Extracellular vesicles secreted by Schistosoma mansoni contain protein vaccine candidates

Whole-Proteome Differential Screening Identifies Novel Vaccine Candidates for Schistosomiasis japonica

Schistosomiasis remains a leading cause of chronic morbidity in endemic regions despite decades of widespread mass chemotherapy with praziquantel. Using our whole proteome differential screening approach, and plasma and epidemiologic data from a longitudinal cohort of individuals living in a Schistosoma japonicum-endemic region of the Philippines, we interrogated the parasite proteome to identify novel vaccine candidates for Schistosoma japonicum. We identified 16 parasite genes which encoded proteins that were recognized by immunoglobulin G or immunoglobulin E antibodies in the plasma of individuals who had developed resistance to reinfection, but were not recognized by antibodies in the plasma of individuals who remained susceptible to reinfection. Antibody levels to Sj6-8 and Sj4-1 measured in the entire cohort (N = 505) 1 month after praziquantel treatment were associated with significantly decreased risk of reinfection and lower intensity of reinfection over 18 months of follow-up.

T Cell Peptides Derived from Invasive Stages of Schistosoma mansoni as Potential Schistosomiasis Vaccine

Schistosomiasis is a parasitic disease that affects 143 million people in endemic countries. This work analyzed overexpressed sequences from the cercaria phase to the early schistosomulum phase using bioinformatics tools to predict host interaction and selected proteins for predicting T cell epitopes. The final peptides were chemically synthesized, and their toxicity was evaluated in vitro. Peptides were formulated in the Adjuvant Adaptation (ADAD) vaccination system and injected into BALB/c mice that were challenged with S. mansoni cercariae to assess protection and immunogenicity. A total of 39 highly expressed S.mansoni proteins were identified as being of potential interest. Three T cell peptides predicted to bind MHC mouse and human class II were synthesized and formulated for vaccination. SmGSP and SmIKE reduced the number of eggs trapped in the liver by more than 50% in challenged BALB/c mice. The liver of mice vaccinated with either SmGSP or SmTNP had a significantly reduced affected liver surface. Transcriptome-based T cell peptides elicit partial protection and could be candidates for a multiantigen vaccine.

Proteomic approaches to drive advances in helminth extracellular vesicle research

Helminths can interact with their hosts in many different ways, including through the secretion of soluble molecules (such as lipids, glycans and proteins) and extracellular vesicles (EVs). The field of helminth secreted EVs has significantly advanced in recent years, mainly due to the molecular characterisation of EV proteomes and research highlighting the potential of EVs and their constituent molecules in the diagnosis and control of parasitic infections. Despite these advancements, the lack of appropriate isolation and purification methods is impeding the discovery of suitable biomarkers for the differentiation of helminth EV populations. In the present review we offer our viewpoint on the different proteomic techniques and approaches that have been developed, as well as solutions to common pitfalls and challenges that could be applied to advance the study of helminth EVs.

Immune Regulation by Dendritic Cell Extracellular Vesicles in Cancer Immunotherapy and Vaccines

Extracellular vesicles (EVs) play a crucial role in intercellular communication as vehicles for the transport of membrane and cytosolic proteins, lipids, and nucleic acids including different RNAs. Dendritic cells (DCs)-derived EVs (DEVs), albeit variably, express major histocompatibility complex (MHC)-peptide complexes and co-stimulatory molecules on their surface that enable the interaction with other immune cells such as CD8⁺ T cells, and other ligands that stimulate natural killer (NK) cells, thereby instructing tumor rejection, and counteracting immune-suppressive tumor microenvironment. Malignant cells oppose this effect by secreting EVs bearing a variety of molecules that block DCs function. For instance, tumor-derived EVs (TDEVs) can impair myeloid cell differentiation resulting in myeloid-derived suppressor cells (MDSCs) generation. Hence, the unique composition of EVs makes them suitable candidates for the development of new cancer treatment approaches including prophylactic vaccine targeting oncogenic pathogens, cancer vaccines, and cancer immunotherapeutics. We offer a perspective from both cell sides, DCs, and tumor cells, on how EVs regulate the antitumor immune response, and how this translates into promising therapeutic options by reviewing the latest advancement in DEV-based cancer therapeutics.

A comparative proteomics analysis of the egg secretions of three major schistosome species

Morbidity associated with hepatic and urogenital schistosomiasis stems primarily from the host immune response directed against schistosome eggs. When eggs become entrapped in host tissues, the development of fibrotic plaques drives downstream pathology. These events occur due to the antigenic nature of egg excretory/secretory products (ESPs). Both Schistosoma mansoni and S. japonicum ESPs have been shown to interact with several cell populations in the host liver including hepatocytes, macrophages, and hepatic stellate cells, with both immunomodulatory and pathological consequences. Several protein components of the ESPs of S. mansoni and S. japonicum eggs have been characterised; however, studies into the collective contents of schistosome egg ESPs are lacking. Utilising shotgun mass spectrometry and an array of in silico analyses, we identified 266, 90 and 50 proteins within the S. mansoni, S. japonicum and S. haematobium egg secretomes respectively. We identified numerous proteins with already established immunomodulatory activities, vaccine candidates and vesicle markers. Relatively few common orthologues within the ESPs were identified by BLAST, indicating that the three egg secretomes differ in content significantly. Having a clearer understanding of these components may lead to the identification of new proteins with uncharacterised immunomodulatory potential or pathological relevance. This will enhance our understanding of host-parasite interactions, particularly those occurring during chronic schistosomiasis, and pave the way towards novel therapeutics and vaccines.

A sensitive S-Trap-based approach to the analysis of T cell lipid raft proteome

The analysis of T cell lipid raft proteome is challenging due to the highly dynamic nature of rafts and the hydrophobic character of raft-resident proteins. We explored an innovative strategy for bottom-up lipid raftomics based on suspension-trapping (S-Trap) sample preparation. Mouse T cells were prepared from splenocytes by negative immunoselection, and rafts were isolated by a detergent-free method and OptiPrep gradient ultracentrifugation. Microdomains enriched in flotillin-1, LAT, and cholesterol were subjected to proteomic analysis through an optimized protocol based on S-Trap and high pH fractionation, followed by nano-LC-MS/MS. Using this method, we identified 2,680 proteins in the raft-rich fraction and established a database of 894 T cell raft proteins. We then performed a differential analysis on the raft-rich fraction from nonstimulated versus anti-CD3/CD28 T cell receptor (TCR)-stimulated T cells. Our results revealed 42 proteins present in one condition and absent in the other. For the first time, we performed a proteomic analysis on rafts from ex vivo T cells obtained from individual mice, before and after TCR activation. This work demonstrates that the proposed method utilizing an S-Trap-based approach for sample preparation increases the specificity and sensitivity of lipid raftomics.

Antitumor Activity of Cabazitaxel and MSC-TRAIL Derived Extracellular Vesicles in Drug-Resistant Oral Squamous Cell Carcinoma

INTRODUCTION

TRAIL (tumor necrosis factor-related apoptosis-inducing ligand) can induce apoptosis in a variety of cancer cells. However, drug resistance of tumor and short half-life seriously affects its clinical targeted therapy. Cabazitaxel (CTX) is a taxane drug, which can induce apoptosis or autophagy by inhibiting the phosphorylation of PI3K/Akt/mTOR and sensitive to some drug-resistant tumors. Therefore, we explored the possibility of developing a mesenchymal stem cell-derived exosomes (MSC-EXO) vector for oral squamous cell carcinoma (OSCC) to deliver CTX/TRAIL combinations.

METHODS

After ultracentrifugation and dialysis, CTX/TRAIL loaded exosomes transfected MSC (MSCT)-derived exosome (EXO) (MSCT-EXO/CTX) were isolated and purified. The expression of CD63, CD9 and TRAIL was detected by BCA to confirm the origin of EXO. High-performance liquid chromatography (HPLC) was used to determine the drug loading of VPF and draw the in vitro release profile. MTT assay, flow cytometry and Western blot were used to detect the antitumor effect of MSCT-EXO/CTX in vitro. Subsequently, the antitumor effect of MSCT-EXO/CTX in vivo was verified by mouse model.

RESULTS

The diameter of the membrane particles was about 60-150 nm. We have proved that the incorporation and release of CTX in MSCT-EXO can inhibit the activation of PI3K, Akt and mTOR, which is a possible synergistic mechanism of CTX. MSCT-EXO and CTX can induce the apoptosis of SCC25 tumor cells in a dose-dependent manner and exert a good synergistic effect in the proportion range of 10:1-5:1. The inherent activity of MSCT-EXO and the direct effect of MSCT-EXO/CTX on OSCC confirm that MSCT-EXO/CTX makes MSCT-EXO and CTX have an efficient synergistic effect and a highly effective pharmacological inhibition on cancer cells, as verified by the subsequent mouse model. MSCT-EXO/CTX showed the lowest relative tumor volume and the highest tumor inhibition rate (P<0.05) in vivo.

CONCLUSION

An MSCT-EXO-based CTX delivery system might be an effective anticancer method.

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

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

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

Pathogen-host interaction mediated by vesicle-based secretion in schistosomes

As part of the parasite's excretory/secretory system, extracellular vesicles (EVs) represent a potent communication tool of schistosomes with their human host to strike the balance between their own survival in a hostile immunological environment and a minimal damage to the host tissue. Their cargo consists of functional proteins, lipids, and nucleic acids that facilitate biological processes like migration, nutrient acquisition, or reproduction. The most important impact of the vesicle-mediated communication, however, is the promotion of the parasite survival via mimicking host protein function and directly or indirectly modulating the immune response of the host. Overcoming this shield of immunological adaption in the schistosome-host relation is the aim of current research activities in this field and crucial for the development of a reliable anti-schistosomal therapy. Not least because of their prospective use in clinical applications, research on EVs is now a rapidly expanding field. We herein focus on the current state of knowledge of vesicle-based communication of schistosomes and discussing the role of EVs in facilitating biological processes and immune modulatory properties of EVs considering the different life stages of the parasite.

Schistosoma haematobium Extracellular Vesicle Proteins Confer Protection in a Heterologous Model of Schistosomiasis

Helminth parasites release extracellular vesicles which interact with the surrounding host tissues, mediating host-parasite communication and other fundamental processes of parasitism. As such, vesicle proteins present attractive targets for the development of novel intervention strategies to control these parasites and the diseases they cause. Herein, we describe the first proteomic analysis by LC-MS/MS of two types of extracellular vesicles (exosome-like, 120 k pellet vesicles and microvesicle-like, 15 k pellet vesicles) from adult Schistosoma haematobium worms. A total of 57 and 330 proteins were identified in the 120 k pellet vesicles and larger 15 k pellet vesicles, respectively, and some of the most abundant molecules included homologues of known helminth vaccine and diagnostic candidates such as Sm-TSP2, Sm23, glutathione S-transferase, saponins and aminopeptidases. Tetraspanins were highly represented in the analysis and found in both vesicle types. Vaccination of mice with recombinant versions of three of these tetraspanins induced protection in a heterologous challenge (S. mansoni) model of infection, resulting in significant reductions (averaged across two independent trials) in liver (47%, 38% and 41%) and intestinal (47%, 45% and 41%) egg burdens. These findings offer insight into the mechanisms by which anti-tetraspanin antibodies confer protection and highlight the potential that extracellular vesicle surface proteins offer as anti-helminth vaccines.

Fluorescent Labeling of Helminth Extracellular Vesicles Using an In Vivo Whole Organism Approach

In the last two decades, extracellular vesicles (EVs) from the three domains of life, Archaea, Bacteria and Eukaryotes, have gained increasing scientific attention. As such, the role of EVs in host-pathogen communication and immune modulation are being intensely investigated. Pivotal to EV research is the determination of how and where EVs are taken up by recipient cells and organs in vivo, which requires suitable tracking strategies including labelling. Labelling of EVs is often performed post-isolation which increases risks of non-specific labelling and the introduction of labelling artefacts. Here we exploited the inability of helminths to de novo synthesise fatty acids to enable labelling of EVs by whole organism uptake of fluorescent lipid analogues and the subsequent incorporation in EVs. We showed uptake of 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine-N-(lissamine rhodamine B sulfonyl) (DOPE-Rho) in Anisakis spp. and Trichuris suis larvae. EVs isolated from the supernatant of Anisakis spp. labelled with DOPE-Rho were characterised to assess the effects of labelling on size, structure and fluorescence of EVs. Fluorescent EVs were successfully taken up by the human macrophage cell line THP-1. This study, therefore, presents a novel staining method that can be utilized by the EV field in parasitology and potentially across multiple species.

The protein and microRNA cargo of extracellular vesicles from parasitic helminths - current status and research priorities

Helminth parasites have a remarkable ability to persist within their mammalian hosts, which is largely due to their secretion of molecules with immunomodulatory properties. Although the soluble components of helminth secretions have been extensively studied, the discovery that helminths release extracellular vesicles (EVs) has added further complexity to the host-parasite interaction. Whilst several studies have begun to characterise the molecules carried by helminth EVs, work aimed at investigating their biological functions has been hindered by a lack of helminth-specific EV markers. To begin to address this, we summarised helminth EV literature to date. With a focus on the protein and microRNA (miRNA) cargo, we aimed to detect similarities and differences across those major groups of helminths for which data are available; namely nematodes, trematodes and cestodes. Pfam analysis revealed that although there is no universal EV marker for all helminth species, the EF-hand protein family was present in all EV datasets from cestodes and trematodes, and could serve as a platyhelminth EV biomarker. In contrast, M13 metallopeptidases and actin may have potential as markers for nematode EVs. As with proteins, many miRNA families appeared to be species-, stage-, or dataset-specific. Two miRNA families were common to nematode EVs (mir-10 and let-7); the miRNA cargo of EVs secreted by clade I species appeared somewhat different from species from other clades. Five miRNA families (mir-71, mir-10, mir-190, let-7 and mir-2) were shared by all trematode species examined. Our analysis has identified novel markers that may be used in studies aimed at characterising helminth EVs and interrogating their function at the host-parasite interface. In addition, we discuss the heterogeneity of methods used for helminth EV isolation and emphasise the need for a standardised approach in reporting on helminth EV data.

Schistosoma mansoni infection affects the proteome and lipidome of circulating extracellular vesicles in the host

Eggs, schistosomula and adult Schistosoma worms are known to release extracellular vesicles (EV) during in vitro incubations and these EVs are postulated to affect the host responses. So far only those EVs released during in vitro incubations of schistosomes have been studied and it is unknown whether in blood of infected hosts the schistosomal EVs can be detected amidst all the circulating EVs of the host itself. In this study we analyzed the protein as well as the phospholipid composition of EVs circulating in blood plasma of S. mansoni infected hamsters and compared those with the EVs circulating in blood of non-infected hamsters. Although neither proteins nor lipids specific for schistosomes could be detected in the circulating EVs of the infected hamsters, the infection with schistosomes had a marked effect on the circulating EVs of the host, as the protein as well as the lipid composition of EVs circulating in infected hamsters were different from the EVs of uninfected hamsters. The observed changes in the EV lipid and protein content suggest that more EVs are released by the diseased liver, the affected erythrocytes and activated immune cells.

Screening of a library of recombinant Schistosoma mansoni proteins with sera from murine and human controlled infections identifies early serological markers

Background

Schistosomiasis is a major global health problem caused by blood-dwelling parasitic worms, which is currently tackled primarily by mass administration of the drug praziquantel. Appropriate drug treatment strategies are informed by diagnostics that establish the prevalence and intensity of infection, which, in regions of low transmission, should be highly sensitive.

Methods

To identify sensitive new serological markers of Schistosoma mansoni infections, we have compiled a recombinant protein library of parasite cell-surface and secreted proteins expressed in mammalian cells.

Results

Together with a time series of sera samples from volunteers experimentally infected with a defined number of male parasites, we probed this protein library to identify several markers that can detect primary infections with as low as 10 parasites and as early as 5 weeks postinfection.

Conclusions

These new markers could be further explored as valuable tools to detect ongoing and previous S mansoni infections, including in endemic regions where transmission is low.

Extracellular Vesicle-Contained microRNA of C. elegans as a Tool to Decipher the Molecular Basis of Nematode Parasitism

Among the fundamental biological processes affected by microRNAs, small regulators of gene expression, a potential role in host-parasite communication is intriguing. We compared the miRNA complement of extracellular vesicles released by the free-living nematode Caenorhabditis elegans in culture to that of other adult parasitic nematodes. Expecting convergent functional roles for secreted miRNAs due to the common parasitic lifestyle of the organisms under investigation, we performed a miRNA sequence analysis as well as target search and pathway enrichment for potential mRNA targets within host immune functions. We found that the parasite miRNA seed sequences were more often identical to those of C. elegans, rather than to those of their hosts. However, we observed that the nematode-secreted miRNA fractions shared more often seed sequences with host miRNAs than those that are not found in the extracellular environment. Development and proliferation of immune cells was predicted to be affected several-fold by nematode miRNA release. In addition, we identified the AGE-RAGE signaling as a convergent targeted pathway by species-specific miRNAs from several parasitic species. We propose a multi-species comparative approach to differentiate those miRNAs that may have critical functions in host modulation, from those that may not. With our simple analysis, we put forward a workflow to study traits of parasitism at the miRNA level. This work will find even more resonance and significance, as an increasing amount of parasite miRNA collections are expected to be produced in the future.

Immunogenicity of Exosomes from Dendritic Cells Stimulated with Toxoplasma gondii Lysates in Ocularly Immunized Mice

Immunogenicity of dendritic cell-derived exosomes stimulated with Toxoplasma gondii lysates (TLA exo), mixed with cholera toxin as an adjuvant, was investigated in mice immunized via 2 mucosal routes (ocular vs intranasal). BALB/c mice were injected 3 times with TLA exo vaccine at 2 week interval, and the levels of IgG in serum and IgA in tear, saliva, feces, and vaginal wash were measured. To observe the expression of T. gondii-specific B1 gene, mice infected with ME49 T. gondii cysts were immunized with TLA exo or PBS exo (not stimulated with TLA), and their brain tissues were examined. The mice vaccinated via intranasal route elicited significantly higher humoral and mucosal immune responses compared with mice treated with PBS alone. Also, mice immunized via ocular route (by eyedrop) induced significantly higher T. gondii-specific IgG in serum and IgA in tear and feces in comparison with PBS controls. B1 gene expression was significantly lower in TLA exo vaccinated mice than in PBS or PBS exo vaccinated mice. These results demonstrated that ocular immunization of mice with TLA exo vaccine has the potential to stimulate systemic or local antibody responses. This study also highlighted an advantage of an eyedrop vaccine as an alternative for T. gondii intranasal vaccines.

DC-SIGN mediated internalisation of glycosylated extracellular vesicles from Schistosoma mansoni increases activation of monocyte-derived dendritic cells

Helminths like Schistosoma mansoni release excretory/secretory (E/S) products that modulate host immunity to enable infection. Extracellular vesicles (EVs) are among these E/S products, yet molecular mechanisms and functionality of S. mansoni EV interaction with host immune cells is unknown. Here we demonstrate that EVs released by S. mansoni schistosomula are internalised by human monocyte-derived dendritic cells (moDCs). Importantly, we show that this uptake was mainly mediated via DC-SIGN (CD209). Blocking DC-SIGN almost completely abrogated EV uptake, while blocking mannose receptor (MR, CD206) or dendritic cell immunoreceptor (DCIR, CLEC4A) had no effect on EV uptake. Mass spectrometric analysis of EV glycans revealed the presence of surface N-glycans with terminal Galβ1-4(Fucα1-3)GlcNAc (LewisX) motifs, and a wide array of fucosylated lipid-linked glycans, including LewisX, a known ligand for DC-SIGN. Stimulation of moDCs with schistosomula EVs led to increased expression of costimulatory molecules CD86 and CD80 and regulatory surface marker PD-L1. Furthermore, schistosomula EVs increased expression of IL-12 and IL-10 by moDCs, which was partly dependent on the interaction with DC-SIGN. These results provide the first evidence that glycosylation of S. mansoni EVs facilitates the interaction with host immune cells and reveals a role for DC-SIGN and EV-associated glycoconjugates in parasite-induced immune modulation.

Partial protection with a chimeric tetraspanin-leucine aminopeptidase subunit vaccine against Opisthorchis viverrini infection in hamsters

Opisthorchiasis is a serious public health problem in East Asia and Europe. The pathology involves hepatobiliary abnormalities such as cholangitis, choledocholithiasis and tissue fibrosis that can develop into cholangiocarcinoma. Prevention of infection is difficult as multiple social and behavioral factors are involved, thus, progress on a prophylactic vaccine against opisthorchiasis is urgently needed. Opisthorchis viverrini tetraspanin-2 (Ov-TSP-2) was previously described as a potential vaccine candidate conferring partial protection against O. viverrini infections in hamsters. In this study, we generated a recombinant chimeric form of the large extracellular loop of Ov-TSP-2 and O. viverrini leucine aminopeptidase, designated rOv-TSP-2-LAP. Hamsters were vaccinated with 100 and 200 µg of rOv-TSP-2-LAP formulated with alum-CpG adjuvant via intraperitoneal injection and evaluated the level of protection against O. viverrini infection. Our results demonstrated that the number of worms recovered from hamsters vaccinated with either 100 or 200 µg of rOv-TSP-2-LAP were significantly reduced by 27% compared to the adjuvant control group. Furthermore, the average length of worms recovered from animals vaccinated with 200 μg of rOv-TSP-2-LAP was significantly shorter than those from the control adjuvant group. Immunized hamsters showed significantly increased serum levels of anti-rOv-TSP-2 IgG and IgG1 compared to adjuvant control group, suggesting that rOv-TSP-2-LAP vaccination induces a mixed Th1/Th2 immune response in hamsters. Therefore, the development of a suitable vaccine against opisthorchiasis requires further work involving new vaccine technologies to improve immunogenicity and protective efficacy.

Deep phosphoproteome analysis of Schistosoma mansoni leads development of a kinomic array that highlights sex-biased differences in adult worm protein phosphorylation

Although helminth parasites cause enormous suffering worldwide we know little of how protein phosphorylation, one of the most important post-translational modifications used for molecular signalling, regulates their homeostasis and function. This is particularly the case for schistosomes. Herein, we report a deep phosphoproteome exploration of adult Schistosoma mansoni, providing one of the richest phosphoprotein resources for any parasite so far, and employ the data to build the first parasite-specific kinomic array. Complementary phosphopeptide enrichment strategies were used to detect 15,844 unique phosphopeptides mapping to 3,176 proteins. The phosphoproteins were predicted to be involved in a wide range of biological processes and phosphoprotein interactome analysis revealed 55 highly interconnected clusters including those enriched with ribosome, proteasome, phagosome, spliceosome, glycolysis, and signalling proteins. 93 distinct phosphorylation motifs were identified, with 67 providing a ‘footprint’ of protein kinase activity; CaMKII, PKA and CK1/2 were highly represented supporting their central importance to schistosome function. Within the kinome, 808 phosphorylation sites were matched to 136 protein kinases, and 68 sites within 37 activation loops were discovered. Analysis of putative protein kinase-phosphoprotein interactions revealed canonical networks but also novel interactions between signalling partners. Kinomic array analysis of male and female adult worm extracts revealed high phosphorylation of transformation:transcription domain associated protein by both sexes, and CDK and AMPK peptides by females. Moreover, eight peptides including protein phosphatase 2C gamma, Akt, Rho2 GTPase, SmTK4, and the insulin receptor were more highly phosphorylated by female extracts, highlighting their possible importance to female worm function. We envision that these findings, tools and methodology will help drive new research into the functional biology of schistosomes and other helminth parasites, and support efforts to develop new therapeutics for their control.

Schistosomes are formidable parasites that cause the debilitating and life-threatening disease human schistosomiasis. We need to better understand the cellular biology of these parasites to develop novel strategies for their control. Within cells, a process called protein phosphorylation controls many aspects of molecular communication or ‘signalling’ and is central to cellular function and homeostasis. Here, using complementary strategies, we have performed the first in-depth characterisation and functional annotation of protein phosphorylation events in schistosomes, providing one of the richest phosphoprotein resources for any parasite to date. Using this knowledge, we have developed a novel tool to simultaneously evaluate signalling processes in these worms and highlight sex-biased differences in adult worm protein phosphorylation. Several proteins were found to be more greatly phosphorylated by female worm extracts, suggesting their possible importance to female worm function. This work will help drive new research into the fundamental biology of schistosomes, as well as related parasites, and will support efforts to develop new drug or vaccine-based therapeutics for their control.

Secreted microRNA data from the parasitic filarial nematode Acanthocheilonema viteae

microRNAs (miRNAs) are an abundant class of non-coding RNA species with important regulatory roles in gene expression at the posttranscriptional level. The helminth Acanthocheilonema viteae serves as model organism for research on parasitic filarial nematodes.

Total RNA secreted or excreted in vitro by 1500 adult female and male A. viteae over 3 weeks was isolated from culture media previously processed by differential ultracentrifugation. miRNA sequencing revealed the presence of 360 unique miRNA candidates released by adult A. viteae in vitro. Among them, 74 high-confidence unique miRNAs, as well as several potential novel miRNA candidates were discovered. A large proportion of the sequenced miRNA candidates appeared differentially expressed between the male and female samples based on normalized copy count.

The presence of extracellular vesicles, often rich in miRNAs, could not be confirmed unambiguously by transmission electron microscopy.

Heat shock protein 70 (Hsp70) in Schistosoma mansoni and its role in decreased adult worm sensitivity to praziquantel

Schistosoma mansoni is the most common species causing schistosomiasis. It has a complex life cycle involving a vertebrate definitive host and a snail intermediate host of the genus Biomphalaria. Each stage encounters a plethora of environmental stresses specially heat stress. Another sort of stress arises from repeated exposure of the parasite to praziquantel (PZQ), the only drug used for treatment, which leads to the development of resistance in the fields and the labs. Heat shock protein 70 (Hsp70) is found in different developmental stages of S. mansoni. It is immunogenic and regulate cercarial invasion besides its chaperone function. In the Biomphalaria/S. mansoni interaction, epigenetic modulations of the Hsp70 gene underscore the susceptibility phenotype of the snail. Hsp70 is up-regulated in adult S. mansoni with decreased sensitivity to PZQ. This could be due to the induction of oxidative and endoplasmic reticulum stress, induction of apoptosis, exposure to the stressful drug pressure and increase influx of calcium ions. Up-regulation of Hsp70 might help the worm to survive the schistosomicidal effect of the drug mainly by dealing with misfolded proteins, inhibition of apoptosis, induction of autophagy, up-regulation of the P-glycoprotein transporter and attenuation of the signalling from G protein coupled receptors.

Recent advances in Schistosoma mekongi ecology, transcriptomics and proteomics of relevance to snail control

Mekong schistosomiasis caused by Schistosoma mekongi is a public health problem that occurs along the border between southern Laos and northern Cambodia. Given its restricted distribution and low prevalence, eventual eradication via an effective control program can be expected to be successful. To achieve this goal detailed knowledge of its basic biology, molecular biology, biochemistry, and pathology is urgently required. In this regard, recent studies on transcriptome analysis of adult male and female S. mekongi worms, and proteome analysis of developmental stages have been reported and are discussed here. The biology, habitat, and distribution of the snail intermediate host Neotricula aperta, which are factors in disease transmission, are discussed in this review. These have initiated renewed interest in S. mekongi research and contributed promising data that will be utilized in the generation of effective control and prevention strategies.

A Review of Nanotechnology for Targeted Anti-schistosomal Therapy

Schistosomiasis is one of the major parasitic diseases and second most prevalent among the group of neglected diseases. The prevalence of schistosomiasis may be due to environmental and socio-economic factors, as well as the unavailability of vaccines for schistosomiasis. To date, current treatment; mainly the drug praziquantel (PZQ), has not been effective in treating the early forms of schistosome species. The development of drug resistance has been documented in several regions globally, due to the overuse of PZQ, rate of parasitic mutation, poor treatment compliance, co-infection with different strains of schistosomes and the overall parasite load. Hence, exploring the schistosome tegument may be a potential focus for the design and development of targeted anti-schistosomal therapy, with higher bioavailability as molecular targets using nanotechnology. This review aims to provide a concise incursion on the use of various advance approaches to achieve targeted anti-schistosomal therapy, mainly through the use of nano-enabled drug delivery systems. It also assimilates the molecular structure and function of the schistosome tegument and highlights the potential molecular targets found on the tegument, for effective specific interaction with receptors for more efficacious anti-schistosomal therapy.

Schistosomal extracellular vesicle-enclosed miRNAs modulate host T helper cell differentiation

During the chronic stage of Schistosoma infection, the female lays fertile eggs, triggering a strong anti-parasitic type 2 helper T-cell (Th2) immune response. It is unclear how this Th2 response gradually declines even though the worms live for years and continue to produce eggs. Here, we show that Schistosoma mansoni downregulates Th2 differentiation in an antigen-presenting cell-independent manner, by modulating the Th2-specific transcriptional program. Adult schistosomes secrete miRNA-harboring extracellular vesicles that are internalized by Th cells in vitro. Schistosomal miRNAs are found also in T helper cells isolated from Peyer's patches and mesenteric lymph nodes of infected mice. In T helper cells, the schistosomal miR-10 targets MAP3K7 and consequently downmodulates NF-κB activity, a critical transcription factor for Th2 differentiation and function. Our results explain, at least partially, how schistosomes tune down the Th2 response, and provide further insight into the reciprocal geographic distribution between high prevalence of parasitic infections and immune disorders such as allergy. Furthermore, this worm-host crosstalk mechanism can be harnessed to develop diagnostic and therapeutic approaches for human schistosomiasis and Th2-associated diseases.

Preliminary evaluation of the diagnostic potential of Schistosoma japonicum extracellular vesicle proteins for Schistosomiasis japonica

Schistosomiasis is a chronic parasitic disease caused by the genus Schistosoma and poses a great threat to human and animal health. Identification of effective biomarkers would facilitate evaluation of drug efficacy and recognition of infected hosts, which are crucial for effective schistosomiasis control. Extracellular vesicle (EV) proteins are considered ideal biomarkers for developing invasive diagnostic tools. In this study, we evaluated the potential of Schistosoma japonicum EV (SjEV) proteins as biomarkers for diagnosing schistosomiasis. Several SjEV proteins were subject to epitope prediction using DNASTAR software, and the diagnostic potential of selected peptides was evaluated using enzyme-linked immunosorbent assay (ELISA). The results indicated that the sera showed detectable antibody levels against the two antigens in mice, rabbits, and humans infected with S. japonicum. Further analysis of the combined epitope protein demonstrated a modest sensitivity for detection of Schistosomiasis japonica. Our preliminary study suggests that S. japonicum EV proteins could serve as potential biomarkers for developing diagnostic tools for schistosomiasis.

Recombinant Opisthorchis viverrini tetraspanin expressed in Pichia pastoris as a potential vaccine candidate for opisthorchiasis

Opisthorchiasis affects millions of people in Southeast Asia and has been strongly associated with bile duct cancer. Current strategic control approaches such as chemotherapy and health education are not sustainable, and a prophylactic vaccine would be a major advance in the prevention of the disease. Tetraspanins are transmembrane proteins previously described as potential vaccine candidates for other helminth infections and are also found in the membranes of the tegument and extracellular vesicles of O. viverrini. Here, we investigated the potential of a recombinant protein encoding for the large extracellular loop of O. viverrini tetraspanin-2 (rOv-LEL-TSP-2) in a hamster vaccination model. Hamsters were vaccinated with 50 and 100 μg of rOv-LEL-TSP-2 produced from Pichia pastoris yeast combined with alum CpG adjuvant via the intraperitoneal route. The number of worms recovered from hamsters vaccinated with rOv-LEL-TSP-2 was significantly reduced compared to adjuvant control groups. Fecal egg output was also significantly reduced in vaccinated animals, and the average length of worms recovered from vaccinated animals was significantly shorter than that of the control group. Vaccinated animals showed significantly increased levels of anti-rOv-TSP-2 IgG in the sera after three immunizations, as well as increased levels of several T helper type 1 cytokines in the spleen including IFN-γ and IL-6 but not the Th2/regulatory cytokines IL-4 or IL-10. These results suggest that rOv-TSP-2 could be a potential vaccine against opisthorchiasis and warrants further exploration.

Proteomic Analysis on Exosomes Derived from Patients' Sera Infected with Echinococcus granulosus

Cystic echinococcosis (CE), a zoonotic disease caused by Echinococcus granulosus at the larval stage, predominantly develops in the liver and lungs of intermediate hosts and eventually results in organ malfunction or even death. The interaction between E. granulosus and human body is incompletely understood. Exosomes are nanosized particles ubiquitously present in human body fluids. Exosomes carry biomolecules that facilitate communication between cells. To the best of our knowledge, the role of exosomes in patients with CE is not reported. Here, we isolated exosomes from the sera of patients with CE (CE-exo) and healthy donors and subjected them to liquid chromatography-tandem mass spectrometry analysis. Proteomic analysis identified 49 proteins specifically expressed in CE-exo, including 4 proteins of parasitic origin. The most valuable parasitic proteins included tubulin alpha-1C chain and histone H4. And 8 proteins were differentially regulated in CE-exo (fold change>1.5), as analyzed with bioinformatic methods such as annotation and functional enrichment analyses. These findings may improve our understanding about the interaction between E. granulosus and human body, and may contribute to the diagnosis and prevention of CE.

Identification and molecular characterization of exosome-like vesicles derived from the Taenia asiatica adult worm

Taenia asiatica is an important food-borne parasite that poses a threat to food-safety and animal husbandry hygine, yet little is known about its specific infection and immune escape mechanisms. Exosome-like vesicles have recently emerged as a regulator in the interactions between parasites and hosts, providing a new direction for research on infection of T. asiatica. In this experiment, exosome-like vesicles were collected from the excretory/secretory products of cultured T. asiatica and isolated by differential centrifugation. The purified vesicles, ranging from 30 to 150 nm in size, were identified as exosome-like vesicles by transmission electron microscope and Nanoparticle tracking analysis. Proteomics analysis identified 455 proteins in the exosome-like vesicles. Of these proteins, enzymes involved in metabolic processes were identified, including glyceraldehyde 3 phosphate dehydrogenase, fructose-1, 6-bisphosphate aldolase, cytosolic malate dehydrogenase, and enolase. The two most abundant proteins from proteomic analysis, 14-3-3 and enolase, were shown to be present in the exosome-like vesicles by immunogold labeling. High-throughput RNA sequencing yielded twenty known miRNAs present in exosome-like vesicle sRNA libraries. Nine of the miRNAs, including six known miRNAs (tas-miR-71, tas-miR-1, tas-miR-7, tas-miR-9, tas-miR-10, and tas-let-7) and three newly discovered miRNAs (tas-m0022-3p, tas-m0816-3p, tas-m0082-5p), were confirmed by RT-qPCR as present in T. asiatica adult worm extracts and secreted exosome-like vesicles in T. asiatica. Additionally, we demonstrated that exosome-like vesicles experimentally labeled with PKH67 were internalized by LoVo cells in vitro. These findings provide new insights into the interaction between tapeworms and hosts mediated by exosome-like vesicles.

Research progress on the composition and function of parasite-derived exosomes

Parasites use excretory-secretory pathways to communicate with the host. Characterization of exosomes within the excretory-secretory products reveal by which parasites manipulate their hosts. Parasite derived exosomes provide a mechanistic framework for protein and miRNAs transfer. Transcriptomics and proteomics of parasite exosomes identified a large number of miRNAs and proteins being utilized by parasites in their survival, reproduction and development. Characterization of proteins and miRNAs in parasite secreted exosomes provide important information on host-parasite communication and forms the basis for future studies. In this review, we summarize recent advances in isolation and molecular characterization (protein and miRNAs) of parasite derived exosomes.

Schistosoma japonicum extracellular vesicle miRNA cargo regulates host macrophage functions facilitating parasitism

Schistosome infection persists for decades. Parasites are in close contact with host peripheral blood immune cells, yet little is known about the regulatory interactions between parasites and these immune cells. Here, we report that extracellular vesicles (EVs) released from Schistosoma japonicum are taken up primarily by macrophages and other host peripheral blood immune cells and their miRNA cargo transferred into recipient cells. Uptake of S. japonicum EV miR-125b and bantam miRNAs into host cells increased macrophage proliferation and TNF-α production by regulating the corresponding targets including Pros1, Fam212b, and Clmp. Mice infected with S. japonicum exhibit an increased population of monocytes and elevated levels of TNF-α. Reduction of host monocytes and TNF-α level in S. japonicum infected mice led to a significant reduction in worm and egg burden and pathology. Overall, we demonstrate that S. japonicum EV miRNAs can regulate host macrophages illustrating parasite modulation of the host immune response to facilitate parasite survival. Our findings provide valuable insights into the schistosome-host interaction which may help to develop novel intervention strategies against schistosomiasis.

Schistosomes that cause schistosomiasis infection persist for decades despite a host immune response. Therefore, elucidating the mechanism of schistosome survival will not only contribute to the understanding of host-parasite interaction but also lead to the development of novel strategies against schistosomiasis. Extracellular vesicles (EVs) and their miRNA cargo have been shown to be mediators of intercellular communication involved in the regulation of many biological processes. Here, we demonstrated that EVs released from Schistosoma japonicum (SjEVs) are taken up primarily by macrophages and other host peripheral blood immune cells and their miRNA cargo transferred into recipient cells. Uptake of S. japonicum EV miR-125b and bantam miRNAs into host cells increased macrophage proliferation and TNF-α production that contributes to parasite survival. Our findings reveal key roles of SjEV miRNAs for facilitating parasitism in schistosomes.

Vaccination of hamsters with Opisthorchis viverrini extracellular vesicles and vesicle-derived recombinant tetraspanins induces antibodies that block vesicle uptake by cholangiocytes and reduce parasite burden after challenge infection

Background

The liver fluke Opisthorchis viverrini infects several million people in Southeast Asia. Adult flukes live in the bile ducts of humans, where they cause hepatobiliary pathology, including cholangiocarcinoma. Here, we investigated the potential of extracellular vesicles (EVs) secreted by the fluke and defined recombinant proteins derived from EVs to generate protective immunity in a hamster vaccination-challenge model.

Methodology/Principal findings

EVs isolated from the excretory-secretory products of O. viverrini and two recombinant EV surface proteins encoding the large extracellular loops (LEL) of Ov-TSP-2 (rOv-TSP-2) and Ov-TSP-3 (rOv-TSP-3) were adjuvanted and used to vaccinate hamsters intraperitoneally followed by challenge infection with O. viverrini metacercariae. The number of adult flukes recovered from hamsters immunized with EVs, rOv-TSP-2, rOv-TSP-3 and rOv-TSP-2+rOv-TSP-3 were significantly reduced compared to control animals vaccinated with adjuvant alone. The number of eggs per gram feces was also significantly reduced in hamsters vaccinated with rOv-TSP-2 compared to controls, but no significant differences were found in the other groups. The average length of worms recovered from hamsters vaccinated with EVs, rOv-TSP-2 and rOv-TSP-3 was significantly shorter than that of worms recovered from the control group. Anti-EV IgG levels in serum and bile were significantly higher in hamsters vaccinated with EVs compared to control hamsters both pre- and post-challenge. In addition, levels of anti-rOv-TSP antibodies in the serum and bile were significantly higher than control hamsters both pre- and post-challenge. Finally, antibodies against rOv-TSP-2 and rOv-TSP-3 blocked uptake of EVs by human primary cholangiocyte in vitro, providing a plausible mechanism by which these vaccines exert partial efficacy and reduce the intensity of O. viverrini infection.

Conclusion/Significance

Liver fluke EVs and recombinant tetraspanins derived from the EV surface when administered to hamsters induce antibody responses that block EV uptake by target bile duct cells and exert partial efficacy and against O. viverrini challenge.

Cholangiocarcinoma (CCA) is a significant public health problem in countries throughout Southeast Asia. In these areas CCA has a strong association with chronic infection with the food-borne liver fluke Opisthorchis viverrini. Current control of the infection relies on chemotherapy and health education, however these approaches are not sustainable in isolation. Hence, there is an urgent need for a vaccine against this neglected tropical disease. A vaccine against O. viverrini would confer anti-cancer protection in similar fashion to the acclaimed vaccine for human papillomavirus and cervical cancer. Toward this goal, secreted extracellular vesicles (EVs) of O. viverrini and recombinant proteins from the surface of EVs were generated and tested as vaccines in a hamster challenge model. Vaccination of hamsters with EVs and recombinant proteins induced production of antibodies in serum and bile, and those antibodies blocked uptake of EVs by primary bile duct cells in vitro. Challenge of vaccinated hamsters with infective stage flukes markedly reduced adult fluke recovery compared to the adjuvant control group. This is the first report of successful vaccination of hamsters with O. viverrini EVs and recombinant vesicle surface proteins, and provides proof-of-concept for development of subunit vaccines for this carcinogenic infection.

In-depth proteomic characterization of Schistosoma haematobium: Towards the development of new tools for elimination

BACKGROUND

Schistosomiasis is a neglected disease affecting hundreds of millions worldwide. Of the three main species affecting humans, Schistosoma haematobium is the most common, and is the leading cause of urogenital schistosomiasis. S. haematobium infection can cause different urogenital clinical complications, particularly in the bladder, and furthermore, this parasite has been strongly linked with squamous cell carcinoma. A comprehensive analysis of the molecular composition of its different proteomes will contribute to developing new tools against this devastating disease.

METHODS AND FINDINGS

By combining a comprehensive protein fractionation approach consisting of OFFGEL electrophoresis with high-throughput mass spectrometry, we have performed the first in-depth characterisation of the different discrete proteomes of S. haematobium that are predicted to interact with human host tissues, including the secreted and tegumental proteomes of adult flukes and secreted and soluble egg proteomes. A total of 662, 239, 210 and 138 proteins were found in the adult tegument, adult secreted, soluble egg and secreted egg proteomes, respectively. In addition, we probed these distinct proteomes with urine to assess urinary antibody responses from naturally infected human subjects with different infection intensities, and identified adult fluke secreted and tegument extracts as being the best predictors of infection.

CONCLUSION

We provide a comprehensive dataset of proteins from the adult and egg stages of S. haematobium and highlight their utility as diagnostic markers of infection intensity. Protein composition was markedly different between the different extracts, highlighting the distinct subsets of proteins that different development stages present in their different niches. Furthermore, we have identified adult fluke ES and tegument extracts as best predictors of infection using urine antibodies of naturally infected people. This study provides the first steps towards the development of novel tools to control this important neglected tropical disease.

Exploration of extracellular vesicles from Ascaris suum provides evidence of parasite-host cross talk

The prevalent porcine helminth, Ascaris suum, compromises pig health and reduces farm productivity worldwide. The closely related human parasite, A. lumbricoides, infects more than 800 million people representing a disease burden of 1.31 million disability-adjusted life years. The infections are often chronic in nature, and the parasites have a profound ability to modulate their hosts' immune responses. This study provides the first in-depth characterisation of extracellular vesicles (EVs) from different developmental stages and body parts of A. suum and proposes the role of these vesicles in the host-parasite interplay. The release of EVs from the third- (L3) and fourth-stage (L4) larvae and adults was demonstrated by transmission electron microscopy (TEM), and sequencing of EV-derived RNA identified a number of microRNAs (miRNAs) and transcripts of potential host immune targets, such as IL-13, IL-25 and IL-33, were identified. Furthermore, proteomics of EVs identified several proteins with immunomodulatory properties and other proteins previously shown to be associated with parasite EVs. Taken together, these results suggest that A. suum EVs and their cargo may play a role in host-parasite interactions. This knowledge may pave the way to novel strategies for helminth infection control and knowledge of their immune modulatory potential.

The importance of extracellular vesicle purification for downstream analysis: A comparison of differential centrifugation and size exclusion chromatography for helminth pathogens

BACKGROUND

Robust protocols for the isolation of extracellular vesicles (EVs) from the rest of their excretory-secretory products are necessary for downstream studies and application development. The most widely used purification method of EVs for helminth pathogens is currently differential centrifugation (DC). In contrast, size exclusion chromatography (SEC) has been included in the purification pipeline for EVs from other pathogens, highlighting there is not an agreed research community 'gold standard' for EV isolation. In this case study, Fasciola hepatica from natural populations were cultured in order to collect EVs from culture media and evaluate a SEC or DC approach to pathogen helminth EV purification.

METHODOLOGY/PRINCIPAL FINDINGS

Transmission electron and atomic force microscopy demonstrated that EVs prepared by SEC were both smaller in size and less diverse than EV resolved by DC. Protein quantification and Western blotting further demonstrated that SEC purification realised a higher EV purity to free excretory-secretory protein (ESP) yield ratio compared to DC approaches as evident by the reduction of soluble free cathepsin L proteases in SEC EV preparations. Proteomic analysis further highlighted DC contamination from ESP as shown by an increased diversity of protein identifications and unique peptide hits in DC EVs as compared to SEC EVs. In addition, SEC purified EVs contained less tegumental based proteins than DC purified EVs.

CONCLUSIONS/SIGNIFICANCE

The data suggests that DC and SEC purification methods do not isolate equivalent EV population profiles and caution should be taken in the choice of EV purification utilised, with certain protocols for DC preparations including more free ES proteins and tegumental artefacts. We propose that SEC methods should be used for EV purification prior to downstream studies.

Extracellular Vesicle-Mediated Communication Within Host-Parasite Interactions

Extracellular vesicles (EVs) are small membrane-surrounded structures released by different kinds of cells (normal, diseased, and transformed cells) in vivo and in vitro that contain large amounts of important substances (such as lipids, proteins, metabolites, DNA, RNA, and non-coding RNA (ncRNA), including miRNA, lncRNA, tRNA, rRNA, snoRNA, and scaRNA) in an evolutionarily conserved manner. EVs, including exosomes, play a role in the transmission of information, and substances between cells that is increasingly being recognized as important. In some infectious diseases such as parasitic diseases, EVs have emerged as a ubiquitous mechanism for mediating communication during host-parasite interactions. EVs can enable multiple modes to transfer virulence factors and effector molecules from parasites to hosts, thereby regulating host gene expression, and immune responses and, consequently, mediating the pathogenic process, which has made us rethink our understanding of the host-parasite interface. Thus, here, we review the present findings regarding EVs (especially exosomes) and recognize the role of EVs in host-parasite interactions. We hope that a better understanding of the mechanisms of parasite-derived EVs may provide new insights for further diagnostic biomarker, vaccine, and therapeutic development.

A new level of complexity in parasite-host interaction: The role of extracellular vesicles

Humans and animals have co-existed with parasites in a battle of constant adaptation to one another. It is becoming increasingly clear that extracellular vesicles (EVs) play important roles in this co-existence and pathology. This chapter reviews the current research on EVs released by protozoa, nematodes, trematodes, and cestodes with a special focus on EVs in parasite life cycles. The environmental changes experienced by the parasite during its life cycle is associated with distinct changes in EV release and content. The function of these EV seems to have a significant influence on parasite pathology and survival in the host by concomitantly modulating host immune responses and triggering parasite differentiation. The role of EVs in communication between the parasites and the host adds a new level of complexity in our understanding of parasite biology, which may be a key to further understand the complexity behind host-parasite interactions and communication. This increased understanding can, in turn, open up new avenues for vaccine, diagnostic, and therapeutic development for a wide variety of diseases such as parasite infection, cancers, and immunological disorders.

Hookworms in Emergency Department: The ＂Vampire＂ Within

Hookworms infection is a soil-transmitted helminthic disease particularly endemic in developing counties of tropical regions. It is attributed mainly to two human pathogens nematodes namely Necator americanus and Ancylostoma duodenale. Although the disease has been characterized as "neglected" is very diffi cult to be eliminated and the economic consequences are great. Worms are fed with blood of hosts in small intestine and cause typically iron deficiency anemia with relevant symptoms as well as eosinophilia. Patients admitted in emergency department claim often diffuse general symptoms, whereas cases with obscure gastrointestinal bleeding can be seen. Within this brief review, after introducing some basic elements of hookworms' epidemiology, taxonomy and socioeconomic problem is emphasized, pathogenesis, and life cycle of parasite are concisely explained. Furthermore, clinical manifestations often or rarely seen in emergency department are described. Therapeutic options are also enclosed. Awareness of the problem and critical thinking of patients coming from endemic regions could result to identifying more hookworm cases and their therapy will efficiently alleviate not only the patients per se but health system and societies as well.

Helminth parasites and immune regulation

Helminth parasites are complex metazoans that belong to different taxonomic families but that collectively share the capacity to downregulate the host immune response directed toward themselves (parasite-specific immunoregulation). During long-standing chronic infection, these helminths appear able to suppress immune responses to bystander pathogens/antigens and atopic, autoimmune, and metabolic disorders. Helminth-induced immunoregulation occurs through the induction of regulatory T cells or Th2-type cells (or both). However, secreted or excreted parasite metabolites, proteins, or extracellular vesicles (or a combination of these) may also directly induce signaling pathways in host cells. Therefore, the focus of this review will be to highlight recent advances in understanding the immune responses to helminth infection, emphasizing the strategies/molecules and some of the mechanisms used by helminth parasites to modulate the immune response of their hosts.

Immunomodulation by Helminths: Intracellular Pathways and Extracellular Vesicles

Helminth parasites are masters at manipulating host immune responses, using an array of sophisticated mechanisms. One of the major mechanisms enabling helminths to establish chronic infections is the targeting of pattern recognition receptors (PRRs) including toll-like receptors, C-type lectin receptors, and the inflammasome. Given the critical role of these receptors and their intracellular pathways in regulating innate inflammatory responses, and also directing adaptive immunity toward Th1 and Th2 responses, recognition of the pathways triggered and/or modulated by helminths and their products will provide detailed insights about how helminths are able to establish an immunoregulatory environment. However, helminths also target PRRs-independent mechanisms (and most likely other yet unknown mechanisms and pathways) underpinning the battery of different molecules helminths produce. Herein, the current knowledge on intracellular pathways in antigen presenting cells activated by helminth-derived biomolecules is reviewed. Furthermore, we discuss the importance of helminth-derived vesicles as a less-appreciated components released during infection, their role in activating these host intracellular pathways, and their implication in the development of new therapeutic approaches for inflammatory diseases and the possibility of designing a new generation of vaccines.

Roles of microRNAs in T cell immunity: Implications for strategy development against infectious diseases

T cell immunity plays a vital role in pathogen infections. MicroRNA (miRNAs) are small, single-stranded noncoding RNAs that regulate T cell immunity by targeting key transcriptional factors, signaling proteins, and cytokines associated with T cell activation, differentiation, and function. The dysregulation of miRNA expression in T cells may lead to specific immune responses and can provide new therapeutic opportunities against various infectious diseases. Here, we summarize recent studies that focus on the roles of miRNAs in T cell immunity and highlight miRNA functions in prevalent infectious diseases. Additionally, we also provide insights into the functions of extracellular vesicle miRNAs and attempt to delineate the mechanism of miRNA sorting into extracellular vesicles and their immunomodulatory functions. Moreover, methodologies and strategies for miRNA delivery against infectious diseases are summarized. Finally, potential strategies for miRNA-based therapies are proposed.

Extracellular vesicles induce protective immunity against Trichuris muris

Gastrointestinal nematodes, such as Trichuris trichiura (human whipworm), are a major source of morbidity in humans and their livestock. There is a paucity of commercially available vaccines against these parasites, and vaccine development for T. trichiura has been impeded by a lack of known host protective antigens. Experimental vaccinations with T. muris (murine whipworm) soluble Excretory/Secretory (ES) material have demonstrated that it is possible to induce protective immunity in mice; however, the potential for extracellular vesicles (EVs) as a source of antigenic material has remained relatively unexplored. Here, we demonstrate that EVs isolated from T. muris ES can induce protective immunity in mice when administered as a vaccine without adjuvant and show that the protective properties of these EVs are dependent on intact vesicles. We also identified several proteins within EV preparations that are targeted by the host antibodies following vaccination and subsequent infection with T. muris. Many of these proteins, including VWD and vitellogenin N and DUF1943-domain-containing protein, vacuolar protein sorting-associated protein 52 and TSP-1 domain-containing protein, were detected in both soluble ES and EV samples and have homologues in other parasites of medical and veterinary importance, and as such are possible protective antigens.

Immunobiology of parasitic worm extracellular vesicles

Helminth parasites (worms) have evolved a vast array of strategies to manipulate their vertebrate hosts. Extracellular vesicles (EVs) are secreted by all helminth species investigated thus far, and their salient roles in parasite-host interactions are being revealed. Parasite EVs directly interact with various cell types from their hosts, including immune cells, and roles for their molecular cargo in both regulation and promotion of inflammation in the host have been reported. Despite the growing body of literature on helminth EVs, limited availability of genetic manipulation tools for helminth research has precluded detailed investigation of specific molecular interactions between parasite EVs and host target cells. Here, we review the current state of the field and discuss innovative strategies targeting helminth EVs for the discovery and development of new therapeutic strategies, placing particular emphasis on both anti-helminth vaccines and EV small RNAs for treating noninfectious inflammatory diseases.

Biochemical analysis and identification of linear B-cell epitopes from recombinant Sm21.7 antigen from Schistosoma mansoni

Schistosoma mansoni tegument is a dynamic host-interactive layer that is an essential source of parasite antigens and a relevant field for schistosome vaccine research. Sm21.7 is a cytoskeleton antigen found in S. mansoni tegument that engenders protection in experimental challenge infection. Because of its crucial role in the parasite tegument and its promising protective capability, Sm21.7 is an exciting target for the development of therapeutic strategies. The present study describes Sm21.7 structural and biophysical features using circular dichroism spectroscopy and identifies linear B-cell epitopes of Sm21.7 using in-silico methods and immunoassay. The Sm21.7 gene was cloned into the pETDEST42 vector, and the recombinant protein was overexpressed in Escherichia coli DE3. The soluble protein was purified by affinity chromatography followed by ion-exchange chromatography. Purified recombinant Sm21.7 was analyzed by circular dichroism spectroscopy which demonstrated that the rSm21.7 structure was comprised of approximately 38% α-helices and its conformation remains stable at temperatures of up to 60 °C. Prediction of rSm21.7 B-cell epitopes was based on amino acid physicochemical properties. Sixteen peptides corresponding to predicted epitopes were synthesized and immunoreactivity assessed by spot peptide array using pooled rSm21.7-immunized mice sera or patients' sera with different clinical forms of S. mansoni infection. Immunoassays revealed that sera from rSm21.7-immunized mice reacted predominantly with peptides located in the dynein-light chain domain (DLC) at the C-terminal region of rSm21.7. Comparative analysis of the antibody response of acute, intestinal and hepatosplenic patients' sera to the Sm21.7 peptides showed that a differential recognition pattern of Sm21.7-derived peptides by intestinal patients' sera might contribute to down-regulate the immune response in chronic intestinal patients. Together, the results may help the development of S. mansoni vaccine strategies based on the rSm21.7 antigen.

Isolation and Characterization of Extracellular Vesicles from Adult Schistosoma japonicum

Extracellular vesicles (EVs) are membranous vesicles released by a variety of cells into the extracellular microenvironment. EVs represent a population of heterogeneous vesicles, whose size range between 40 and 1,000 nm. Accumulated evidence indicated that EVs play important regulatory roles in pathogen-host interactions. A deep understanding of schistosome EVs should provide insights into the mechanisms underlying schistosome-host interactions, enabling development of novel strategies against schistosomiasis. Here, we aim to further study EVs functions in schistosomes by presenting a protocol for the isolation and characterization of EVs from adult Schistosoma japonicum (S. japonicum). EVs were isolated from in vitro culture medium using centrifugation combined with a commercial exosome isolation kit. The isolated S. japonicum EVs (SjEVs) typically possess a diameter of 100 - 400 nm, and are characterized by transmission electronic microscopy and western blotting. The usage of PKH67 dye-labeled SjEVs has demonstrated that SjEVs are internalized by the recipient cells. Overall, our protocol provides an alternative method for isolating EVs from adult schistosomes; the isolated SjEVs may be suitable for functional analysis.

Hookworm Secreted Extracellular Vesicles Interact With Host Cells and Prevent Inducible Colitis in Mice

Gastrointestinal (GI) parasites, hookworms in particular, have evolved to cause minimal harm to their hosts, allowing them to establish chronic infections. This is mediated by creating an immunoregulatory environment. Indeed, hookworms are such potent suppressors of inflammation that they have been used in clinical trials to treat inflammatory bowel diseases (IBD) and celiac disease. Since the recent description of helminths (worms) secreting extracellular vesicles (EVs), exosome-like EVs from different helminths have been characterized and their salient roles in parasite–host interactions have been highlighted. Here, we analyze EVs from the rodent parasite Nippostrongylus brasiliensis, which has been used as a model for human hookworm infection. N. brasiliensis EVs (Nb-EVs) are actively internalized by mouse gut organoids, indicating a role in driving parasitism. We used proteomics and RNA-Seq to profile the molecular composition of Nb-EVs. We identified 81 proteins, including proteins frequently present in exosomes (like tetraspanin, enolase, 14-3-3 protein, and heat shock proteins), and 27 sperm-coating protein-like extracellular proteins. RNA-Seq analysis revealed 52 miRNA species, many of which putatively map to mouse genes involved in regulation of inflammation. To determine whether GI nematode EVs had immunomodulatory properties, we assessed their potential to suppress GI inflammation in a mouse model of inducible chemical colitis. EVs from N. brasiliensis but not those from the whipworm Trichuris muris or control vesicles from grapes protected against colitic inflammation in the gut of mice that received a single intraperitoneal injection of EVs. Key cytokines associated with colitic pathology (IL-6, IL-1β, IFNγ, and IL-17a) were significantly suppressed in colon tissues from EV-treated mice. By contrast, high levels of the anti-inflammatory cytokine IL-10 were detected in Nb-EV-treated mice. Proteins and miRNAs contained within helminth EVs hold great potential application in development of drugs to treat helminth infections as well as chronic non-infectious diseases resulting from a dysregulated immune system, such as IBD.

SmSP2: A serine protease secreted by the blood fluke pathogen Schistosoma mansoni with anti-hemostatic properties

BACKGROUND

Serine proteases are important virulence factors for many pathogens. Recently, we discovered a group of trypsin-like serine proteases with domain organization unique to flatworm parasites and containing a thrombospondin type 1 repeat (TSR-1). These proteases are recognized as antigens during host infection and may prove useful as anthelminthic vaccines, however their molecular characteristics are under-studied. Here, we characterize the structural and proteolytic attributes of serine protease 2 (SmSP2) from Schistosoma mansoni, one of the major species responsible for the tropical infectious disease, schistosomiasis.

METHODOLOGY/PRINCIPAL FINDINGS

SmSP2 comprises three domains: a histidine stretch, TSR-1 and a serine protease domain. The cleavage specificity of recombinant SmSP2 was determined using positional scanning and multiplex combinatorial libraries and the determinants of specificity were identified with 3D homology models, demonstrating a trypsin-like endopeptidase mode of action. SmSP2 displayed restricted proteolysis on protein substrates. It activated tissue plasminogen activator and plasminogen as key components of the fibrinolytic system, and released the vasoregulatory peptide, kinin, from kininogen. SmSP2 was detected in the surface tegument, esophageal glands and reproductive organs of the adult parasite by immunofluorescence microscopy, and in the excretory/secretory products by immunoblotting.

CONCLUSIONS/SIGNIFICANCE

The data suggest that SmSP2 is secreted, functions at the host-parasite interface and contributes to the survival of the parasite by manipulating host vasodilatation and fibrinolysis. SmSP2 may be, therefore, a potential target for anti-schistosomal therapy.