Application of small RNA technology for improved control of parasitic helminths

Inhibition of Trichinella spiralis Membrane-Associated Progesterone Receptor (MAPR) Results in a Reduction in Worm Burden

Trichinella spiralis (T. spiralis), a nematode parasite, is the major cause of Trichinellosis, a zoonotic disease. A key role of MAPR in the reproductive system is to maintain pregnancy. Previous studies found that antihormone drug design and vaccine therapy of recombinant protein (rTs-MAPRC2) control T. spiralis infection. The current study investigates the inhibitory effects of different ratios of antibodies against Ts-MAPRC2 on the development of muscle larvae (ML) and newborn larvae (NBL). First, we performed indirect immunofluorescence assays and examined the effects of rTs-MAPRC2-Ab on ML and NBL in vitro as well as in vivo. Afterward, siRNA-Ts-MAPRC2 was transfected into T. spiralis muscle larvae. Following that, Ts-MAPRC2 protein was detected by Western Blotting, and mRNA levels were determined by qPCR. We also assessed whether siRNA-treated NBLs were infective by analyzing muscle larvae burden (MLs). Our results showed that rTs-MAPRC2-Ab greatly inhibited the activity of the Ts-MAPRC2 in ML and NBL of T. spiralis and rTs-MAPRC2-Ab reduced larval infectivity and survival in the host in a dose-dependent manner (1:50, 1:200, 1:800 dilutions). Furthermore, siRNA-Ts-MAPRC2 effectively silenced the Ts-MAPRC2 gene in muscle larvae (ML) in vitro, as well as in newborn larvae (NBL) of T. spiralis in vivo. In addition, siRNA-Ts-MAPRC2 (siRNA180, siRNA419, siRNA559) reduced host larval survival and infectivity significantly. This study, therefore, suggests that Ts-MAPRC2 might be a novel molecular target useful in the development of vaccines against T. spiralis infection.

piRNA-like small RNAs target transposable elements in a Clade IV parasitic nematode

The small RNA (sRNA) pathways identified in the model organism Caenorhabditis elegans are not widely conserved across nematodes. For example, the PIWI pathway and PIWI-interacting RNAs (piRNAs) are involved in regulating and silencing transposable elements (TE) in most animals but have been lost in nematodes outside of the C. elegans group (Clade V), and little is known about how nematodes regulate TEs in the absence of the PIWI pathway. Here, we investigated the role of sRNAs in the Clade IV parasitic nematode Strongyloides ratti by comparing two genetically identical adult stages (the parasitic female and free-living female). We identified putative small-interfering RNAs, microRNAs and tRNA-derived sRNA fragments that are differentially expressed between the two adult stages. Two classes of sRNAs were predicted to regulate TE activity including (i) a parasite-associated class of 21-22 nt long sRNAs with a 5' uridine (21-22Us) and a 5' monophosphate, and (ii) 27 nt long sRNAs with a 5' guanine/adenine (27GAs) and a 5' modification. The 21-22Us show striking resemblance to the 21U PIWI-interacting RNAs found in C. elegans, including an AT rich upstream sequence, overlapping loci and physical clustering in the genome. Overall, we have shown that an alternative class of sRNAs compensate for the loss of piRNAs and regulate TE activity in nematodes outside of Clade V.

MicroRNAs in helminth parasites: a systematic review

BACKGROUND

MicroRNAs (miRNAs) are about 22-nucleotide, small, non-coding RNAs that control gene expression post-transcriptionally. Helminth parasites usually express a unique repertoire of genes, including miRNAs, across different developmental stages with subtle regulatory mechanisms.

OBJECTIVE

There is a necessity to investigate the involvement of miRNAs in the development of parasites, host-parasite interaction, immune evasion and their abilities to govern infection in hosts. miRNAs present in helminth parasites have been summarized in the current systematic review (SR).

METHODS

Electronic databases, including PubMed, Scopus, ProQuest, Embase, and Google Scholar search engine, were searched to identify helminth miRNA studies published from February 1993 till December 2019. Only the published articles in English were included in the study.

RESULTS

A total of 1769 articles were preliminarily recorded. Following the strict inclusion and exclusion criteria, 105 studies were included in this SR. Most of these studies focused on the identification of miRNAs in helminth parasites and/or probing of differentially expressed host miRNA profiles in specific relevant tissues, while 12 studies aimed to detect parasite-derived miRNAs in host circulating system and 15 studies characterized extracellular vesicles (EV)-derived miRNAs secreted by parasites.

CONCLUSION

In the current SR, information regarding all miRNAs expressed in helminth parasites has been comprehensively provided and the utility of helminth parasites-derived miRNAs in diagnosis and control of parasitic infections has been discussed. Furthermore, functional studies on helminth-derived miRNAs have also been presented.

The challenging world of extracellular RNAs of helminth parasites

In the last years, cell free or extracellular RNAs (ex-RNAs) have emerged as novel intercellular messengers between animal cells, including pathogens. In infectious diseases, ex-RNAs represent novel players in the host-pathogen and pathogen-pathogen interplays and have been described in parasitic helminths from the three major taxonomic groups: nematodes, trematodes and cestodes. Altogether, it is estimated that approximately 30 percent of the world's population is infected with helminths, which cause debilitating diseases and syndromes. Ex-RNAs are protected from degradation by encapsulation in extracellular vesicles (EV), or association to proteins or lipoproteins, and have been detected in the excretion/secretion products of helminth parasites, with EV as the preferred extracellular compartment under study. EV is the generic term used to describe a heterogenous group of subcellular membrane-bound particles, with varying sizes, biogenesis, density and composition. However, recent data suggests that this is not the only means used by helminth parasites to secrete RNAs since ex-RNAs can also be found in EV-depleted samples. Furthermore, the use of pathogen ex-RNAs as biomarkers promise the advent of new diagnostic tools though this field is still in early stages of exploration. In this review, we summarize current knowledge of vesicular and non-vesicular ex-RNAs secretion in helminth parasites, their potential as biomarkers and the evidence of their role in parasite and host reciprocal communication, together with unanswered questions in the field.

Expression of Mir-21 and Mir-103a in Toxocara canis: Potential for Diagnosis of Human Toxocariasis

Background:

Toxocariasis is one of the most neglected zoonotic diseases, predominantly caused by Toxocara canis. We aimed to evaluate the expression of microRNAs 21 and 103a in seropositive individuals for human toxocariasis as diagnostic biomarkers.

Methods:

This study was conducted on 324 individuals for ELISA test on toxocariasis in Tehran and Karaj, Iran 2019. Then positive samples for anti-Toxocara IgG were obtained to quantitative Real-time PCR (qRT-PCR) assays to investigate the transcriptional profiles of miRNAs predicted to be involved in developmental and reproductive processes. qPCR was employed to assess levels of transcription for miRNAs of 103a and 21 in plasma samples.

Results:

After the experiments, the results were evaluated by REST software, Livak formula and quantitative t-test. The analyzes performed on human samples showed that in the case group compared to the control group, only in Tc-miR-21 gene, a 0.3-fold increase in expression was obtained with REST software (Fold change ≤ 1.5, P>0.05), which was statistically significant by t-test (P<0.05).

Conclusion:

To our knowledge, this is the first study to evaluate miR-21 and miR-103a in toxocariasis, which shed light on the fundamental role of it as a biomarker and diagnostic tool. However, due to the changes in expression of these miRNAs were not vast to be used as biomarkers in diagnosis. Despite of that the changes in the expression of these miRNAs were not vast but they could serve as novel promising biomarkers for diagnosis of toxocariasis.

Extracellular non-coding RNA signatures of the metacestode stage of Echinococcus multilocularis

Extracellular RNAs (ex-RNAs) are secreted by cells through different means that may involve association with proteins, lipoproteins or extracellular vesicles (EV). In the context of parasitism, ex-RNAs represent new and exciting communication intermediaries with promising potential as novel biomarkers. In the last years, it was shown that helminth parasites secrete ex-RNAs, however, most work mainly focused on RNA secretion mediated by EV. Ex-RNA study is of special interest in those helminth infections that still lack biomarkers for early and/or follow-up diagnosis, such as echinococcosis, a neglected zoonotic disease caused by cestodes of the genus Echinococcus. In this work, we have characterised the ex-RNA profile secreted by in vitro grown metacestodes of Echinococcus multilocularis, the casuative agent of alveolar echinococcosis.

We have used high throughput RNA-sequencing together with RT-qPCR to characterise the ex-RNA profile secreted towards the extra- and intra-parasite milieus in EV-enriched and EV-depleted fractions. We show that a polarized secretion of small RNAs takes place, with microRNAs mainly secreted to the extra-parasite milieu and rRNA- and tRNA-derived sequences mostly secreted to the intra-parasite milieu. In addition, we show by nanoparticle tracking analyses that viable metacestodes secrete EV mainly into the metacestode inner vesicular fluid (MVF); however, the number of nanoparticles in culture medium and MVF increases > 10-fold when metacestodes show signs of tegument impairment. Interestingly, we confirm the presence of host miRNAs in the intra-parasite milieu, implying their internalization and transport through the tegument towards the MVF. Finally, our assessment of the detection of Echinococcus miRNAs in patient samples by RT-qPCR yielded negative results suggesting the tested miRNAs may not be good biomarkers for this disease.

A comprehensive study of the secretion mechanisms throughout the life cycle of these parasites will help to understand parasite interaction with the host and also, improve current diagnostic tools.

Extracellular RNAs (ex-RNAs) are secreted by cells through association with proteins or extracellular vesicles (EV). In the context of parasitism, ex-RNAs represent novel communication intermediaries with promising potential as biomarkers. In order to better understand the role ex-RNAs may play in the context of the zoonotic disease echinococcosis, we have characterised the RNA profile secreted by the larval stage (metacestode) of Echinococcus multilocularis.

By analysing the products secreted towards the extra- and intra-parasite milieus, we demonstrate that the metacestode displays a polarized secretion of different classes of small non-coding RNAs (sRNAs). In addition, we show that EV secretion occurs mainly towards the inner fluid of the metacestodes. Interestingly, we confirm the presence of host sRNAs in the intra-parasite milieu, implying their internalization and transport through the tegument. Finally, the detection of Echinococcus miRNAs in patient samples yielded negative results suggesting the tested miRNAs may not be good biomarkers for this disease.

In summary, our results provide a detailed description of the ex-RNA landscape of the E. multilocularis metacestode together with information on the distribution of the detected RNA classes in different extracellular compartments. This information is of importance to better understand host-parasite interaction and also, to improve current diagnostic tools.

Taenia solium and Taenia crassiceps: miRNomes of the larvae and effects of miR-10-5p and let-7-5p on murine peritoneal macrophages

Neurocysticercosis (NCC), a major cause of neurological morbidity worldwide, is caused by the larvae of Taenia solium. Cestodes secrete molecules that block the Th1 response of their hosts and induce a Th2 response permissive to their establishment. Mature microRNAs (miRs) are small noncoding RNAs that regulate gene expression and participate in immunological processes. To determine the participation of Taenia miRs in the immune response against cysticercosis, we constructed small RNA (sRNA) libraries from larvae of Taenia solium and Taenia crassiceps. A total of 12074504 and 11779456 sequencing reads for T. solium and T. crassiceps, respectively, were mapped to the genomes of T. solium and other helminths. Both larvae shared similar miRNome, and miR-10-5p was the most abundant in both species, followed by let-7-5p in T. solium and miR-4989-3p in T. crassiceps, whereas among the genus-specific miRs, miR-001-3p was the most abundant in both, followed by miR-002-3p in T. solium and miR-003a-3p in T. crassiceps. The sequences of these miRs were identical in both. Structure and target prediction analyses revealed that these pre-miRs formed a hairpin and had more than one target involved in immunoregulation. Culture of macrophages, RT-PCR and ELISA assays showed that cells internalized miR-10-5p and let-7-5p into the cytoplasm and the miRs strongly decreased interleukin 16 (Il6) expression, tumor necrosis factor (TNF) and IL-12 secretion, and moderately decreased nitric oxide synthase inducible (Nos2) and Il1b expression (pro-inflammatory cytokines) in M(IFN-γ) macrophages and expression of Tgf1b, and the secretion of IL-10 (anti-inflammatory cytokines) in M(IL-4) macrophages. These findings could help us understand the role of miRs in the host–Taenia relationship.

Toward integrative 'omics of the barber's pole worm and related parasitic nematodes

Advances in nucleic acid sequencing, mass spectrometry and computational biology have facilitated the identification, annotation and analysis of genes, transcripts, proteins and metabolites in model nematodes (Caenorhabditis elegans and Pristionchus pacificus) and socioeconomically important parasitic nematodes (Clades I, III, IV and V). Significant progress has been made in genomics and transcriptomics as well as in the proteomics and lipidomics of Haemonchus contortus (the barber's pole worm) - one of the most pathogenic representatives of the order Strongylida. Here, we review salient aspects of genomics, transcriptomics, proteomics, lipidomics, glycomics and functional genomics, and discuss the rise of integrative 'omics of this economically important parasite. Although our knowledge of the molecular biology, genetics and biochemistry of H. contortus and related species has progressed significantly, much remains to be explored, particularly in areas such as drug resistance, unique/unknown genes, host-parasite interactions, parasitism and the pathogenesis of disease, by integrating the use of multiple 'omics methods. This approach should lead to a better understanding of H. contortus and its relatives at a 'systems biology' level, and should assist in developing new interventions against these parasites.

Regulation of hepatic microRNAs in response to early stage Echinococcus multilocularis egg infection in C57BL/6 mice

We present a comprehensive analysis of the hepatic miRNA transcriptome at one month post-infection of experimental primary alveolar echinococcosis (AE), a parasitic infection caused upon ingestion of E. multilocularis eggs. Liver tissues were collected from infected and non-infected C57BL/6 mice, then small RNA libraries were prepared for next-generation sequencing (NGS). We conducted a Stem-loop RT-qPCR for validation of most dysregulated miRNAs. In infected mice, the expression levels of 28 miRNAs were significantly altered. Of these, 9 were up-regulated (fold change (FC) ≥ 1.5) and 19 were down-regulated (FC ≤ 0.66) as compared to the non-infected controls. In infected livers, mmu-miR-148a-3p and mmu-miR-101b-3p were 8- and 6-fold down-regulated, respectively, and the expression of mmu-miR-22-3p was reduced by 50%, compared to non-infected liver tissue. Conversely, significantly higher hepatic levels were noted for Mus musculus (mmu)-miR-21a-5p (FC = 2.3) and mmu-miR-122-5p (FC = 1.8). In addition, the relative mRNA expression levels of five genes (vegfa, mtor, hif1-α, fasn and acsl1) that were identified as targets of down-regulated miRNAs were significantly enhanced. All the five genes exhibited a higher expression level in livers of E. multilocularis infected mice compared to non-infected mice. Finally, we studied the issue related to functionally mature arm selection preference (5p and/or 3p) from the miRNA precursor and showed that 9 pre-miRNAs exhibited different arm selection preferences in normal versus infected liver tissues. In conclusion, this study provides first evidence that miRNAs are regulated early in primary murine AE. Our findings raise intriguing questions such as (i) how E. multilocularis affects hepatic miRNA expression;(ii) what are the alterations in miRNA expression patterns in more advanced AE-stages; and (iii) which hepatic cellular, metabolic and/or immunologic processes are modulated through altered miRNAs in AE. Thus, further research on the regulation of miRNAs during AE is needed, since miRNAs constitute an attractive potential option for development of novel therapeutic approaches against AE.

Various infectious diseases in humans have been associated with altered expression patterns of microRNAs (miRNAs), a class of small non-coding RNAs involved in negative regulation of gene expression. Herein, we revealed that significant alteration of miRNAs expression occurred in murine liver subsequently to experimental infection with E. multilocularis eggs when compared to non-infected controls. At the early stage of murine AE, hepatic miRNAs were mainly down-regulated. Respective target genes of the most extensively down-regulated miRNAs were involved in angiogenesis and fatty acid synthesis. Furthermore, we found higher mRNA levels of three angiogenic and two lipogenic genes in E. multilocularis infected livers compared to non-infected controls. Angiogenesis and fatty acid biosynthesis may be beneficial for development of the E. multilocularis metacestodes. In fact the formation of new blood vessels in the periparasitic area may ensure that parasites are supplied with oxygen and nutrients and get rid of waste products. Additionally, E. multilocularis is not able to undertake de novo fatty acid synthesis, thus lipids must be scavenged from its host. More research on the regulation of the hepatic miRNA transcriptome at more advanced stages of AE is needed.

Elucidating the molecular and developmental biology of parasitic nematodes: Moving to a multiomics paradigm

In the past two decades, significant progress has been made in the sequencing, assembly, annotation and analyses of genomes and transcriptomes of parasitic worms of socioeconomic importance. This progress has somewhat improved our knowledge and understanding of these pathogens at the molecular level. However, compared with the free-living nematode Caenorhabditis elegans, the areas of functional genomics, transcriptomics, proteomics and metabolomics of parasitic nematodes are still in their infancy, and there are major gaps in our knowledge and understanding of the molecular biology of parasitic nematodes. The information on signalling molecules, molecular pathways and microRNAs (miRNAs) that are known to be involved in developmental processes in C. elegans and the availability of some molecular resources (draft genomes, transcriptomes and some proteomes) for selected parasitic nematodes provide a basis to start exploring the developmental biology of parasitic nematodes. Indeed, some studies have identified molecules and pathways that might associate with developmental processes in related, parasitic nematodes, such as Haemonchus contortus (barber's pole worm). However, detailed information is often scant and 'omics resources are limited, preventing a proper integration of 'omic data sets and comprehensive analyses. Moreover, little is known about the functional roles of pheromones, hormones, signalling pathways and post-transcriptional/post-translational regulations in the development of key parasitic nematodes throughout their entire life cycles. Although C. elegans is an excellent model to assist molecular studies of parasitic nematodes, its use is limited when it comes to explorations of processes that are specific to parasitism within host animals. A deep understanding of parasitic nematodes, such as H. contortus, requires substantially enhanced resources and the use of integrative 'omics approaches for analyses. The improved genome and well-established in vitro larval culture system for H. contortus provide unprecedented opportunities for comprehensive studies of the transcriptomes (mRNA and miRNA), proteomes (somatic, excretory/secretory and phosphorylated proteins) and lipidomes (e.g., polar and neutral lipids) of this nematode. Such resources should enable in-depth explorations of its developmental biology at a level, not previously possible. The main aims of this review are (i) to provide a background on the development of nematodes, with a particular emphasis on the molecular aspects involved in the dauer formation and exit in C. elegans; (ii) to critically appraise the current state of knowledge of the developmental biology of parasitic nematodes and identify key knowledge gaps; (iii) to cover salient aspects of H. contortus, with a focus on the recent advances in genomics, transcriptomics, proteomics and lipidomics as well as in vitro culturing systems; (iv) to review recent advances in our knowledge and understanding of the molecular and developmental biology of H. contortus using an integrative multiomics approach, and discuss the implications of this approach for detailed explorations of signalling molecules, molecular processes and pathways likely associated with nematode development, adaptation and parasitism, and for the identification of novel intervention targets against these pathogens. Clearly, the multiomics approach established recently is readily applicable to exploring a wide range of interesting and socioeconomically significant parasitic worms (including also trematodes and cestodes) at the molecular level, and to elucidate host-parasite interactions and disease processes.

Small RNAs in parasitic nematodes - forms and functions

Small RNAs are important regulators of gene expression. They were first identified in Caenorhabditis elegans, but it is now apparent that the main small RNA silencing pathways are functionally conserved across diverse organisms. Availability of genome data for an increasing number of parasitic nematodes has enabled bioinformatic identification of small RNA sequences. Expression of these in different lifecycle stages is revealed by small RNA sequencing and microarray analysis. In this review we describe what is known of the three main small RNA classes in parasitic nematodes – microRNAs (miRNAs), Piwi-interacting RNAs (piRNAs) and small interfering RNAs (siRNAs) – and their proposed functions. miRNAs regulate development in C. elegans and the temporal expression of parasitic nematode miRNAs suggest modulation of target gene levels as parasites develop within the host. miRNAs are also present in extracellular vesicles released by nematodes in vitro, and in plasma from infected hosts, suggesting potential regulation of host gene expression. Roles of piRNAs and siRNAs in suppressing target genes, including transposable elements, are also reviewed. Recent successes in RNAi-mediated gene silencing, and application of small RNA inhibitors and mimics will continue to advance understanding of small RNA functions within the parasite and at the host–parasite interface.

Circulatory microRNAs: promising non-invasive prognostic and diagnostic biomarkers for parasitic infections

MicroRNAs (miRNAs) are a non-coding subclass of endogenous small regulatory RNAs, with about 18-25 nucleotides length which play a critical role in the regulation of gene expression at the post-transcriptional level in eukaryotes. Aberrant expression of miRNAs has the potential to become powerful non-invasive biomarkers in pathological diagnosis and prognosis of different disorders including infectious diseases. Parasite's life cycle may require the ability to respond to environmental and developmental signals through miRNA-mediated gene expressions. Over the last years, thousands of miRNAs have been identified in the helminthic and protozoan parasites and many pieces of evidence have demonstrated the functional role of miRNAs in the parasites' life cycle. Detection of these miRNAs in biofluids of infected hosts as prognostic and diagnostic biomarkers in infectious diseases is growing rapidly. In this review, we have highlighted altered expressions of host miRNAs, detected parasitic miRNAs in the infected hosts, and suggested some perspectives for future studies.

Detecting Fasciola hepatica and Fasciola gigantica microRNAs with loop-mediated isothermal amplification (LAMP)

Fascioliasis is a parasitic infection typically caused by two common parasites of class Trematodo, genus Fasciola, namely Fasciola hepatica and Fasciola gigantica. The widespread of these species in water and food makes fascioliasis become a global zoonotic disease that affects 2.4 million people in more than 75 countries worldwide. Typically, F. hepatica and F. gigantica can be recognized by parasitological techniques to detect Fasciola spp. eggs, immunological techniques to detect worm-specific antibodies, or by molecular techniques such as PCR to detect parasitic genomic DNA. Recently, miRNAs have been raised as a key regulator and potential diagnostic biomarkers of diseases, including parasitic infection. An isothermal PCR called loop-mediated isothermal amplification (LAMP) is rapid, sensitive, and its amplification process is so extensive that making LAMP well-suited for field diagnostics. LAMP reactions for miRNA detection have been introduced and were able to detect the target miRNA amounts in the wide range of 1.0 amol to 1.0 pmol, exhibiting high selectivity to differentiate one-base between miRNA sequences. Here, we introduced a modified LAMP to detect a species-specific miRNA of F. hepatica and F. gigantica. Our method did not demand an initial heating step and the reactions had a high sensitivity that greater than 1000 times in comparison to that reported in previous studies. Most importantly, the technique could perform well with parasitic miRNA presenting in bovine serum samples without sophisticated equipment required. These results create a promising technique basis for some novel and simple device to diagnose fascioliasis and other parasitic infection diseases at point-of-care.

Human toxocariasis - A look at a neglected disease through an epidemiological 'prism'

Toxocariasis, a disease caused by infection with larvae of Toxocara canis, T. cati and/or congeners, represents clinical syndromes in humans including visceral and ocular larva migrans, neurotoxocariasis and covert/common toxocariasis. It is reported to be one of the most widespread public health and economically important zoonotic parasitic infections that humans share with dogs, wild canids, including foxes, and possibly other mammals. Humans become infected by accidental ingestion of embryonated Toxocara eggs, or larvae from tissues from domestic or wild paratenic hosts. Most infections are asymptomatic, and human disease may go unnoticed, as clinical investigation is often not pursued and/or diagnostic testing not conducted. Sometimes toxocariasis can be associated with complications, such as allergic and/or neurological disorders, possibly including cognitive or developmental delays in children. There is no anti-toxocariasis vaccine, and chemotherapy in humans varies, depending on symptoms and location of larvae, and may include the administration of albendazole or mebendazole, together with anti-inflammatory corticosteroids. Some recent studies indicate that toxocariasis is having an increased, adverse impact on human health in some, particularly underprivileged, tropical and subtropical communities around the world. Although tens of millions of people, especially children, are expected to be exposed to, or infected with Toxocara species, there is limited precise epidemiological data or information on the relationship between seropositivity and disease (toxocariasis) on a global scale. To gain an improved insight into this area, the present article reviews salient clinical aspects of human toxocariasis and the epidemiology of this disease, with particular reference to seroprevalence, and discusses future research and approaches/measures to understand and prevent/control this socioeconomically important, yet neglected zoonosis.

The effect of albendazole sulfoxide on the expression of miR-61 and let-7 in different in vitro developmental stages of Echinococcus granulosus

Albendazole, as the main anti-echinococcal benzimidazole, has demonstrated safe and effective therapeutic outcomes in the treatment of echinococcosis. The emergence of resistance or reduced response to albendazole sulfoxide (ABZ_SOX) and other benzimidazoles have been demonstrated in several parasitic helminths of medical and veterinary importance. As the genetic makeup and miRNA profile of helminths affects their response to albendazole sulfoxide, the present study was conducted to investigate the expression of miRNAs in different developmental stages of Echinococcus granulosus exposed to albendazole sulfoxide in vitro. Different developmental stages of the helminth were obtained from in vitro cultured E. granulosus in monophasic and diphasic media. In both ABZ-SOX-treated and control parasites miRNAs were extracted from microcysts, intact protoscoleces and strobilated worms with one and three segments. Expression of two miRNAs, let-7 and miR-61 was evaluated using RT-qPCR for each stage. Results of the present study revealed significant differential expression of both let-7 and miR-61 at different drug concentrations. A significant difference of let-7 expression was observed between the strobilated and metacestode stages of E. granulosus exposed to ABZ-SOX. In the treated protoscoleces, let-7 expression was significantly reduced in the presence of ABZ-SOX at 1000 μg/ml concentration. In contrast higher expression levels were documented in the segmented worms. In the microcysts exposed to different drug concentrations a significant decline of miR-61 expression was demonstrated. Also, a significant increase in expression of miR-61 was observed in one proglottid worms as well as the protoscoleces. Under high drug concentration or long-term exposure of the protoscoleces to ABZ-SOX significantly higher miR-61 expression was observed compared to the controls. Our findings suggested that under in vitro benzimidazole exposure the expression of two E. granulosus miRNAs were significantly affected in the microcyst stage. This study presents the first evidence of the nature of benzimidazole effects on miRNA expression in platyhelminths.

Casein-Conjugated Gold Nanoparticles for Amperometric Detection of Leishmania infantum

Sensitive and reliable approaches targeting the detection of Leishmania are critical for effective early diagnosis and treatment of leishmaniasis. In this frame, this paper describes a rapid quantification assay to detect Leishmania parasites based on the combination of the electrocatalytic ability of gold nanoparticles (AuNPs) to act as a catalyst for the hydrogen formation reaction along with the specificity of the interaction between casein and the major surface protease of the Leishmania parasite, GP63. First, pure and casein-modified AuNPs were prepared and characterized by scanning electron microscopy and ultraviolet-visible spectroscopy. Then, casein-conjugated AuNPs were incubated with Leishsmania parasites in solution; the formed complex was collected by centrifugation, treated by acidic solution, and the pelleted AuNPs were placed on screen-printed carbon electrodes (SPCEs) and chronoamperometric measurements were carried out. Our results suggest that it is possible to detect Leishmania parasites, with a limit less than 1 parasite/mL. A linear response over a wide concentration interval, ranging from 2 × 10^-2 to 2 × 10⁵ parasites/mL, was achieved. Additionally, a pretreatment of Leishmania parasites with Amphotericin B, diminished their interaction with casein. This findings and methodology are very useful for drug efficacy assessment.

Echinococcus granulosus sensu stricto: silencing of thioredoxin peroxidase impairs the differentiation of protoscoleces into metacestodes

Cystic echinococcosis (CE) is a cosmopolitan parasitic disease caused by infection with the larval stage of Echinococcus granulosus sensu lato. Thioredoxin peroxidase (TPx) may play an essential role in the antioxidant defence system of E. granulosus s.l. as neither catalase nor glutathione peroxidase activities have been detected in the parasite. However, it is not known whether TPx affects the survival and growth of E. granulosus s.l. during development. In this study, three fragments of siRNA specific for EgTPx (siRNA-1/2/3) were designed and transfected into protoscoleces of E. granulosus sensu stricto by electroporation. Quantitative real-time PCR and Western blotting analysis showed that siRNA-3 significantly reduced the expression of EgTPx. Coincidentally, knockdown of EgTPx expression in protoscoleces with siRNA-3 significantly reduced the viability of the parasite under oxidative stress induced by 0.6 mM H₂O₂. In vitro culture studies showed that protoscoleces treated with siRNA-3 reduced pre-microcyst formation. In vivo experiments showed that injecting mice intraperitoneally with protoscoleces treated with siRNA-3 resulted in a significant reduction in the number, size and weight of CE cysts compared with those of control animals. Silencing of EgTPx led to the impairment of growth of E. granulosus s.s. both in vitro and in vivo, indicating that EgTPx is an important factor for protoscoleces survival and plays an important role in the antioxidant defence against the host during development.

Role of alarmin cytokines and microRNAs in the host-schistosome interaction

Schistosomiasis is a serious but neglected tropical infectious disease, afflicting more than 240 million people in 78 countries. Lack of an effective vaccine and obscuring disease mechanism could be the main hurdles to effectively control and eradicate this disease. A better understanding of the host-schistosome interaction is the key to clearing these hurdles. Recently, accumulating evidence shows that alarmin cytokines and microRNAs (miRNAs) are crucial regulators in the host-schistosome interaction. Alarmin cytokines are proven to be potent mechanisms driving type 2 immunity, which is the central disease mechanism of schistosomiasis. MiRNA deregulation is a hallmark of a variety of human diseases, including schistosomiasis. In this review, we summarize the research advances on the role of alarmin cytokines and miRNAs in the host-schistosome interaction.

In Vivo Nematicidal Potential of Camel Milk on Heligmosomoides Polygyrus Gastro-intestinal Nematode of Rodents

Following our previous findings on the in vitro anthelmintic effect of camel milk on Haemonchus contortus, the current study aimed at investigating its in vivo effect. Investigations were carried out using mice infected with Heligmosomoides polygyrus which is a parasite commonly used to test the efficacy of anthelmintics. Thirty six Swiss white mice of both sexes aged 5 – 6 weeks old, and weighing between 20 and 25 g were orally infected with 0.5 ml dose of 100, 1-week-old H. polygyrus infective larvae (L₃). After the pre-patent period, infected animals were randomly divided into 6 groups of 6 animals each. The nematicidal efficacy of camel milk was monitored through faecal egg count reduction (FECR) and total worm count reduction (TWCR). Four doses (8.25; 16.5; 33.0; 66.0 ml/kg body weight (bw)) for fresh camel milk and 22 mg/kg bw for albendazole were studied using a bioassay. Albendazole and 4 % dimethylsulfoxide were included in the protocol as reference drug and placebo, respectively. For all tested doses except 8.25 ml/kg bw, camel milk was effective in vivo against H. polygyrus reducing both faecal egg count and worm count (p < 0.05). The dose 66 ml/kg bw showed the highest nematicidal activity causing a 76.75 % FECR and a 69.62 % TWCR 7 day after initiating the treatment. These results support the possible use of camel milk in the control of gastro-intestinal helminthiasis.

Exosomes in Pathogen Infections: A Bridge to Deliver Molecules and Link Functions

Exosomes are extracellular vesicles derived from cell endocytosis which act as transmitters between cells. They are composed of proteins, lipids, and RNAs through which they participate in cellular crosstalk. Consequently, they play an important role in health and disease. Our view is that exosomes exert a bidirectional regulatory effect on pathogen infections by delivering their content. First, exosomes containing proteins and RNAs derived from pathogens can promote infections in three ways: (1) mediating further infection by transmitting pathogen-related molecules; (2) participating in the immune escape of pathogens; and (3) inhibiting immune responses by favoring immune cell apoptosis. Second, exosomes play anti-infection roles through: (1) inhibiting pathogen proliferation and infection directly; (2) inducing immune responses such as those related to the function of monocyte-macrophages, NK cells, T cells, and B cells. We believe that exosomes act as “bridges” during pathogen infections through the mechanisms mentioned above. The purpose of this review is to describe present findings regarding exosomes and pathogen infections, and highlight their enormous potential in clinical diagnosis and treatment. We discuss two opposite aspects: infection and anti-infection, and we hypothesize a balance between them. At the same time, we elaborate on the role of exosomes in immune regulation.

Human toxocariasis

Parasitic nematodes of the genus Toxocara are socioeconomically important zoonotic pathogens. These parasites are usually directly transmitted to the human host via the faecal-oral route and can cause toxocariasis and associated complications, including allergic and neurological disorders. Although tens of millions of people are estimated to be exposed to or infected with Toxocara spp, global epidemiological information on the relationship between seropositivity and toxocariasis is limited. Recent findings suggest that the effect of toxocariasis on human health is increasing in some countries. Here we review the salient background on Toxocara and biology, summarise key aspects of the pathogenesis, diagnosis, and treatment of toxocariasis, describe what is known about its geographic distribution and prevalence, and make some recommendations for future research towards the prevention and control of this important disease.

Mining Filarial Genomes for Diagnostic and Therapeutic Targets

Filarial infections of humans cause some of the most important neglected tropical diseases. The global efforts for eliminating filarial infections by mass drug administration programs may require additional tools (safe macrofilaricidal drugs, vaccines, and diagnostic biomarkers). The accurate and sensitive detection of viable parasites is essential for diagnosis and for surveillance programs. Current community-wide treatment modalities do not kill the adult filarial worms effectively; hence, there is a need to identify and develop safe macrofilaricidal drugs. High-throughput sequencing, mass spectroscopy methods and advances in computational biology have greatly accelerated the discovery process. Here, we describe post-genomic developments toward the identification of diagnostic biomarkers and drug targets for the filarial infection of humans.

MicroRNA expression profile in RAW264·7 macrophage cells exposed to Echinococcus multilocularis metacestodes

MicroRNAs (miRNAs) are short noncoding RNAs, involved in the regulation of parasite diseases. However, a role of miRNAs in Echinococcus multilocularis infection remains largely unknown. In this study, we first found the expression levels of key genes involved in miRNA biogenesis and function, including Ago2, Xpo5, Tarbp2 and DgcR8, were obviously altered in the macrophage RAW264·7 cells exposed to E. multilocularis metacestodes. Compared with the control, 18 and 32 known miRNAs were found to be differentially expressed (P 2) in the macrophages exposed to E. multilocularis metacestodes for 6 and 12 h, respectively. Among these, several are known to be involved in regulating cytokine activities and immune responses. Quantitative real-time polymerase chain reaction results showed that the expression of nine selected miRNAs was consistent with the sequencing data at each treatment time points. Moreover, there were statistically significant correlations between the expression levels of miRNAs and their corresponding targeted genes. Our data give us some clues to pinpoint a role of miRNAs in the course of infection and immunity of E. multilocularis.

Small RNAs and extracellular vesicles in filarial nematodes: From nematode development to diagnostics

Parasitic nematodes have evolved sophisticated mechanisms to communicate with their hosts in order to survive and successfully establish an infection. The transfer of RNA within extracellular vesicles (EVs) has recently been described as a mechanism that could contribute to this communication in filarial nematodes. It has been shown that these EVs are loaded with several types of RNAs, including microRNAs, leading to the hypothesis that parasites could actively use these molecules to manipulate host gene expression and to the exciting prospect that these pathways could result in new diagnostic and therapeutic strategies. Here, we review the literature on the diverse RNAi pathways that operate in nematodes and more specifically our current knowledge of extracellular RNA (exRNA) and EVs derived from filarial nematodes in vitro and within their hosts. We further detail some of the issues and questions related to the capacity of RNA-mediated communication to function in parasite-host interactions and the ability of exRNA to enable us to distinguish and detect different nematode parasites in their hosts.

Genome-wide identification of microRNA targets in the neglected disease pathogens of the genus Echinococcus

MicroRNAs (miRNAs), a class of small non-coding RNAs, are key regulators of gene expression at post-transcriptional level and play essential roles in biological processes such as development. MiRNAs silence target mRNAs by binding to complementary sequences in the 3'untranslated regions (3'UTRs). The parasitic helminths of the genus Echinococcus are the causative agents of echinococcosis, a zoonotic neglected disease. In previous work, we performed a comprehensive identification and characterization of Echinococcus miRNAs. However, current knowledge about their targets is limited. Since target prediction algorithms rely on complementarity between 3'UTRs and miRNA sequences, a major limitation is the lack of accurate sequence information of 3'UTR for most species including parasitic helminths. We performed RNA-seq and developed a pipeline that integrates the transcriptomic data with available genomic data of this parasite in order to identify 3'UTRs of Echinococcus canadensis. The high confidence set of 3'UTRs obtained allowed the prediction of miRNA targets in Echinococcus through a bioinformatic approach. We performed for the first time a comparative analysis of miRNA targets in Echinococcus and Taenia. We found that many evolutionarily conserved target sites in Echinococcus and Taenia may be functional and under selective pressure. Signaling pathways such as MAPK and Wnt were among the most represented pathways indicating miRNA roles in parasite growth and development. Genome-wide identification and characterization of miRNA target genes in Echinococcus provide valuable information to guide experimental studies in order to understand miRNA functions in the parasites biology. miRNAs involved in essential functions, especially those being absent in the host or showing sequence divergence with respect to host orthologs, might be considered as novel therapeutic targets for echinococcosis control.

Molecular characterization of the unique Mesostephanus appendiculatus (Trematoda: Cyathocotylidae) by small ribosomal RNA from Egypt

M esostephanus appendiculatus (Family: Cyathocotylidae) is one of the unique trematodes that complete their cycles in human and animal intestines in many countries of the world. The main source of its transmission is eating raw or undercooked infected fish muscle. Earliest analyses of genes to different parasites supported the analysis of helminthes either biological or morphological. This paper detected M. appendiculatus sequence with GenBank accession number gb (KY026782). Comparison of M. appendiculatus with other helminthes using BioEdit 7 and MEGA7 program shows some similarity in different points along its sequence. The phylogenetic analysis clarifies that it was closely related to both trematodes (Clinostomum complanatum and Echinochasmus japonicus) and some cestodes of fish origin such as Polyonchobothrium polypteri, Bothriocephalus sp., and Haplobothrium globuliforme. The obtained results provide a good source for genome analysis of M. appendiculatus in relation to other Platyhelminthes.

RNA interference mediated knockdown of Brugia malayi UDP-Galactopyranose mutase severely affects parasite viability, embryogenesis and in vivo development of infective larvae

Background

Galactofuranose is an essential cell surface component present in bacteria, fungi and several nematodes such as Caenorhabditis spp., Brugia spp., Onchocerca spp. and Strongyloides spp. This sugar maintains the integrity of parasite surface and is essential for virulence. UDP-Galactopyranose mutase (bmugm) plays a key role in Galf biosynthesis by catalyzing conversion of UDP-Galactopyranose into UDP-galactofuranose and knockout studies of the gene in Leishmania major, Mycobacterium and Aspergillus fumigatus displayed attenuated virulence while RNA interference study in C. elegans exhibited detrimental effects. Presence of UGM in several prokaryotic and eukaryotic microbial pathogens and its absence in higher eukaryotes renders it an attractive drug target. In the present study, RNA interference studies have been carried out to validate bmugm as an antifilarial drug target.

Methods

RNA interference studies using two different sequences of siRNAs targeting bmugm were carried out. The in vitro gene silencing of adult B. malayi parasites was undertaken to observe the effects on parasites. Infective larvae were also exposed to siRNAs and their in vivo development in jirds was observed.

Results

The in vitro gene silencing induced by siRNA1 and 2 individually as well as together knocked down the bmugm gene expression causing impaired viability of the exposed worms along with extremely reduced motility, abridged microfilarial release and adversely effected embryogenesis. The combinatorial in vitro gene silencing revealed marginally better results than both the siRNAs individually. Thus, infective larvae were treated with siRNA combination which showed downregulation of bmugm mRNA expression resulting into sluggish larval movements and/or death. The siRNA-treated actively motile larvae when inoculated intraperitoneally into jirds demonstrated highly reduced transformation of these larvae into adult worms with detrimental effects on embryogenesis. The effects of gene silencing were long-lasting as the adult worms developed from siRNA-treated larvae showed noticeable knockdown in the target gene expression.

Conclusions

The validation studies undertaken here conclude that bmugm is essential for the proper development and survival of the parasite and support its candidature as an antifilarial drug target.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-017-1967-1) contains supplementary material, which is available to authorized users.

Helminth Regulation of Immunity: A Three-pronged Approach to Treat Colitis

By reputation, the parasite is a pariah, an unwelcome guest. Infection with helminth parasites evokes stereotypic immune responses in humans and mice that are dominated by T helper (Th)-2 responses; thus, a hypothesis arises that infection with helminths would limit immunopathology in concomitant inflammatory disease. Although infection with some species of helminths can cause devastating disease and affect the course of microbial infections, analyses of rodent models of inflammatory disease reveal that infection with helminth parasites, or treatment with helminth extracts, can limit the severity of autoinflammatory disease, including colitis. Intriguing, but fewer, studies show that adoptive transfer of myeloid immune cells treated with helminth products/extracts in vitro can suppress inflammation. Herein, 3 facets of helminth therapy are reviewed and critiqued: treatment with viable ova or larvae, treatment with crude extracts of the worm or purified molecules, and cellular immunotherapy. The beneficial effect of helminth therapy often converges on the mobilization of IL-10 and regulatory/alternatively activated macrophages, while there are reports on transforming growth factor (TGF)-β, regulatory T cells and dendritic cells, and recent data suggest that helminth-evoked changes in the microbiota should be considered when defining anticolitic mechanisms. We speculate that if the data from animal models translate to humans, noting the heterogeneity therein, then the choice between use of viable helminth ova, helminth extracts/molecules or antigen-pulsed immune cells could be matched to disease management in defined cohorts of patients with inflammatory bowel disease.

Functional Genomics Tools for Haemonchus contortus and Lessons From Other Helminths

The availability of genome and transcriptome data for parasitic nematodes, including Haemonchus contortus, has highlighted the need to develop functional genomics tools. Comparative genomic analysis, particularly using data from the free-living nematode Caenorhabditis elegans, can help predict gene function. Reliable approaches to study function directly in parasitic nematodes are currently lacking. However, gene knockdown by RNA interference (RNAi) is being successfully used in schistosome and planarian species to define gene functions. Lessons from these systems may be applied to improve RNAi in H. contortus. Previous studies in H. contortus and related nematodes demonstrated reliable RNAi-mediated silencing of some genes, but not others. Current data suggest that susceptibility to RNAi in these nematodes is limited to genes expressed in sites accessible to the environment, such as the gut, amphids and excretory cell. Therefore, RNAi is functional in H. contortus, but improvements are needed to develop this system as a functional genomics platform. Here, we summarize RNAi studies on H. contortus and discuss the optimization of RNA delivery and improvements to culture methods to enhance larval development, protein turnover and the induction of phenotypic effects in vitro. The transgenic delivery of RNA or dominant-negative gene constructs and the recently developed CRISPR/Cas genome-editing technique are considered as potential alternative approaches for gene knockout. This is a key time to devote greater effort in progressing from genome to function, to improve our understanding of the biology of Haemonchus and identify novel targets for parasite control.

Sensing parasites: Proteomic and advanced bio-detection alternatives

Parasitic diseases have a great impact in human and animal health. The gold standard for the diagnosis of the majority of parasitic infections is still conventional microscopy, which presents important limitations in terms of sensitivity and specificity and commonly requires highly trained technicians. More accurate molecular-based diagnostic tools are needed for the implementation of early detection, effective treatments and massive screenings with high-throughput capacities. In this respect, sensitive and affordable devices could greatly impact on sustainable control programmes which exist against parasitic diseases, especially in low income settings. Proteomics and nanotechnology approaches are valuable tools for sensing pathogens and host alteration signatures within microfluidic detection platforms. These new devices might provide novel solutions to fight parasitic diseases. Newly described specific parasite derived products with immune-modulatory properties have been postulated as the best candidates for the early and accurate detection of parasitic infections as well as for the blockage of parasite development. This review provides the most recent methodological and technological advances with great potential for bio-sensing parasites in their hosts, showing the newest opportunities offered by modern "-omics" and platforms for parasite detection and control.