Comparative proteomic analysis of Fasciola hepatica juveniles and Schistosoma bovis schistosomula

Other Schistosomatoidea and Diplostomoidea

Trematodes of the order Diplostomida are well known as serious pathogens of man, and both farm and wild animals; members of the genus Schistosoma (Schistosomatidae) are responsible for human schistosomosis (schistosomiasis) affecting more than 200 million people in tropical and subtropical countries, and infections of mammals and birds by animal schistosomes are of great veterinary importance. The order Diplostomida is also rich in species parasitizing other major taxa of vertebrates. The "Aporocotylidae" sensu lato are pathogenic in fish, "Spirorchiidae" sensu lato in reptiles. All these flukes have two-host life cycles, with asexually reproducing larvae usually in mollusks and occasionally in annelids, and adults usually live in the blood vessels of their vertebrate hosts. Pathology is frequently associated with inflammatory reactions to eggs trapped in various tissues/organs. On the other hand, the representatives of Diplostomidae and Strigeidae have three- or four-host life cycles in which vertebrates often serve not only as definitive but also as intermediate or paratenic hosts. Pathology is usually associated with migration of metacercariae and mesocercariae within the host tissues. The impact of these trematode infections on both farm and wild animals may be significant.

Proteomic Analysis of Extracellular Vesicles From Fasciola hepatica Hatching Eggs and Juveniles in Culture

The identification of extracellular vesicles (EVs) in Fasciola hepatica has provided a new way to understand parasite-host communication. Most of the studies on EVs have focused on the adult stage of F. hepatica, but recently, the presence of EVs from different developmental stages has been reported. To better understand the potential role of EVs in the biology of the parasite and in the infection process, the protein cargo of EVs from embryonated eggs and newly-excysted juvenile (NEJs) flukes cultured up to 28 days, has been analyzed. EVs were isolated by size exclusion chromatography and evaluated by nanoparticle tracking analysis and transmission electron microscopy. LC-MS/MS proteomic analysis of EVs revealed the presence of 23 different proteins from embryonated egg-derived EVs and 29 different proteins from NEJ-derived EVs. Most of the identified proteins had been previously described in EVs from F. hepatica adults, including cytoskeletal proteins, glycolytic enzymes, stress-related proteins and tetraspanins. Nevertheless, EVs from hatching eggs and NEJs exhibited qualitative differences in composition, when compared to EVs form adults, including the absence of cathepsin cysteine peptidases. The differential content of the EVs released by the different developmental stages of the parasite reflect the intense activity of NEJs at this early stage, with several proteins involved in membrane traffic and cell physiology. This new set of identified proteins could help to understand key metabolic, biochemical and molecular mechanisms mediated by EVs that take place upon egg hatching and after parasite excystment.

Trichuris trichiura egg extract proteome reveals potential diagnostic targets and immunomodulators

Embryonated eggs are the infectious developmental stage of Trichuris trichiura and are the primary stimulus for the immune system of the definitive host. The intestinal-dwelling T. trichiura affects an estimated 465 million people worldwide with an estimated global burden of disease of 640 000 DALYs (Disability Adjusted Life Years). In Latin America and the Caribbean, trichuriasis is the most prevalent soil transmitted helminthiasis in the region (12.3%; 95% CI). The adverse health consequences impair childhood school performance and reduce school attendance resulting in lower future wage-earning capacity. The accumulation of the long-term effects translates into poverty promoting sequelae and a cycle of impoverishment. Each infective T. trichiura egg carries the antigens needed to face the immune system with a wide variety of proteins present in the shell, larvae’s surface, and the accompanying fluid that contains their excretions/secretions. We used a proteomic approach with tandem mass spectrometry to investigate the proteome of soluble non-embryonated egg extracts of T. trichiura obtained from naturally infected African green monkeys (Chlorocebus sabaeus). A total of 231 proteins were identified, 168 of them with known molecular functions. The proteome revealed common proteins families which are known to play roles in energy and metabolism; the cytoskeleton, muscle and motility; proteolysis; signaling; the stress response and detoxification; transcription and translation; and lipid binding and transport. In addition to the study of the T. trichiura non-embryonated egg proteome, the antigenic profile of the T. trichiura non-embryonated egg and female soluble proteins against serum antibodies from C. sabaeus naturally infected with trichuriasis was investigated. We used an immunoproteomic approach by Western blot and tandem mass spectrometry from the corresponding SDS-PAGE gels. Vitellogenin N and VWD and DUF1943 domain containing protein, poly-cysteine and histidine tailed protein isoform 2, heat shock protein 70, glyceraldehyde-3-phosphate dehydrogenase, actin, and enolase, were among the potential immunoactive proteins. To our knowledge, this is the first study on the T. trichiura non-embryonated egg proteome as a novel source of information on potential targets for immunodiagnostics and immunomodulators from a neglected tropical disease. This initial list of T. trichiura non-embryonated egg proteins (proteome and antigenic profile) can be used in future research on the immunobiology and pathogenesis of human trichuriasis and the treatment of human intestinal immune-related diseases.

Who came first the worm or its egg? In the case of whipworm, we know it is the egg. The infective life cycle stage of the human whipworm (Trichuris trichiura) is the primary stimulus for the immune system of the definitive host. Each infective whipworm egg carries the information needed to face the immune system of the host with a wide variety of proteins present in the shell, larvae’s surface, and the accompanying fluid that contains their excretions/secretions. We investigated the soluble proteins of the non-embryonated egg using an immunoproteomic approach and then selected the top five proteins using a series of bioinformatic analysis. We used these top five proteins to recognize potential targets for immunodiagnostics and immunomodulation while comparing them to known female worm proteins. We found that the proteins we selected were involved in lipid transport, energy and metabolism, and muscle and motility. One protein has unknown function.

Insights into Fasciola hepatica Juveniles: Crossing the Fasciolosis Rubicon

Unraveling the molecular interactions governing the first contact between parasite and host tissues is of paramount importance to the development of effective control strategies against parasites. In fasciolosis, a foodborne trematodiasis caused mainly by Fasciola hepatica, these early interactions occur between the juvenile worm and the host intestinal wall a few hours after ingestion of metacercariae, the infectious stage of the parasite. However, research on these early events is still scarce and the majority of studies have focused on the adult worm. Here, we review current knowledge on the biology and biochemistry of F. hepatica juveniles and their molecular relationships with the host tissues and identify the research needs and gaps to be covered in the future.

Isolation of Secreted and Tegumental Surface Proteins from Fasciola hepatica

Proteins secreted by, or displayed on the surface tegument of, trematodes have key functions in the host-parasite interaction. As such, they are often leading targets for diagnostic tests or vaccine candidates. Here we describe methods for the isolation and analysis of soluble secreted proteins (i.e., the secretome) released during in vitro culture of adult Fasciola hepatica. We also describe two methods for the enrichment of proteins displayed on the outer tegumental surface of F. hepatica. These approaches enable downstream identification of the isolated proteins by mass spectrometry-based proteomics.

Fasciola gigantica: Ultrastructural cytochemistry of the tegumental surface in newly- excysted metacercariae and in vitro-penetrated juvenile flukes informs a concept of parasite defence at the interface with the host

Cytochemical staining techniques were carried out en bloc with in vitro excysted and gut-penetrated Fasciola gigantica larvae in order to visualise the glycocalyx of the tegument, a structure which comprises the parasite component of the host-parasite interface, yet is incompletely preserved by conventional fixation and preparation techniques for electron microscopy. Positive reactivity with ruthenium red and periodic acid-thiocarbohydrazine-osmium (PATCO) techniques revealed that the glycocalyx is polyanionic and carbohydrate-rich throughout its depth. It comprises a trilaminate arrangement, with a thin dense zone and fibrillar layer closely apposed to the outer aspect of the apical plasma membrane, invested by an irregular thick mucopolysaccharide capsule. The latter, not recorded in adult flukes, may represent a specific adaptation to facilitate invasion in the face of host immunity, and may also protect the parasite surface from the action of host- and parasite-derived proteases. Early in the invasion of a naïve host, the glycocalyx may be partly responsible for triggering the responses of innate immunity, while later in infection, or when an anamnestic response is initiated in an immunocompetent host, the antibodies and activated lymphocytes of specific acquired immunity are invoked to interact with the parasite surface. The cytochemical properties of the glycocalyx, together with its potential for dynamic turnover due to exocytosis of the T0 tegumental secretory bodies, are likely to aid neutralisation of potentially damaging immune effectors and ensure their removal from the vicinity of the parasite by sloughing in complex with glycocalyx components.

Fascioliasis

Fascioliasis is a major parasitic disease caused by the digenetic trematodes Fasciola hepatica and Fasciola gigantica. The disease is a well-known veterinary problem of worldwide distribution. Fascioliasis is the vector-borne parasitic disease presenting the widest latitudinal, longitudinal, and altitudinal distribution known at present. In the last two decades, many surveys have shown it to be an important public health problem as well, including estimations of 2.4 million, up to 17 million people, or even higher depending on the hitherto unknown situations mainly in several regions of Asia and Africa. In recent years, the increasing number of human case reports in many countries of the five continents and the results of studies on pathogenicity and immunity, mainly regarding the chronic period of the disease, were the reasons why it was decided to no longer consider fascioliasis merely a secondary zoonotic disease but an important human parasitic disease. In this chapter, we review the most relevant features in relation to fascioliasis, including from the most traditional to the most innovative aspects.

Schistosomatoidea and Diplostomoidea

Trematodes of the order Diplostomida are well known as serious pathogens of man, and both farm and wild animals; members of the genus Schistosoma (Schistosomatidae) are responsible for human schistosomosis affecting more than 200 million people in tropical and subtropical countries, infections of mammals and birds by animal schistosomes are of great veterinary importance. The order Diplostomida is also rich in species parasitizing other major taxa of vertebrates. The Aporocotylidae are pathogenic in fish, Spirorchiidae in reptiles. All these flukes have two-host life cycles, with asexually reproducing larvae usually in molluscs and occasionally in annelids, and adults usually live in the blood vessels of their vertebrate hosts. Pathology is frequently associated with inflammatory reactions to eggs trapped in various tissues/organs. On the other hand, the representatives of Diplostomidae and Strigeidae have three- or four-host life cycles in which vertebrates often serve not only as definitive, but also as intermediate or paratenic hosts. Pathology is usually associated with migration of metacercariae and mesocercariae within the host tissues. The impact of these trematode infections on both farm and wild animals may be significant.

Pathological, immunological and parasitological study of sheep vaccinated with the recombinant protein 14-3-3z and experimentally infected with Fasciola hepatica

In this study, the immunogenicity and protective capacity of a new recombinant vaccine candidate, the rFh14-3-3z protein was analysed in sheep experimentally challenged with Fasciola hepatica, in terms of fluke burden, faecal egg counts, hepatic damage and humoral immune response. Three groups of 8 animals each were used for study, group 1 was immunised with the rFh14-3-3z in Montanide adjuvant, whereas group 2 and 3 remained as adjuvant control and infection control groups, respectively. The parasitological analysis showed that no significant reduction in fluke burden, fluke size and faecal egg counts was detected. The extent of hepatic damage was very similar between groups. Nonetheless, animals immunised with the rFh14-3-3z protein induced the development of specific IgG1 and IgG2, being the IgG1 the predominant antibody; which confirms the immunogenicity of this protein in sheep. This is the first report of the 14-3-3z proteins as vaccine against the infection with F. hepatica.

Comparative Proteomic Analysis of Hymenolepis diminuta Cysticercoid and Adult Stages

Cestodiases are common parasitic diseases of animals and humans. As cestodes have complex lifecycles, hexacanth larvae, metacestodes (including cysticercoids), and adults produce proteins allowing them to establish invasion and to survive in the hostile environment of the host. Hymenolepis diminuta is the most commonly used model cestode in experimental parasitology. The aims of the present study were to perform a comparative proteomic analysis of two consecutive developmental stages of H. diminuta (cysticercoid and adult) and to distinguish proteins which might be characteristic for each of the stages from those shared by both stages. Somatic proteins of H. diminuta were isolated from 6-week-old cysticercoids and adult tapeworms. Cysticercoids were obtained from experimentally infected beetles, Tenebrio molitor, whereas adult worms were collected from experimentally infected rats. Proteins were separated by GeLC-MS/MS (one dimensional gel electrophoresis coupled with liquid chromatography and tandem mass spectrometry). Additionally protein samples were digested in-liquid and identified by LC-MS/MS. The identified proteins were classified according to molecular function, cellular components and biological processes. Our study showed a number of differences and similarities in the protein profiles of cysticercoids and adults; 233 cysticercoid and 182 adult proteins were identified. From these proteins, 131 were present only in the cysticercoid and 80 only in the adult stage samples. Both developmental stages shared 102 proteins; among which six represented immunomodulators and one is a potential drug target. In-liquid digestion and LC-MS/MS complemented and confirmed some of the GeLC-MS/MS identifications. Possible roles and functions of proteins identified with both proteomic approaches are discussed.

Across intra-mammalian stages of the liver f luke Fasciola hepatica: a proteomic study

Fasciola hepatica is the agent of fasciolosis, a foodborne zoonosis that affects livestock production and human health. Although flukicidal drugs are available, re-infection and expanding resistance to triclabendazole demand new control strategies. Understanding the molecular mechanisms underlying the complex interaction with the mammalian host could provide relevant clues, aiding the search for novel targets in diagnosis and control of fasciolosis. Parasite survival in the mammalian host is mediated by parasite compounds released during infection, known as excretory/secretory (E/S) products. E/S products are thought to protect parasites from host responses, allowing them to survive for a long period in the vertebrate host. This work provides in-depth proteomic analysis of F. hepatica intra-mammalian stages, and represents the largest number of proteins identified to date for this species. Functional classification revealed the presence of proteins involved in different biological processes, many of which represent original findings for this organism and are important for parasite survival within the host. These results could lead to a better comprehension of host-parasite relationships, and contribute to the development of drugs or vaccines against this parasite.

Mass spectrometry analysis of the excretory-secretory (E-S) products of the model cestode Hymenolepis diminut a reveals their immunogenic properties and the presence of new E-S proteins in cestodes

Hymenolepis diminuta is an important model species in studies of therapeutics, biochemical processes, immune responses and other aspects of cestodiasis. The parasite produces numerous excretory-secretory (E-S) proteins and a glycocalyx covering its body. Our study focused on the mass spectrometry analysis of the E-S material with an objective to determine if E-S contains any new proteins, in particular those that can be identified as: antigens, vaccine candidates and drug targets. These proteins might engage directly in host-parasite interactions. Adult parasites collected from experimentally infected rats were cultured in vitro for 5 and 18h. Immunoblotting was used to verify which E-S protein bands separated in SDS-PAGE (sodium dodecyl sulfate-polyacrylamide gel electrophoresis) react with specific antibodies from sera of infected rats. We identified thirty-nine proteins by LC-MS/MS (liquid chromatography mass spectrometry). Results indicated the presence of proteins that have never been identified in cestode E-S material. Immunoblotting showed the immunogenicity of E-S products of H. diminuta, most probably associated with the presence of proteins known as antigens in other flatworm species. Among identified proteins are those engaged in immunomodulatory processes (eg. HSP), in response to oxidative stress (peroxidasin) or metabolism (eg. GAPDH). The predominant functions are associated with metabolism and catalytic activity. This is the first study identifying E-S-proteins in adult tapeworms, thus providing information for better understanding host-parasite interrelationships, and may point out potential targets for vaccines or drug discovery studies, as among the proteins observed in our study are those known to be antigens.

Clinical implications of recent findings in schistosome proteomics

Schistosomiasis is a neglected tropical disease of clinical significance that, despite years of research, still requires an effective vaccine and improved diagnostics for surveillance, control and potential elimination. Furthermore, the causes of host pathology during schistosomiasis are still not completely understood. The recent sequencing of the genomes of the three key schistosome species has enabled the discovery of many new possible vaccine and drug targets, as well as diagnostic biomarkers, using high-throughput and sensitive proteomics methods. This review focuses on the literature of the last 5 years that has reported on the use of proteomics to both better understand the biology of the schistosome parasites and the disease they cause in definitive mammalian hosts.

The helminth parasite proteome at the host-parasite interface - Informing diagnosis and control

Helminth parasites are a significant health burden for humans in the developing world and also cause substantial economic losses in livestock production across the world. The combined lack of vaccines for the major human and veterinary helminth parasites in addition to the development of drug resistance to anthelmintics in sheep and cattle mean that controlling helminth infection and pathology remains a challenge. However, recent high throughput technological advances mean that screening for potential drug and vaccine candidates is now easier than in previous decades. A better understanding of the host-parasite interactions occurring during infection and pathology and identifying pathways that can be therapeutically targeted for more effective and 'evolution proof' interventions is now required. This review highlights some of the advances that have been made in understanding the host-parasite interface in helminth infections using studies of the temporal expression of parasite proteins, i.e. the parasite proteome, and discuss areas for potential future research and translation.

A quantitative proteomic analysis of the tegumental proteins from Schistosoma mansoni schistosomula reveals novel potential therapeutic targets

The tegument of Schistosoma mansoni plays an integral role in host-parasite interactions, particularly during the transition from the free-living cercariae to the intra-mammalian schistosomula stages. This developmental period is characterised by the transition from a trilaminate surface to a heptalaminate tegument that plays key roles in immune evasion, nutrition and excretion. Proteins exposed at the surface membranes of newly transformed schistosomula are therefore thought to be prime targets for the development of new vaccines and drugs for schistosomiasis. Using a combination of tegumental labelling and high-throughput quantitative proteomics, more than 450 proteins were identified on the apical membrane of S. mansoni schistosomula, of which 200 had significantly regulated expression profiles at different stages of schistosomula development in vitro, including glucose transporters, sterols, heat shock proteins, antioxidant enzymes and peptidases. Current vaccine antigens were identified on the apical membrane (Sm-TSP-1, calpain) or sub-tegumental (Sm-TSP-2, Sm29) fractions of the schistosomula, displaying localisation patterns that, in some cases, differ from that in the adult stage fluke. This work provides the first known in-depth proteomic analysis of the surface-exposed proteins in the schistosomula tegument, and some of the proteins identified are clear targets for the generation of new vaccines and drugs against schistosomiasis.

Serological screening of the Schistosoma mansoni adult worm proteome

BACKGROUND

New interventions tools are a priority for schistosomiasis control and elimination, as the disease is still highly prevalent. The identification of proteins associated with active infection and protective immune response may constitute the basis for the development of a successful vaccine and could also indicate new diagnostic candidates. In this context, post-genomic technologies have been progressing, resulting in a more rational discovery of new biomarkers of resistance and antigens for diagnosis.

METHODOLOGY/PRINCIPAL FINDINGS

Two-dimensional electrophoresed Schistosoma mansoni adult worm protein extracts were probed with pooled sera of infected and non-infected (naturally resistant) individuals from a S. mansoni endemic area. A total of 47 different immunoreactive proteins were identified by mass spectrometry. Although the different pooled sera shared most of the immunoreactive protein spots, nine protein spots reacted exclusively with the serum pool of infected individuals, which correspond to annexin, major egg antigen, troponin T, filamin, disulphide-isomerase ER-60 precursor, actin and reticulocalbin. One protein spot, corresponding to eukaryotic translation elongation factor, reacted exclusively with the pooled sera of non-infected individuals living in the endemic area. Western blotting of two selected recombinant proteins, major egg antigen and hemoglobinase, showed a similar recognition pattern of that of the native protein.

CONCLUDING/SIGNIFICANCE

Using a serological proteome analysis, a group of antigens related to the different infection status of the endemic area residents was identified and may be related to susceptibility or resistance to infection.

Surface analysis of Dicrocoelium dendriticum. The molecular characterization of exosomes reveals the presence of miRNAs

With the aim of characterizing the molecules involved in the interaction of Dicrocoelium dendriticum adults and the host, we have performed proteomic analyses of the external surface of the parasite using the currently available datasets including the transcriptome of the related species Echinostoma caproni. We have identified 182 parasite proteins on the outermost surface of D. dendriticum. The presence of exosome-like vesicles in the ESP of D. dendriticum and their components has also been characterized. Using proteomic approaches, we have characterized 84 proteins in these vesicles. Interestingly, we have detected miRNA in D. dendriticum exosomes, thus representing the first report of miRNA in helminth exosomes.

BIOLOGICAL SIGNIFICANCE

In order to identify potential targets for intervention against parasitic helminths, we have analyzed the surface of the parasitic helminth Dicrocoelium dendriticum. Along with the proteomic analyses of the outermost layer of the parasite, our work describes the molecular characterization of the exosomes of D. dendriticum. Our proteomic data confirm the improvement of protein identification from "non-model organisms" like helminths, when using different search engines against a combination of available databases. In addition, this work represents the first report of miRNAs in parasitic helminth exosomes. These vesicles can pack specific proteins and RNAs providing stability and resistance to RNAse digestion in body fluids, and provide a way to regulate host-parasite interplay. The present data should provide a solid foundation for the development of novel methods to control this non-model organism and related parasites. This article is part of a Special Issue entitled: Proteomics of non-model organisms.

Immunomodulatory molecules of Fasciola hepatica: candidates for both vaccine and immunotherapeutic development

The liver fluke, Fasciola hepatica, causes fascioliasis in domestic animals (sheep, cattle), a global disease that is also an important infection of humans. As soon as the parasite invades the gut wall its interaction with various host immune cells (e.g. dendritic cells, macrophages and mast cells) is complex. The parasite secretes a myriad of molecules that direct the immune response towards a favourable non-protective Th2-mediate/regulatory environment. These immunomodulatory molecules, such as cathepsin L peptidase (FhCL1), are under development as the first generation of fluke vaccines. However, this peptidase and other molecules, such as peroxiredoxin (FhPrx) and helminth defence molecule (FhHDM-1), exhibit various immunomodulatory properties that could be harnessed to help treat immune-related conditions in humans and animals.