Proteolytic degradation of host hemoglobin by schistosomes

Development and evaluation of an indirect ELISA using a multiepitope antigen for the diagnosis of intestinal schistosomiasis

The laboratory diagnosis of intestinal schistosomiasis, carried out by detecting parasite eggs in feces, has low sensitivity when applied to individuals with low parasitic load. Serological tests can be more sensitive for the diagnosis of the disease. Therefore, the objective of this work was to develop and evaluate an ELISA-based immunoenzymatic assay, using a Schistosoma mansoni multiepitope antigen (ELISA IgG anti-SmME). For this, the amino acid sequences of S. mansoni cathepsin B and asparaginyl endopeptidase were submitted to the prediction of B cell epitopes and, together with peptide sequences obtained from earlier works, were used in the construction of a minigene. The multiepitope protein was expressed in Escherichia coli and the performance of the ELISA IgG anti-SmME for schistosomiasis was evaluated using serum samples from 107 individuals either egg positive or negative. In addition, 11 samples from individuals with other helminth infections were included. The ELISA IgG anti-SmME showed a sensitivity of 81.1% and a specificity of 46.1%. Further analysis revealed a 77.2% sensitivity in diagnosis of individuals with egg counts of ≤12 epg (eggs per gram feces) and 87.5% for individuals with 13–99 epg. It is worth mentioning that, to our knowledge, this was the first study using a multiepitope recombinant antigen in an ELISA for diagnosis of intestinal schistosomiasis, which demonstrated promising results in the diagnosis of individuals with low parasitic loads.

Parasite Metalo-aminopeptidases as Targets in Human Infectious Diseases

BACKGROUND

Parasitic human infectious diseases are a worldwide health problem due to the increased resistance to conventional drugs. For this reason, the identification of novel molecular targets and the discovery of new chemotherapeutic agents are urgently required. Metalo- aminopeptidases are promising targets in parasitic infections. They participate in crucial processes for parasite growth and pathogenesis.

OBJECTIVE

In this review, we describe the structural, functional and kinetic properties, and inhibitors, of several parasite metalo-aminopeptidases, for their use as targets in parasitic diseases.

CONCLUSION

Plasmodium falciparum M1 and M17 aminopeptidases are essential enzymes for parasite development, and M18 aminopeptidase could be involved in hemoglobin digestion and erythrocyte invasion and egression. Trypanosoma cruzi, T. brucei and Leishmania major acidic M17 aminopeptidases can play a nutritional role. T. brucei basic M17 aminopeptidase down-regulation delays the cytokinesis. The inhibition of Leishmania basic M17 aminopeptidase could affect parasite viability. L. donovani methionyl aminopeptidase inhibition prevents apoptosis but not the parasite death. Decrease in Acanthamoeba castellanii M17 aminopeptidase activity produces cell wall structural modifications and encystation inhibition. Inhibition of Babesia bovis growth is probably related to the inhibition of the parasite M17 aminopeptidase, probably involved in host hemoglobin degradation. Schistosoma mansoni M17 aminopeptidases inhibition may affect parasite development, since they could participate in hemoglobin degradation, surface membrane remodeling and eggs hatching. Toxoplasma gondii M17 aminopeptidase inhibition could attenuate parasite virulence, since it is apparently involved in the hydrolysis of cathepsin Cs- or proteasome-produced dipeptides and/or cell attachment/invasion processes. These data are relevant to validate these enzymes as targets.

Molecular characterization and determination of the biochemical properties of cathepsin L of Trichinella spiralis

Cathepsin L is an important cysteine protease, but its function in T. spiralis remains unclear. The aim of this research was to explore the biological characteristics of T. spiralis cathepsin L (TsCatL) and its role in T. spiralis-host interactions. Bioinformatic analysis revealed the presence of the cysteine protease active site residues Gln, Cys, His and Asn in mature TsCatL, as well as specific motifs of cathepsin L similar to ERFNIN and GYLND in the prepeptide of TsCatL. Molecular docking of mature TsCatL and E64 revealed hydrophobic effects and hydrogen bonding interactions. Two domains of TsCatL (TsCatL2) were cloned and expressed, and recombinant TsCatL2 (rTsCatL2) was autocatalytically cleaved under acidic conditions to form mature TsCatL. TsCatL was transcribed and expressed in larvae and adults and located in the stichosome, gut and embryo. Enzyme kinetic tests showed that rTsCatL2 degraded the substrate Z-Phe-Arg-AMC under acidic conditions, which was inhibited by E64 and PMSF and enhanced by EDTA, L-cysteine and DTT. The kinetic parameters of rTsCatL2 were a Km value of 48.82 μM and Vmax of 374.4 nM/min at pH 4.5, 37 °C and 5 mM DTT. In addition, it was shown that rTsCatL2 degraded haemoglobin, serum albumin, immunoglobulins (mouse IgG, human IgG and IgM) and extracellular matrix components (fibronectin, collagen I and laminin). The proteolytic activity of rTsCatL2 was host specific and significantly inhibited by E64. rTsCatL2 possesses the natural activity of a sulfhydryl-containing cysteine protease, and TsCatL is an important digestive enzyme that seems to be important for the nutrient acquisition, immune evasion and invasion of Trichinella in the host.

Human serum activates the tegument of female schistosomes and supports recovery from Praziquantel

Schistosomiasis is one of the most devastating parasitic disease in the world. Schistosoma spp. survive for decades within the vasculature of their human hosts. They have evolved a vast array of mechanisms to avoid the immune reaction of the host. Due to their sexual dimorphism, with the female worm lying within the gynecophoric canal of the male worm, it is the male that is exposed to the immediate environment and the soluble parts of the host’s immune response. To understand how the worms are so successful in fending off the immune attacks of the host, comparative analyses of both worm sexes in human serum (with or without Praziquantel) were performed using scanning electron microscopy, transmission electron microscopy, and immunohistochemistry. Further, gene expression analyses of tegument-specific genes were performed. Following the incubation in human serum, males and females out of pairs show morphological changes such as an altered structure of the pits below the surface and an increased number of pits per area. In addition, female schistosomes presented a marked tuft-like repulsion of their opsonized surface. The observed resistance of females to Praziquantel seemed to depend on active proteins in the human serum. Moreover, different expression profiles of tegument-specific genes indicate different functions of female_single and male_single teguments in response to human serum. Our results indicate that female schistosomes developed different evasion strategies toward the host’s immune system in comparison to males that might lead to more robustness and has to be taken into account for the development of new anti-schistosomal drugs.

Hc-hrg-2, a glutathione transferase gene, regulates heme homeostasis in the blood-feeding parasitic nematode Haemonchus contortus

BACKGROUND

Haemonchus contortus, a blood-feeding parasite, is constantly surrounded by large quantities of heme released from the catabolism of host red blood cells. To cope with the toxicity of free heme, H. contortus needs to uptake and detoxify the heme, a process believed to be paramount for parasite survival.

METHODS

A heme-responsive gene Hc-hrg-2 was identified which is the homologue of Ce-hrg-2. The transcriptional levels in all developmental stages and heme-responsive ability of Hc-hrg-2 were analyzed by qRT-PCR. Immunofluorescence analysis and cell transfections were performed to analyze the expression pattern of Hc-HGR-2. Statistical analyses were performed with GraghPad Prism 6.0 using Student's t-test.

RESULTS

To investigate the heme homeostasis of H. contortus, we first identified a heme-responsive gene Hc-hrg-2, a homolog of Ce-hrg-2 that is involved in heme transport in the hypodermis of Caenorhabditis elegans. Using qRT-PCR, we showed that Hc-hrg-2 mRNA was expressed throughout all life-cycle stages of H. contortus with the highest level in the third-stage larvae (L3s). Notably, transcription of Hc-hrg-2 in the exsheathed L3s was significantly upregulated in the presence of high concentration of heme. We found that Hc-HRG-2 protein was mainly located in the hypodermal tissues of adult H. contortus in vivo and the endoplasmic reticulum in the transfected mammalian cells. Our in vitro assay demonstrated that Hc-HRG-2 is a heme-binding protein with glutathione S-transferase activity and heme had a significant effect on its enzymatic activity when a model substrate 1-chloro-2, 4-dinitrobenzene (CDNB) was used.

CONCLUSIONS

Hc-hrg-2 is a heme-responsive gene and engaged in heme homeostasis regulation in hypodermal tissues during the free-living stages of H. contortus.

Development of a conserved chimeric vaccine based on helper T-cell and CTL epitopes for induction of strong immune response against Schistosoma mansoni using immunoinformatics approaches

Currently, three recombinant antigens based vaccines are under clinical trials against Schistosomiasis, but there is no vaccine available for prophylaxis or therapeutic. This study was conducted to construct a multi-epitope based vaccine against Schistosoma mansoni via utilizing Sm14, Sm21.7, Sm23, Sm29, Smp80, Sm-CB and SM-TSP-2 antigens. Helper T lymphocyte (HTL), cytotoxic T lymphocyte (CTL) and IFN-γ epitopes were predicted. Furthermore, Pan HLA DR-binding epitope was added to the vaccine. Moreover, 50S ribosomal protein L7/L12 of Mycobacterium tuberculosis as a novel TLR4 agonist was applied. The TAT peptide was added to the vaccine to augment intracellular delivery. The selected epitopes were linked together through appropriate linkers and chimeric vaccine was constructed with 617 amino acids with molecular weight of 65.43 kDa. Physico-chemical properties revealed a soluble protein with antigenic and non-allergic properties. Further analyses validated the stability of the construct that was able to interact with TLR4. Immunoinformatics analysis demonstrated the strong potential of constructed vaccine to stimulate T and B-cell mediated immune responses. In summary, obtained data indicated that the proposed vaccine can properly induce both T and B cells immune responses and could possibly be utilized for prophylactic or therapeutic aims in response to infection caused by S. mansoni.

Highly tunable thiosulfonates as a novel class of cysteine protease inhibitors with anti-parasitic activity against Schistosoma mansoni

The development of a new class of cysteine protease inhibitors utilising the thiosulfonate moiety as an SH specific electrophile is described. This moiety has been introduced into suitable amino acid derived building blocks, which were incorporated into peptidic sequences leading to very potent i.e. sub micromolar inhibitors of the cysteine protease papain in the same range as the vinyl sulfone based inhibitor K11777. Therefore, their inhibitory effect on Schistosoma mansoni, a human blood parasite, that expresses several cysteine proteases, was evaluated. The homophenylalanine side chain containing compounds 27-30 and especially 36 showed promising activities compared with K11777 and warrant further investigations of these peptidic thiosulfonate inhibitors as new potential anti-parasitic compounds.

Effects of iron chelating agent on Schistosoma mansoni infected murine model

Schistosomiasis is one of the major health problems in many tropical and developing countries. Infection takes place once cerceriae penetrate human skin, then it changed into schistosomules. The schistosomules takes iron in the form of heme from host's haemoglobin, ferritin and transferrin. Iron is a vital element not only for growth and sexual maturity of schistosomules to adults but also for oogenesis. Since the trapped eggs are the pathological causative agent for most of pathogenesis and complications, the current work was designed to study the effects of early deprivation of schistosomules from iron in the host (in vivo) by chelating it with deferoxamine (DFO). The iron chelation has effects on growth, maturity and egg deposition, as well as it has ameliorative effects on liver pathology such as hepatic fibrosis. Mice were classified into four groups, normal control, DFO treated only, Schistosoma mansoni (S. mansoni) infected DFO untreated and S. mansoni infected DFO treated. The infected DFO treated mice showed significant reduction in fecal egg excretion with increased percentage of dead eggs and this was accompanied with a significant reduction of both total worm burden and hepatic egg load and increased dead egg percentage compared to the infected DFO untreated group. There was also a significant reduction in both serum and hepatic tissue ferritin concentrations in the infected DFO treated mice in comparison to the infected DFO untreated group. Additionally, a significant decrease in number and size of granulomas with subsequent improvement of liver fibrosis was recorded in the infected DFO treated group. This immunopathology was also associated with significant up regulation of Interlukine12 (IL12), Interferon gamma (IFN γ) and significant down regulation in interleukin4 (IL4), interleukin10 (IL10) in both serum and hepatic tissue in the infected DFO treated compared to other groups. Entirely, DFO succeeded in diminishing the growth, maturity and fecundity of S. mansoni with a subsequent improvement of hepatic pathology. As a result of the above findings, it can be concluded that DFO could be considered as a useful treatment against schistosomal infection.

Cysteine proteases as digestive enzymes in parasitic helminths

We briefly review cysteine proteases (orthologs of mammalian cathepsins B, L, F, and C) that are expressed in flatworm and nematode parasites. Emphasis is placed on enzyme activities that have been functionally characterized, are associated with the parasite gut, and putatively contribute to degrading host proteins to absorbable nutrients [1–4]. Often, gut proteases are expressed as multigene families, as is the case with Fasciola [5] and Haemonchus [6], presumably expanding the range of substrates that can be degraded, not least during parasite migration through host tissues [5]. The application of the free-living planarian and Caenorhabditis elegans as investigative models for parasite cysteine proteases is discussed. Finally, because of their central nutritive contribution, targeting the component gut proteases with small-molecule chemical inhibitors and understanding their utility as vaccine candidates are active areas of research [7].

Immune Mechanisms Involved in Schistosoma mansoni-Cathepsin B Vaccine Induced Protection in Mice

A vaccine against schistosomiasis would contribute to a long-lasting decrease in disease spectrum and transmission. Our previous protection studies in mice using Schistosoma mansoni Cathepsin B (Sm-Cathepsin B) resulted in 59 and 60% worm burden reduction with CpG oligodeoxynucleotides and Montanide ISA720 VG as adjuvants, respectively. While both formulations resulted in significant protection in a mouse model of schistosomiasis, the elicited immune responses differed. Therefore, in this study, we aimed to decipher the mechanisms involved in Sm-Cathepsin B vaccine-mediated protection. We performed in vitro killing assays using schistosomula stage parasites as targets for lung-derived leukocytes and serum obtained from mice immunized with Sm-Cathepsin B adjuvanted with either Montanide ISA 720 VG or CpG and from non-vaccinated controls. Lung cells and immune sera from the Sm-Cathepsin B + Montanide group induced the highest killing (63%) suggesting the importance of antibodies in cell-mediated parasite killing. By contrast, incubation with lung cells from Sm-Cathepsin B + CpG immunized animals induced significant parasite killing (53%) independent of the addition of immune serum. Significant parasite killing was also observed in the animals immunized with Sm-Cathepsin B alone (41%). For the Sm-Cathepsin B + Montanide group, the high level killing effect was lost after the depletion of CD4⁺ T cells or natural killer (NK) cells from the lung cell preparation. For the Sm-Cathepsin B + CpG group, high parasite killing was lost after CD8⁺ T cell depletion, and a reduction to 39% was observed upon depletion of NK cells. Finally, the parasite killing in the Sm-Cathepsin B alone group was lost after the depletion of CD4⁺ T cells. Our results demonstrate how the different Sm-Cathepsin B formulations influence the immune mechanisms involved in parasite killing and protection against schistosomiasis.

Modulation of mitochondrial metabolism as a biochemical trait in blood feeding organisms: the redox vampire hypothesis redux

Hematophagous organisms undergo remarkable metabolic changes during the blood digestion process, increasing fermentative glucose metabolism, and reducing respiratory rates, both consequence of functional mitochondrial remodeling. Here, we review the pathways involved in energy metabolism and mitochondrial functionality in a comparative framework across different hematophagous species, and consider how these processes regulate redox homeostasis during blood digestion. The trend across distinct species indicate that a switch in energy metabolism might represent an important defensive mechanism to avoid the potential harmful interaction of oxidants generated from aerobic energy metabolism with products derived from blood digestion. Indeed, in insect vectors, blood feeding transiently reduces respiratory rates and oxidant production, irrespective of tissue and insect model. On the other hand, a different scenario is observed in several unrelated parasite species when exposed to blood digestion products, as respiratory rates reduce and mitochondrial oxidant production increase. The emerging picture indicates that re-wiring of energy metabolism, through reduced mitochondrial function, culminates in improved tolerance to redox insults and seems to represent a key step for hematophagous organisms to cope with the overwhelming and potentially toxic blood meal.

A novel type I cystatin of parasite origin with atypical legumain-binding domain

Parasite inhibitors of cysteine peptidases are known to influence a vast range of processes linked to a degradation of either the parasites' own proteins or proteins native to their hosts. We characterise a novel type I cystatin (stefin) found in a sanguinivorous fish parasite Eudiplozoon nipponicum (Platyhelminthes: Monogenea). We have identified a transcript of its coding gene in the transcriptome of adult worms. Its amino acid sequence is similar to other stefins except for containing a legumain-binding domain, which is in this type of cystatins rather unusual. As expected, the recombinant form of E. nipponicum stefin (rEnStef) produced in Escherichia coli inhibits clan CA peptidases - cathepsins L and B of the worm - via the standard papain-binding domain. It also blocks haemoglobinolysis by cysteine peptidases in the worm's excretory-secretory products and soluble extracts. Furthermore, we had confirmed its ability to inhibit clan CD asparaginyl endopeptidase (legumain). The presence of a native EnStef in the excretory-secretory products of adult worms, detected by mass spectrometry, suggests that this protein has an important biological function at the host-parasite interface. We discuss the inhibitor's possible role in the regulation of blood digestion, modulation of antigen presentation, and in the regeneration of host tissues.

Schistosoma hemozoin and its possible roles

More than 95years ago Schistosoma pigment had been deemed as a degradation product of haemoglobin. Until the 1950s, scientists initiated to pay attention to understand the hematophagous habit of schistosomes, and to study the degradation of haemoglobin as well as the formation of hemozoin inside the gut of the worms. For a long time, the formation of hemozoin in both Plasmodium and in Schistosoma was considered to be the major route of heme detoxification, and hemozoin served a role in waste disposal. At the beginning of this century, the chemical structure of Schistosoma pigment was confirmed to be identical to that of malarial pigment (hemozoin) and its synthetic analogue, β-hematin. Since then, studies on Schistosoma hemozoin have been investigated by some workers and the results showed that Schistosoma hemozoin may play important roles in pathogenicity, immune modulation, iron supply for egg formation, and interaction with some anti-schistosomal drugs. In this review, we briefly review and discuss the hematophagous habit of schistosomes, degradation of haemoglobin, formation of hemozoin in the worm gut, and possible roles of hemozoin.

Cysteine and Aspartyl Proteases Contribute to Protein Digestion in the Gut of Freshwater Planaria

Proteases perform numerous vital functions in flatworms, many of which are likely to be conserved throughout the phylum Platyhelminthes. Within this phylum are several parasitic worms that are often poorly characterized due to their complex life-cycles and lack of responsiveness to genetic manipulation. The flatworm Schmidtea mediterranea, or planaria, is an ideal model organism to study the complex role of protein digestion due to its simple life cycle and amenability to techniques like RNA interference (RNAi). In this study, we were interested in deconvoluting the digestive protease system that exists in the planarian gut. To do this, we developed an alcohol-induced regurgitation technique to enrich for the gut enzymes in S. mediterranea. Using a panel of fluorescent substrates, we show that this treatment produces a sharp increase in proteolytic activity. These enzymes have broad yet diverse substrate specificity profiles. Proteomic analysis of the gut contents revealed the presence of cysteine and metallo-proteases. However, treatment with class-specific inhibitors showed that aspartyl and cysteine proteases are responsible for the majority of protein digestion. Specific RNAi knockdown of the cathepsin B-like cysteine protease (SmedCB) reduced protein degradation in vivo. Immunohistochemistry and whole-mount in situ hybridization (WISH) confirmed that the full-length and active forms of SmedCB are found in secretory cells surrounding the planaria intestinal lumen. Finally, we show that the knockdown of SmedCB reduces the speed of tissue regeneration. Defining the roles of proteases in planaria can provide insight to functions of conserved proteases in parasitic flatworms, potentially uncovering drug targets in parasites.

A vaccine consisting of Schistosoma mansoni cathepsin B formulated in Montanide ISA 720 VG induces high level protection against murine schistosomiasis

Background

Schistosomiasis is the most important human helminth infection due to its impact on public health. The clinical manifestations are chronic and significantly decrease an individual’s quality of life. Infected individuals suffer from long-term organ pathologies including fibrosis which eventually leads to organ failure. The development of a vaccine against this parasitic disease would contribute to a long-lasting decrease in disease spectrum and transmission.

Method

Our group has chosen Schistosoma mansoni (Sm) cathepsin B, a peptidase involved in parasite feeding, as a prospective vaccine candidate. Our experimental formulation consisted of recombinant Sm-cathepsin B formulated in Montanide ISA 720 VG, a squalene based adjuvant containing a mannide mono-oleate emulsifier. Parasitological burden was assessed by determining adult worm, hepatic egg, and intestinal egg numbers in each mouse. Serum was used in ELISAs to evaluate production of antigen-specific antibodies, and isolated splenocytes were stimulated with the antigen for the analysis of cytokine secretion levels.

Results

The Sm-cathepsin B and Montanide formulation conferred protection against a challenge infection by significantly reducing all forms of parasitological burdens. Worm burden, hepatic egg burden and intestinal egg burden were decreased by 60 %, 62 %, and 56 %, respectively in immunized animals compared to controls (P = 0.0002, P < 0.0001, P = 0.0009, respectively). Immunizations with the vaccine elicited robust production of Sm-cathepsin B specific antibodies (endpoint titers = 122,880). Both antigen-specific IgG1 and IgG2c titers were observed, with the former having more elevated titers. Furthermore, splenocytes isolated from the immunized animals, compared to control animals, secreted higher levels of key Th1 cytokines, IFN-γ, IL-12, and TNF-α, as well as the Th2 cytokines IL-5 and IL-4 when stimulated with recombinant Sm-cathepsin B. The Th17 cytokine IL-17, the chemokine CCL5, and the growth factor GM-CSF were also significantly increased in the immunized animals compared to the controls.

Conclusion

The formulation tested in this study was able to significantly reduce all forms of parasite burden, stimulate robust production of antigen-specific antibodies, and induce a mixed Th1/Th2 response. These results highlight the potential of Sm-cathepsin B/Montanide ISA 720 VG as a vaccine candidate against schistosomiasis.

Electronic supplementary material

The online version of this article (doi:10.1186/s12879-016-1444-z) contains supplementary material, which is available to authorized users.

Schistosoma mekongi cathepsin B and its use in the development of an immunodiagnosis

Schistosomiasis mekongi is one of the most important human parasitic diseases caused by Schistosoma mekongi in South-east Asia. The endemic area is the Mekong River sub-region from Laos to Cambodia. This parasite also infects dogs and pigs which are its alternative host species. Currently, the lack of reliable rapid diagnosis makes it difficult to monitor the infection and spreading of the disease. In this study, we screened the antigens of the parasite with sera of infected mice using Western blotting and identified proteins of interest with LC-MS/MS to obtain potential candidate proteins for diagnostic development. This assay yielded 2 immunoreactive bands at molecular masses of 31 and 22kDa. The 31kDa protein was the major band identified as cathepsin B, and its gene was cloned to obtain a full cDNA sequence (SmekCatB). The cDNA consisted of 1123bp and its longest reading frame encoded for 342 amino acids with some putative post translation modifications. The recombinant SmekCatB (rSmekCatB) with hexahistidine tag at the C-terminus was expressed in Escherichia coli and purified by Ni-NTA resin under denaturing conditions. The rSmekCatB reacted with sera of S. mekongi-infected mice. Indirect ELISA using rSmekCatB as the antigen to detect mouse antibodies, revealed a sensitivity of 91.67% for schistosomiasis mekongi and the specificity of 100%. Our data suggested that SmekCatB is one of the most promising parasitic antigens that could be used for the diagnosis of S. mekongi infection.

Lysosome-associated membrane glycoprotein (LAMP)--preliminary study on a hidden antigen target for vaccination against schistosomiasis

Our previously reported gene atlasing of schistosome tissues revealed transcripts that were highly enriched in the digestive tract of Schistosoma mansoni. From these, we selected two candidates, Sm-LAMP and Sm-NPC2 for testing as vaccine targets. The two molecules were selected on the basis of relatively high expression in the gastrodermis, their potentially important biological function, divergence from homologous molecules of the host and possible apical membrane expression in the gastrodermis. Bacterially expressed recombinant peptides corresponding to regions excluding trans-membrane domains of the selected vaccine targets were used in blinded vaccine trials in CBA mice using alum-CpG as adjuvant. Vaccine trials using the recombinant insoluble Sm-LAMP protein showed 16-25% significant reduction in total worm burden. Faecal egg count reduction was 52% and 60% in two trials, respectively, with similar results for the solubly expressed protein. Liver egg burden was reduced significantly (20% and 38%) with an insoluble recombinant Sm-LAMP in two trials, but not with the soluble recombinant form. Parasite fecundity was not affected by either Sm-LAMP protein preparations in the trials. It is concluded that Sm-LAMP may provide limited protection towards S. mansoni infections but could be used in combination with other vaccine candidates, to provide more comprehensive protection.

Proteomic Analysis on Cercariae and Schistosomula in Reference to Potential Proteases Involved in Host Invasion of Schistosoma japonicum Larvae

Schistosomiasis is a parasitic zoonosis posing great threat to human health. The infection is acquired by larval cercariae penetrating host skin and transforming into juveniles, schistosomula. Proteolytic enzymes secreted from the cercarial acetabular glands are known to aid to the skin penetration, but molecular mechanisms remain largely unclear. To profile the protein composition and identify potential invasive proteases, we developed a new method for simulating cercarial transformation and collecting schistosomula, and for the first time, we compared the proteomes of Schistosoma japonicum cercariae and schistosomula by using in-gel shotgun proteomic analysis. Totally, 1972 proteins were identified in association with ten main biological processes based on Gene Ontology analysis; 46 proteases were detected in cercariae, and among them, 25 proteases disappeared after penetrated. Notably, leishmanolysins and serine and cysteine proteases were found abundant but differentially expressed. Recombinant serine protease SjCE2b and cysteine protease SjCB2 were produced and used for validation of native proteins. Immunofluorescence and Western blotting assays detected SjCE2b and SjCB2 in cercariae but not in schistosomula, suggesting the two enzymes might be consumed upon skin migration. Our data comprehensively chart the proteomic changes during cercarial invasion, revealing the potential proteases involved, providing a platform for the development of molecular anti-infection strategy.

Structure and function of legumain in health and disease

The last years have seen a steady increase in our understanding of legumain biology that is driven from two largely uncoupled research arenas, the mammalian and the plant legumain field. Research on legumain, which is also referred to as asparaginyl endopeptidase (AEP) or vacuolar processing enzyme (VPE), is slivered, however. Here we summarise recent important findings and put them into a common perspective. Legumain is usually associated with its cysteine endopeptidase activity in lysosomes where it contributes to antigen processing for class II MHC presentation. However, newly recognized functions disperse previously assumed boundaries with respect to their cellular compartmentalisation and enzymatic activities. Legumain is also found extracellularly and even translocates to the cytosol and the nucleus, with seemingly incompatible pH and redox potential. These different milieus translate into changes of legumain's molecular properties, including its (auto-)activation, conformational stability and enzymatic functions. Contrasting its endopeptidase activity, legumain can develop a carboxypeptidase activity which remains stable at neutral pH. Moreover, legumain features a peptide ligase activity, with intriguing mechanistic peculiarities in plant and human isoforms. In pathological settings, such as cancer or Alzheimer's disease, the proper association of legumain activities with the corresponding cellular compartments is breached. Legumain's increasingly recognized physiological and pathological roles also indicate future research opportunities in this vibrant field.

Intake of Erythrocytes Required for Reproductive Development of Female Schistosoma japonicum

The reproductive development and maturation of female schistosomes are crucial since their released eggs are responsible for the host immunopathology and transmission of schistosomiasis. However, little is known about the nutrients required by female Schistosoma japonicum during its sexual maturation. We evaluated the promoting effect of several nutrients (calf serum, red blood cells (RBCs), ATP and hypoxanthine) on the reproductive development of pre-adult females at 18 days post infection (dpi) from mixed infections and at 50 dpi from unisexual infections of laboratory mice in basic medium RPMI-1640. We found RBCs, rather than other nutrients, promoted the female sexual maturation and egg production with significant morphological changes. In 27% of females (18 dpi) from mixed infections that paired with males in vitro on day 14, vitelline glands could be positively stained by Fast Blue B; and in 35% of females (50 dpi) from unisexual infections on day 21, mature vitelline cells were observed. Infertile eggs were detected among both groups. To analyze which component of mouse RBCs possesses the stimulating effect, RBCs were fractionated and included in media. However, the RBC fractions failed to stimulate development of the female reproductive organs. In addition, bovine hemoglobin hydrolysate, digested by neutral protease, was found to exhibit the promoting activity instead of untreated bovine hemoglobin. The other protein hydrolysate, lactalbumin hydrolysate, exhibited a similar effect with bovine hemoglobin hydrolysate. Using quantitative RT-PCR, we found the expression levels of four reproduction-related genes were significantly stimulated by RBCs. These data indicate that RBCs provide essential nutrients for the sexual maturation of female S. japonicum and that the protein component of RBCs appeared to constitute the key nutrient. These findings would improve laboratory culture of pre-adult schistosomes to adult worms in medium with well-defined components, which is important to investigate the function of genes related to female sexual maturation.

Activation route of the Schistosoma mansoni cathepsin B1 drug target: structural map with a glycosaminoglycan switch

Cathepsin B1 (SmCB1) is a digestive protease of the parasitic blood fluke Schistosoma mansoni and a drug target for the treatment of schistosomiasis, a disease that afflicts over 200 million people. SmCB1 is synthesized as an inactive zymogen in which the N-terminal propeptide blocks the active site. We investigated the activation of the zymogen by which the propeptide is proteolytically removed and its regulation by sulfated polysaccharides (SPs). We determined crystal structures of three molecular forms of SmCB1 along the activation pathway: the zymogen, an activation intermediate with a partially cleaved propeptide, and the mature enzyme. We demonstrate that SPs are essential for the autocatalytic activation of SmCB1, as they interact with a specific heparin-binding domain in the propeptide. An alternative activation route is mediated by an S. mansoni asparaginyl endopeptidase (legumain) which is downregulated by SPs, indicating that SPs act as a molecular switch between both activation mechanisms.

Induction of protective immune responses against schistosomiasis using functionally active cysteine peptidases

Each year schistosomiasis afflicts up to 600 million people in 74 tropical and sub-tropical countries, predominantly in the developing world. Yet we depend on a single drug, praziquantel, for its treatment and control. There is no vaccine available but one is urgently needed especially since praziquantel-resistant parasites are likely to emerge at some time in the future. The disease is caused by several worm species of the genus Schistosoma. These express several classes of papain-like cysteine peptidases, cathepsins B and L, in various tissues but particularly in their gastrodermis where they employ them as digestive enzymes. We have shown that sub-cutaneous injection of recombinant and functionally active Schistosoma mansoni cathepsin B1 (SmCB1), or a cathepsin L from a related parasite Fasciola hepatica (FhCL1), elicits highly significant protection (up to 73%) against an experimental challenge worm infection in murine models of schistosomiasis. The immune modulating properties of this subcutaneous injection can boost protection levels (up to 83%) when combined with other S. mansoni vaccine candidates, glyceraldehyde 3-phosphate dehydrogenase (SG3PDH) and peroxiredoxin (PRX-MAP). Here, we discuss these data in the context of the parasite's biology and development, and provide putative mechanism by which the native-like cysteine peptidase induce protective immune responses.

Inhibition of cathepsin B by E-64 induces oxidative stress and apoptosis in filarial parasite

BACKGROUND

Current available antifilarial drug strategies only eliminate the larval stages of filarial parasites. Therefore, there is an urgent need of drugs which are macrofilaricidals. Identification of molecular targets crucial for survival of parasite is a prerequisite for drug designing. Cathepsin B, a cysteine protease family member is known to play crucial role in the normal growth, digestion of nutrients, exsheathment of the helminth parasites. Therefore, we targeted this enzyme in the filarial parasite using its specific inhibitor, E-64.

METHODS AND FINDINGS

We have exposed the parasites to E-64 and observed their motility and viability at various time intervals. It caused marked decrease in the motility and viability of the parasites ultimately leading to their death after 8 hours. It is well known that E-64 protects the cell from apoptosis, however, it causes apoptotic effect in carcinoma cell lines. To understand the mechanism of action of E-64 on parasite survival, we have measured levels of different apoptotic markers in the treated parasites. E-64 significantly reduced the level of ced-9 and activity of tyrosine phosphatases, cytochrome c oxidase. It also activated ced-3, homolog of mammalian caspase 3 suggesting initiation of an apoptotic like event in the filarial parasites. Different antioxidant enzymes were also evaluated to further explore the mechanism behind the death of the parasites. There was marked decrease in the level of GSH and activity of Glutathione reductase and glutathione-s-transferase leading to increased generation of reactive oxygen species. This led to the induced oxidation of fatty acids and protein which might alter the mitochondrial membrane permeability.

CONCLUSION

This study suggests that inhibition of cathepsin B by E-64 generates oxidative stress followed by mitochondrial mediated apoptotic like event in filarial parasites leading to their death. Hence, suggesting filarial cathepsin B as a potential chemotherapeutic target for lymphatic filariasis.

In vitro effects of amodiaquine on paired Schistosoma mansoni adult worms at concentrations of less than 5 µg/mL

In this study, the in vitro effects of amodiaquine (AQ) monotherapy on the egg output of paired adult Schistosoma mansoni worms and their survival during in vitro culture were assessed. In addition, the gross morphological alterations of male and female worms caused by AQ were visually observed under a dissecting microscope. AQ significantly reduced the daily egg output of paired adult S. mansoni worms following incubation for 14 days at 1-5 µg/mL, but not at 0.5 µg/mL, compared with the control group. AQ also reduced the survival of male and female worms at concentrations of 2 and 5 µg/mL, respectively. Moreover, exposure to 5 µg/mL AQ caused severe swelling and/or localisation of black content in the body of all male and female worms within one or two days of incubation; subsequently, shrinkage in the male worms and elongation in the female worms were observed. The initial morphological alterations caused by AQ occurred along the intestinal tract of the male and female worms. To our knowledge, this is the first study to report not only the efficacy of AQ at concentrations lower than 5 µg/mL on paired adult S. mansoni worms, but also the effects of AQ on the intestinal tracts of worms in in vitro culture.

Lipid core peptide targeting the cathepsin D hemoglobinase of Schistosoma mansoni as a component of a schistosomiasis vaccine

The self-adjuvanting lipid core peptide (LCP) system offers a safe alternative vaccine delivery strategy, eliminating the need for additional adjuvants such as CpG Alum. In this study, we adopted the LCP as a scaffold for an epitope located on the surface of the cathepsin D hemoglobinase (Sm-CatD) of the human blood fluke Schistosoma mansoni. Sm-CatD plays a pivotal role in digestion of the fluke's bloodmeal and has been shown to be efficacious as a subunit vaccine in a murine model of human schistosomiasis. Using molecular modeling we showed that S. mansoni cathepsin D possesses a predicted surface exposed α-helix (A₂₆₃K) that corresponds to an immunodominant helix and target of enzyme-neutralizing antibodies against Necator americanus APR-1 (Na-APR-1), the orthologous protease and vaccine antigen from blood-feeding hookworms. The A₂₆₃K epitope was engineered as two peptide variants, one of which was flanked at both termini with a coil maintaining sequence, thereby promoting the helical characteristics of the native A₂₆₃K epitope. Some of the peptides were fused to a self-adjuvanting lipid core scaffold to generate LCPs. Mice were vaccinated with unadjuvanted peptides, peptides formulated with Freund's adjuvants, or LCPs. Antibodies generated to LCPs recognized native Sm-CatD within a soluble adult schistosome extract, and almost completely abolished its enzymatic activity in vitro. Using immunohistochemistry we showed that anti-LCP antibodies bound to the native Sm-CatD protein in the esophagus and anterior regions of the gastrodermis of adult flukes. Vaccines offer an alternative control strategy in the fight against schistosomiasis, and further development of LCPs containing multiple epitopes from this and other vaccine antigens should become a research priority.

Proteomic analysis of tegument-exposed proteins of female and male Schistosoma japonicum worms

The interplay between sexes is a prerequisite for female growth, reproductive maturation, and egg production, and the basis of schistosome pathopoiesis and propagation. The tegument is in direct contact with the host environment and its surface membranes are particularly crucial for schistosome survival in the definitive host. In this study, a streptavidin-biotin affinity purification technique combined with LC-MS/MS was used to analyze putative tegument-exposed proteins in female and male adult Schistosoma japonicum worms. In total, 179 proteins were identified in females and 300 in males, including 119 proteins common to both sexes, and 60 female biased and 181 male biased proteins. Some (e.g., serpin and CD36-like class B scavenger receptor) were involved in host-schistosome interactions, while some (e.g., gynecophoral canal protein) were important in the interplay between sexes. Gene Ontology analysis revealed that proteins involved in protein glycosylation and lysosome were highly expressed in females, while proteins involved in intracellular signal transduction, regulation of actin filament polymerization, and proteasome core complex were highly expressed in males. These results might elucidate physiological differences between the sexes. Our study provides new insights into schistosome growth and sexual maturity in the final host and permits the screening of vaccine candidates or drug targets for schistosomiasis.

Schistosomiasis chemotherapy

After malaria, schistosomiasis (or bilharzia) is the second most prevalent disease in Africa, and is occurring in over 70 countries in tropical and subtropical regions. It is estimated that 600 million people are at risk of infection, 200 million people are infected, and at least 200,000 deaths per year are associated with the disease. All schistosome species are transmitted through contact with fresh water that is infested with free-swimming forms of the parasite, which is known as cercariae and produced by snails. When located in the blood vessels of the host, larval and adult schistosomes digest red cells to acquire amino acids for growth and development. Vaccine candidates have been unsuccessful up to now. Against such devastating parasitic disease, the antischistosomal arsenal is currently limited to a single drug, praziquantel, which has been used for more than 35 years. Because the question of the reduction of the activity of praziquantel was raised recently, it is thus urgent to create new and safe antischistosomal drugs that should be combined with praziquantel to develop efficient bitherapies.

New insights into the machinery of blood digestion by ticks

Blood-protein digestion is a key physiological process providing essential nutrients for ticks and is a prerequisite for the transmission of tick-borne pathogens. Recently, substantial progress has been made in determining the proteolytic machinery in tick gut tissue, which is based on a dynamic multienzyme network capable of processing a vast amount of host blood. In this article we summarize our current knowledge of the molecular mechanisms of tick hematophagy and their similarities to those of Platyhelminthes, nematodes, and Plasmodium. Future research perspectives, including the potential for rational control of ticks and transmitted diseases, are also discussed.

Legumain: a biomarker for diagnosis and prognosis of human ovarian cancer

Legumain is a member of the asparaginyl endopeptidase family that is over-expressed in response to hypoxic stress on mammary adenocarcinoma, colorectal cancer, proliferating endothelial cells, and tumor-associated macrophages (TAMs). Here, we demonstrate that elevated expression of legumain in ovarian cancer by a proteomic approach using isobaric tags for relative and absolute quantification (iTRAQ) followed by liquid chromatography-mass spectrometry (LC-MS/MS). To investigate the relationship between legumain expression and ovarian cancer development, we tested legumain expression in malignant human ovarian tumors (n = 60), borderline ovarian tumors (n = 20), benign ovarian tumors (n = 20), and normal ovary samples (n = 20) using immunohistochemical assay (IHC). A correlation between legumain expression, and clinocopathologic and biological variables was also established. Importantly, increased legumain expression was validated by real-time PCR and Western blots, correlated positively with an increased malignancy of ovarian tumors (P < 0.01). In fact, patients with strong legumain expression had a worse prognosis (P = 0.03). In addition, results of in vitro experiments revealed that over-expression of legumain correlates with increased cell migration and invasion of ovarian cancer cells. Although legumain's functional role and clinical utility remain to be established, our results indicated that a sensitive assay for early expression of legumain may serve as both a potential biomarker and a molecular target for treatment of ovarian cancer.

Functional genomics approaches in parasitic helminths

As research on parasitic helminths is moving into the post-genomic era, an enormous effort is directed towards deciphering gene function and to achieve gene annotation. The sequences that are available in public databases undoubtedly hold information that can be utilized for new interventions and control but the exploitation of these resources has until recently remained difficult. Only now, with the emergence of methods to genetically manipulate and transform parasitic worms will it be possible to gain a comprehensive understanding of the molecular mechanisms involved in nutrition, metabolism, developmental switches/maturation and interaction with the host immune system. This review focuses on functional genomics approaches in parasitic helminths that are currently used, to highlight potential applications of these technologies in the areas of cell biology, systems biology and immunobiology of parasitic helminths.

Cathepsin B-like and hemoglobin-type cysteine proteases: stage-specific gene expression in Angiostrongy cantonensis

Three cysteine protease genes, cathepsin B-like enzyme gene 1, 2 (AC-cathB-1, AC-cathB-2) and hemoglobin-type cysteine protease gene (AC-hem) were isolated and described from Angiostrongylus cantonensis adult. The deduced amino acid sequence of Ac-cathB-1 and AC-cathB-2 contain all of the conserved regions of cathepsin B. AC-cathB-2 is similar to a host intrusion-related cysteine protease B from Parelaphostrongylus tenuis, and the AC-hem shares high similarity to legumain from Haemonchus contortus. AC-cathB-1 was expressed significantly higher in L1 as compared with AC-hem, the AC-cathB-2 followed; AC-cathB-2 transcripts in L3 were found increased rapidly and obviously abundant, suggesting that AC-cathB-1 and AC-cathB-2 may play an important role in intermediate and final host invasion, separately. The cysteine protease genes were more or less expressed in adult stage excepted for AC-cathB-2. As the AC-cathB-1 and AC-hem highly expressed in adult worms, suggesting AC-hem may activate AC-cathB-1 which involved in the host invasion and feeding process.

Surface-expressed enolase contributes to the adhesion of Paracoccidioides brasiliensis to host cells

Paracoccidioidomycosis is a systemic mycosis caused by the dimorphic fungus Paracoccidioides brasiliensis. Understanding the interactions between P. brasiliensis and the host tissue depends on the study of the different steps of the process of colonization, especially adhesion, in which the pathogen recognizes ligands on the surface of host cells. This study aimed to verify the role of enolase in the host cell-fungus interaction and the ability of enolase to bind to extracellular matrix components, to determine its subcellular localization, and to study the P. brasiliensis enolase amino acid sequence. The data revealed that fibronectin is the major ligand of enolase. Evaluation of the location of enolase at an ultrastructural level revealed that it is distributed in various cellular compartments, but at a high level in the cell wall. The analysis of the amino acid sequence revealed an internal plasminogen-binding motif ((254)FYKADEKKY(262)), which is conserved in most organisms and described as an important interaction site of the enolase with the host cell surface. This suggests that enolase performs additional functions related to the glycolytic pathway and also plays a role of adhesion in P. brasiliensis. Therefore, this study increases the knowledge about the characteristics of enolase and its influence on the binding process of P. brasiliensis.

Structural basis for inhibition of cathepsin B drug target from the human blood fluke, Schistosoma mansoni

Schistosomiasis caused by a parasitic blood fluke of the genus Schistosoma afflicts over 200 million people worldwide. Schistosoma mansoni cathepsin B1 (SmCB1) is a gut-associated peptidase that digests host blood proteins as a source of nutrients. It is under investigation as a drug target. To further this goal, we report three crystal structures of SmCB1 complexed with peptidomimetic inhibitors as follows: the epoxide CA074 at 1.3 Å resolution and the vinyl sulfones K11017 and K11777 at 1.8 and 2.5 Å resolutions, respectively. Interactions of the inhibitors with the subsites of the active-site cleft were evaluated by quantum chemical calculations. These data and inhibition profiling with a panel of vinyl sulfone derivatives identify key binding interactions and provide insight into the specificity of SmCB1 inhibition. Furthermore, hydrolysis profiling of SmCB1 using synthetic peptides and the natural substrate hemoglobin revealed that carboxydipeptidase activity predominates over endopeptidolysis, thereby demonstrating the contribution of the occluding loop that restricts access to the active-site cleft. Critically, the severity of phenotypes induced in the parasite by vinyl sulfone inhibitors correlated with enzyme inhibition, providing support that SmCB1 is a valuable drug target. The present structure and inhibitor interaction data provide a footing for the rational design of anti-schistosomal inhibitors.

Heme and blood-feeding parasites: friends or foes?

Hemoparasites, like malaria and schistosomes, are constantly faced with the challenges of storing and detoxifying large quantities of heme, released from their catabolism of host erythrocytes. Heme is an essential prosthetic group that forms the reactive core of numerous hemoproteins with diverse biological functions. However, due to its reactive nature, it is also a potentially toxic molecule. Thus, the acquisition and detoxification of heme is likely to be paramount for the survival and establishment of parasitism. Understanding the underlying mechanism involved in this interaction could possibly provide potential novel targets for drug and vaccine development, and disease treatment. However, there remains a wide gap in our understanding of these mechanisms. This review summarizes the biological importance of heme for hemoparasite, and the adaptations utilized in its sequestration and detoxification.

Vector-based RNA interference of cathepsin B1 in Schistosoma mansoni

In helminth parasites, proteolytic enzymes have been implicated in facilitating host invasion, moulting, feeding, and evasion of the host immune response. These key functions render them potential targets for anti-parasite chemotherapy and immunotherapy. Schistosomes feed on host blood and the digested haemoglobin is their major source of amino acids. Haemoglobin digestion is essential for parasite development, growth, and reproduction. We recently reported the use of pseudotyped Moloney murine leukaemia virus to accomplish transformation of Schistosoma mansoni. Here, we report the design of a viral vector expressing a dsRNA hairpin to silence expression of the schistosome cathepsin B1 (SmCB1) gene. We observed 80% reduction in transcript level 72 h after virus exposure and complete silencing of enzyme activity in transduced worms. This is the first report using this technology in any helminth parasite. It will facilitate the evaluation of potential drug targets and biochemical pathways for novel interventions in schistosomes.

Molecular cloning, characterization and expression analysis of cathepsin C gene involved in the antibacterial response in Chinese mitten crab, Eriocheir sinensis

Cathepsins, a superfamily of hydrolytic enzymes produced and enclosed within lysosomes, function in immune response in vertebrates; however, their function within the innate immune system of invertebrates remains largely unknown. Therefore, we investigated the immune functionality of cathepsin C (catC) in Chinese mitten crab (Eriocheir sinensis), a commercially important and disease vulnerable aquaculture species. The full-length catC cDNA (1481 bp) was cloned via PCR based upon an initial expressed sequence tag (EST) isolated from a hepatopancreatic cDNA library. The catC cDNA contained a 1284 bp open reading frame (ORF) that encoded a putative 427 amino acid (aa) protein. Comparisons with other reported invertebrate and vertebrate cathepsins sequences revealed high percent identity. CatC mRNA expression in E. sinensis was responsive in hemocytes to a Vibrio anguillarum challenge, with peak exposure observed 6 h post-injection. Collectively, data demonstrate the successful isolation of catC from the Chinese mitten crab, and its involvement in the innate immune system of an invertebrate.

Survey of transcripts expressed by the invasive juvenile stage of the liver fluke Fasciola hepatica

Background

The common liver fluke Fasciola hepatica is the agent of a zoonosis with significant economic consequences in livestock production worldwide, and increasing relevance to human health in developing countries. Although flukicidal drugs are available, re-infection and emerging resistance are demanding new efficient and inexpensive control strategies. Understanding the molecular mechanisms underlying the host-parasite interaction provide relevant clues in this search, while enlightening the physiological adaptations to parasitism. Genomics and transcriptomics are still in their infancy in F. hepatica, with very scarce information available from the invasive newly excysted juveniles (NEJ). Here we provide an initial glimpse to the transcriptomics of the NEJ, the first stage to interact with the mammalian host.

Results

We catalogued more than 500 clusters generated from the analysis of F. hepatica juvenile expressed sequence tags (EST), several of them not detected in the adult stage. A set of putative F. hepatica specific transcripts, and a group of sequences conserved exclusively in flatworms were identified. These novel sequences along with a set of parasite transcripts absent in the host genomes are putative new targets for future anti-parasitic drugs or vaccine development.

Comparisons of the F. hepatica sequences with other metazoans genomes or EST databases were consistent with the basal positioning of flatworms in the bilaterian phylogeny. Notably, GC content, codon usage and amino acid frequencies are remarkably different in Schistosomes to F. hepatica and other trematodes.

Functional annotation of predicted proteins showed a general representation of diverse biological functions. Besides proteases and antioxidant enzymes expected to participate in the early interaction with the host, various proteins involved in gene expression, protein synthesis, cell signaling and mitochondrial enzymes were identified. Differential expression of secreted protease gene family members between juvenile and adult stages may respond to different needs during host colonization.

Conclusion

The knowledge of the genes expressed by the invasive stage of Fasciola hepatica is a starting point to unravel key aspects of this parasite's biology. The integration of the emerging transcriptomics, and proteomics data and the advent of functional genomics tools in this organism are positioning F. hepatica as an interesting model for trematode biology.

Differential patterns of liver proteins in experimental murine hepatosplenic schistosomiasis

Schistosoma mansoni eggs produced by adult worms in the mesenteric vasculature become trapped in the liver, where they induce granulomatous lesions and strong immune responses. Infected individuals suffer from intestinal schistosomiasis (INT) in 90% of cases, whereas the remaining 10% present with severe hepatosplenic schistosomiasis (HS). The CBA/J mouse model mimics human disease, with 20% of infected mice developing hypersplenomegaly syndrome (HSS) that resembles HS and 80% developing moderate splenomegaly syndrome (MSS) similar to INT. We studied differential patterns of protein expression in livers of 20-week-infected CBA/J mice with MSS or HSS to understand the molecular changes that underlie these two disease forms. Using differential in-gel electrophoresis to identify differentially expressed protein spots, we found 80 protein spots significantly changed with infection and 35 changes specific to severe disease. In particular, the abundances of prohibitin 2, transferrin isoforms, and major urinary protein isoforms were significantly altered in HSS mice. Furthermore, annexin 5, glutathione S-transferase pi class, and S. mansoni phosphoenolpyruvate carboxykinase expression levels changed significantly with schistosome infection. Additionally, levels of major urinary protein decreased and levels of transferrin increased significantly in the sera of HSS mice compared to levels in sera of MSS or control mice, and these differences correlated to the degree of splenomegaly. These findings indicate that the liver protein abundances differ between MSS and HSS mice and may be used for the development of diagnostic markers for the early detection of hepatosplenic schistosomiasis.

Schistosoma genomics: new perspectives on schistosome biology and host-parasite interaction

Schistosomiasis, caused mainly by Schistosoma japonicum, S. mansoni, and S. hematobium, remains one of the most prevalent and serious parasitic diseases worldwide. The blood flukes have a complex life cycle requiring adaptation for survival in fresh water as free-living forms and as parasites in snail intermediate and vertebrate definitive hosts. Functional genomics analyses, including transcriptomic and proteomic approaches, have been performed on schistosomes, in particular S. mansoni and S. japonicum, using powerful high-throughput methodologies. These investigations have not only chartered gene expression profiles across genders and developmental stages within mammalian and snail hosts, but have also characterized the features of the surface tegument, the eggshell and excretory-secretory proteomes of schistosomes. The integration of the genomic, transcriptomic, and proteomic information, together with genetic manipulation on individual genes, will provide a global insight into the molecular architecture of the biology, pathogenesis, and host-parasite interactions of the human blood flukes. Importantly, these functional genomics analyses lay a foundation on which to develop new antischistosome vaccines as well as drug targets and diagnostic markers for treatment and control of schistosomiasis.

Immunodominant antigens in Naegleria fowleri excretory--secretory proteins were potential pathogenic factors

Naegleria fowleri, a ubiquitous pathogenic free-living amoeba, is the most virulent species and causes primary amoebic meningoencephalitis in laboratory animals and humans. The parasite secretes various inducing molecules as biological responses, which are thought to be involved in pathophysiological and immunological events during infection. To investigate what molecules of N. fowleri excretory-secretory proteins (ESPs) are related with amoebic pathogenicity, N. fowleri ESPs fractionated by two-dimensional electrophoresis were reacted with N. fowleri infection or immune sera. To identify immunodominant ESPs, six major protein spots were selected and analyzed by N-terminal sequencing. Finally, six proteins, 58, 40, 24, 21, 18, and 16 kDa of molecular weight, were partially cloned and matched with reference proteins as follow: 58 kDa of exendin-3 precursor, 40 kDa of secretory lipase, 24 kDa of cathepsin B-like proteases and cysteine protease, 21 kDa of cathepsin B, 18 kDa of peroxiredoxin, and 16 kDa of thrombin receptor, respectively. These results suggest that N. fowleri ESPs contained important proteins, which may play an important role in the pathogenicity of N. fowleri.