Fructose-bisphosphate aldolase and enolase from Echinococcus granulosus: genes, expression patterns and protein interactions of two potential moonlighting proteins

A Comparative Analysis of the Protein Cargo of Extracellular Vesicles from Helminth Parasites

Helminth parasites cause debilitating-sometimes fatal-diseases in humans and animals. Despite their impact on global health, mechanisms underlying host-parasite interactions are still poorly understood. One such mechanism involves the exchange of extracellular vesicles (EVs), which are membrane-enclosed subcellular nanoparticles. To date, EV secretion has been studied in helminth parasites, including EV protein content. However, information is highly heterogeneous, since it was generated in multiple species, using varied protocols for EV isolation and data analysis. Here, we compared the protein cargo of helminth EVs to identify common markers for each taxon. For this, we integrated published proteomic data and performed a comparative analysis through an orthology approach. Overall, only three proteins were common in the EVs of the seven analyzed species. Additionally, varied repertoires of proteins with moonlighting activity, vaccine antigens, canonical and non-canonical proteins related to EV biogenesis, taxon-specific proteins of unknown function and RNA-binding proteins were observed in platyhelminth and nematode EVs. Despite the lack of consensus on EV isolation protocols and protein annotation, several proteins were shown to be consistently detected in EV preparations from organisms at different taxa levels, providing a starting point for a selective biochemical characterization.

Proteomic profiling of hydatid fluid from pulmonary cystic echinococcosis

BACKGROUND

Most cystic echinococcosis cases in Southern Brazil are caused by Echinococcus granulosus and Echinococcus ortleppi. Proteomic studies of helminths have increased our knowledge about the molecular survival strategies that are used by parasites. Here, we surveyed the protein content of the hydatid fluid compartment in E. granulosus and E. ortleppi pulmonary bovine cysts to better describe and compare their molecular arsenal at the host-parasite interface.

METHODS

Hydatid fluid samples from three isolates of each species were analyzed using mass spectrometry-based proteomics (LC-MS/MS). In silico functional analyses of the identified proteins were performed to examine parasite survival strategies.

RESULTS

The identified hydatid fluid protein profiles showed a predominance of parasite proteins compared to host proteins that infiltrate the cysts. We identified 280 parasitic proteins from E. granulosus and 251 from E. ortleppi, including 52 parasitic proteins that were common to all hydatid fluid samples. The in silico functional analysis revealed important molecular functions and processes that are active in pulmonary cystic echinococcosis, such as adhesion, extracellular structures organization, development regulation, signaling transduction, and enzyme activity.

CONCLUSIONS

The protein profiles described here provide evidence of important mechanisms related to basic cellular processes and functions that act at the host-parasite interface in cystic echinococcosis. The molecular tools used by E. granulosus and E. ortleppi for survival within the host are potential targets for new therapeutic approaches to treat cystic echinococcosis and other larval cestodiases.

PROTEOMIC PROFILE OF ECHINOCOCCUS GRANULOSUS: A SYSTEMATIC REVIEW

Cystic echinococcosis is a zoonotic disease caused by the larval stage of Echinococcus granulosus. This affliction is an endemic worldwide condition that represents a neglected parasitic disease with important socioeconomic repercussions. Proteomic characterization of larval and adult stages of E. granulosus, as well as the association between expression profiles and host interactions, is relevant for a better understanding of parasite biology, and eventually for drug design and vaccine development. This study aimed to develop a synthesis of the evidence available related to proteomics of E. granulosus. A systematic review was carried out to collect data concerning the proteomics of E. granulosus, without language or host restriction, published between 1980 and 2019. A systematic search was carried out in the Trip Database, BIREME-BVS, SciELO, Web of Science, PubMed, EMBASE, SCOPUS, EBSCO host, and LILACS, using MeSH terms, free words, and Boolean connectors, and adapting strategies to each source of information. Additionally, a manual cross-reference search was performed. Variables studied were the year of publication, geographic origin of the study, number of samples, hosts, parasitic organs, proteomic techniques, and parasite proteins verified. Nine-hundred and thirty-six related articles were identified: 17 fulfilled selection criteria, including slightly more than 188 samples. Most articles were published between 2014 and 2019 (64.7%) and were from Brazil and China (35.3% each). In reference to confirmed hosts in the primary articles, cattle (41.2%) and humans (23.5%) were the most frequently reported. Concerning proteomic techniques applied in the primary articles, LC-MS/MS was the most used (41.1%), and 890 proteins were reported by the primary articles. As the results of our search suggest, the information related to E. granulosus proteomics is scarce, heterogeneous, and scattered throughout several articles that include a diversity of tissues, samples, intermediate hosts, and proteomic techniques. Consequently, the level of evidence generated by our search is type 4.

Characterization of Fructose-1,6-Bisphosphate Aldolase 1 of Echinococcus multilocularis

Glycolysis is one of the important ways by which Echinococcus multilocularis acquires energy. Fructose-1, 6-bisphosphate aldolase (FBA) plays an important role in this process, but it is not fully characterized in E. multilocularis yet. The results of genome-wide analysis showed that the Echinococcus species contained four fba genes (FBA1-4), all of which had the domain of FBA I and multiple conserved active sites. EmFBA1 was mainly located in the germinal layer and the posterior of the protoscolex. The enzyme activity of EmFBA1 was 67.42 U/mg with K_m and V_max of 1.75 mM and 0.5 mmol/min, respectively. EmFBA1 was only susceptible to Fe³⁺ but not to the other four ions (Na⁺, Ca²⁺, K⁺, Mg²⁺), and its enzyme activity was remarkably lost in the presence of 0.5 mM Fe³⁺. The current study reveals the biochemical characters of EmFBA1 and is informative for further investigation of its role in the glycolysis in E. multilocularis.

Mining nematode protein secretomes to explain lifestyle and host specificity

Parasitic nematodes are highly successful pathogens, inflicting disease on humans, animals and plants. Despite great differences in their life cycles, host preference and transmission modes, these parasites share a common capacity to manipulate their host's immune system. This is at least partly achieved through the release of excretory/secretory proteins, the most well-characterized component of nematode secretomes, that are comprised of functionally diverse molecules. In this work, we analyzed published protein secretomes of parasitic nematodes to identify common patterns as well as species-specific traits. The 20 selected organisms span 4 nematode clades, including plant pathogens, animal parasites, and the free-living species Caenorhabditis elegans. Transthyretin-like proteins were the only component common to all adult secretomes; many other protein classes overlapped across multiple datasets. The glycolytic enzymes aldolase and enolase were present in all parasitic species, but missing from C. elegans. Secretomes from larval stages showed less overlap between species. Although comparison of secretome composition across species and life-cycle stages is challenged by the use of different methods and depths of sequencing among studies, our workflow enabled the identification of conserved protein families and pinpointed elements that may have evolved as to enable parasitism. This strategy, extended to more secretomes, may be exploited to prioritize therapeutic targets in the future.

Multifunctional Fructose 1,6-Bisphosphate Aldolase as a Therapeutic Target

Fructose 1,6-bisphosphate aldolase is a ubiquitous cytosolic enzyme that catalyzes the fourth step of glycolysis. Aldolases are classified into three groups: Class-I, Class-IA, and Class-II; all classes share similar structural features but low amino acid identity. Apart from their conserved role in carbohydrate metabolism, aldolases have been reported to perform numerous non-enzymatic functions. Here we review the myriad "moonlighting" functions of this classical enzyme, many of which are centered on its ability to bind to an array of partner proteins that impact cellular scaffolding, signaling, transcription, and motility. In addition to the cytosolic location, aldolase has been found the extracellular surface of several pathogenic bacteria, fungi, protozoans, and metazoans. In the extracellular space, the enzyme has been reported to perform virulence-enhancing moonlighting functions e.g., plasminogen binding, host cell adhesion, and immunomodulation. Aldolase's importance has made it both a drug target and vaccine candidate. In this review, we note the several inhibitors that have been synthesized with high specificity for the aldolases of pathogens and cancer cells and have been shown to inhibit classical enzyme activity and moonlighting functions. We also review the many trials in which recombinant aldolases have been used as vaccine targets against a wide variety of pathogenic organisms including bacteria, fungi, and metazoan parasites. Most of such trials generated significant protection from challenge infection, correlated with antigen-specific cellular and humoral immune responses. We argue that refinement of aldolase antigen preparations and expansion of immunization trials should be encouraged to promote the advancement of promising, protective aldolase vaccines.

Molecular characterization and serodiagnostic potential of Echinococcus granulosus hexokinase

Background

Cystic echinococcosis (CE), caused by the larval stage of Echinococcus granulosus (sensu stricto), is a life-threatening but neglected zoonosis. Glycolytic enzymes are crucial molecules for the survival and development of E. granulosus. The aim of this study was to investigate the molecular characterization, immunogenicity, tissue distribution and serodiagnostic potential of E. granulosus hexokinase (EgHK), the first key enzyme in the glycolytic pathway.

Methods

EgHK was cloned and expressed in Escherichia coli. Specific serum antibodies were evaluated in mice immunized with recombinant EgHK (rEgHK). The location of EgHK in the larval stage of E. granulosus was determined using fluorescence immunohistochemistry, and the potential of rEgHK as a diagnostic antigen was investigated in patients with CE using indirect enzyme-linked immunosorbent assay (ELISA).

Results

Recombinant EgHK could be identified in the sera of patients with CE and in mouse anti-rEgHK sera. High titers of specific immunoglobulin G were induced in mice after immunization with rEgHK. EgHK was mainly located in the tegument, suckers and hooklets of protoscoleces and in the germinal layer and laminated layer of the cyst wall. The sensitivity and specificity of the rEgHK-ELISA reached 91.3% (42/46) and 87.8% (43/49), respectively.

Conclusions

We have characterized the sequence, structure and location of EgHK and investigated the immunoreactivity, immunogenicity and serodiagnostic potential of rEgHK. Our results suggest that EgHK may be a promising candidate for the development of vaccines against E. granulosus and an effective antigen for the diagnosis of human CE.

Functional characterization of the putative FAD synthase from Mycoplasma hyopneumoniae

In bacteria, the biosynthesis of the cofactor flavin adenine dinucleotide (FAD), important in many physiological responses, is catalyzed by the bifunctional enzyme FAD synthase (FADSyn) which converts riboflavin into FAD by both kinase and adenylylation activity. The in silico 3D structure of a putative FADSyn from Mycoplasma hyopneumoniae (MhpFADSyn), the etiological agent of enzootic pneumonia was already reported, nevertheless, the in vitro functional characterization was not yet demonstrated. Our phylogenetic analysis revealed that MhpFADSyn is close related to the bifunctional FADSyn from Corynebacterium ammoniagenes. However, only the domain related to adenylylation was assigned by InterPro database. The activity of MhpFADSyn was evaluated through in vitro enzymatic assays using cell extracts from IPTG-inducible heterologous expression of MhpFADSyn in Escherichia coli. The flavoproteins were analyzed by HPLC and results showed that IPTG-induced cell lysate resulted in the formation of twofold increased amounts of FAD if compared to non IPTG-induced cells. Consumption of riboflavin substrate was also threefold greater in IPTG-induced lysate compared to non IPTG-induced cell extract. Thus, the recombinant MhpFADSyn protein could be associated to FAD biosynthesis. These findings contribute to expand the range of potential drug targets in diseases control and unveil metabolic pathways that could be attribute to mycoplasmas.

Interactome analysis of CD5 and CD6 ectodomains with tegumental antigens from the helminth parasite Echinococcus granulosus sensu lato

Echinococcus granulosus sensu lato (s.l.) is a cestode parasite affecting both human and livestock health. Recombinant ectodomains of human scavenger receptors CD5 (rshCD5) and CD6 (rshCD6) were previously reported to bind its tegumental antigens and to exert prophylactic effects in a murine model of infection. Although the properties of mammalian scavenger receptors include the binding to diverse pathogen-derived structures, their interaction with helminth parasites has been scarcely explored. Therefore, we report here a search for CD5 and CD6 interactors within E. granulosus s.l. antigens. Mass spectrometry analysis of pull-downs from soluble tegumental components with biotinylated rshCD5 and rshCD6 resulted in 17 and 11 overrepresented interactors, respectively, 8 of which were shared. The interactors included previously reported protective molecules against E. granulosus s.l. and/or other helminths. Similar studies performed with 11-mer peptides mapping to each of the three extracellular scavenger domains of CD5 and CD6 allowed an estimated molecular topology of the interactions. In conclusion, the fact that most helminth interactors identified for rshCD5 and rshCD6 were already reported as vaccine candidates or pharmacological targets against different helminthiases, supports the view that their beneficial effects in experimental infection results from binding to multiple relevant tegumental antigens.

Proteomics Analysis of Hydatigera taeniaeformis Metacestode Stage

Hydatigera taeniaeformis (H. taeniaeformis) is one of the most robust of tapeworm parasites that is widely distributed around the world. Information of proteins of H. taeniaeformis has not previously been reported. Using liquid chromatography tandem-mass spectrometry (LC-MS/MS) analysis, the proteome of H. taeniaeformis metacestode was profiled and a total of 408 proteins were identified. Of these, 26.5% (108/408) were annotated to be associated with metabolic pathways. Consistently, Gene Ontology analysis showed that those identified proteins were mainly classified into metabolic process of the biological processes. A set of metabolic enzymes, including Fructose-1,6-bisphosphate aldolase, enolase, Glucan phosphorylase, and phosphoenolpyruvate carboxykinase, were abundant in H. taeniaeformis metacestodes. In addition, some rare but interesting proteins like antigens (such as tegument protein and Antigen B) were identified. The two recombinant proteins of tegument protein and Antigen B were well-recognized by the sera from the H. taeniaeformis-infected mice. The H. taeniaeformis metacestode proteome might help to find new candidates for the immunodiagnosis and vaccine development and provide valuable information on H. taeniaeformis biology.

Linking murine resistance to secondary cystic echinococcosis with antibody responses targeting Echinococcus granulosus tegumental antigens

Successful establishment of a parasite infection depends partially on the host intrinsic susceptibility to the pathogen. In cystic echinococcosis (CE), a zoonotic disease caused by the cestode parasite Echinococcus granulosus, the infection outcome in the murine model of secondary CE varies according to the mouse strain used. In this regard, intrinsic differences in susceptibility to the infection were previously reported for Balb/c and C57Bl/6 mice, being C57Bl/6 animals less permissive to secondary CE. Induction of parasite-specific antibodies has been suggested to play relevant roles in such susceptibility/resistance phenomena. Here, we report an in deep comparison of antibody responses induced in both mouse strains. Firstly, only C57Bl/6 mice were shown to induce specific-antibodies with efficient anti-parasite activities during early secondary CE. Then, through ImmunoTEM and Serological Proteome Analysis (SERPA), an evaluation of specific antibody responses targeting parasite tegumental antigens was performed. Both strategies showed that infected C57Bl/6 mice -unlike Balb/c animals- narrowed their IgG recognition repertoire against tegumental antigens, targeting fewer but potentially more relevant parasite components. In this sense, tegumental antigens recognition between Balb/c and C57Bl/6 mice, either by natural and/or induced antibodies, was analyzed through SERPA and MALDI-TOF/TOF studies. A total of 13 differentially recognized proteins (DRPs) uniquely targeted by antibodies from C57Bl/6 mice were successfully identified, wherein a subset of 7 DRPs were only recognized by infection-induced antibodies, suggesting their potential as natural protective antigens. In this regard, immunoinformatic analyses showed that such DRPs exhibited higher numbers of possible T cell epitopes towards the H-2-IA^b haplotype, which is present in C57Bl/6 mice but absent in Balb/c animals. In summary, our results showed that the genetic predisposition to generate better T-dependent antibody responses against particular tegumental antigens might be a key factor influencing host susceptibility in the murine model of secondary CE.

Functional characterization of the translation initiation factor eIF4E of Echinococcus granulosus

The eukaryotic initiation factor 4E (eIF4E) specifically recognizes the 5' mRNA cap, a rate-limiting step in the translation initiation process. Although the 7-methylguanosine cap (MMGcap) is the most common 5' cap structure in eukaryotes, the trans-splicing process that occurs in several organism groups, including nematodes and flatworms, leads to the addition of a trimethylguanosine cap (TMGcap) to some RNA transcripts. In some helminths, eIF4E can have a dual capacity to bind both MMGcap and TMGcap. In the present work, we evaluated the distribution of eIF4E protein sequences in platyhelminths and we showed that only one gene coding for eIF4E is present in most parasitic flatworms. Based on this result, we cloned the Echinococcus granulosus cDNA sequence encoding eIF4E in Escherichia coli, expressed the recombinant eIF4E as a fusion protein to GST, and tested its ability to capture mRNAs through the 5' cap using pull-down assay and qPCR. Our results indicate that the recombinant eIF4E was able to bind preferentially 5'-capped mRNAs compared with rRNAs from total RNA preparations of E. granulosus. By qPCR, we observed an enrichment in MMG-capped mRNA compared with TMG-capped mRNAs among Eg-eIF4E-GST pull-down RNAs. Eg-eIF4E structural model using the Schistosoma mansoni eIF4E as template showed to be well preserved with only a few differences between chemically similar amino acid residues at the binding sites. These data showed that E. granulosus eIF4E can be used as a potential tool to study full-length 5'-capped mRNA, besides being a potential drug target against parasitic flatworms.

A class I fructose-1,6-bisphosphate aldolase is associated with salt stress tolerance in a halotolerant cyanobacterium Halothece sp. PCC 7418

Fructose-1,6-bisphosphate aldolase (FBA) is a key metabolic enzyme, which is involved in glycolysis, gluconeogenesis and the Calvin cycle. The distinct physiological roles of FBAs in various organisms have been reported; however, in cyanobacteria, the functional characterization of FBAs and investigation of the intracellular dynamics of FBAs largely remains unknown. Here, we utilized a two-step chromatographic technique to identify a class I FBA (CI-FBA), which we named H2846. H2846 was induced by salt stress in the halotolerant cyanobacterium Halothece sp. PCC 7418 (hereafter referred to as Halothece 7418). Phylogenetic analysis showed that H2846-like CI-FBAs existed mainly in cyanobacterial species that inhabit hypersaline environments. Subcellular fractionation revealed that H2846 localized in the cytosolic and periplasmic spaces and size-exclusion chromatography suggested that H2846 formed a homohexamer. The CI-FBA activity of recombinant H2846-mediated cleavage of fructose bisphosphate (FBP) was characterized using a coupled enzymatic assay. This analysis allowed us to determine the K_m and V_max values of recombinant H2846, which were then compared to previously reported K_m and V_max values of several FBAs. Our data suggested that H2846 was likely responsible for the salt stress-induced CI-FBA activity from the total soluble protein extracts derived from Halothece 7418 cells. Moreover, heterologous expression of H2846 but not H2847, a class II FBA (CII-FBA), conferred salt stress tolerance to the salt-sensitive freshwater cyanobacterium, Synechococcus elongatus PCC 7942, which only contains the CII-FBA, S1443. S. elongatus PCC 7942 with a S1443 gene deletion was complemented by H2847 expression, but was not complemented by expression of H2846. Taken together, these results indicate the functional differences between two distinct sets of FBAs in cyanobacteria. H2846 is an active CI-FBA that contributes to the mechanism of salt stress tolerance in Halothece 7418.

Comparative Transcriptomic Analysis of the Larval and Adult Stages of Taenia pisiformis

Taenia pisiformis is a tapeworm causing economic losses in the rabbit breeding industry worldwide. Due to the absence of genomic data, our knowledge on the developmental process of T. pisiformis is still inadequate. In this study, to better characterize differential and specific genes and pathways associated with the parasite developments, a comparative transcriptomic analysis of the larval stage (TpM) and the adult stage (TpA) of T. pisiformis was performed by Illumina RNA sequencing (RNA-seq) technology and de novo analysis. In total, 68,588 unigenes were assembled with an average length of 789 nucleotides (nt) and N50 of 1485 nt. Further, we identified 4093 differentially expressed genes (DEGs) in TpA versus TpM, of which 3186 DEGs were upregulated and 907 were downregulated. Gene Ontology (GO) and Kyoto Encyclopedia of Genes (KEGG) analyses revealed that most DEGs involved in metabolic processes and Wnt signaling pathway were much more active in the TpA stage. Quantitative real-time PCR (qPCR) validated that the expression levels of the selected 10 DEGs were consistent with those in RNA-seq, indicating that the transcriptomic data are reliable. The present study provides comparative transcriptomic data concerning two developmental stages of T. pisiformis, which will be of great value for future functional studies on the regulatory mechanisms behind adult worm pathogenesis and for developing drugs and vaccines against this important parasite.

Biological role of excretory-secretory proteins in endemic parasites of Latin America and the Caribbean

Neglected tropical diseases (NTDs) share certain traits: they are parasitic infections, prevailing in tropical environments and affecting marginalized sectors of the population. Six NTDs - ascariasis, cysticercosis, echinococcosis, hookworm infection, onchocerciasis and trichuriasis - all of them endemic in Latin America and the Caribbean (LAC), are analysed in this work. This review aims to discuss key information on the function of excretory/secretory (E/S) proteins from these parasites in their infectivity, pathogeny and diagnosis. The modulation of the host immune system to favour the permanence and survival of the parasite is also discussed. An updated knowledge on the function of E/S molecules in endemic parasitoses in LAC may lead to new approaches for the clinical management and diagnosis of these diseases. In turn, this could allow us to optimize their treatment and make it more affordable - a relevant goal given the economic constraints that the region is facing.

Exploring the Potential Role of Moonlighting Function of the Surface-Associated Proteins From Mycobacterium bovis BCG Moreau and Pasteur by Comparative Proteomic

Surface-associated proteins from Mycobacterium bovis BCG Moreau RDJ are important components of the live Brazilian vaccine against tuberculosis. They are important targets during initial BCG vaccine stimulation and modulation of the host's immune response, especially in the bacterial-host interaction. These proteins might also be involved in cellular communication, chemical response to the environment, pathogenesis processes through mobility, colonization, and adherence to the host cell, therefore performing multiple functions. In this study, the proteomic profile of the surface-associated proteins from M. bovis BCG Moreau was compared to the BCG Pasteur reference strain. The methodology used was 2DE gel electrophoresis combined with mass spectrometry techniques (MALDI-TOF/TOF), leading to the identification of 115 proteins. Of these, 24 proteins showed differential expression between the two BCG strains. Furthermore, 27 proteins previously described as displaying moonlighting function were identified, 8 of these proteins showed variation in abundance comparing BCG Moreau to Pasteur and 2 of them presented two different domain hits. Moonlighting proteins are multifunctional proteins in which two or more biological functions are fulfilled by a single polypeptide chain. Therefore, the identification of such proteins with moonlighting predicted functions can contribute to a better understanding of the molecular mechanisms unleashed by live BCG Moreau RDJ vaccine components.

Molecular Characterization of Fructose-1,6-bisphosphate Aldolase From Trichinella spiralis and Its Potential in Inducing Immune Protection

Trichinella spiralis is a major food-borne parasite worldwide. Trichinellosis caused by T. spiralis is not only a public health problem, but also an economic hazard in food safety. The development of effective vaccines to prevent Trichinella infection in domestic animals and humans is urgently needed for controlling of this zoonosis. Fructose-1, 6-bisphosphate aldolase (FBPA) is involved in energy production in glycolysis and is also associated with many non-glycolysis functions in the parasite, such as adhesion to host cells, plasminogen binding, and invasion. FBPA has been considered as a potential vaccine candidate or as a target for chemotherapeutic treatment. Here, we report for the first time the characterization of FBPA of T. spiralis and an evaluation of its potential as a vaccine candidate antigen against T. spiralis infection in mice. The results of qPCR and western blot analysis showed that the Ts-FBPA gene was expressed at various developmental stages of T. spiralis and was also detected in excretory–secretory products (ES) of T. spiralis muscle larvae (ML). Immunostaining with anti-Ts-FBPA mouse sera indicated that it localized principally to the surface and embryos of this parasitic nematode. Vaccination of mice with recombinant Ts-FBPA (rTs-FBPA) resulted in a Th1/Th2 mixed humoral and cellular immune response with Th2 predominant, as well as remarkably elevated IgE levels. Moreover, mice vaccinated with rTs-FBPA displayed a 48.7% reduction in adult worm burden and 52.5% reduction in muscle larval burden. These studies indicated that Ts-FBPA is a promising target for developing an effective vaccine to prevent and control Trichinella infection.

A multi-method and structure-based in silico vaccine designing against Echinococcus granulosus through investigating enolase protein

Introduction: Hydatid disease is a ubiquitous parasitic zoonotic disease, which causes different medical, economic and serious public health problems in some parts of the world. The causal organism is a multi-stage parasite named Echinococcus granulosus whose life cycle is dependent on two types of mammalian hosts viz definitive and intermediate hosts.

Methods: In this study, enolase, as a key functional enzyme in the metabolism of E. granulosus (EgEnolase), was targeted through a comprehensive in silico modeling analysis and designing a host-specific multi-epitope vaccine. Three-dimensional (3D) structure of enolase was modeled using MODELLER v9.18 software. The B-cell epitopes (BEs) were predicted based on the multi-method approach and via some authentic online predictors. ClusPro v2.0 server was used for docking-based T-helper epitope prediction. The 3D structure of the vaccine was modeled using the RaptorX server. The designed vaccine was evaluated for its immunogenicity, physicochemical properties, and allergenicity. The codon optimization of the vaccine sequence was performed based on the codon usage table of E. coli K12. Finally, the energy minimization and molecular docking were implemented for simulating the vaccine binding affinity to the TLR-2 and TLR-4 and the complex stability.

Results: The designed multi-epitope vaccine was found to induce anti-EgEnolase immunity which may have the potential to prevent the survival and proliferation of E. granulosus into the definitive host.

Conclusion: Based on the results, this step-by-step immunoinformatics approach could be considered as a rational platform for designing vaccines against such multi-stage parasites. Furthermore, it is proposed that this multi-epitope vaccine is served as a promising preventive anti-echinococcosis agent.

Transcriptomic profile of two developmental stages of the cestode parasite Mesocestoides corti

Cestode development involves complex morphological and physiological changes. Here, we performed a differential expression analysis of gene transcripts between two developmental stages of the model cestode Mesocestoides corti. A RNA-seq-based approach was used to compare the transcriptomes of the tetrathyridium (larval, TT) and strobilated worm (ST) stages of the parasite. We found 19,053 transcripts, from which ∼45% were complete matches to genes previously annotated in the available M. corti draft genome sequence, ∼24% were considered novel isoforms, and ∼24% were considered potential novel transcripts. Stage-specific transcripts were found for both TTs (66) and STs (136), along with shared transcripts significantly overrepresented in one stage (342 in TTs, and 559 in STs). Differential expression and Gene Ontology term enrichment analyzes provided evidence of upregulation of different sets of transcripts associated with 'cytoskeleton', 'metabolism' and 'oxidation-reduction' processes in each stage, suggesting functional involvement of the corresponding genes with stage-specific features. Transcripts and processes enriched in the TT reflect typical larval processes that occur with the parasite in the intermediate host, such as asexual reproduction and budding, as well as active migration from the peritoneum to the liver and vice versa. In STs, transcripts associated with 'development', 'cell growth', and 'morphogenesis' were enriched, along with processes related to sexual reproduction, represented by the upregulation of numerous transcription factors, protein kinases, and histones. Overall, our results contributed to significantly increase the knowledge on the M. corti gene repertoire and expression profile in two developmental stages. Functional implications for the biology of larval and adult cestode parasites and for host-parasite interactions are discussed.

Molecular and biochemical characterization of Taenia solium α-enolase

Enolase (EC 4.2.1.11) acts as a multifunctional enzyme in many organisms, being involved in metabolism, transcription regulation and pathogenesis. In the current study, the recombinant α-enolase from Taenia solium (His-Tseno) was prepared and antiserum against His-Tseno was generated in rabbits. Consequently, we analyzed the enzymatic characteristics, plasminogen binding activity, tissue localization and expression patterns of Tseno. The study demonstrated that the enzymatic activity of His-Tseno was enhanced at pH around 7.0-7.5 and affected by addition of metal ions. Kinetic measurements using 2-phospho-d-glycerate (2-PGA) substrates gave a specific activity of 60.72 ± 0.84 U/mg and 1.1 mM of Km_2-PGA value. Plasminogen binding assay showed that His-Tseno could bind to human plasminogen and generate plasmin activated by a tissue-type plasminogen activator (t-PA). In addition, the lysine analogue 6-aminocaproic acid (ε-ACA) could inhibit the binding of plasminogen to His-Tseno. Quantitative real-time PCR confirmed that Tseno was expressed 2.38 folds higher in the adult worms (p < 0.05) than in the cysticerci. Further, an immunolocalization assay indicated that native Tseno was mainly distributed in the tegument and eggs of gravid proglottis from adult T. solium. In conclusion, Tseno executes the innate glycolytic function to supply energy for the growth, egg production, and even invasion of T. solium.

Comparison of Echinococcus multilocularis and Echinococcus granulosus hydatid fluid proteome provides molecular strategies for specialized host-parasite interactions

Alveolar and cystic echinococcoses, caused by the metacestodes of Echinococcus multilocularis and E. granulosus, are prevalent in several regions and invoke deleterious zoonotic helminthiases. Hydatid fluid (HF), which contains proteinaceous and non-proteinaceous secretions of the parasite- and host-derived components, critically affects the host-parasite interplay and disease progression. We conducted HF proteome profiling of fully mature E. multilocularis vesicle (nine months postinfection) and E. granulosus cyst (stage 2). We identified 120 and 153 proteins, respectively, in each fluid. Fifty-six and 84 proteins represented distinct species; 44 and 66 were parasites, and 12 and 18 were host-derived proteins. The five major parasite protein populations, which included antigen B isoforms, metabolic enzymes, proteases and inhibitors, extracellular matrix molecules (ECMs), and developmental proteins, were abundantly distributed in both fluids and also exclusively in one sample or the other. Carbohydrate-metabolizing enzymes were enriched in E. granulosus HF. In the E. multilocularis HF, proteins that constitute ECMs, which might facilitate adhesion and cytogenesis, were highly expressed. Those molecules had physical and functional relationships along with their biochemical properties through protein-protein interaction networks. Twelve host-derived proteins were largely segregated to serum components. The major proteins commonly and uniquely detected in these HFs and their symbiotic interactome relationships might reflect their biological roles in similar but distinct modes of maturation, invasion, and the longevity of the parasites in the hosts.

Screening of antigenic vesicular fluid proteins of Echinococcus multilocularis as potential viability biomarkers to monitor drug response in alveolar echinococcosis patients

PURPOSE

The only drugs available to treat alveolar echinococcosis (AE) are mostly parasitostatic and in many cases prescribed for life. Decision criteria for discontinuation rely on the absence of parasitic viability. The aim of the present study is to search for candidate proteins that may exhibit good potential as biomarkers for viability.

EXPERIMENTAL DESIGN

Sixteen serum samples (five healthy controls, 11 patients with AE), are used. AE-patients are classified into three groups "Cured" (n = 2), "ABZ-responders" (n = 4) and "ABZ-nonresponders" (n = 5). Immunoreactive proteins from vesicular fluid (VF) are identified and quantified by LC-MS/MS analysis after immunoprecipitation (IP) using all 16 serum samples.

RESULTS

Shotgun analysis of VF lead to the identification of 107 E. multilocularis proteins. Comparative proteomics reveal nine proteins more abundant in IP eluates from ABZ-nonresponder patients (cathepsin b, prosaposin a preprotein, actin modulator protein, fucosidase alpha L1 tissue, gluthatione-S-tranferase, beta galactosidase, elongation factor 2, H17g protein tegumental antigen, and NiemannPick C2 protein).

CONCLUSIONS AND CLINICAL RELEVANCE

Detection of antibodies against these proteins by ELISA could be helpful to monitor the course of alveolar echinococcosis under albendazole (ABZ) treatment.

Comparative proteome profiling of hydatid fluid from Algerian patients reveals cyst location-related variation in Echinococcus granulosus

Human cystic echinococcosis, an endemic zoonosis in Algeria, is caused by larvae of the cestode Echinococcus granulosus. Parasitic modulation of the immune response allows E. granulosus to persist in intermediate hosts. Previous in vitro and in vivo immunological studies have shown differences in host immune responses according to the status and location of the hydatid cysts in the body. In this study, a proteomic analysis of human hydatid fluids was performed to identify the proteins in hydatid cyst fluids. Hydatid fluid was obtained after cystic surgical removal from three patients with these cysts. The study was conducted on fertile hydatid fluids from lungs, vertebra, and infertile paravertebral fluids. Comparisons of the protein compositions of these fluids revealed differences in their protein profiles. These differences are probably related to the cyst location and fertility status of the parasite. Notably, our analysis identified new proteins from the parasite and human host. The identification of host proteins in hydatid fluids indicates that the hydatid walls are permeable allowing a high protein exchange rate between the metacestode and the affected tissue. Interestingly, our study also revealed that parasite antigenic protein expression variations reflect the differences observed in host immunostimulation.

Echinococcus-Host Interactions at Cellular and Molecular Levels

The potentially lethal zoonotic diseases alveolar and cystic echinococcosis are caused by the metacestode larval stages of the tapeworms Echinococcus multilocularis and Echinococcus granulosus, respectively. In both cases, metacestode growth and proliferation occurs within the inner organs of mammalian hosts, which is associated with complex molecular host-parasite interactions that regulate nutrient uptake by the parasite as well as metacestode persistence and development. Using in vitro cultivation systems for parasite larvae, and informed by recently released, comprehensive genome and transcriptome data for both parasites, these molecular host-parasite interactions have been subject to significant research during recent years. In this review, we discuss progress in this field, with emphasis on parasite development and proliferation. We review host-parasite interaction mechanisms that occur early during an infection, when the invading oncosphere stage undergoes a metamorphosis towards the metacestode, and outline the decisive role of parasite stem cells during this process. We also discuss special features of metacestode morphology, and how this parasite stage takes up nutrients from the host, utilizing newly evolved or expanded gene families. We comprehensively review mechanisms of host-parasite cross-communication via evolutionarily conserved signalling systems and how the parasite signalling systems might be exploited for the development of novel chemotherapeutics. Finally, we point to an urgent need for the development of functional genomic techniques in this parasite, which will be imperative for hypothesis-driven analyses into Echinococcus stem cell biology, developmental mechanisms and immunomodulatory activities, which are all highly relevant for the development of anti-infective measures.

Parasite molecules and host responses in cystic echinococcosis

Cystic echinococcosis is the infection by the larvae of cestode parasites belonging to the Echinococcus granulosus sensu lato species complex. Local host responses are strikingly subdued in relation to the size and persistence of these larvae, which develop within mammalian organs as 'hydatid cysts' measuring up to tens of cm in diameter. In a context in which helminth-derived immune-suppressive, as well as Th2-inducing, molecules garner much interest, knowledge on the interactions between E. granulosus molecules and the immune system lags behind. Here, we discuss what is known and what are the open questions on E. granulosus molecules and structures interacting with the innate and adaptive immune systems, potentially or in demonstrated form. We attempt a global biological approach on molecules that have been given consideration primarily as protective (Eg95) or diagnostic antigens (antigen B, antigen 5). We integrate glycobiological information, which traverses the discussions on antigen 5, the mucin-based protective laminated layer and immunologically active preparations from protoscoleces. We also highlight some less well-known molecules that appear as promising candidates to possess immune-regulatory activities. Finally, we point out gaps in the molecular-level knowledge of this infectious agent that hinder our understanding of its immunology.

Multifunctional Thioredoxin-Like Protein from the Gastrointestinal Parasitic Nematodes Strongyloides ratti and Trichuris suis Affects Mucosal Homeostasis

The cellular redox state is important for the regulation of multiple functions and is essential for the maintenance of cellular homeostasis and antioxidant defense. In the excretory/secretory (E/S) products of Strongyloides ratti and Trichuris suis sequences for thioredoxin (Trx) and Trx-like protein (Trx-lp) were identified. To characterize the antioxidant Trx-lp and its interaction with the parasite's mucosal habitat, S. ratti and T. suis Trx-lps were cloned and recombinantly expressed. The primary antioxidative activity was assured by reduction of insulin and IgM. Further analysis applying an in vitro mucosal 3D-cell culture model revealed that the secreted Trx-lps were able to bind to monocytic and intestinal epithelial cells and induce the time-dependent release of cytokines such as TNF-α, IL-22, and TSLP. In addition, the redox proteins also possessed chemotactic activity for monocytic THP-1 cells and fostered epithelial wound healing activity. These results confirm that the parasite-secreted Trx-lps are multifunctional proteins that can affect the host intestinal mucosa.

Excretory/secretory products in the Echinococcus granulosus metacestode: is the intermediate host complacent with infection caused by the larval form of the parasite?

The genus Echinococcus consists of parasites that have a life cycle with two mammalian hosts. Their larval stage, called the hydatid cyst, develops predominantly in the liver and lungs of intermediate hosts. The hydatid cyst is the causative agent of cystic hydatid disease and the species Echinococcus granulosus, G1 haplotype, is responsible for the vast majority of cases in humans, cattle and sheep. Protein characterization in hydatid cysts is essential for better understanding of the host-parasite relationship and the fertility process of Echinococcus. The aims of this work were the identification and quantitative comparison of proteins found in hydatid fluid from fertile and infertile cysts from E. granulosus, in order to highlight possible mechanisms involved in cyst fertility or infertility. Hydatid fluid samples containing proteins from both E. granulosus and Bos taurus were analysed by LC-MS/MS. Our proteomic analysis of fertile and infertile cysts allowed identification of a total of 498 proteins, of which 153 proteins were exclusively identified in the fertile cyst, 271 in the infertile cyst, and 74 in both. Functional in silico analysis allowed us to highlight some important aspects: (i) clues about the possible existence of an "arms race" involving parasite and host responses in fertile and infertile cysts; (ii) a number of proteins in hydatid fluid without functional annotation or with possible alternative functions; (iii) the presence of extracellular vesicles such as exosomes, which was confirmed by transmission electron microscopy.

Characterization and localization of Opisthorchis viverrini fructose-1,6-bisphosphate aldolase

Opisthorchis viverrini (Ov) infection is a long-time public health problem in Thailand that can lead to bile duct cancer, cholangiocarcinoma (CCA). Characterization of the Ov proteins at a molecular level will increase our knowledge of host-parasite interaction that can be applied to new drug, vaccine, or immunodiagnostic development. In this study, an important enzyme in the Ov glycolytic pathway, fructose-1,6-bisphosphate aldolase (FBPA), that had been obtained from a previous study was characterized and immunolocalized. The full-length sequence of OvFBPA gene is 1089bp and encodes 362 amino acids with a predicted molecular weight and isoelectric point of 39.54kDa and 7.61, respectively. Additionally, three OvFBPA isoforms were identified by sequence analysis. The amino acid sequence of OvFBPA-1 characterized in this study shared 98% identity to FBPA isoform 1 of Clonorchis sinensis that was classified based on highly conserved active residues to class-I FBPA. The recombinant OvFBPA-1 protein was expressed as a soluble form in Escherichia coli at 25°C with N-terminal His-tagged fusion protein and the purified OvFBPA-1 protein was used to generate polyclonal antibody in mice. Antibody against rOvFBPA-1 protein was able to detect the native OvFBPA-1 protein in both Ov infected hamster liver section and Ov excretory-secretory (ES) products by immunohistochemistry and western blotting, respectively.

Top Down Proteomics Reveals Mature Proteoforms Expressed in Subcellular Fractions of the Echinococcus granulosus Preadult Stage

Echinococcus granulosus is the causative agent of cystic hydatid disease, a neglected zoonosis responsible for high morbidity and mortality. Several molecular mechanisms underlying parasite biology remain poorly understood. Here, E. granulosus subcellular fractions were analyzed by top down and bottom up proteomics for protein identification and characterization of co-translational and post-translational modifications (CTMs and PTMs, respectively). Nuclear and cytosolic extracts of E. granulosus protoscoleces were fractionated by 10% GELFrEE and proteins under 30 kDa were analyzed by LC-MS/MS. By top down analysis, 186 proteins and 207 proteoforms were identified, of which 122 and 52 proteoforms were exclusively detected in nuclear and cytosolic fractions, respectively. CTMs were evident as 71% of the proteoforms had methionine excised and 47% were N-terminal acetylated. In addition, in silico internal acetylation prediction coupled with top down MS allowed the characterization of 9 proteins differentially acetylated, including histones. Bottom up analysis increased the overall number of identified proteins in nuclear and cytosolic fractions to 154 and 112, respectively. Overall, our results provided the first description of the low mass proteome of E. granulosus subcellular fractions and highlighted proteoforms with CTMs and PTMS whose characterization may lead to another level of understanding about molecular mechanisms controlling parasitic flatworm biology.

Expression of the histone chaperone SET/TAF-Iβ during the strobilation process of Mesocestoides corti (Platyhelminthes, Cestoda)

The histone chaperone SET/TAF-Iβ is implicated in processes of chromatin remodelling and gene expression regulation. It has been associated with the control of developmental processes, but little is known about its function in helminth parasites. In Mesocestoides corti, a partial cDNA sequence related to SET/TAF-Iβ was isolated in a screening for genes differentially expressed in larvae (tetrathyridia) and adult worms. Here, the full-length coding sequence of the M. corti SET/TAF-Iβ gene was analysed and the encoded protein (McSET/TAF) was compared with orthologous sequences, showing that McSET/TAF can be regarded as a SET/TAF-Iβ family member, with a typical nucleosome-assembly protein (NAP) domain and an acidic tail. The expression patterns of the McSET/TAF gene and protein were investigated during the strobilation process by RT-qPCR, using a set of five reference genes, and by immunoblot and immunofluorescence, using monospecific polyclonal antibodies. A gradual increase in McSET/TAF transcripts and McSET/TAF protein was observed upon development induction by trypsin, demonstrating McSET/TAF differential expression during strobilation. These results provided the first evidence for the involvement of a protein from the NAP family of epigenetic effectors in the regulation of cestode development.

Alteration of immunoproteome profile of Echinococcus granulosus hydatid fluid with progression of cystic echinococcosis

BACKGROUND

Cystic echinococcosis (CE), caused by Echinococcus granulosus metacestode, invokes a serious public health concern. Early diagnosis has great impacts on reduction of disability-adjusted life years. Several antigen B-related molecules (EgAgB; EgAgB1-5) are known to be immunopotent, but detection of EgAgB is variable in many patients and may not allow reliable interpretation of its immunological relevance. More importantly, the immunoproteome profile of hydatid fluid (HF) has not been addressed.

METHODS

We conducted a proteome analysis of the HF of a single fertile cyst of CE1 and CE2 stages through two-dimensional electrophoresis (2-DE). Each protein spot was analyzed by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). We subsequently determined the immunoproteome profile employing patient sera of entire disease spectrum from CE1 to CE5 stages.

RESULTS

We identified 40 parasite proteins, of which EgAgB (28 spots) and antigen 5 (EgAg5; 5 molecules) were abundant. EgAgB proteoforms constituted the majority, mostly EgAgB1 (24 spots), followed by EgAgB2 and EgAgB4 (2 spots each). EgAgB3 was detected only by liquid chromatography-MS/MS. EgAgB5 was not recognized. We also detected 38 host proteins, which were largely composed of serum components, antioxidant/xenobiotic enzymes, and enzymes involved in carbohydrate metabolism. CE1 and CE2 HF exhibited comparable spotting patterns, but CE2 HF harbored greater amounts of EgAgB and EgAg5 complexes. CE sera demonstrated complicated immune recognition patterns according to the disease progression; CE2 and CE3 stages exhibited strong antibody responses against diverse EgAgB and EgAg5 proteoforms, while CE1, CE4, and CE5 stages mainly reacted to EgAg5 and cathepsin B. Patient sera of alveolar echinococcosis (AE) cross-reacted with diverse EgAgB isoforms (36%). EgAg5 and cathepsin B also demonstrated cross-reactions with sera from neurocysticercosis and sparganosis.

CONCLUSIONS

Our results demonstrated that detection of a single defined molecule may not properly diagnose CE, since specific immunodominant epitopes changed as the disease progresses. Immunoproteome analysis combined with imaging studies may be practical in the differential diagnosis of CE from AE and other cystic lesions, as well as for staging CE, which are pertinent to establish appropriate patient management.