Molecular cloning and characterization of an Echinococcus multilocularis and Echinococcus granulosus stress protein homologous to the mammalian 78 kDa glucose regulated protein

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.

Identification of immunogenic proteins of the cysticercoid of Hymenolepis diminuta

Background

A wide range of molecules are used by tapeworm metacestodes to establish successful infection in the hostile environment of the host. Reports indicating the proteins in the cestode-host interactions are limited predominantly to taeniids, with no previous data available for non-taeniid species. A non-taeniid, Hymenolepis diminuta, represents one of the most important model species in cestode biology and exhibits an exceptional developmental plasticity in its life-cycle, which involves two phylogenetically distant hosts, arthropod and vertebrate.

Results

We identified H. diminuta cysticercoid proteins that were recognized by sera of H. diminuta-infected rats using two-dimensional gel electrophoresis (2DE), 2D-immunoblotting, and LC-MS/MS mass spectrometry. Proteomic analysis of 42 antigenic spots revealed 70 proteins. The largest number belonged to structural proteins and to the heat-shock protein (HSP) family. These results show a number of the antigenic proteins of the cysticercoid stage, which were present already in the insect host prior to contact with the mammal host. These are the first parasite antigens that the mammal host encounters after the infection, therefore they may represent some of the molecules important in host-parasite interactions at the early stage of infection.

Conclusions

These results could help in understanding how H. diminuta and other cestodes adapt to their diverse and complex parasitic life-cycles and show universal molecules used among diverse groups of cestodes to escape the host response to infection.

Electronic supplementary material

The online version of this article (10.1186/s13071-017-2519-4) contains supplementary material, which is available to authorized users.

Bortezomib initiates endoplasmic reticulum stress, elicits autophagy and death in Echinococcus granulosus larval stage

Cystic echinococcosis (CE) is a worldwide distributed helminthic zoonosis caused by Echinococcus granulosus. Benzimidazole derivatives are currently the only drugs for chemotherapeutic treatment of CE. However, their low efficacy and the adverse effects encourage the search for new therapeutic targets. We evaluated the in vitro efficacy of Bortezomib (Bz), a proteasome inhibitor, in the larval stage of the parasite. After 96 h, Bz showed potent deleterious effects at a concentration of 5 μM and 0.5 μM in protoscoleces and metacestodes, respectively (P < 0.05). After 48 h of exposure to this drug, it was triggered a mRNA overexpression of chaperones (Eg-grp78 and Eg-calnexin) and of Eg-ire2/Eg-xbp1 (the conserved UPR pathway branch) in protoscoleces. No changes were detected in the transcriptional expression of chaperones in Bz-treated metacestodes, thus allowing ER stress to be evident and viability to highly decrease in comparison with protoscoleces. We also found that Bz treatment activated the autophagic process in both larval forms. These facts were evidenced by the increase in the amount of transcripts of the autophagy related genes (Eg-atg6, Eg-atg8, Eg-atg12, Eg-atg16) together with the increase in Eg-Atg8-II detected by western blot and by in toto immunofluorescence labeling. It was further confirmed by direct observation of autophagic structures by electronic microscopy. Finally, in order to determine the impact of autophagy induction on Echinococcus cell viability, we evaluated the efficacy of Bz in combination with rapamycin and a synergistic cytotoxic effect on protoscolex viability was observed when both drugs were used together. In conclusion, our findings demonstrated that Bz induced endoplasmic reticulum stress, autophagy and subsequent death allowing to identify unstudied parasite-host pathways that could provide a new insight for control of parasitic diseases.

Analysis on Gene Expression Profile in Oncospheres and Early Stage Metacestodes from Echinococcus multilocularis

Alveolar echinococcosis is a worldwide zoonosis of great public health concern. Analysis of genome data for Echinococcus multilocularis has identified antigen families that can be used in diagnostic assays and vaccine development. However, little gene expression data is available for antigens of the egg and early larval stages. To address this information gap, we used a Next-Generation Sequencing approach to investigate three different stages (non-activated and activated oncospheres, and early stage metacestodes) of E. multilocularis (Nemuro strain). Transcriptome data analysis revealed that some diagnostic antigen gp50 isoforms and the antigen Eg95 family dominated in activated oncospheres, and the antigen B family dominated in early stage metacestodes. Furthermore, heat shock proteins and antigen II/3 are constantly expressed in the three stages. The expression pattern of various known antigens in E. multilocularis may give fundamental information for choosing candidate genes used in diagnosis and vaccine development.

Antitumor activity of human hydatid cyst fluid in a murine model of colon cancer

This study evaluates the antitumor immune response induced by human hydatic cyst fluid (HCF) in an animal model of colon carcinoma. We found that anti-HCF antibodies were able to identify cell surface and intracellular antigens in CT26 colon cancer cells. In prophylactic tumor challenge experiments, HCF vaccination was found to be protective against tumor formation for 40% of the mice (P = 0.01). In the therapeutic setting, HCF vaccination induced tumor regression in 40% of vaccinated mice (P = 0.05). This vaccination generated memory immune responses that protected surviving mice from tumor rechallenge, implicating the development of an adaptive immune response in this process. We performed a proteomic analysis of CT26 antigens recognized by anti-HCF antibodies to analyze the immune cross-reactivity between E. granulosus (HCF) and CT26 colon cancer cells. We identified two proteins: mortalin and creatine kinase M-type. Interestingly, CT26 mortalin displays 60% homology with E. granulosus hsp70. In conclusion, our data demonstrate the capacity of HCF vaccination to induce antitumor immunity which protects from tumor growth in an animal model. This new antitumor strategy could open new horizons in the development of highly immunogenic anticancer vaccines.

Proteomic characterization of larval and adult developmental stages in Echinococcus granulosus reveals novel insight into host-parasite interactions

Cystic hydatid disease is an important zoonosis caused by Echinococcus granulosus infection. The expression profiles of its parasitic life stages and host-Echinococcus interactions remain to be elucidated. Here, we identified 157 adult and 1588 protoscolex proteins (1610 in all), including 1290 novel identifications. Paramyosins and an antigen B (AgB) were the dominant adult proteins. Dog proteins (30) identified in adults indicated diminished local inflammation caused by adult infection. The protoscolex expresses proteins that have been reported to be antigens in other parasites, such as 6-phosphofructokinase and calcineurin B. Pathway analyses suggested that E. granulosus uses both aerobic and anaerobic carbohydrate metabolisms to generate ATP. E. granulosus expresses proteins involved in synthesis and metabolism of lipids or steroids. At least 339 of 390 sheep proteins identified in protoscolex were novel identifications not seen in previous analyses. IgGs and lambda light chains were the most abundant antibody species. Sheep proteins were enriched for detoxification pathways, implying that host detoxification effects play a central role during host-parasite interactions. Our study provides valuable data on E. granulosus expression characteristics, allowing novel insights into the molecular mechanisms involved in host-parasite interactions.

BIOLOGICAL SIGNIFICANCE

In this study, the Echinococcus granulosus adult worm proteome was analyzed for the first time. The protein identification of E. granulosus protoscoleces was extended dramatically. We also identified the most abundant host proteins co-purified with Echinococcus. The results provide useful information pertaining to the molecular mechanisms behind host-Echinococcus interaction and Echinococcus biology. This data also increases the potential for identifying vaccine candidates and new therapeutic targets, and may aid in the development of protein probes for selective and sensitive diagnosis of echinococcosis infection. In addition, the data collected here represents a valuable proteomic resource for subsequent genome annotation.

Proteomic analysis of the Echinococcus granulosus metacestode during infection of its intermediate host

Cystic hydatid disease (CHD) is caused by infection with the Echinococcus granulosus metacestode and affects both humans and livestock. In this work, we performed a proteomic analysis of the E. granulosus metacestode during infection of its intermediate bovine host. Parasite proteins were identified in different metacestode components (94 from protoscolex, 25 from germinal layer and 20 from hydatid cyst fluid), along with host proteins (58) that permeate into the hydatid cyst, providing new insights into host-parasite interplay. E. granulosus and platyhelminth EST data allowed successful identification of proteins potentially involved in downregulation of host defenses, highlighting possible evasion mechanisms adopted by the parasite to establish infection. Several intracellular proteins were found in hydatid cyst fluid, revealing a set of newly identified proteins that were previously thought to be inaccessible for inducing or modulating the host immune response. Host proteins identified in association with the hydatid cyst suggest that the parasite may bind/adsorb host molecules with nutritional and/or immune evasion purposes, masking surface antigens or inhibiting important effector molecules of host immunity, such as complement components and calgranulin. Overall, our results provide valuable information on parasite survival strategies in the adverse host environment and on the molecular mechanisms underpinning CHD immunopathology.

Serodiagnosis of Echinococcus spp. infection: explorative selection of diagnostic antigens by peptide microarray

Background

Production of native antigens for serodiagnosis of helminthic infections is laborious and hampered by batch-to-batch variation. For serodiagnosis of echinococcosis, especially cystic disease, most screening tests rely on crude or purified Echinococcus granulosus hydatid cyst fluid. To resolve limitations associated with native antigens in serological tests, the use of standardized and highly pure antigens produced by chemical synthesis offers considerable advantages, provided appropriate diagnostic sensitivity and specificity is achieved.

Methodology/Principal Findings

Making use of the growing collection of genomic and proteomic data, we applied a set of bioinformatic selection criteria to a collection of protein sequences including conceptually translated nucleotide sequence data of two related tapeworms, Echinococcus multilocularis and Echinococcus granulosus. Our approach targeted alpha-helical coiled-coils and intrinsically unstructured regions of parasite proteins potentially exposed to the host immune system. From 6 proteins of E. multilocularis and 5 proteins of E. granulosus, 45 peptides between 24 and 30 amino acids in length were designed. These peptides were chemically synthesized, spotted on microarrays and screened for reactivity with sera from infected humans. Peptides reacting above the cut-off were validated in enzyme-linked immunosorbent assays (ELISA). Peptides identified failed to differentiate between E. multilocularis and E. granulosus infection. The peptide performing best reached 57% sensitivity and 94% specificity. This candidate derived from Echinococcus multilocularis antigen B8/1 and showed strong reactivity to sera from patients infected either with E. multilocularis or E. granulosus.

Conclusions/Significance

This study provides proof of principle for the discovery of diagnostically relevant peptides by bioinformatic selection complemented with screening on a high-throughput microarray platform. Our data showed that a single peptide cannot provide sufficient diagnostic sensitivity whereas pooling several peptide antigens improved sensitivity; thus combinations of several peptides may lead the way to new diagnostic tests that replace, or at least complement conventional immunodiagnosis of echinococcosis. Our strategy could prove useful for diagnostic developments in other pathogens.

Crude or purified, somatic or metabolic extracts of native antigens are routinely used for the serodiagnosis of human helminthic infections. These antigens are often cross-reactive, i.e., recognized by sera from patients infected with heterologous helminth species. To overcome limitations in antigen production, test sensitivity and specificity, chemically synthesized peptides offer a pure and standardized alternative, provided they yield acceptable operative characteristics. Ongoing genome and proteome work create new resources for the identification of antigens. Making use of the growing amount of genomic and proteomic data available in public databases, we tested a bioinformatic procedure for the selection of potentially antigenic peptides from a collection of protein sequences including conceptually translated nucleotide sequence data of Echinococcus multilocularis and E. granulosus (Plathyhelminthes, Cestoda). The in silico selection was combined with high-throughput screening of peptides on microarray and systematic validation of reactive candidates in enzyme-linked immunosorbent assay. Our study proved the applicability of this approach for selection of peptide antigens with good diagnostic characteristics. Our results suggested the pooling of several peptides to reach a high level of sensitivity required for reliable immunodiagnosis.

Characterization of a putative hsp70 pseudogene transcribed in protoscoleces and adult worms of Echinococcus granulosus

Searching for hsp70 genes in Echinococcus granulosus, a divergent cytoplasmic hsp70-like sequence (EgpsiHsp70) was isolated, possessing a small truncation in the region coding for the C-terminal glycine-rich linker and EEVD-Ct motif. Southern Blot analyses of E. granulosus, and in silico analyses of E. multilocularis indicate that this truncated sequence is repeated several times in both genomes, in some cases containing clear cut features of pseudogenization. Phylogenetic analyses and comparison of surrounding regions indicate that all these copies originated by successive genomic duplications of one originally truncated copy. These copies are diverging at an increased rate compared to functional cytoplasmic hsp70 genes, and ratios of non-synonymous over synonymous substitutions rates (dN/dS) point to a relaxation of sequence constraint, suggesting that these sequences are pseudogenes. Interestingly, RT-PCR demonstrates that EgpsiHsp70 is transcribed in protoscoleces and adult individuals of E. granulosus. We suggest that this sequence does not code for a functional polypeptide, although some features are unexpected for a sequence evolving under a strictly neutral mode. Transcription could either be vestigial or have a specific, non-coding function.

A 78 kDa glucose-regulated protein gene of Spirometra erinacei plerocercoid induced by chemical and physiological stresses

To adapt to different environmental conditions between poikilothermic and homeothermic hosts, the plerocercoid of Spirometra erinacei (sparganum) might express a variety of biologically active molecules. We have identified a 78 kDa glucose-regulated protein of the sparganum (SpGrp78) by differential display of mRNA, employing RNAs each from sparganum adjusted at 9 degrees C and 37 degrees C. A full-length cDNA of 2148 bp encodes for a protein of 651 amino acids with a predicted molecular mass of 71 610 Da and shares molecular characteristics with heat-shock protein 70, including a putative ATP binding site, signal peptide cleavage site and endoplasmic reticulum retention signal. Phylogenetic analysis revealed that SpGrp78 was mostly related to those of Echinococcus multilocularis and E. granulosus. Expression of SpGrp78 mRNA increased approximately 7-fold by inhibition of glycosylation by tunicamycin, 2-fold by temperature-shift from 9 degrees C to 37 degrees C and slightly by pH-shift to 4.0 or 5.5. These results suggested that induction of SpGrp78 mRNA is related to the functional role of SpGrp78 as a molecular chaperone when the parasite adapts to a new host environment.

Heat shock and stress response of Taenia solium and T. crassiceps (Cestoda)

Heat shock and stress responses are documented for the first time in larval stages of the cestodes Taenia solium and Taenia crassiceps. Radioactive metabolic labelling after in vitro incubation of cysts at 43 degrees C, revealed the induction of heat shock proteins. In T. crassiceps, the major heat shock proteins were 80, 70 and 60 kDa. After prolonged incubation, a set of low molecular weight heat shock proteins (27, 31, 33 and 38 kDa), were also induced. In vitro incubation of cysts at 4 degrees C, induced the synthesis of stress proteins ranging from 31 to 80 kDa, indicating the parasite is also able to respond to cold shock. T. solium cysts exposure to temperature stress also resulted in an increased synthesis of 2 major heat shock proteins of 80 and 70 kDa. Western blots using the excretory-secretory products of T. solium showed that 2 heat shock proteins were recognized by antibodies in the sera of cysticercotic patients: one of 66 kDa and another migrating close to the run front. The T. solium 66 kDa protein was also recognized by specific antibodies directed to a 60 kDa bacterial heat shock protein, suggesting that it belongs to this family of proteins.

Serological diagnosis of human cysticercosis by use of recombinant antigens from Taenia solium cysticerci

A Taenia solium metacestode cDNA expression library in the lambda ZAPII vector was screened with pooled sera from patients with neurocysticercosis. Sixty primary clones were identified and shown to belong to two classes. The clones NC-3 and NC-9 did not reveal any significant homologies to sequences deposited in the databases and were further characterized. Both recombinant antigens were expressed as glutathione S-transferase fusion proteins and applied for serological diagnosis of human cysticercosis. An enzyme-linked immunosorbent assay was established and evaluated with 27 serum samples of La Réunion and Madagascar patients with cysticercosis. Diagnosis in these patients was established with radiological and serological procedures. For antigen NC-3 a sensitivity of 96.3% and a specificity of 91.5% for the serodiagnosis were achieved. In contrast, the sensitivity of antigen NC-9 was only 33.3%.

Identification of novel 70-kDa heat shock protein-encoding cDNAs from Schistosoma japonicum

A diverse range of organisms respond to a variety of chemical, physiological and temperature-associated stresses by a rapid and transient increase in the synthesis of heat shock proteins. We immunoscreened a Uni-ZAP XR cDNA library, prepared from mRNA isolated from the Philippine strain of the Asian bloodfluke, Schistosoma japonicum, using hyperimmune rabbit sera raised against soluble adult S. japonicum proteins. Six 70-kDa heat shock protein-encoding cDNA clones were identified which, upon further analysis, were separated into two distinct protein groups within the 70-kDa heat shock protein family, the 70-kDa heat shock proteins and the immunoglobulin heavy chain-binding proteins/glucose-related proteins (Grp78). A representative from both groups was fully sequenced and compared with homologous sequences available in the GenBank/EMBL database as the first stage in determining the role of their expression products in the regulation of S. japonicum development, in the induction of immunity, and whether they act as molecular chaperones capable of modulating the correct folding or repair of proteins within this species of schistosome.