all biological processes, since most proteins execute their functions through large supramolecular structures. Yeast two-hybrid screenings using SMYB1 as bait identified a partner in S. mansoni similar to the SmD3 protein of Drosophila melanogaster (SmRNP), which is important in the assembly of small nuclear ribonucleoprotein complexes. Also, pull-down assays were conducted using immobilized GST-SMYB1 proteins and confirmed the SMYB1-SmRNP interaction. The interaction of SMYB1 with a protein involved in mRNA processing suggests that it may act in processes such as turnover, transport and stabilization of RNA molecules.

Modeling the zing finger protein SmZF1 from Schistosoma mansoni: Insights into DNA binding and gene regulation

Zinc finger proteins are widely found in eukaryotes, representing an important class of DNA-binding proteins frequently involved in transcriptional regulation. Zinc finger motifs are composed by two antiparallel β-strands and one α-helix, stabilized by a zinc ion coordinated by conserved histidine and cysteine residues. In Schistosoma mansoni, these regulatory proteins are known to modulate morphological and physiological changes, having crucial roles in parasite development. A previously described C(2)H(2) zinc finger protein, SmZF1, was shown to be present in cell nuclei of different life stages of S. mansoni and to activate gene transcription in a heterologous system. A high-quality SmZF1 tridimensional structure was generated using comparative modeling. Molecular dynamics simulations of the obtained structure revealed stability of the zinc fingers motifs and high flexibility on the terminals, comparable to the profile observed on the template X-ray structure based on thermal b-factors. Based on the protein tridimensional features and amino acid composition, we were able to characterize four C(2)H(2) zinc finger motifs, the first involved in protein-protein interactions while the three others involved in DNA binding. We defined a consensus DNA binding sequence using three distinct algorithms and further carried out docking calculations, which revealed the interaction of fingers 2-4 with the predicted DNA. A search for S. mansoni genes presenting putative SmZF1 binding sites revealed 415 genes hypothetically under SmZF1 control. Using an automatic annotation and GO assignment approach, we found that the majority of those genes code for proteins involved in developmental processes. Taken together, these results present a consistent base to the structural and functional characterization of SmZF1.