Calcium-dependent proapoptotic effect of Taenia solium metacestodes annexin B1 on human eosinophils: A novel strategy to prevent host immune response

Functional identification of Annexin B1 and Annexin B2 from Cysticercus cellulosae and their mechanism in plasma membrane repair

BACKGROUND

Cysticercosis is a severe foodborne zoonotic parasitosis infected by the metacestode larvae of Taenia solium. However, its invasion mechanism is still not clear, which might provide the important evidence for treatment or vaccine. It was reported the annexin involved in the physiological and pathological functions of Cysticercus cellulosae. However, the regulatory mechanisms and roles of annexin B1 and annexin B2 in the invasion and immune escape of Cysticercus cellulosae have not been fully explored.

METHODS

The annexin was acquired by cloning in prokaryotic expression vector, expressed in Escherichia coli, and purified by affinity chromatography. Its expression was determined by immunohistochemistry. The anticoagulant function and its underlying mechanism was verified by the determination of activated partial thromboplastin time, prothrombin time and phospholipid binding activity. The membrane repair function was verified by cell culture, transfection, and laser confocal technology.

RESULTS

Immunohistochemistry results showed the B1 and B2 were mainly expressed on the body surface and the surface of digestive glands of Cysticercus cellulosae. The Blood coagulation results illustrated the B1 and B2 can prolong the time of both exogenous and endogenous coagulation pathways, with B2 having a more significant effect. They tend to bind to phosphatidylserine, possibly interfering with coagulation complex formation and inhibiting the coagulation pathway, and may assist in the worm's penetration through blood vessels and migration to parasitic sites. The plasma membrane repair test revealed the cells transfected with B1 and B2 genes have a significantly shorter plasma membrane repair time than the control group, suggesting that these proteins may be involved in repairing the worm's body surface to resist the immune system's attack when the host immune system attacks.

CONCLUSIONS

The Annexin B1 and Annexin B2 of Cysticercus cellulosae possess anticoagulant properties and can assist in membrane repair. Given these functions, it is speculated that they play a crucial role in immune evasion and invasion. However, further experiments are required to provide direct evidence to further validate these speculations.

Identification and Immunological Characterization of Annexin B8 and Annexin E1 from Spirometra Erinaceieuropaei Spargana

Sparganosis is a parasitic zoonotic disease that poses a serious threat to public hygiene and human health. Annexin is a phospholipid-binding protein with calcium ion binding activity, serving various important functions, including interaction with the parasite and regulation of the host's immune response. In this study, two annexin (ANX) family genes, Spirometra erinaceieuropaei (S. erinaceieuropaei) Annexin B8 (SeANXB8) and E1 (SeANXE1), isolated from spargana, were cloned and immunologically characterized. Both recombinant S. erinaceieuropaei Annexin B8 (rSeANXB8) and E1 (rSeANXE1) were specifically recognized by serum from rats immunized with the recombinant proteins, displaying strong immunoreactivity. They are also among the major components of sparganum excretion/secretion products (ESPs). SeANXE1 was identified in the parasite's tegument, testis, genital pore, ovary, and eggs, while SeANXB8 was found in the parasite's tegument and eggs. Plasminogen (PLG)-binding assays revealed that the two annexins could bind to human PLG in a concentration-dependent manner, which was blocked by the corresponding antibodies. These findings suggest that SeANXB8 and SeANXE1 may be involved in host-parasite interaction and may influence the host's immune response during sparganosis. They could be potential diagnosis and vaccination targets for sparganosis.

Protein profile of extracellular vesicles derived from adult Parascaris spp

BACKGROUND

Parascaris spp. represent a significant threat to equine health worldwide, particularly in foals. The long-term survival of parasites in the host necessitates persistent modulation of the host immune response. Intercellular communication achieved through the exchange of molecules via extracellular vesicles (EVs) released from the parasite could be a crucial factor in this regard. This study aimed to isolate and characterize EVs released by adult male and female Parascaris worms and conduct a proteomic analysis to identify sex-specific proteins and potential immunomodulatory factors.

METHODS

Live adult Parascaris worms were collected, and EVs were isolated from spent culture media using differential ultracentrifugation. Nanoparticle tracking analysis and transmission electron microscopy confirmed the size, concentration, and morphology of the isolated EVs. Proteins within the isolated EVs were analyzed using mass spectrometry-based proteomics (LC-MS/MS).

RESULTS

Proteomic analysis revealed a total of 113 proteins in Parascaris EVs, with several proteins showing homology to known helminth exosome proteins and exhibiting immunomodulatory functions. Sex-specific differences in EV protein composition were observed, with a distinct abundance of C-type lectins in female EVs, suggesting potential sex-specific roles or regulation. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses revealed metabolic pathways shared between male and female Parascaris EVs, as well as differences in signal transduction, and cell growth and death pathways, indicating sex-specific variations.

CONCLUSIONS

These findings imply that Parascaris EVs and their protein cargo are complex. This data potentially opens avenues for discovering innovative approaches to managing and understanding helminth infection.

Characterization of antigenic proteins of the Taenia solium postoncospheral form

Neurocysticercosis is the leading cause for acquired epilepsy worldwide, and it is caused by the larval stage of the parasite Taenia solium. Several proteins of this stage have been characterized and studied to understand the parasite-host interaction, however, the proteins from the early cysticercus stages (the postoncospheral form) have not yet been characterized. The study of the postoncospheral form proteins is important to understand the host-parasite relationship in the early stages of infection. The aim of this work was to identify postoncospheral form antigenic proteins using sera from neurocysticercosis patients. T. solium activated oncospheres were cultured in HCT-8 cells to obtain the postoncospheral form. Soluble total and excretory/secretory proteins were obtained from the postoncospheral form and were incubated with both pool sera and individual serum of neurocysticercosis positive human patients. Immunoblotting showed target antigenic proteins with apparent molecular weights of 23 kDa and 46-48 kDa. The 46-48 kDa antigen bands present in soluble total and excretory/secretory postoncospheral form proteins were analyzed by LC-MS/MS; proteins identified were: nuclear elongation factor 1 alpha, enolase, unnamed protein product/antigen diagnostic GP50, calcium binding protein calreticulin precursor and annexin. The postoncospheral form expresses proteins related to interaction with the host, some of these proteins are predicted to be exosomal proteins. In conclusion, postoncospheral proteins are consistent targets of the humoral immune response in human and may serve as targets for diagnosis and vaccines.

Proteomic analysis of Neobenedenia sp. and Rhabdosynochus viridisi (Monogenea, Monopisthocotylea): Insights into potential vaccine targets and diagnostic markers for finfish aquaculture

Monogeneans are parasitic flatworms that represent a significant threat to the aquaculture industry. Species like Neobenedenia melleni (Capsalidae) and Rhabdosynochus viridisi (Diplectanidae) have been identified as causing diseases in farmed fish. In the past years, molecular research on monogeneans of the subclass Monopisthocotylea has focused on the generation of genomic and transcriptomic information and the identification in silico of some protein families of veterinary interest. Proteomic analysis has been suggested as a powerful tool to investigate proteins in parasites and identify potential targets for vaccine development and diagnosis. To date, the proteomic dataset for monogeneans has been restricted to a species of the subclass Polyopisthocotylea, while in monopisthocotyleans there is no proteomic data. In this study, we present the first proteomic data on two monopisthocotylean species, Neobenedenia sp. and R. viridisi, obtained from three distinct sample types: tissue, excretory-secretory products (ESPs), and eggs. A total of 1691 and 1846 expressed proteins were identified in Neobenedenia sp. and R. viridisi, respectively. The actin family was the largest protein family, followed by the tubulin family and the heat shock protein 70 (HSP70) family. We focused mainly on ESPs because they are important to modulate the host immune system. We identified proteins of the actin, tubulin, HSP70 and HSP90 families in both tissue and ESPs, which have been recognized for their antigenic activities in parasitic flatworms. Furthermore, our study uncovered the presence of proteins within ESPs, such as annexin, calcium-binding protein, fructose bisphosphate aldolase, glutamate dehydrogenase, myoferlin, and paramyosin, that are targets for immunodiagnostic and vaccine development and hold paramount relevance in veterinary medicine. This study expands our knowledge of monogeneans and identified proteins that, in other platyhelminths are potential targets for vaccines and drug discovery.

Mass Spectrometry Identifies Taenia solium Proteins in Sera of Patients With and Without Parenchymal Neurocysticercosis

Neurocysticercosis (NCC), a major cause of global acquired epilepsy, results from Taenia solium larval brain infection. T. solium adult worms release large numbers of infective eggs into the environment contributing to high levels of exposure in endemic areas. This study identifies T. solium proteins in the sera of individuals with and without NCC using mass spectrometry to examine exposure in endemic regions. Forty-seven patients (18-51 years), 24 parenchymal NCC (pNCC), 8 epilepsy of unknown aetiology, 7 glioma, 8 brain tuberculoma, and 7 healthy volunteers were studied. Trypsin digested sera were subject to liquid chromatography-tandem mass spectrometry and spectra of 375-1700 m/z matched against T. solium WormBase ParaSite database with MaxQuant software to identify T. solium proteins. Three hundred and nineteen T. solium proteins were identified in 87.5% of pNCC and 56.6% of non-NCC subjects. Three hundred and four proteins were exclusive to pNCC sera, seven to non-NCC sera and eight in both. Ten percent, exhibiting immune-modulatory properties, originated from the oncosphere and cyst vesicular fluid. In conclusion, in endemic regions, T. solium proteins are detected in sera of individuals with and without pNCC. The immunomodulatory nature of these proteins may influence susceptibility and course of infection.

Effects of annexin B18 from Echinococcus granulosus sensu lato on mouse macrophages

Cystic echinococcosis (CE) is a zoonotic disease, caused by Echinococcus granulosus sensu lato (E. granulosus s. l.), which posed significant public health concern globally. E. granulosus s. l. annexin B18 (EgANXB18) acts as a secretory protein, exerting a crucial influence in mediating host-parasite interactions. Recombinant annexin B18 (rEgANXB18) was expressed by Escherichia coli and the immunoreactivity was assessed by western blotting. The binding affinity between rEgANXB18 and total protein of RAW264.7 cells was assessed by ELISA. The impact of rEgANXB18 on the metabolic activity of RAW264.7 cells was assayed by Cell Counting Kit-8 assay. The mRNA levels of polarization markers (inducible nitrous oxide synthase (iNOS) and arginase 1 (Arg1)) and key cellular factors (IL-1β，IL-6，IL-10 and TNFα) were evaluated by qRT-PCR. rEgANXB18 was successfully expressed and recognized by E. granulosus s.l. infected canine sera, as well as could bind to the total protein of RAW264.7 cells. Additionally, rEgANXB18 could promote metabolic activity at 5, 10, 20, and 40 μg/mL while no significant impact on metabolic activity was observed at 80 μg/mL. Co-culture RAW264.7 cells with rEgANXB18 resulted in significantly upregulation of the transcript levels of polarization markers iNOS and Arg1. Moreover, rEgANXB18 significantly upregulated the transcript levels of IL-1β, IL-6, TNFα, and IL-10, while dose-effect relationship was observed in IL-1β, IL-6, and IL-10. Our results indicated that EgANXB18 showed the potential to regulate immune response of macrophages by shifting the cell polarization and cytokine profile, thereby promoting the parasitism of CE.

Molecular characterization and functional implications on mouse peripheral blood mononuclear cells of annexin proteins from Echinococcus granulosus sensu lato

BACKGROUND

Cystic echinococcosis (CE) is a life-threatening zoonotic disease caused by the larval stage of Echinococcus granulosus sensu lato, which employs various strategies to evade the host immune system for survival. Recent advances have revealed the role of annexins as excretory/secretory products, providing new insights into the immune regulation by these proteins in the pathogenesis of CE.

METHODS

Echinococcus granulosus annexin B proteins EgANXB2, EgANXB18, EgANXB20, and EgANXB23 were cloned, expressed, and analyzed using bioinformatic tools. Membrane binding analysis was used to assess their bioactivity, while their immunoreactivity and tissue distribution characteristics were determined experimentally using western blotting and immunofluorescence staining, respectively. Furthermore, quantitative real-time reverse transcription PCR (qRT-PCR) was used to analyze the mRNA expression profiles of EgANXBs in different developmental stages of E. granulosus. Finally, immunofluorescence staining, cell counting kit 8 assays, flow cytometry, transwell migration assays, and qRT-PCR were used to evaluate the functional effects of rEgANXB18 and rEgANXB20 on mouse peripheral blood mononuclear cells (PBMCs).

RESULTS

In this study, we identified four EgANXBs with conserved protein structures and calcium-dependent phospholipid binding activities. rEgANXBs were recognized by serum from sheep infected with E. granulosus and distributed in the germinal layer of fertile cysts. Interestingly, transcription levels of the four EgANXBs were significantly higher in protoscoleces than in 28-day strobilated worms. Moreover, we demonstrated that rEgANXB18 and rEgANXB20 were secretory proteins that could bind to PBMCs and regulate their function. Specifically, rEgANXB18 inhibited cell proliferation and migration while promoting cell apoptosis, NO production, and cytokine profile shifting. In contrast, rEgANXB20 showed limited effects on apoptosis but inhibited NO production.

CONCLUSIONS

Our findings suggested that among the four identified EgANXBs, EgANXB2 and EgANXB23 might play a pivotal role for the development of protoscoleces, while EgANXB18 and EgANXB20, as secretory proteins, appeared to participate in the host-parasite interaction by regulating the function of immune cells.

The Impact of Intestinal Inflammation on Nematode's Excretory-Secretory Proteome

Parasitic nematodes and their products are promising candidates for therapeutics against inflammatory bowel diseases (IBD). Two species of nematodes, the hookworm Necator americanus and the whipworm Trichuis suis, are being used in clinical treatment trials of IBD referred to as "helminth therapy". Heligmosomoides polygyrus is a well-known model for human hookworm infections. Excretory-secretory (ES) products of H. polygyrus L4 stage that developed during colitis show a different immunomodulatory effect compared to the ES of H. polgyrus from healthy mice. The aim of the study was to evaluate excretory-secretory proteins produced by H. polygyrus L4 stage males and females that developed in the colitic milieu. Mass spectrometry was used to identify proteins. Blast2GO was used to investigate the functions of the discovered proteins. A total of 387 proteins were identified in the ES of H. polygyrus L4 males (HpC males), and 330 proteins were identified in the ES of L4 females that developed in the colitic milieu (HpC females). In contrast, only 200 proteins were identified in the ES of L4 males (Hp males) and 218 in the ES of L4 females (Hp females) that developed in control conditions. Most of the proteins (123) were detected in all groups. Unique proteins identified in the ES of HpC females included annexin, lysozyme-2, apyrase, and galectin. Venom allergen/Ancylostoma-secreted protein-like, transthyretin-like family proteins, and galectins were found in the secretome of HpC males but not in the secretome of control males. These molecules may be responsible for the therapeutic effects of nematodes in DSS-induced colitis.

The most prominent modulated annexins during parasitic infections

Annexins (ANXs) exert different functions in cell biological and pathological processes and are thus known as double or multi-faceted proteins. These sophisticated proteins might express on both parasite structure and secretion and in parasite-infected host cells. In addition to the characterization of these pivotal proteins, describing their mechanism of action can be also fruitful in recognizing their roles in the pathogenesis of parasitic infections. Accordingly, this study presents the most prominent ANXs thus far identified and their relevant functions in parasites and infected host cells during pathogenesis, especially in the most important intracellular protozoan parasitic infections including leishmaniasis, toxoplasmosis, malaria and trypanosomiasis. The data provided in this study demonstrate that the helminth parasites most probably express and secret ANXs to develop pathogenesis while the modulation of the host-ANXs could be employed as a crucial strategy by intracellular protozoan parasites. Moreover, such data highlight that the use of analogs of both parasite and host ANX peptides (which mimic or regulate ANXs physiological functions through various strategies) might suggest novel therapeutic insights into the treatment of parasitic infections. Furthermore, due to the prominent immunoregulatory activities of ANXs during most parasitic infections and the expression levels of these proteins in some parasitic infected tissues, such multifunctional proteins might be also potentially relevant as vaccine and diagnostic biomarkers. We also suggest some prospects and insights that could be useful and applicable to form the basis of future experimental studies.

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 and Immunological Identification of Diagnostic Antigens from Spirometra erinaceieuropaei Plerocercoid

Human sparganosis is a food-borne parasitic disease caused by the plerocercoids of Spirometra species. Clinical diagnosis of sparganosis is crucial for effective treatment, thus it is important to identify sensitive and specific antigens of plerocercoids. The aim of the current study was to identify and characterize the immunogenic proteins of Spirometra erinaceieuropaei plerocercoids that were recognized by patient sera. Crude soluble extract of the plerocercoids were separated using 2-dimensional gel electrophoresis coupled with immunoblot and mass spectrometry analysis. Based on immunoblotting patterns and mass spectrometry results, 8 antigenic proteins were identified from the plerocercoid. Among the proteins, cysteine protease protein might be developed as an antigen for diagnosis of sparganosis.

Zone of Interaction Between the Parasite and the Host: Protein Profile of the Body Cavity Fluid of Gasterosteus aculeatus L. Infected with the Cestode Schistocephalus solidus (Muller, 1776)

PURPOSE

During infection, the host and the parasite "communicate" with each other through various molecules, including proteins. The aim of this study was to describe the excretory-secretory proteins from the helminth Schistocephalus solidus and its intermediate host, the three-spined stickleback Gasterosteus aculeatus L., which are likely to be involved in interactions between them.

METHODS

Combined samples of washes from the G. aculeatus sticklebacks cavity infected with the S. solidus, and washes from the parasite surface were used as experimental samples, while washes from the uninfected fish body cavity were used as control. The obtained samples were analyzed using mass-spectrometry nLC-MS/MS.

RESULTS

As a result of mass-spectrometry analysis 215 proteins were identified. Comparative quantitative analysis revealed significant differences in LFQ intensity between experimental and control samples for 20 stickleback proteins. In the experimental samples, we found an increase in the content of serpins, plasminogen, angiotensin 1-10, complement component C9, and a decrease in the content of triosephosphate isomerase, creatine kinase, fructose-biphosphate aldolase, superoxide dismutase, peroxidoxin-1, homocysteine-binding and fatty acid-binding proteins, compared to uninfected fish samples. In the experimental group washes, 30 S. solidus proteins were found, including malate dehydrogenase, annexin family proteins, serpins, peptidyl-prolyl cis-trans isomerase and fatty acid-binding protein.

CONCLUSIONS

Thus, the protein composition of washes from the helminth S. solidus surface and the body cavity of infected and uninfected stickleback G. aculeatus were studied. As a result, it was shown that various components of the immune defense system predominated in the washes of infected fish and helminths.

Eudiplozoon nipponicum (Monogenea, Diplozoidae) and its adaptation to haematophagy as revealed by transcriptome and secretome profiling

Background

Ectoparasites from the family Diplozoidae (Platyhelminthes, Monogenea) belong to obligate haematophagous helminths of cyprinid fish. Current knowledge of these worms is for the most part limited to their morphological, phylogenetic, and population features. Information concerning the biochemical and molecular nature of physiological processes involved in host–parasite interaction, such as evasion of the immune system and its regulation, digestion of macromolecules, suppression of blood coagulation and inflammation, and effect on host tissue and physiology, is lacking. In this study, we report for the first time a comprehensive transcriptomic/secretome description of expressed genes and proteins secreted by the adult stage of Eudiplozoon nipponicum (Goto, 1891) Khotenovsky, 1985, an obligate sanguivorous monogenean which parasitises the gills of the common carp (Cyprinus carpio).

Results

RNA-seq raw reads (324,941 Roche 454 and 149,697,864 Illumina) were generated, de novo assembled, and filtered into 37,062 protein-coding transcripts. For 19,644 (53.0%) of them, we determined their sequential homologues. In silico functional analysis of E. nipponicum RNA-seq data revealed numerous transcripts, pathways, and GO terms responsible for immunomodulation (inhibitors of proteolytic enzymes, CD59-like proteins, fatty acid binding proteins), feeding (proteolytic enzymes cathepsins B, D, L1, and L3), and development (fructose 1,6-bisphosphatase, ferritin, and annexin). LC-MS/MS spectrometry analysis identified 721 proteins secreted by E. nipponicum with predominantly immunomodulatory and anti-inflammatory functions (peptidyl-prolyl cis-trans isomerase, homolog to SmKK7, tetraspanin) and ability to digest host macromolecules (cathepsins B, D, L1).

Conclusions

In this study, we integrated two high-throughput sequencing techniques, mass spectrometry analysis, and comprehensive bioinformatics approach in order to arrive at the first comprehensive description of monogenean transcriptome and secretome. Exploration of E. nipponicum transcriptome-related nucleotide sequences and translated and secreted proteins offer a better understanding of molecular biology and biochemistry of these, often neglected, organisms. It enabled us to report the essential physiological pathways and protein molecules involved in their interactions with the fish hosts.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12864-021-07589-z.

Molecular characterization and expression analysis of annexin B3 and B38 as secretory proteins in Echinococcus granulosus

Background

Cystic echinococcosis is a parasitic zoonotic disease, which poses a threat to public health and animal husbandry, and causes significant economic losses. Annexins are a family of phospholipid-binding proteins with calcium ion-binding activity, which have many functions.

Methods

Two annexin protein family genes [Echinococcus granulosus annexin B3 (EgAnxB3) and EgAnxB38] were cloned and molecularly characterized using bioinformatic analysis. The immunoreactivity of recombinant EgAnxB3 (rEgAnxB3) and rEgAnxB38 was investigated using western blotting. The distribution of EgAnxB3 and EgAnxB38 in protoscoleces (PSCs), the germinal layer, 18-day strobilated worms and 45-day adult worms was analyzed by immunofluorescence localization, and their secretory characteristics were analyzed preliminarily; in addition, quantitative real-time reverse transcription polymerase chain reaction was used to analyze their transcript levels in PSCs and 28-day strobilated worms stages. The phospholipid-binding activities of rEgAnxB3 and rEgAnxB38 were also analyzed.

Results

EgAnxB3 and EgAnxB38 are conserved and contain calcium-binding sites. Both rEgAnxB3 and rEgAnxB38 could be specifically recognized by the serum samples from E. granulosus-infected sheep, indicating that they had strong immunoreactivity. EgAnxB3 and EgAnxB38 were distributed in all stages of E. granulosus, and their transcript levels were high in the 28-day strobilated worms. They were found in liver tissues near the cysts. In addition, rEgAnxB3 has Ca²⁺-dependent phospholipid-binding properties.

Conclusions

EgAnxB3 and EgAnxB38 contain calcium-binding sites, and rEgAnxB3 has Ca²⁺-dependent phospholipid-binding properties. EgAnxB3 and EgAnxB38 were transcribed in PSCs and 28-day strobilated worms. They were expressed in all stages of E. granulosus, and distributed in the liver tissues near the hydatid cyst, indicating that they are secreted proteins that play a crucial role in the development of E. granulosus.

Molecular Characterization of Annexin B2, B3 and B12 in Taenia multiceps

Coenurus cerebralis, the metacestode of Taenia multiceps, causes coenurosis, a disease severely affecting goat, sheep, cattle and yak farming and resulting in huge economic losses annually. Annexins bind calcium ions and play an important role in flatworm parasite development. To explore potential functions of annexins in T. multiceps, three homologous genes, namely, TmAnxB2, TmAnxB3 and TmAnxB12, were screened from the transcriptome dataset, amplified from C. cerebralis cDNA and subjected to bioinformatics analysis. Then, polyclonal antibodies recognizing the recombinant TmAnxB2 (rTmAnxB2) and rTmAnxB3 were prepared for localization of TmAnxB2 and TmAnxB3 in different tissues and developmental stages by immunofluorescence. The transcription of all three genes was also measured by relative fluorescent quantitative PCR. The sizes of rTmAnxB2, rTmAnxB3 and rTmAnxB12 were 58.00, 53.06 and 53.51 kDa, respectively, and rTmAnxB12 was unstable. Both rTmAnxB2 and rTmAnxB3 were recognized by goat-positive T. multiceps sera in Western blots. Immunofluorescence revealed that TmAnxB2 and TmAnxB3 were localized in the protoscolex and cyst wall and TmAnxB3 was also detected in adult cortex. TmAnxB2 and TmAnxB12 mRNA levels were determined to be highest in oncospheres and protoscolex, whereas transcription of TmAnxB3 was highest in scolex and immature segments. Taken together, these findings indicate that TmAnxB2 and TmAnxB12 may play critical roles in T. multiceps larvae, while TmAnxB3 may have important functions in adults. These results will lay the foundation for functional research of annexins in T. multiceps.

Helminth-induced apoptosis: a silent strategy for immunosuppression

During microbial infections, both innate and adaptive immunity are activated. Viruses and bacteria usually induce an acute inflammation in the first setting of infection, which helps the eliciting an effective immune response. In contrast, macroparasites such as helminths are a highly successful group of invaders known to be capable of maintaining a chronic infestation with the minimum instigation. Undoubtedly, generating such an immunoregulatory environment requires the exploitation of various immunosuppressive mechanisms to debilitate host immunity supporting their survival and replication. Several mechanisms have been recognized whereby helminths prolong their infections including an increase of immunoregulatory cells, inhibition of Th1 or Th2 responses, targeting pattern recognition receptors (PRRs) and lowering the immune cells quantity via induction of apoptosis. Apoptosis is a programmed intracellular process involving a series of consecutive downstream signalling event evolved to cell death. It plays a pivotal role in several immunological reactions in particular deletion of autoreactive immune cells. Helminth-triggered apoptosis in immune cells exhausts host immunity, which paves the way for generating a permissive environment and chronic infection. This review provides a compilation of recent investigations discussing the apoptotic mechanisms exploited by different worms and the immunological consequences of immune cell death. Finally, the anti-cancer effects of some worm-derived molecules due to their apoptotic effects are discussed, highlighting as potentially druggable candidates to combat cancer.

Characterization of Ostertagia ostertagi annexin-like proteins at different developmental stages

Ostertagiosis remains an economically important parasitic disease in cattle in the temperate regions of the world. Repeated exposures to Ostertagia ostertagi in calves cause significant pathology in the abomasum but elicit little protective immunity. The larvae use the host's gastric glands as a niche for development, where the parasite completes its parasitic stages, while in the gastric glands, the larvae must down-regulate the host inflammatory immune responses. Annexin (ANX) A1, commonly found in most eukaryotes, is heavily involved in controlling anti-inflammatory responses by binding receptors on leukocytes. We hypothesized, therefore, that parasite proteins of the ANX family may be involved in host-parasite interactions during ostertagiosis. BLASTN search with the bovine ANXA1 identified two families of Oos-ANX like proteins (Oos-ANXL), each of which was highly conserved at the genetic level and identical at the amino acid sequence level. Oos-ANXL-1 is encoded by two transcripts and Oos-ANXL-2 by 20 transcripts. The present study characterized one Oos-ANXL, representing the most abundant Oos-ANXL, which was further defined as Oost-ANXL-2.1. Oos-ANXL-2.1 with a coding sequence of 519 bp was PCR-amplified, cloned, and expressed. Oos-ANXL-2.1 was immunolocalized to both L3 and adult, but not L4. The staining appeared to be associated with the gut and hypodermis in L3, but it was specifically localized to the hypodermis in adult worms. Western blots detected three protein bands in parasite lysates using anti-recombinant Oos-ANXL-2.1 antibody. Integrated optical density for each of the 3 Oos-ANXL-2s or the total Oos-ANXL-2s detected by Western blots (P < 0.05) was higher in adult worms than in L3 or L4. The results indicate that the production of Oos-ANXL-2s is developmentally regulated and most abundant in the adult worm. This rather large family of proteins could be a potential vaccine target against O. ostertagi infection and warrants further investigation.

Characterization of a Secretory Annexin in Echinococcus granulosus

Cystic echinococcosis, caused by Echinococcus granulosus, is a widespread parasitic zoonosis causing economic loss and public health problems. Annexins are important proteins usually present in the plasma membrane, but previous studies have shown that an annexin B33 protein of E. granulosus (Eg-ANX) could be detected in the excretory/secretory products and cyst fluid. In this study, we cloned and characterized Eg-ANX. In silico analysis showed that the amino acid sequence of Eg-ANX was conserved and lacked any signal peptides. The phospholipid-binding activity of recombinant Eg-ANX (rEg-ANX) was tested; liposomes could bind to rEg-ANX only in the presence of Ca(2+). In addition, we performed western blotting and immunohistochemical analyses to further validate the secretory properties of Eg-ANX. The protein could be detected in the cyst fluid of E. granulosus and was also present in the intermediate host tissues, which suggested that Eg-ANX might play an important role in parasite-host interaction.

Fasciola hepatica induces eosinophil apoptosis in the migratory and biliary stages of infection in sheep

The aim of the present work was to evaluate the number of apoptotic eosinophils in the livers of sheep experimentally infected with Fasciola hepatica during the migratory and biliary stages of infection. Four groups (n=5) of sheep were used; groups 1-3 were orally infected with 200 metacercariae (mc) and sacrificed at 8 and 28 days post-infection (dpi), and 17 weeks post-infection (wpi), respectively. Group 4 was used as an uninfected control. Apoptosis was detected using immunohistochemistry with a polyclonal antibody against anti-active caspase-3, and transmission electron microscopy (TEM). Eosinophils were identified using the Hansel stain in serial sections for caspase-3, and by ultrastructural features using TEM. At 8 and 28 dpi, numerous caspase-3(+) eosinophils were mainly found at the periphery of acute hepatic necrotic foci. The percentage of caspase -3(+) apoptotic eosinophils in the periphery of necrotic foci was high (46.1-53.9) at 8 and 28 dpi, respectively, and decreased in granulomas found at 28 dpi (6%). Transmission electron microscopy confirmed the presence of apoptotic eosinophils in hepatic lesions at 8 and 28 dpi. At 17 wpi, apoptotic eosinophils were detected in the infiltrate surrounding some enlarged bile ducts containing adult flukes. This is the first report of apoptosis induced by F. hepatica in sheep and the first study reporting apoptosis in eosinophils in hepatic inflammatory infiltrates in vivo. The high number of apoptotic eosinophils in acute necrotic tracts during the migratory and biliary stages of infection suggests that eosinophil apoptosis may play a role in F. hepatica survival during different stages of infection.

Genome analysis of Excretory/Secretory proteins in Taenia solium reveals their Abundance of Antigenic Regions (AAR)

Excretory/Secretory (ES) proteins play an important role in the host-parasite interactions. Experimental identification of ES proteins is time-consuming and expensive. Alternative bioinformatics approaches are cost-effective and can be used to prioritize the experimental analysis of therapeutic targets for parasitic diseases. Here we predicted and functionally annotated the ES proteins in T. solium genome using an integration of bioinformatics tools. Additionally, we developed a novel measurement to evaluate the potential antigenicity of T. solium secretome using sequence length and number of antigenic regions of ES proteins. This measurement was formalized as the Abundance of Antigenic Regions (AAR) value. AAR value for secretome showed a similar value to that obtained for a set of experimentally determined antigenic proteins and was different to the calculated value for the non-ES proteins of T. solium genome. Furthermore, we calculated the AAR values for known helminth secretomes and they were similar to that obtained for T. solium. The results reveal the utility of AAR value as a novel genomic measurement to evaluate the potential antigenicity of secretomes. This comprehensive analysis of T. solium secretome provides functional information for future experimental studies, including the identification of novel ES proteins of therapeutic, diagnosis and immunological interest.

Improvement of cytocompatibility of polylactide by filling with marine algae powder

This work evaluated the cytocompatibility, thermal and mechanical properties of composites of polylactide (PLA) and marine algae powder (MAP). To improve the thermal and mechanical properties of PLA-MAP composites, glycidyl methacrylate (GMA) was used as the compatibilizer for the blending of PLA and MAP. The PLA-g-GMA/MAP composites exhibited superior mechanical properties, attributing to higher compatibility between the polymer and MAP, comparing to PLA/MAP composites. The dispersion of MAP in the PLA-g-GMA matrix was highly homogeneous as a result of etherification. The lower melt torque of the PLA-g-GMA/MAP composites also made them more processable than PLA/MAP. To assess the cytocompatibility, normal human foreskin fibroblasts (FBs) were seeded onto each type of the composites. Results of FB proliferation, collagen production, and cytotoxicity assays indicated greater cytocompatibility for the PLA/MAP composites than for the PLA-g-GMA/MAP composites. Furthermore, both PLA/MAP and PLA-g-GMA/MAP composites were more cytocompatible than pure PLA.

Biochemical and immunological characterization of annexin B30 from Clonorchis sinensis excretory/secretory products

Clonorchis sinensis has been classified as group I biological carcinogen for cholangiocarcinoma by the World Health Organization. Biological studies on excretory/secretory products (ESPs) enabled us to understand the pathogenesis mechanism of C. sinensis and develop new strategies for the prevention of clonorchiasis. In this study, sequence analysis showed that annexin B30 from C. sinensis (CsANXB30) is composed of four annexin repeats which were characterized by type II and III Ca(2+)-binding sites or KGD motif with the capability of Ca(2+)-binding. In addition, immunoblot assay revealed that recombinant CsANXB30 (rCsANXB30) could be recognized by the sera from rats infected with C. sinensis and the sera from rats immunized by CsESPs. Real-time PCR showed that its transcriptional level was the highest at the stage of metacercaria. Immunofluorescence assay was employed to confirm that CsANXB30 was distributed in the tegument, intestine, and egg of adult worms, as well as the tegument and vitellarium of metacercaria. rCsANXB30 was able to bind phospholipid in a Ca(2+)-dependent manner and human plasminogen in a dose-dependent manner. Moreover, cytokine and antibody measurements indicated that rats subcutaneously immunized with rCsANXB30 developed a strong IL-10 production in spleen cells and a high level of IgG1 isotype, indicating that rCsANXB30 could trigger specific humoral and cellular immune response in rats. The present results implied that CsANXB30 might be involved in a host-parasite interaction and affected the immune response of the host during C. sinensis infection.

Strategies of Echinococcus species responses to immune attacks: implications for therapeutic tool development

Echinococcus species have been studied as a model to investigate parasite-host interactions. Echinococcus spp. can actively communicate dynamically with a host to facilitate infection, growth and proliferation partially via secretion of molecules, especially in terms of harmonization of host immune attacks. This review systematically outlines our current knowledge of how the Echinococcus species have evolved to adapt to their host's microenvironment. This understanding of parasite-host interplay has implications in profound appreciation of parasite plasticity and is informative in designing novel and effective tools including vaccines and drugs for the treatment of echinococcosis and other diseases.

Granulocytes in helminth infection -- who is calling the shots?

Helminths are parasitic organisms that can be broadly described as “worms” due to their elongated body plan, but which otherwise differ in shape, development, migratory routes and the predilection site of the adults and larvae. They are divided into three major groups: trematodes (flukes), which are leaf-shaped, hermaphroditic (except for blood flukes) flatworms with oral and ventral suckers; cestodes (tapeworms), which are segmented, hermaphroditic flatworms that inhabit the intestinal lumen; and nematodes (roundworms), which are dioecious, cylindrical parasites that inhabit intestinal and peripheral tissue sites. Helminths exhibit a sublime co-evolution with the host´s immune system that has enabled them to successfully colonize almost all multicellular species present in every geographical environment, including over two billion humans. In the face of this challenge, the host immune system has evolved to strike a delicate balance between attempts to neutralize the infectious assault versus limitation of damage to host tissues. Among the most important cell types during helminthic invasion are granulocytes: eosinophils, neutrophils and basophils. Depending on the specific context, these leukocytes may have pivotal roles in host protection, immunopathology, or facilitation of helminth establishment. This review provides an overview of the function of granulocytes in helminthic infections.

Molecular and functional characterization of a Schistosoma bovis annexin: fibrinolytic and anticoagulant activity

Annexins belong to an evolutionarily conserved multigene family of proteins expressed throughout the animal and plant kingdoms. Although they are soluble cytosolic proteins that lack signal sequences, they have also been detected in extracellular fluids and have been associated with cell surface membranes, where they could be involved in anti-haemostatic and anti-inflammatory functions. Schistosome annexins have been identified on the parasite's tegument surface and excretory/secretory products, but their functions are still unknown. Here we report the cloning, sequencing, in silico analysis, and functional characterization of a Schistosoma bovis annexin. The predicted protein has typical annexin secondary and tertiary structures. Bioassays with the recombinant protein revealed that the protein is biologically active in vitro, showing fibrinolytic and anticoagulant properties. Finally, the expression of the native protein on the tegument surface of S. bovis schistosomula and adult worms is demonstrated, revealing the possibility of exposure to the host's immune system and thus offering a potential vaccine target for the control of schistosomiasis in ruminants.

Parasite annexins--new molecules with potential for drug and vaccine development

In the last few years, annexins have been discovered in several nematodes and other parasites, and distinct differences between the parasite annexins and those of the hosts make them potentially attractive targets for anti-parasite therapeutics. Annexins are ubiquitous proteins found in almost all organisms across all kingdoms.Here, we present an overview of novel annexins from parasitic organisms, and summarize their phylogenetic and biochemical properties, with a view to using them as drug or vaccine targets. Building on structural and biological information that has been accumulated for mammalian and plant annexins, we describe a predicted additional secondary structure element found in many parasite annexins that may confer unique functional properties, and present a specific antigenic epitope for use as a vaccine.

Schistosoma mansoni Annexin 2: molecular characterization and immunolocalization

We here describe the cloning and characterization of the Schistosoma mansoni Annexin 2, previously identified in the tegument by proteomic studies, and as an up-regulated gene in schistosomulum stage by microarray data. In silico analysis predicts a conserved core containing four repeat domains of Annexin (ANX) and a variable N-terminal region similar to that described for mammalian isoforms. Real-time RT-PCR and Western blot analysis determined that S. mansoni Annexin 2 is significantly up-regulated in the transition from free-living cercaria to schistosomulum and adult worm parasitic stages. Immunolocalization experiments and tegument membrane preparations confirmed Annexin 2 as a protein mainly localized in the tegument of schistosomula and adult worms. Furthermore, it binds to the tegument surface membranes in a calcium-dependent manner. These results suggest that S. mansoni Annexin 2 is closely associated to the tegument arrangement, being a potential target for immune intervention.