Echinococcus multilocularis laminated-layer components and the E14t 14-3-3 recombinant protein decrease NO production by activated rat macrophages in vitro

Comparative characterization of microRNA-71 of Echinococcus granulosus exosomes

Cystic echinococcosis (CE) is a global zoonotic disease caused by Echinococcus granulosus, posing a great threat to human and animal health. MiRNAs are small regulatory noncoding RNA involved in the pathogenesis of parasitic diseases, possibly via exosomes. Egr-miR-71 has been identified as one of the miRNAs in the blood of CE patients, but its secretory characteristics and functions remains unclear. Herein, we studied the secretory and biological activity of exosomal egr-miR-71 and its immunoregulatory functions in sheep peripheral blood mononuclear cells (PBMCs). Our results showed that egr-miR-71 was enriched in the exosome secreted by protoscoleces with biological activity. These egr-miR-71-containing exosomes were easily internalized and then induced the dysregulation of cytokines (IL-10 and TNF-α), nitric oxide (NO) and key components (CD14 and IRF5) in the LPS/TLR4 pathway in the coincubated sheep PBMCs. Similarly, egr-miR-71 overexpression also altered the immune functions but exhibited obvious differences in regulation of the cytokines and key components, preferably inhibiting proinflammatory cytokines (IL-1α, IL-1β and TNF-α). These results demonstrate that exosomal egr-miR-71 is bioactive and capacity of immunomodulation of PBMCs, potentially being involved in immune responses during E. granulosus infection.

Ex vivo Immuno-modulatory effect of Echinococcus granulosus laminated layer during allergic rhinitis and allergic asthma: A study in Algerian Patients

The effect of helminthic infections on allergic diseases and asthma is still inconclusive. Moreover, there is considerable evidence suggesting that nitric oxide (NO), metalloproteinases and pro-inflammatory cytokines play a significant role in the physiopathology of these diseases. In this sense, the aim of our study is to investigate the ex vivo immunomodulatory effect of the laminated layer (LL, outside layer of parasitic cyst) of the helminth Echinococcus granulosus on NO, IL-17A and IL-10 production. In the first step of our study, we evaluated in vivo the NO, MMP-9, IL-17A, IL-10 levels in Algerian patients with allergic asthma and allergic rhinitis and their changes in relation with exacerbation status of the patients. In the principal part of our work, we assessed NO, IL-10 and IL-17A levels in supernatants of patients PBMCs cultures before and after stimulation with LL. Our results indicate a significant reduction in NO production by PBMCs of patients with allergic rhinitis and allergic asthma whether mild, moderate or severe after stimulation with LL. Interestingly, LL induces a significant decrease in the production of NO and IL17-A levels as well as an increase in the production of IL-10 in the cultures performed with PBMC of patients with severe allergic asthma. Importantly, our data indicate that LL exert a down-modulatory effect on inflammatory mediators (NO, IL-17A) and up immune-regulatory effect on IL-10 production. Collectively, our study supports the hygiene hypothesis suggesting that Echinococcus granulosus infection like other helminths could prevent and/or modulate inflammation responses during inflammatory diseases.

Sinomenine attenuated dextran sulfate sodium-induced inflammatory responses by promoting 14-3-3θ protein and inhibiting NF-κB signaling

ETHNOPHARMACOLOGICAL RELEVANCE

The rhizome of Chinese medical plant QingTeng (scientific name: Sinomenium acutum (Thunb.) Rehd. et Wils.) is widely used by traditional medical doctors for anti-inflammation and immunoregulatory in China and other Asian countries.

AIM OF THE STUDY

The purpose of this study was to evaluate the effects and possible mechanisms of sinomenine resistance against DSS-induced inflammation in vitro and in vivo.

MATERIALS AND METHODS

The UC model was induced by treating female mice with 3% DSS in vivo and human colonic epithelial cells (Hcoepic) with 0.8 mg/ml DSS in vitro. The mice and Hcoepic were then treated with sinomenine. Inflammatory factors were detected using ELISA and qRT-PCR. Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) p65 and 14-3-3θ were analyzed by bioinformatic analysis and verified by western blotting, immunofluorescent staining or immunohistochemistry.

RESULTS

DSS-induced Hcoepic underwent high inflammation and oxidative stress conditions, whereas sinomenine reduced the uncontrolled immune microenvironment by suppressing NF-κB signaling and targeting 14-3-3θ. Knockdown of 14-3-3θ decreased the protective effect of sinomenine against DSS-induced inflammation in vitro. Moreover, sinomenine promoted 14-3-3θ protein expression and inhibited NF-κB p65 signaling in DSS-induced mice.

CONCLUSION

These findings suggest that 14-3-3θ plays an important role in sinomenine against DSS treatment, and sinomenine could be considered a potential drug for the treatment of UC.

Extracellular vesicles from Fasciola gigantica induce cellular response to stress of host cells

Extracellular vesicles (EVs) from parasitic helminths play an important role in immunomodulation. However, EVs are little studied in the important parasite Fasciola gigantica. Here the ability of EVs from F. gigantica to induce cellular response to stress (reactive oxygen species generation, autophage and DNA damage response) in human intrahepatic biliary epithelial cells (HIBEC) was investigated. F. gigantica-derived EVs were isolated by ultracentrifugation, and identified with transmission electron microscopy, nanoparticle size analysis and parasite-derived EV markers. Internalization of EVs by HIBEC was determined by confocal immunofluorescence microscopy and flow cytometry. ROS levels in HIBEC were detected by molecular probing. EVs-induced autophagy and DNA-damaging effects were determined by evaluating expression levels of light chain 3B protein (LC3B), phosphor- H2A.X and phosphor-Chk1, respectively. Results revealed that EVs with sizes predominately ranging from 39 to 110 nm in diameter were abundant in adult F. gigantica and contained the parasite-derived marker proteins enolase and 14-3-3, and EVs were internalized by HIBEC. Further, uptake of EVs into HIBEC was associated with increased levels of reactive oxygen species, LC3Ⅱ, phosphor-H2A.X and phosphor-Chk1, suggesting EVs are likely to induce autophagy and DNA damage & repair processes. These results indicate F. gigantica EVs are associated with modulations of host cell responses and have a potential important role in the host-parasite interactions.

Dual Role of Hepatic Macrophages in the Establishment of the Echinococcus multilocularis Metacestode in Mice

Echinococcus multilocularis larvae, predominantly located in the liver, cause a tumor-like parasitic disease, alveolar echinococcosis (AE), that is characterized by increased infiltration of various immune cells, including macrophages, around the lesion that produces an "immunosuppressive" microenvironment, favoring its persistent infection. However, the role of hepatic macrophages in the host defense against E. multilocularis infection remains poorly defined. Using human liver tissues from patients with AE and a hepatic experimental mouse model of E. multilocularis, we investigated the phenotype and function of hepatic macrophages during the parasite infection. In the present study, we found that a large number of CD68⁺ macrophages accumulated around the metacestode lesion in the liver of human AE samples and that both S100A9⁺ proinflammatory (M1 phenotype) and CD163⁺ anti-inflammatory (M2 phenotype) macrophages were significantly higher in close liver tissue (CLT) than in distant liver tissue (DLT), whereas M2 macrophages represent the dominant macrophage population. Furthermore, E. multilocularis-infected mice exhibited a massive increase in macrophage (F4/80⁺) infiltration in the liver as early as day 5, and the infiltrated macrophages were mainly monocyte-derived macrophages (CD11b^hi F4/80^int MoMFs) that preferentially differentiated into the M1 phenotype (iNOS⁺) at the early stage of E. multilocularis infection and then polarized to anti-inflammatory macrophages of the M2 phenotype (CD206⁺) at the chronic stage of infection. We further showed that elimination of macrophages by treatment of mice with clodronate-liposomes before E. multilocularis infection impaired worm expulsion and was accompanied by a reduction in liver fibrosis, yielding a high parasite burden. These results suggest that hepatic macrophages may play a dual role in the establishment and development of E. multilocularis metacestodes in which early larvae clearance is promoted by M1 macrophages while persistent metacestode infection is favored by M2 macrophages.

Proteomic analysis of soluble protein extract of adult Toxocara cati

Toxocara cati is a cat roundworm and the causative agent of toxocariasis as a cosmopolitan zoonotic disease. As no information has been reported so far, identification of T. cati proteins can be useful for the development of new diagnostic strategies. This study was conducted to identify the major proteins in the adult T. cati tegument using bi-dimensional electrophoresis (2-DE) and shotgun proteomics. A total proteins were identified, among them the metabolic enzymes were the largest group, including: Enolase, triose phosphate isomerase, fructose-bisphosphate aldolase, aldehyde dehydrogenase. The other important protein groups recognized in T. cati, belong to the HSP-family, the structure and motor proteins, such as actin. The role of these proteins have been implicated in parasite-host interactions and modulating cellular immune response, immune regulation in evasion mechanisms of the host immune response. Characterizing T. cati adult proteins play a key role not only in host-parasite interactions, but also in the discovery of drug targets, subunit vaccines against toxocariasis, immunodiagnostic kits for toxocariasis and the identification of novel immuno-modulators that can form the next generation of therapeutic possibilities for inflammatory diseases.

miRNA-seq of Echinococcus multilocularis Extracellular Vesicles and Immunomodulatory Effects of miR-4989

Alveolar echinococcosis caused by Echinococcus multilocularis is an important zoonotic disease. In the infected mice, emu-miR-4989-3p is present in sera, but its role remains unknown. Using high-throughput sequencing and qPCR, emu-miR-4989-3p was herein confirmed to be encapsulated into E. multilocularis extracellular vesicles. In the transfected macrophages, emu-miR-4989-3p was demonstrated to significantly inhibit NO production compared to the control (p < 0.05). Moreover, transfection of emu-miR-4989-3p also gave rise to the increased expression of TNF-α (p < 0.01). Furthermore, emu-miR-4989-3p induced the dysregulation of several key components in the LPS/TLR4 signaling pathway compared with the control, especially TLR4 and NF-κB that both were upregulated. Conversely, the NO production and the expression of TNF-α, TLR4 and NF-κB tended to be increased and decreased in the mimics-transfected cells upon emu-miR-4989-3p low expression, respectively. These results suggest that emu-miR-4989-3p is one of ‘virulence’ factors encapsulated into the extracellular vesicles, potentially playing a role in the pathogenesis of E. multilocularis.

Proteomic identification of galectin-11 and -14 ligands from Fasciola hepatica

Fasciola hepatica is a globally distributed zoonotic trematode that causes fasciolosis in livestock, wildlife, ruminants and humans. Fasciolosis causes a significant economic impact on the agricultural sector and affects human health. Due to the increasing prevalence of triclabendazole resistance in F. hepatica, alternative treatment methods are required. Many protein antigens have been trialled as vaccine candidates with low success, however, the tegument of F. hepatica is highly glycosylated and the parasite-derived glycoconjugate molecules have been identified as an important mediator in host-parasite interactions and as prime targets for the host immune system. Galectin-11 (LGALS-11) and galectin-14 (LGALS-14) are two ruminant-specific glycan-binding proteins, showing upregulation in the bile duct of sheep infected with F. hepatica, which are believed to mediate host-parasite interaction and innate immunity against internal parasites. For the first known time, this study presents the ligand profile of whole worm and tegument extracts of F. hepatica that interacted with immobilised LGALS-11 and LGALS-14. LGALS-14 interacted with a total of 255 F. hepatica proteins. The protein which had the greatest interaction was identified as an uncharacterised protein which contained a C-type lectin domain. Many of the other proteins identified were previously trialled vaccine candidates including glutathione S-transferase, paramyosin, cathepsin L, cathepsin B, fatty acid binding protein and leucine aminopeptidase. In comparison to LGALS-14, LGALS-11 interacted with only 49 F. hepatica proteins and it appears to have a much smaller number of binding partners in F. hepatica. This is, to our knowledge, the first time host-specific lectins have been used for the enrichment of F. hepatica glycoproteins and this study has identified a number of glycoproteins that play critical roles in host-parasite interactions which have the potential to be novel vaccine candidates.

Inducible nitric oxide synthase controls experimental Strongyloides infection

Infection with Strongyloides sp. induces a host immune response, predominantly the Th2 type, that is able to eliminate the parasite. However, little is known about the role of the nitric oxide (NO) mediator, induced by the enzyme nitric oxide synthase (NOS), in strongyloidiasis. Therefore, in this study, we investigated the immune response of mice genetically deficient in the enzyme inducible nitric oxide synthase (iNOS^-/- ), infected with Strongyloides venezuelensis. C57BL/6 wild-type (WT) and iNOS^-/- mice were individually inoculated by subcutaneous injection of 3000 S. venezuelensis L3 larvae. In the absence of iNOS, mice were more susceptible to the infection than WT animals, in which the parasite was completely eliminated. The overall production of cytokines and specific IgG, IgG1 or IgE antibodies against the parasite was significantly lowered in infected iNOS^-/- mice. The expression of iNOS was observed in the intestine of WT hosts but mainly in the wall of the parasite, despite the presence of iNOS in mice. Altogether, we concluded that iNOS expression may play an important role in the control of S. venezuelensis infection.

A 53 KDa Glycan Antigen of Hydatid Cyst Wall May Involve in Evasion from Host Immune System

Background:

Recent studies have shown that similar host glycan antigens are expressed by helminths such as Echinococcus granulosus hydatid cysts to evade from host immune system. In this work to investigate these antigens further, immunological cross-reactivity between human sera and hydatid cyst wall antigens has been investigated.

Materials and Methods:

Hydatid cyst wall antigens were used in enzyme-linked immunosorbent assay and Western immunoblotting and probed with pooled sera of hydatidosis patients and healthy controls. Sodium metaperiodate treatment was used to investigate glycan antigens.

Results:

A band with molecular weight about 53 KDa reacted with both hydatid patients' sera and also normal human sera. It has been shown that this band was a glycan antigen.

Conclusions:

A 53 KDa glycan antigen of hydatid cyst wall that reacted with all human sera may have an important role for evasion from host immune system.

Identification of emu-TegP11, an EF-hand domain-containing tegumental protein of Echinococcus multilocularis

Tegumental proteins (TegPs) are a group of proteins that coat on the surface of worms, mainly being involved in ion uptake and immune evasion. Echinococcus species have many TegPs, but none of them have been characterized and their role remains unclear. The genome-wide analysis revealed that there were at least 14 tegp genes (tegp1 - 14) in Echinococcus species, the majority of which were found to contain an EF-hand domain or a dynein light chain-like domain or both. Despite low identity, all TegP11 proteins from 25 flatworms were conserved in structure. Echinococcus multilocularis TegP11 (emu-TegP11) was verified to be secreted by extracellular vesicles and to be localized in different spatiotemporal patterns in protoscoleces. Moreover, emu-TegP11 was also shown to have weak or no Ca²⁺-binding capacity. In treated macrophages, emu-TegP11 interfered with the small RNA-induced silencing pathway via inducing ectopic expression of some key component genes. Additionally, emu-TegP11 remarkably promoted NO secretion possibly by upregulation of inos gene expression (p < 0.05). It was further shown that emu-TegP11 acted as a suppressor of inflammation, with il-12B and il-1β being significantly down-regulated (p < 0.01), and il-10 and il-4 being significantly upregulated (p < 0.05). The study demonstrates a regulatory role of emu-TegP11, likely acting as a immunomodulator to be involved in regulation of host immune system during Echinococcus infection.

Larval Echinococcus multilocularis infection reduces dextran sulphate sodium-induced colitis in mice by attenuating T helper type 1/type 17-mediated immune reactions

The tumour‐like growth of larval Echinococcus multilocularis tissue (causing alveolar echinococcosis, AE) is directly linked to the nature/orientation of the periparasitic host immune‐mediated processes. Parasite‐mediated immune suppression is a hallmark triggering infection outcome in both chronic human and murine AE. So far, little is known about secondary systemic immune effects of this pathogen on other concomitant diseases, e.g. endogenous gut inflammation. We examined the influence of E. multilocularis infection on murine dextran sodium sulphate (DSS) ‐induced colitis. At 3 months after E. multilocularis infection (chronic stage), the mice were challenged with 3% DSS in the drinking water for 5 days plus subsequently with tap water (alone) for another 4 days. After necropsy, fixed tissues/organs were sectioned and stained with haematoxylin & eosin for assessing inflammatory reactions. Cytokine levels were measured by flow cytometry and quantitative RT‐PCR. Colitis severity was assessed (by board‐certified veterinary pathologists) regarding (i) colon length, (ii) weight loss and (iii) a semi‐quantitative score of morphological changes. The histopathological analysis of the colon showed a significant reduction of DSS‐induced gut inflammation by concomitant E. multilocularis infection, which correlated with down‐regulation of T helper type 1 (Th1)/Th17 T‐cell responses in the colon tissue. Echinococcus multilocularis infection markedly reduced the severity of DSS‐induced gut inflammation upon down‐regulation of Th1/Th17 cytokine expression and attenuation of CD11b⁺ cell activation. In conclusion, E. multilocularis infection remarkably reduces DSS‐induced colitis in mice by attenuating Th1/Th17‐mediated immune reactions.

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

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

Immunoregulation in larval Echinococcus multilocularis infection

Alveolar echinococcosis (AE) is a clinically very severe zoonotic helminthic disease, characterized by a chronic progressive hepatic damage caused by the continuous proliferation of the larval stage (metacestode) of Echinococcus multilocularis. The proliferative potential of the parasite metacestode tissue is dependent on the nature/function of the periparasitic immune-mediated processes of the host. Immune tolerance and/or down-regulation of immunity are a marked characteristic increasingly observed when disease develops towards its chronic (late) stage of infection. In this context, explorative studies have clearly shown that T regulatory (Treg) cells play an important role in modulating and orchestrating inflammatory/immune reactions in AE, yielding a largely Th2-biased response, and finally allowing thus long-term parasite survival, proliferation and maturation. AE is fatal if not treated appropriately, but the current benzimidazole chemotherapy is far from optimal, and novel options for control are needed. Future research should focus on the elucidation of the crucial immunological events that lead to anergy in AE, and focus on providing a scientific basis for the development of novel and more effective immunotherapeutical options to support cure AE by abrogating anergy, anticipating also that a combination of immuno- and chemotherapy could provide a synergistic therapeutical effect.

Immunology of Alveolar and Cystic Echinococcosis (AE and CE)

Cystic and alveolar echinococcosis are severe chronic helminthic diseases caused by the cystic growth or the intrahepatic tumour-like growth of the metacestode of Echinococcus granulosus or Echinococcus multilocularis, respectively. Both parasites have evolved sophisticated strategies to escape host immune responses, mainly by manipulating and directing this immune response towards anergy and/or tolerance. Recent research studies have revealed a number of respective immunoregulatory mechanisms related to macrophages and dendritic cell as well as T cell activities (regulatory T cells, Tregs). A better understanding of this complex parasite-host relationship, and the elucidation of specific crucial events that lead to disease, represents targets towards the development of novel treatment strategies and options.

Recombinant protein of Haemonchus contortus 14-3-3 isoform 2 (rHcftt-2) decreased the production of IL-4 and suppressed the proliferation of goat PBMCs in vitro

14-3-3 proteins have been found to be an excreted/secreted antigen and assumed to be released into the host-parasite interface and described in several unicellular and multicellular parasites. However, little is known about the immunomodulatory effects of H. controtus 14-3-3 protein on host cell. In present study, 14-3-3 isoform 2 gene, designated as Hcftt-2, was amplified by reverse transcription-polymerase chain reaction (RT-PCR) from the adult H. contortus cDNA and cloned into expression plasmid pET32a (+) and expression of the recombinant protein (rHcftt-2) was induced by IPTG. Binding activity of rHcftt-2 to goat peripheral blood mononuclear cells (PBMCs) was confirmed by immunofluorescence assay (IFA) and modulatory effects on cytokine production, cell proliferation, cell migration and nitric oxide (NO) production were observed by co-incubation of rHcftt-2 with goat PBMCs. Sequence analysis showed that it had significant homology with the known 14-3-3 protein isoform 2. Results of IFA revealed that, the rHcftt-2 was bound to the cell surface. We found that, the productions of IL10, IL-17, IFN-γ and cell migration of PBMCs were increased after the cells were incubated with rHCftt-2. However, the productions of IL-4, NO and cell proliferation of the PBMCs were significantly decreased in dose depended manner. Our results showed that the Hcftt-2 played important suppressive regulatory effects on the goat PBMCs.

Functional analysis of Paracoccidioides brasiliensis 14-3-3 adhesin expressed in Saccharomyces cerevisiae

BACKGROUND

14-3-3 proteins comprise a family of eukaryotic multifunctional proteins involved in several cellular processes. The Pb14-3-3 of Paracoccidioides brasiliensis seems to play an important role in the Paracoccidioides-host interaction. Paracoccidioides brasiliensis is an etiological agent of paracoccidioidomycosis, which is a systemic mycosis that is endemic in Latin America. In the initial steps of the infection, Paracoccidioides spp. synthetizes adhesins that allow it to adhere and invade host cells. Therefore, the aim of this work was to perform a functional analysis of Pb14-3-3 using Saccharomyces cerevisiae as a model.

RESULTS

The functional analysis of Pb14-3-3 was performed in S. cerevisiae, and it was found that Pb14-3-3 partially complemented S. cerevisiae proteins Bmh1p and Bmh2p, which are recognized as two yeast 14-3-3 homologues. When we evaluated the adhesion profile of S. cerevisiae transformants, Pb14-3-3 acted as an adhesin in S. cerevisiae; however, Bmh1p did not show this function. The influence of Pb14-3-3 in S. cerevisiae ergosterol pathway was also evaluated and our results showed that Pb14-3-3 up-regulates genes involved in ergosterol biosynthesis.

CONCLUSIONS

Our data showed that Pb14-3-3 was able to partially complement Bmh1p and Bmh2p proteins in S. cerevisiae; however, we suggest that Pb14-3-3 has a differential role as an adhesin. In addition, Pb-14-3-3 may be involved in Paracoccidioides spp. ergosterol biosynthesis which makes it an interest as a therapeutic target.

A protective effect of the laminated layer on Echinococcus granulosus survival dependent on upregulation of host arginase

The role of nitric oxide (NO) in host defense against Echinococcus granulosus larvae was previously reported. However, NO production by NOS2 (inducible NO synthase) is counteracted by the expression of Arginase. In the present study, our aim is to evaluate the involvement of the laminated layer (external layer of parasitic cyst) in Arginase induction and the protoscoleces (living and infective part of the cyst) survival. Our in vitro results indicate that this cystic compound increases the Arginase activity in macrophages. Moreover, C-type lectin receptors (CLRs) with specificity for mannan and the TGF-β are implicated in this effect as shown after adding Mannan and Anti-TGFβ. Interestingly, the laminated layer increases protoscoleces survival in macrophages-parasite co-cultures. Our results indicate that the laminated layer protects E. granulosus against the NOS2 protective response through Arginase pathway, a hallmark of M2 macrophages.

Crude extract of hydatid laminated layer from Echinococcus granulosus cyst attenuates mucosal intestinal damage and inflammatory responses in Dextran Sulfate Sodium induced colitis in mice

Background

Inflammatory bowel disease is an immunologically mediated disease. Notably, it is less common in countries where there is a greater risk of exposure to helminths. In our study, we examined the modulatory effect of the laminated layer extracted from the cyst wall of a helminth parasite, Echinococcus granulosus, on dextran sulfate sodium (DSS)-induced colitis in mice.

Methods

An acute colitis was induced in BALB/c mice using 2.5% w/v DSS in drinking water. The crude extract of E. granulosus laminated layer was injected intraperitoneally daily, starting 3 days before colitis induction. The Disease Activity Index was monitored daily, colon length and weight were measured and histological scores were evaluated. Nitric oxide (NO) and cytokine levels (interferon γ (IFN-γ), tumor necrosis factor α (TNF-α) and interleukin 10 (IL-10)) were assessed by enzyme-linked immunosorbent assay. In addition, the colonic expression of inducible nitric oxide synthase (iNOS) and nuclear factor-κB (NF-κB) was examined. Statistical analyses were performed by one-way analysis of variance and the survival rate was analyzed by the long rank test.

Results

Hydatid laminated layer pretreatment significantly improved the clinical symptoms and histological scores (*** p < 0.01) observed during DSS-induced colitis and maintained mucus production by goblet cells. Furthermore, treatment with hydatid laminated layer caused a significant decrease in NO, IFN-γ (** p < 0.01) and TNF-α production (* p < 0.05) and an increase in IL-10 production. These results were associated with localized downregulation of iNOS and NF-κB expression.

Conclusions

Our results demonstrate the potent anti-inflammatory effects of hydatid laminated layer. Furthermore, preventive treatment with the laminated layer played a beneficial role in maintaining the integrity of the intestinal mucosal barrier against DSS-induced injury.

Transcriptome profiles of the protoscoleces of Echinococcus granulosus reveal that excretory-secretory products are essential to metabolic adaptation

Background

Cystic hydatid disease (CHD) is caused by the larval stages of the cestode and affects humans and domestic animals worldwide. Protoscoleces (PSCs) are one component of the larval stages that can interact with both definitive and intermediate hosts. Previous genomic and transcriptomic data have provided an overall snapshot of the genomics of the growth and development of this parasite. However, our understanding of how PSCs subvert the immune response of hosts and maintains metabolic adaptation remains unclear. In this study, we used Roche 454 sequencing technology and in silico secretome analysis to explore the transcriptome profiles of the PSCs from E. granulosus and elucidate the potential functions of the excretory-secretory proteins (ESPs) released by the parasite.

Methodology/Principal Findings

A large number of nonredundant sequences as unigenes were generated (26,514), of which 22,910 (86.4%) were mapped to the newly published E. granulosus genome and 17,705 (66.8%) were distributed within the coding sequence (CDS) regions. Of the 2,280 ESPs predicted from the transcriptome, 138 ESPs were inferred to be involved in the metabolism of carbohydrates, while 124 ESPs were inferred to be involved in the metabolism of protein. Eleven ESPs were identified as intracellular enzymes that regulate glycolysis/gluconeogenesis (GL/GN) pathways, while a further 44 antigenic proteins, 25 molecular chaperones and four proteases were highly represented. Many proteins were also found to be significantly enriched in development-related signaling pathways, such as the TGF-β receptor pathways and insulin pathways.

Conclusions/Significance

This study provides valuable information on the metabolic adaptation of parasites to their hosts that can be used to aid the development of novel intervention targets for hydatid treatment and control.

The successful infection establishment of parasites depends on their ability to combat their host's immune system while maintaining metabolic adaptation to their hosts. The mechanisms of these processes are not well understood. We used the protoscoleces (PSCs) of E. granulosus as a model system to study this complex host-parasite interaction by investigating the role of excretory-secretory proteins (ESPs) in the physiological adaptation of the parasite. Using Roche 454 sequencing technology and in silico secretome analysis, we predicted 2280 ESPs and analyzed their biological functions. Our analysis of the bioinformatic data suggested that ESPs are integral to the metabolism of carbohydrates and proteins within the parasite and/or hosts. We also found that ESPs are involved in mediating the immune responses of hosts and function within key development-related signaling pathways. We found 11 intracellular enzymes, 25 molecular chaperones and four proteases that were highly represented in the ESPs, in addition to 44 antigenic proteins that showed promise as candidates for vaccine or serodiagnostic development purposes. These findings provide valuable information on the mechanisms of metabolic adaptation in parasites that will aid the development of novel hydatid treatment and control targets.

Unconventional maturation of dendritic cells induced by particles from the laminated layer of larval Echinococcus granulosus

The larval stage of the cestode parasite Echinococcus granulosus causes hydatid disease in humans and livestock. This infection is characterized by the growth in internal organ parenchymae of fluid-filled structures (hydatids) that elicit surprisingly little inflammation in spite of their massive size and persistence. Hydatids are protected by a millimeter-thick layer of mucin-based extracellular matrix, termed the laminated layer (LL), which is thought to be a major factor determining the host response to the infection. Host cells can interact both with the LL surface and with materials that are shed from it to allow parasite growth. In this work, we analyzed the response of dendritic cells (DCs) to microscopic pieces of the native mucin-based gel of the LL (pLL). In vitro, this material induced an unusual activation state characterized by upregulation of CD86 without concomitant upregulation of CD40 or secretion of cytokines (interleukin 12 [IL-12], IL-10, tumor necrosis factor alpha [TNF-α], and IL-6). When added to Toll-like receptor (TLR) agonists, pLL-potentiated CD86 upregulation and IL-10 secretion while inhibiting CD40 upregulation and IL-12 secretion. In vivo, pLL also caused upregulation of CD86 and inhibited CD40 upregulation in DCs. Contrary to expectations, oxidation of the mucin glycans in pLL with periodate did not abrogate the effects on cells. Reduction of disulfide bonds, which are known to be important for LL structure, strongly diminished the impact of pLL on DCs without altering the particulate nature of the material. In summary, DCs respond to the LL mucin meshwork with a "semimature" activation phenotype, both in vitro and in vivo.

Identification, immunolocalization, and immunological characterization of nitric oxide synthase-interacting protein from Clonorchis sinensis

Recently, accumulating evidences indicate that nitric oxide (NO) is a potent mediator with diverse roles in regulating cellular functions, signaling pathways, and variety of pathological processes. In the present study, using data from the published genomic for Clonorchis sinensis (C. sinensis), we investigated a gene encoding nitric oxide synthase-interacting protein (NOSIP) of C. sinensis. Recombinant CsNOSIP (rCsNOSIP) was expressed and purified from Escherichia coli BL21. The open reading frame of CsNOSIP comprises 867 bp which encodes 289 amino acids and shares 72.9, 45.2, 47, 46.4, and 45.8% identity with NOSIP from Schistosoma mansoni, Xenopus laevis, Rattus norvegicus, Mus musculus, and Homo sapiens, respectively. Bioinformatics analysis suggested that the full-length sequence contains an eNOS-interacting domain and numerous B-cell epitopes. Quantitative RT-PCR indicated that CsNOSIP differentially transcribed throughout the adult worms, metacercariae, and egg stages of C. sinensis, and were highly expressed in the adult worms. Moreover, western blot analysis showed that the rCsNOSIP could be detected by the serum from BALB/c mice infected with C. sinensis and the serum from BALB/c mice immunized with excretory/secretory products (ESPs). Furthermore, immunolocalization assay showed that CsNOSIP was specifically localized in the intestine, vitellarium, and eggs of adult worm. Both immunoblot and immunolocalization results demonstrated that CsNOSIP was one component of ESPs of C. sinensis, which could be supported by SignalP analysis. Moreover, analysis of the antibody subclass and cytokine profile demonstrated that subcutaneously immunized BALB/c mice with rCsNOSIP could significantly enhance serum IgG1 level and up-regulate expression of IL-4 and IL-6 in the splenocytes. Our results suggested that CsNOSIP was an important antigen exposed to host immune system and probably involved in immune regulation of host by inducing Th2-polarized immune response.

Colitis promotes adaptation of an intestinal nematode: a Heligmosomoides polygyrus mouse model system

The precise mechanism of the very effective therapeutic effect of gastrointestinal nematodes on some autoimmune diseases is not clearly understood and is currently being intensively investigated. Treatment with living helminths has been initiated to reverse intestinal immune-mediated diseases in humans. However, little attention has been paid to the phenotype of nematodes in the IBD-affected gut and the consequences of nematode adaptation. In the present study, exposure of Heligmosomoides polygyrus larvae to the changed cytokine milieu of the intestine during colitis reduced inflammation in an experimental model of dextran sulphate sodium (DSS)- induced colitis, but increased nematode establishment in the moderate-responder BALB/c mouse strain. We used mass spectrometry in combination with two-dimensional Western blotting to determine changes in protein expression and changes in nematode antigens recognized by IgG1 in mice with colitis. We show that nematode larvae immunogenicity is changed by colitis as soon as 6 days post-infection; IgG1 did not recognize highly conserved proteins Lev-11 (isoform 1 of tropomyosin α1 chain), actin-4 isoform or FTT-2 isoform a (14-3-3 family) protein. These results indicate that changes in the small intestine provoked by colitis directly influence the nematode proteome. The unrecognized proteins seem to be key antigenic epitopes able to induce protective immune responses. The proteome changes were associated with weak immune recognition and increased larval adaptation and worm growth, altered localization in the intestine and increased survival of males but reduced worm fecundity. In this report, the mechanisms influencing nematode survival and the consequences of changed immunogenicity that reflect the immune response at the site colonized by the parasite in mice with colitis are described. The results are relevant to the use of live parasites to ameliorate IBD.

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.

Excretory/secretory products from in vitro-cultured Echinococcus granulosus protoscoleces

Cystic hydatid disease (CHD) is caused by infection with Echinococcus granulosus metacestodes and affects humans and livestock. Proteins secreted or excreted by protoscoleces, pre-adult worms found in the metacestode, are thought to play fundamental roles in the host-parasite relationship. In this work, we performed an LC-MS/MS proteomic analysis of the excretory-secretory products obtained from the first 48 h of an in vitro culture of the protoscoleces. We identified 32 proteins, including 18 that were never detected previously in metacestode proteomic studies. Among the novel identified excretory-secretory products are antigenic proteins, such as EG19 and P-29 and a calpain protease. We also identified other important protoscolex excretory-secretory products, such as thioredoxin peroxidase and 14-3-3 proteins, which are potentially involved in evasion mechanisms adopted by parasites to establish infection. Several intracellular proteins were found in the excretory-secretory products, revealing a set of identified proteins not previously thought to be exposed at the host-parasite interface. Additionally, immunological analyses established the antigenic profiles of the newly identified excretory-secretory products and revealed, for the first time, the in vitro secretion of the B antigen by protoscoleces. Considering that the excretory-secretory products obtained in vitro might reflect the products released and exposed to the host in vivo, our results provide valuable information on parasite survival strategies in adverse host environments and on the molecular mechanisms underpinning CHD immunopathology.

Understanding the laminated layer of larval Echinococcus II: immunology

The laminated layer (LL) is the massive carbohydrate-rich structure that protects Echinococcus larvae, which cause cystic echinococcosis (hydatid disease) and alveolar echinococcosis. Increased understanding of the biochemistry of the LL is allowing a more informed analysis of its immunology. The LL not only protects the parasite against host attack but also shapes the overall immune response against it. Because of its dense glycosylation, it probably contains few T-cell epitopes, being important instead in T-cell independent antibody responses. Crucially, it is decoded in non-inflammatory fashion by innate immunity, surely contributing to the strong immune-regulation observed in Echinococcus infections. Defining the active LL molecular motifs and corresponding host innate receptors is a feasible and promising goal in the field of helminth-derived immune-regulatory molecules.

Evaluation of the role of angiogenic factors in the pathogenesis of schistosomiasis

Schistosomiasis is one disease produced by helminths, which affect many people in tropical areas. Granuloma formation is the main mechanism involved in the pathogenesis of this disease. Experimental studies have demonstrated angiogenesis (blood vessels formation from pre-existing vessels) in the initial phase of granuloma formation. In the present work, VEGF (vascular endothelial growth factor) levels were analyzed in sera from people diagnosed with different helminthic infections. Patients with schistosomiasis and filariasis had significantly high VEGF levels in compared with healthy people and patients diagnosed with hookworms. In addition, the effects of angiogenesis inhibition using anti-angiogenic factors (endostatin) were evaluated in a schistosomiasis murine model. A lesion decrease was observed in mice infected with Schistosoma mansoni and treated with endostatin. Finally, mechanisms of angiogenesis induction were studied and observed that cercariae antigens stimulated the angiogenic factors by host alveolar macrophages.

Role of angiogenic factors in acute experimental Strongyloides venezuelensis infection

This study aims to investigate the role of angiogenic factors in the pathogenesis of experimental strongyloidiasis. Two complementary approaches were used: Firstly, CD1 mice were treated with endostatin, an angiogenesis inhibitor, and infected with Strongyloides venezuelensis. Also, the mechanisms involved in this process were studied. Parasitological examination revealed a significant decrease in egg per gram of faeces, number of collected larvae from lung tissue and number of collected adult females in mice treated with endostatin. Direct mechanisms with diminution of angiogenesis factors and an indirect mechanism with increase of eosinophil perhaps produced their effect. Secondly, the effect of the antigens responsible for stimulation of angiogenic factors [vascular endothelial growth factor (VEGF) and fibroblast growth factor 2 (FGF2)] from alveolar macrophages and the mechanisms involved in their production were investigated. Alveolar macrophage cells obtained by bronchoalveolar lavage were incubated at different concentrations of somatic and excretory/secretory antigens of S. venezuelensis. Also, mRNA levels of VEGF and FGF2 in macrophage cells were detected by RT-PCR. L3-PBS larvae antigens induced angiogenic factors. The relationship between angiogenesis factors and nitric oxide has been observed using nitric oxide synthase inhibitors.

Excretory/secretory proteome of the adult stage of Echinostoma caproni

The excretory/secretory proteome of Echinostoma caproni (Trematoda: Echinostomatidae) adults collected from experimentally infected mice was investigated using a proteomic approach. We performed a shot-gun liquid chromatography/tandem mass spectrometry for the separation and identification of tryptic peptides from the excretory/secretory products of E. caproni adult worms. Database search was performed using MASCOT search engine (Matrix-Science) and ProteinPilot software v2.0 (Applied Biosystems). A total of 39 parasite proteins were accurately identified. Strikingly, metabolic enzymes, and particularly glycolytic enzymes, constituted the largest protein family in the excretory/secretory proteome of E. caproni adult worms. Moreover, representative proteins involved in parasite structure, response against stress, chaperones, calcium-binding, and signal transduction were also identified. This work extends our knowledge of host-parasite relationships in the E. caproni-rodent model that is extensively used to analyze the factors determining the intestinal helminth rejection. Consequently, information on many proteins may be useful to better understand the molecular basis that determines the survival of this parasite in the definitive host.

Echinococcus multilocularis and its intermediate host: a model of parasite-host interplay

Host-parasite interactions in the E. multilocularis-intermediate host model depend on a subtle balance between cellular immunity, which is responsible for host's resistance towards the metacestode, the larval stage of the parasite, and tolerance induction and maintenance. The pathological features of alveolar echinococcosis. the disease caused by E. multilocularis, are related both to parasitic growth and to host's immune response, leading to fibrosis and necrosis, The disease spectrum is clearly dependent on the genetic background of the host as well as on acquired disturbances of Th1-related immunity. The laminated layer of the metacestode, and especially its carbohydrate components, plays a major role in tolerance induction. Th2-type and anti-inflammatory cytokines, IL-10 and TGF-β, as well as nitric oxide, are involved in the maintenance of tolerance and partial inhibition of cytotoxic mechanisms. Results of studies in the experimental mouse model and in patients suggest that immune modulation with cytokines, such as interferon-α, or with specific antigens could be used in the future to treat patients with alveolar echinococcosis and/or to prevent this very severe parasitic disease.

Nitric oxide and respiratory helminthic diseases

Nitric oxide (NO) is a very simple molecule that displays very important functions both in helminths (mainly those involved in respiratory pathology) and in mammalian hosts. In this paper we review four issues related to interaction of NO and lung helminthic diseases. Firstly, we evaluated data available on the NO synthesis and release by helminths and their biological role. Next, we summarized the effect of antigens obtained from different phases of the biological cycle on NO production by host mammalian cells (mainly from human sources). Thirdly, we revised the evaluation of NO on the biological activities and/or the viability of respiratory helminths. Lastly, the deleterious consequences of increased production of NO during helminthic human infection are detailed.

The major surface carbohydrates of the Echinococcus granulosus cyst: mucin-type O-glycans decorated by novel galactose-based structures

The cestodes constitute important but understudied human and veterinary parasites. Their surfaces are rich in carbohydrates, on which very little structural information is available. The tissue-dwelling larva (hydatid cyst) of the cestode Echinococcus granulosus is outwardly protected by a massive layer of carbohydrate-rich extracellular matrix, termed the laminated layer. The monosaccharide composition of this layer suggests that its major carbohydrate components are exclusively mucin-type O-glycans. We have purified these glycans after their release from the crude laminated layer and obtained by MS and NMR the complete structure of 10 of the most abundant components. The structures, between two and six residues in length, encompass a limited number of biosynthetic motifs. The mucin cores 1 and 2 are either nondecorated or elongated by a chain of Galpbeta1-3 residues. This chain can be capped by a single Galpalpha1-4 residue, such capping becoming more dominant with increasing chain size. In addition, the core 2 N-acetylglucosamine residue is in cases substituted with the disaccharide Galpalpha1-4Galpbeta1-4, giving rise to the blood P(1)-antigen motif. Larger, also related, glycans exist, reaching at least 18 residues in size. The glycans described are related but larger than those previously described from an Echinococcus multilocularis mucin [Hulsmeier, A. J., et al. (2002) J. Biol. Chem. 277, 5742-5748]. Our results reveal that the E. granulosus cyst exposes to the host only a few different major carbohydrate motifs. These motifs are composed essentially of galactose units and include the elongation by (Galpbeta1-3)(n) and the capping by Galpalpha1-4, novel in animal mucin-type O-glycans.

Triggering and modulation of the host-parasite interplay byEchinococcus multilocularis: a review

As more facts emerge regarding the ways in whichE. multilocularis-derived molecules trigger the host immune response and modulate the host-parasite interplay, it becomes possible to envisage how the parasite can survive and proliferate in its intermediate host, while in other hosts it dies out. Through effects on cells of both the innate and adaptive arms of the immune response,E. multiloculariscan orchestrate a range of outcomes that are beneficial not only to the parasite, in terms of facilitating its intrahepatic proliferation and maturation, and thus life cycle over all, but also to its intermediate host, in limiting pathology. The present review deals with the role of metacestode surface molecules as well as excretory/secretory (E/S) metabolic products of the parasite in the modulation of the host responses such as to optimize its own survival.

Interaction of hookworm 14-3-3 with the forkhead transcription factor DAF-16 requires intact Akt phosphorylation sites

Background

Third-stage infective larvae (L3) of hookworms are in an obligatory state of developmental arrest that ends upon entering the definitive host, where they receive a signal that re-activates development. Recovery from the developmentally arrested dauer stage of Caenorhabditis elegans is analogous to the resumption of development during hookworm infection. Insulin-like signaling (ILS) mediates recovery from arrest in C. elegans and activation of hookworm dauer L3. In C. elegans, phosphorylation of the forkhead transcription factor DAF-16 in response to ILS creates binding cites for the 14-3-3 protein Ce-FTT-2, which translocates DAF-16 out of the nucleus, resulting in resumption of reproductive development.

Results

To determine if hookworm 14-3-3 proteins play a similar role in L3 activation, hookworm FTT-2 was identified and tested for its ability to interact with A. caninum DAF-16 in vitro. The Ac-FTT-2 amino acid sequence was 91% identical to the Ce-FTT-2, and was most closely related to FTT-2 from other nematodes. Ac-FTT-2 was expressed in HEK 293T cells, and was recognized by an antibody against human 14-3-3β isoform. Reciprocal co-immunoprecipitations using anti-epitope tag antibodies indicated that Ac-FTT-2 interacts with Ac-DAF-16 when co-expressed in serum-stimulated HEK 293T cells. This interaction requires intact Akt consensus phosphorylation sites at serine107 and threonine312, but not serine381. Ac-FTT-2 was undetectable by Western blot in excretory/secretory products from serum-stimulated (activated) L3 or adult A. caninum.

Conclusion

The results indicate that Ac-FTT-2 interacts with DAF-16 in a phosphorylation-site dependent manner, and suggests that Ac-FTT-2 mediates activation of L3 by binding Ac-DAF-16 during hookworm infection.

Parasitic helminths: a pharmacopeia of anti-inflammatory molecules

Infection with parasitic helminths takes a heavy toll on the health and well-being of humans and their domestic livestock, concomitantly resulting in major economic losses. Analyses have consistently revealed bioactive molecules in extracts of helminths or in their excretory/secretory products that modulate the immune response of the host. It is our view that parasitic helminths are an untapped source of immunomodulatory substances that, in pure form, could become new drugs (or models for drug design) to treat disease. Here, we illustrate the range of immunomodulatory molecules in selected parasitic trematodes, cestodes and nematodes, their impact on the immune cells in the host and how the host may recognize these molecules. There are many examples of the partial characterization of helminth-derived immunomodulatory molecules, but these have not yet translated into new drugs, reflecting the difficulty of isolating and fully characterizing proteins, glycoproteins and lipid-based molecules from small amounts of parasite material. However, this should not deter the investigator, since analytical techniques are now being used to accrue considerable structural information on parasite-derived molecules, even when only minute quantities of tissue are available. With the introduction of methodologies to purify and structurally-characterize molecules from small amounts of tissue and the application of high throughput immunological assays, one would predict that an assessment of parasitic helminths will yield a variety of novel drug candidates in the coming years.

Echinococcus multilocularis: the parasite-host interplay

Alveolar echinococcosis (AE) is a severe chronic helminthic disease caused by the intrahepatic tumor-like growth of the metacestode of Echinococcus multilocularis. Metacestodes are fluid-filled, asexually proliferating vesicles, which are entirely covered by the laminated layer, an acellular carbohydrate-rich surface structure that protects the parasite from immunological and physiological reactions on part of the host. The E. multilocularis metacestode has acquired specific means of manipulating and using the immunological host response to its own advantage. These include the expression of distinct immunoregulatory parasite molecules that manipulate and interfere in the functional activity of macrophages and T cells. Recent research findings have led to a better understanding of the protein- and glycoprotein composition of the laminated layer and the E/S fraction of the metacestode, including Em2- and Em492-antigens, two metacestode antigen fractions that exhibit immunosuppressive or -modulatory properties. Understanding of the events taking place at the host-parasite interface is the key for development of novel immuno-therapeutical and/or chemotherapeutical tools.

14-3-3 proteins in Echinococcus: their role and potential as protective antigens

14-3-3 Proteins are a family of highly conserved proteins among all eukaryotic organisms studied so far. As basically intracellular proteins, they play a key role in basic cellular events related to cellular proliferation, including signal transduction, cell-cycle control, cell differentiation and cell survival. The 14-3-3 proteins have been described and characterized in several parasites, and mostly studied in Echinococcus granulosus and Echinococcus multilocularis. Here, we review the discoveries regarding this protein family in the genus Echinococcus, describing new data about specific aspects related with their implication in the parasite biology and immunology in the frame of the host-parasite relationship.

Antibody responses in human cystic hydatid disease to the laminated layer of Echinococcus granulosus

The laminated layer of hydatid cysts of Echinococcus granulosus represents a considerable amount of parasite material. Its antigenic role, however, is unclear. Extracts of laminated layer taken from sheep cysts were analysed in sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS/PAGE) and were found to contain bands at 55 and 25-29 kDa, which reacted with an anti-sheep IgG antibody probe, indicating that these were likely to be host-contaminating components within the layer. However, the same bands were also recognised by a significant proportion of human hydatid patients, particularly by IgG4 antibodies, and not by negative control individuals. These individuals did not recognise immunoglobulin heavy and light chains in a sheep serum extract in the same manner. It seems likely that there are either host or parasite antigenic components at similar molecular weights or that certain parasite antigens may share epitopes with sheep immunoglobulins. The antigens at 25-29 kDa were found to be glycoproteins by lectin blot analysis and may be important markers of disease status.

Trichinella: Differing effects of antigens from encapsulated and non-encapsulated species on in vitro nitric oxide production

Trichinellosis is a cosmopolitan zoonotic disease affecting a wide variety of animals, including man. Non-encapsulated and encapsulated species diverge with respect to their developmental strategies. Little is known at the molecular level about parasite-derived mediators responsible for host muscle cell transformation occurring during trichinellosis. In this context, host-parasite relationships in Trichinella-infected animals could be related to different host-immune and cell mediators, e.g. nitric oxide (NO). Here, we investigate the stimulatory/inhibitory role of L1 antigens from four encapsulated (T. spiralis, T. britovi, T. nelsoni and T. nativa) and one non-encapsulated (T. pseudospiralis) Trichinella species on NO production from rat macrophages in vitro. Our results demonstrate that encapsulated and non-encapsulated Trichinella species differ in their capacity to stimulate the secretion of NO from host macrophages. Biological significance of these differences should be further assessed in the available experimental models.

Molecular and immunological characterization of encoding gene and 14-3-3 protein 1 in Fasciola gigantica

A cDNA encoding Fg14-3-3 protein 1 was cloned by immunoscreening of an adult-stage Fasciola gigantica cDNA library using a rabbit antiserum against tegumental antigens of the parasite. The protein has a deduced amino acid sequence of 252 residues and a calculated molecular weight of 28.7 kDa. It shows sequence identity values between 57.6 and 58.1% to the human 14-3-3 beta, zeta, theta, and eta proteins and is in a phylogenetic cluster with the 14-3-3 protein 1 of Schistosoma spp. Nucleic acid analyses indicate that the Fg14-3-3 protein 1 is encoded by a single copy gene and that this gene is expressed as a transcript of 1250 nucleotides. In adult and 4-week-old parasites the gene's transcriptional and translational products were localized in the gut epithelium, parenchyma, tegument cells, and in the reproductive organs. An antiserum against recombinant Fg14-3-3 protein 1 detected a slightly smaller 14-3-3 protein in the parasite's excretion/secretion material and showed cross-reactivity with 14-3-3 proteins in extracts of other trematodes and mouse. Antibodies against Fg14-3-3 protein were detected in the sera of rabbits as early as 2 weeks after infection with metacercariae of F. gigantica and the antibody titre increased continuously over a 10-week observation period.

Intraperitoneal Echinococcus multilocularis infection in C57BL/6 mice affects CD40 and B7 costimulator expression on peritoneal macrophages and impairs peritoneal T cell activation

One of the most important immunopathological consequence of intraperitoneal alveolar echinococcosis (AE) in the mouse is suppression of T cell-mediated immune responses. We investigated whether and how intraperitoneal macrophages (MØs) are, respectively, implicated as antigen-presenting cells (APCs). In a first step we showed that peritoneal MØs from infected mice (AE-MØs) exhibited a reduced ability to present a conventional antigen (chicken ovalbumin, C-Ova) to specific responder lymph node T cells. In a subsequent step, AE-MØs as well as naïve MØs (positive control) proved their ability to uptake and process C-Ova fluorescein isthiocyanate (FITC). Furthermore, in comparison with naïve MØs, the surface expression of Ia molecules was up-regulated on AE-MØs at the early stage of infection, suggesting that AE-MØs provide the first signal via the antigen-Ia complex. To study the accessory activity of MØs, AE-MØs obtained at the early and late stages of infection were found to decrease Con A-induced proliferation of peritoneal naïve T cells as well as of AE-sensitized peritoneal T cells, in contrast to stimulation with naïve MØs. The status of accessory molecules was assessed by analysing the expression level of costimulatory molecules on AE-MØs, with naïve MØs as controls. It was found that B7-1 (CD80) and B7-2 (CD86) expression remained unchanged, whereas CD40 was down-regulated and CD54 (= ICAM-1) was slightly up-regulated. In a leucocyte reaction of AE-MØs with naïve or AE-T cells, both types of T cells increased their proliferative response when CD28 - the ligand of B7 receptors - was exposed to anti-CD28 in cultures. Conversely to naïve MØs, pulsing of AE-MØs with agonistic anti-CD40 did not even partially restore their costimulatory activity and failed to increase naïve or AE-T cell proliferation. Neutralizing anti-B7-1, in combination with anti-B7-2, reduced naïve and AE-T cell proliferation, whereas anti-CD40 treatment of naïve MØs increased their proliferative response to Con A. These results point at the key role of B7 receptors as accessory molecules and the necessity of the integrity of CD40-expression by naïve MØs to improve their accessory activity. Taken together, the obstructed presenting-activity of AE-MØs appeared to trigger an unresponsiveness of T cells, contributing to the suppression of their clonal expansion during the chronic phase of AE-infection.

Increased rat alveolar macrophage expression of functional iNOS induced by a Dirofilaria immitis immunoglobulin superfamily protein

Dirofilaria immitis is a worldwide filarial nematode causing heartworm disease in dogs and cats. Several mosquito species, which are able to feed both on humans and animals, can transmit this parasite. Inflammatory progression of host tissues induced by parasites are mediated by several molecules, including nitric oxide (NO), which usually exerts deleterious effects on parasites and occasionally on the host. We analyze the in vitro effect of total D. immitis adult worm somatic antigens on naïve rat alveolar macrophage NO production and further separation of parasite proteins to define specific D. immitis somatic molecules influencing host cell NO secretion. Additionally, we address the possible influence of Wolbachia spp. on the in vitro production of NO by macrophages. Our results demonstrate that D. immitis adult worm soluble antigens are able to specifically induce NO production from host macrophages. Furthermore, we demonstrated that this effect is due to nematode antigens rather than to defined components (LPS and metabolic molecules) derived from its endosymbiont, Wolbachia spp. In addition, we were able to isolate and identify one of the parasite specific components from the DiSo extract, denominated DiID35.3 and putatively belonging to the Immunoglobulin Superfamily Protein (ISP) group, triggering NO release from macrophages in a dose-dependent and specific manner.

Antigens from Ascaris suum trigger in vitro macrophage NO production

SUMMARY We investigated the in vitro effect of total excretory/secretory and somatic antigens from Ascaris suum adults (ESA and SA) and larvae 3 (ESL3 and SL3), and of 10 purified protein fractions from ESA components on rat alveolar macrophage nitric oxide (NO) production. Our results showed that in vitro incubation of macrophages with SA and SL3 antigens of A. suum did not result in NO release from cells, whereas incubation with ESA or ESL3 antigens resulted in the stimulation of NO production by these cells, both in a specific (inhibited by L-NAME and L-canavanine) and dose-dependent manner. In addition, we could demonstrate that a purified ESA fraction consisting of three Coomassie-stained bands of approximately 37, 44 and 46 kDa is involved in the in vitro triggering of NO production by host cells. These three bands were subjected to MALDI-peptide mass fingerprint, showing similarities with phosphoglycerate kinase, elongation factor Tu and enolase molecules, respectively. Future studies will focus on the characterization of these parasite-derived molecules.

Lung-migrating digenean parasites: in vitro influence on nitric oxide production from normal rat pulmonary macrophages

Nitric oxide (NO) is one of the most versatile players in the immune system. Most parasites induce inflammation in the host associated with NO production. Here, we compare the in vitro effect of Schistosoma bovis somatic (SbS) and excretory-secretory (SbES) antigens, and excretory-secretory Paragonimus mexicanus adult worm (PmES) molecules on rat alveolar macrophages NO production measured by the Griess method and by RT-PCR. Additionally, we address the divergence of the NO stimulatory/inhibitory effects of these two parasites. Polymyxin B was used to assess possible LPS contamination. In vitro incubation of rat alveolar macrophages with PmES (10 microg/ml) and SbS (50 microg/ml), but not with SbES extracts, resulted in NO production and an increase in iNOS cell mRNA. This production was specific and inhibited by L-NAME and L-canavanine. Different effects were observed when cells were incubated with P. mexicanus and S. bovis antigens.