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

The Acute Inflammatory Potential of Particles From the Echinococcus granulosus Laminated Layer Is Moderated by Its Calcium Inositol Hexakisphosphate Component

Cystic echinococcosis is caused by the tissue-dwelling larva (hydatid) of Echinococcus granulosus sensu lato. A salient feature is that this larva is protected by the acellular laminated layer (LL). As the parasite grows, the LL sheds abundant particles that can accumulate in the parasite's vicinity. The potential of LL particles to induce inflammation in vivo has not been specifically analysed. It is not known how each of its two major components, namely highly glycosylated mucins and calcium inositol hexakisphosphate (InsP6) deposits, impacts inflammation induced by the LL as a whole. In this work, we show that LL particles injected intraperitoneally cause infiltration of eosinophils, neutrophils and monocytes/macrophages as well as the disappearance of resident (large peritoneal) macrophages. Strikingly, the absence of calcium InsP6 enhanced the recruitment of all the inflammatory cell types analysed. In contrast, oxidation of the mucin carbohydrates caused decreased recruitment of neutrophils. The carbohydrate-oxidised particles caused cell influx nonetheless, which may be explained by possible receptor-independent effects of LL particles on innate immune cells, as suggested by previous works from our group. In summary, LL particles can induce acute inflammatory cell recruitment partly dependent on its mucin glycans, and this recruitment is attenuated by the calcium InsP6 component.

Immunological Characteristics of Hepatic Dendritic Cells in Patients and Mouse Model with Liver Echinococcus multilocularis Infection

The cestode Echinococcus multilocularis, which mainly dwells in the liver, leads to a serious parasitic liver disease called alveolar echinococcosis (AE). Despite the increased attention drawn to the immunosuppressive microenvironment formed by hepatic AE tissue, the immunological characteristics of hepatic dendritic cells (DCs) in the AE liver microenvironment have not been fully elucidated. Here, we profiled the immunophenotypic characteristics of hepatic DC subsets in both clinical AE patients and a mouse model. Single-cell RNA sequencing (scRNA-Seq) analysis of four AE patient specimens revealed that greater DC numbers were present within perilesional liver tissues and that the distributions of cDC and pDC subsets in the liver and periphery were different. cDCs highly expressed the costimulatory molecule CD86, the immune checkpoint molecule CD244, LAG3, CTLA4, and the checkpoint ligand CD48, while pDCs expressed these genes at low frequencies. Flow cytometric analysis of hepatic DC subsets in an E. multilocularis infection mouse model demonstrated that the number of cDCs significantly increased after parasite infection, and a tolerogenic phenotype characterized by a decrease in CD40 and CD80 expression levels was observed at an early stage, whereas an activated phenotype characterized by an increase in CD86 expression levels was observed at a late stage. Moreover, the expression profiles of major immune checkpoint molecules (CD244 and LAG3) and ligands (CD48) on hepatic DC subsets in a mouse model exhibited the same pattern as those in AE patients. Notably, the cDC and pDC subsets in the E. multilocularis infection group exhibited higher expression levels of PD-L1 and CD155 than those in the control group, suggesting the potential of these subsets to impair T cell function. These findings may provide valuable information for investigating the role of hepatic DC subsets in the AE microenvironment and guiding DC targeting treatments for AE.

Immunomodulatory effects of hydatid antigens on mesenchymal stem cells: gene expression alterations and functional consequences

Background

Cystic echinococcosis, caused by the larval stage of Echinococcus granulosus, remains a global health challenge. Mesenchymal stem cells (MSCs) are renowned for their regenerative and immunomodulatory properties. Given the parasite's mode of establishment, we postulate that MSCs likely play a pivotal role in the interaction between the parasite and the host. This study aims to explore the response of MSCs to antigens derived from Echinococcus granulosus, the etiological agent of hydatid disease, with the hypothesis that exposure to these antigens may alter MSC function and impact the host's immune response to the parasite.

Methods

MSCs were isolated from mouse bone marrow and co-cultured with ESPs, HCF, or pLL antigens. We conducted high-throughput sequencing to examine changes in the MSCs' mRNA expression profile. Additionally, cell cycle, migration, and secretory functions were assessed using various assays, including CCK8, flow cytometry, real-time PCR, Western blot, and ELISA.

Results

Our analysis revealed that hydatid antigens significantly modulate the mRNA expression of genes related to cytokine and chemokine activity, impacting MSC proliferation, migration, and cytokine secretion. Specifically, there was a downregulation of chemokines (MCP-1, CXCL1) and pro-inflammatory cytokines (IL-6, NOS2/NO), alongside an upregulation of anti-inflammatory mediators (COX2/PGE2). Furthermore, all antigens reduced MSC migration, and significant alterations in cellular metabolism-related pathways were observed.

Conclusion

Hydatid disease antigens induce a distinct immunomodulatory response in MSCs, characterized by a shift towards an anti-inflammatory phenotype and reduced cell migration. These changes may contribute to the parasite's ability to evade host defenses and persist within the host, highlighting the complex interplay between MSCs and hydatid disease antigens. This study provides valuable insights into the pathophysiology of hydatid disease and may inform the development of novel therapeutic strategies.

Mucins Shed from the Laminated Layer in Cystic Echinococcosis Are Captured by Kupffer Cells via the Lectin Receptor Clec4F

Cystic echinococcosis is caused by the larval stages (hydatids) of cestode parasites belonging to the species cluster Echinococcus granulosus sensu lato, with E. granulosus sensu stricto being the main infecting species. Hydatids are bladderlike structures that attain large sizes within various internal organs of livestock ungulates and humans. Hydatids are protected by the massive acellular laminated layer (LL), composed mainly of mucins. Parasite growth requires LL turnover, and abundant LL-derived particles are found at infection sites in infected humans, raising the question of how LL materials are dealt with by the hosts. In this article, we show that E. granulosus sensu stricto LL mucins injected into mice are taken up by Kupffer cells, the liver macrophages exposed to the vascular space. This uptake is largely dependent on the intact mucin glycans and on Clec4F, a C-type lectin receptor which, in rodents, is selectively expressed in Kupffer cells. This uptake mechanism operates on mucins injected both in soluble form intravenously (i.v.) and in particulate form intraperitoneally (i.p.). In mice harboring intraperitoneal infections by the same species, LL mucins were found essentially only at the infection site and in the liver, where they were taken up by Kupffer cells via Clec4F. Therefore, shed LL materials circulate in the host, and Kupffer cells can act as a sink for these materials, even when the parasite grows in sites other than the liver.

Immunology of a unique biological structure: the Echinococcus laminated layer

The larval stages of the cestode parasites belonging to the genus Echinococcus grow within internal organs of humans and a range of animal species. The resulting diseases, collectively termed echinococcoses, include major neglected tropical diseases of humans and livestock. Echinococcus larvae are outwardly protected by the laminated layer (LL), an acellular structure that is unique to this genus. The LL is based on a fibrillar meshwork made up of mucins, which are decorated by galactose-rich O-glycans. In addition, in the species cluster termed E. granulosus sensu lato, the LL features nano-deposits of the calcium salt of myo-inositol hexakisphosphate (Insp6). The main purpose of our article is to update the immunobiology of the LL. Major recent advances in this area are (i) the demonstration of LL "debris" at the infection site and draining lymph nodes, (ii) the characterization of the decoy activity of calcium Insp6 with respect to complement, (iii) the evidence that the LL mucin carbohydrates interact specifically with a lectin receptor expressed in Kupffer cells (Clec4F), and (iv) the characterization of what appear to be receptor-independent effects of LL particles on dendritic cells and macrophages. Much information is missing on the immunology of this intriguing structure: we discuss gaps in knowledge and propose possible avenues for research.

CD40-CD154: A perspective from type 2 immunity

The interaction between CD40 and CD154 (CD40 ligand) is central in immunology, participating in CD4⁺ T cell priming by dendritic cells (DC), CD4⁺ T cell help to B cells and classical macrophage activation by CD4⁺ T cells. However, its role in the Th2 side of immunology including helminth infection remains incompletely understood. Contrary to viral and bacterial stimuli, helminth products usually do not cause CD40 up-regulation in DC, and exogenous CD40 ligation drives Th2-biased systems towards Th1. On the other hand, CD40 and CD154 are necessary for induction of most Th2 responses. We attempt to reconcile these observations, mainly by proposing that (i) CD40 up-regulation in DC in Th2 systems is mostly induced by alarmins, (ii) the Th2 to Th1 shift induced by exogenous CD40 ligation is related to the capacity of such ligation to enhance IL-12 production by myeloid cells, and (iii) signals elicited by endogenous CD154 available in Th2 contexts and by exogenous CD40 ligation are probably different. We stress that CD40-CD154 is important beyond cognate cellular interactions. In such a context, we argue that the proliferation response of B-cells to IL-4 plus CD154 reflects a Th2-specific mechanism for polyclonal B-cell amplification and IgE production at infection sites. Finally, we argue that CD154 is a general immune activation signal across immune polarization including Th2, and propose that competition for CD154 at tissue sites may provide negative feedback on response induction at each site.

Modulation of the mTOR pathway plays a central role in dendritic cell functions after Echinococcus granulosus antigen recognition

Immune evasion is a hallmark of persistent echinococcal infection, comprising modulation of innate immune cells and antigen-specific T cell responses. However, recognition of Echinococcus granulosus by dendritic cells (DCs) is a key determinant of the host's response to this parasite. Given that mTOR signaling pathway has been described as a regulator linking metabolism and immune function in DCs, we reported for the first time in these cells, global translation levels, antigen uptake, phenotype, cytokine transcriptional levels, and splenocyte priming activity upon recognition of the hydatid fluid (HF) and the highly glycosylated laminar layer (LL). We found that LL induced a slight up-regulation of CD86 and MHC II in DCs and also stimulated the production of IL-6 and TNF-α. By contrast, HF did not increase the expression of any co-stimulatory molecules, but also down-modulated CD40 and stimulated the expression of the anti-inflammatory cytokine IL-10. Both parasitic antigens promoted protein synthesis through mTOR activation. The use of rapamycin decreased the expression of the cytokines tested, empowered the down-modulation of CD40 and also reduced splenocyte proliferation. Finally, we showed that E. granulosus antigens increase the amounts of LC3-positive structures in DCs which play critical roles in the presentation of these antigens to T cells.

In vitro immunoregulatory activity and anti-inflammatory effect of Echinococcus granulosus laminated layer

The Laminated layer of Echinococcus granulosus (LL) is the outer layer of the hydatic cyst. It plays a pivotal role in protecting the metacestode from host immunity. In our current study, we investigated the immunomodulatory effect of the LL on mouse spleen cells in presence of Lipopolysaccharide (LPS). Mouse spleen cells were cultured with or without LL in presence of LPS. After 24 h, the nitrites level representative of Nitric oxide (NO) production was measured in the culture supernatant by Griess-modified method. In addition, the mRNA expression levels of cytokines (IFN-γ, IL-1β, TGF-β, IL-10), Foxp3, and CTLA-4 were measured by quantitative Real-Time Polymerase chain reaction (qRT-PCR). Interestingly, our results showed a significant decrease (p< 0.01) in NO production and IFN-γ mRNA level (p< 0.001) from LPS- induced spleen cells in response to LL after 24h of culture. Moreover, LPS induced high level of IL-1β that was significantly (p<0.05) down regulated by LL. Importantly, mRNA levels of TGF-β (p< 0.01), Foxp3 and IL-10 (p< 0.05) were significantly upregulated by LL. In conclusion, our data indicated the in vitro immuno-regulatory and anti-inflammatory effects of the hydatic Laminated Layer on mouse spleen cells. These effects are related to an innate response implicating up-regulation of Foxp3, IL-10 and TGF-β expression and down-regulation of IFN-γ and IL-1β expression. LL could constitute a potential candidate for controlling inflammation during inflammatory disease.

Response patterns in adventitial layer of Echinococcus granulosus sensu stricto cysts from naturally infected cattle and sheep

Cystic echinococcosis is a zoonotic disease caused by the metacestode of Echinococcus granulosus sensu lato. The disease is characterized by the development of cystic structures inside viscera of the intermediate host, mainly liver and lungs. These cysts are formed by three layers: germinal, laminated, and adventitial layer, the latter being the local host immune response. Metacestodes that develop protoscoleces, the infective stage to the definitive host, are termed fertile, whereas cysts that do not produce protoscoleces are termed non-fertile. Sheep usually harbor fertile cysts while cattle usually harbor non-fertile cysts. Adventitial layers with fibrotic resolution are associated to fertile cysts, whereas a granulomatous reaction is associated with non-fertile cysts. The aim of this study was to analyze cellular distribution in the adventitial layer of fertile and non-fertile E. granulosus sensu stricto cysts found in liver and lungs of cattle and sheep. A total of 418 cysts were analyzed, 203 from cattle (8 fertile and 195 non-fertile) and 215 from sheep (64 fertile and 151 non-fertile). Fertile cysts from cattle showed mixed patterns of response, with fibrotic resolution and presence of granulomatous response in direct contact with the laminated layer, while sheep fertile cysts always displayed fibrotic resolution next to the laminated layer. Cattle non-fertile cysts display a granulomatous reaction in direct contact with the laminated layer, whereas sheep non-fertile cysts display a granulomatous reaction, but in direct contact with the fibrotic resolution. This shows that cattle and sheep cystic echinococcosis cysts have distinct local immune response patterns, which are associated to metacestode fertility.

Immunohistological detection of small particles of Echinococcus multilocularis and Echinococcus granulosus in lymph nodes is associated with enlarged lymph nodes in alveolar and cystic echinococcosis

BACKGROUND

Alveolar (AE) and cystic echinococcosis (CE) in humans are caused by the metacestode of the tapeworms Echinococcus multilocularis and Echinococcus granulosus sensu lato (s.l.). Immunohistochemistry with the monoclonal antibodies (mAb) Em2G11, specific for AE, and the mAb EmG3, specific for AE and CE, is an important pillar of the histological diagnosis of these two infections. Our aim was to further evaluate mAb EmG3 in a diagnostic setting and to analyze in detail the localization, distribution, and impact of small particles of Echinococcus multilocularis (spems) and small particles of Echinococcus granulosus s.l. (spegs) on lymph nodes.

METHODOLOGY/PRINCIPAL FINDINGS

We evaluated the mAb EmG3 in a cohort of formalin-fixed, paraffin embedded (FFPE) specimens of AE (n = 360) and CE (n = 178). These samples originated from 156 AE-patients and 77 CE-patients. mAb EmG3 showed a specific staining of the metacestode stadium of E. multilocularis and E. granulosus s.l. and had a higher sensitivity for spems than mAb Em2G11. Furthermore, we detected spegs in the surrounding host tissue and in almost all tested lymph nodes (39/41) of infected patients. 38/47 lymph nodes of AE showed a positive reaction for spems with mAb EmG3, whereas 29/47 tested positive when stained with mAb Em2G11. Spegs were detected in the germinal centers, co-located with CD23-positive follicular dendritic cells, and were present in the sinuses. Likewise, lymph nodes with spems and spegs in AE and CE were significantly enlarged in size in comparison to the control group.

CONCLUSIONS/SIGNIFICANCE

mAb EmG3 is specific for AE and CE and is a valuable tool in the histological diagnosis of echinococcosis. Based on the observed staining patterns, we hypothesize that the interaction between parasite and host is not restricted to the main lesion since spegs are detected in lymph nodes. Moreover, in AE the number of spems-affected lymph nodes is higher than previously assumed. The enlargement of lymph nodes with spems and spegs points to an immunological interaction with the small immunogenic particles (spems and spegs) of Echinococcus spp.

Activation of the NLRP3 Inflammasome by Particles from the Echinococcus granulosus Laminated Layer

The interaction of dendritic cells and macrophages with a variety of rigid noncellular particles triggers activation of the NLRP3 inflammasome and consequent secretion of interleukin 1β (IL-1β). Noncellular particles can also be generated in the context of helminth infection, since these large pathogens often shed their outermost structures during growth and/or molting. One such structure is the massive, mucin-based, soft, flexible laminated layer (LL), which protects the larval stages of cestodes of the genus Echinococcus.

The interaction of dendritic cells and macrophages with a variety of rigid noncellular particles triggers activation of the NLRP3 inflammasome and consequent secretion of interleukin 1β (IL-1β). Noncellular particles can also be generated in the context of helminth infection, since these large pathogens often shed their outermost structures during growth and/or molting. One such structure is the massive, mucin-based, soft, flexible laminated layer (LL), which protects the larval stages of cestodes of the genus Echinococcus. We show that particles from the Echinococcus granulosus LL (pLL) trigger NLRP3- and caspase-1-dependent IL-1β in lipopolysaccharide (LPS)-primed mouse bone marrow-derived dendritic cells (BMDC). This response can be elicited by pLL too large for phagocytosis and nonetheless requires actin dynamics, Syk, and phosphatidylinositol 3-kinase (PI3K). These three requirements had already been observed in our previous study on the alteration by pLL of CD86, CD40, IL-10, and IL-12 responses to LPS in BMDC; however, we now show that these alterations are independent of NLRP3 and caspase-1. In other words, an initial interaction with particles requiring actin dynamics, Syk, and PI3K, but not phagocytosis, elicits both NLRP3-dependent and NLRP3-independent responses. Intraperitoneal injection of pLL induced IL-1β, suggesting that contact with LL materials induces IL-1β in the E. granulosus infection setting. Our results extend our understanding of NLRP3 inflammasome activation by noncellular particulate materials both to helminth-derived materials and to flexible/soft materials.

Combining Computed Tomography and Histology Leads to an Evolutionary Concept of Hepatic Alveolar Echinococcosis

Alveolar echinococcosis (AE) is caused by the intermediate stage of Echinococcus multilocularis. We aimed to correlate computed tomography (CT) data with histology to identify distinct characteristics for different lesion types. We classified 45 samples into five types with the Echinococcus multilocularis Ulm Classification for Computed Tomography (EMUC-CT). The various CT lesions exhibited significantly different histological parameters, which led us to propose a progression model. The initial lesion fit the CT type IV classification, which comprises a single necrotic area with the central located laminated layer, a larger distance between laminated layer and border zone, a small fibrotic peripheral zone, and few small particles of Echinococcus multilocularis (spems). Lesions could progress through CT types I, II, and III, characterized by shorter distances between laminated layer and border zone, more spems inside and surrounding the lesion, and a pronounced fibrotic rim (mostly in type III). Alternatively, lesions could converge to a highly calcified, regressive state (type V). Our results suggest that the CT types mark sequential stages of the infection, which progress over time. These distinct histological patterns advance the understanding of interactions between AE and human host; moreover, they might become prognostically and therapeutically relevant.

Recent advances on innate immune pathways related to host-parasite cross-talk in cystic and alveolar echinococcosis

Cystic echinococcosis (CE) and alveolar echinococcosis (AE) are life-threatening parasitic infections worldwide caused by Echinococcus granulosus (sensu lato) and E. multilocularis, respectively. Very little is known about the factors affecting innate susceptibility and resistance to infection with Echinococcus spp. Although benzimidazolic drugs against CE and AE have definitively improved the treatment of these cestodes; however, the lack of successful control campaigns, including the EG95 vaccine, at a continental level indicates the importance of generating novel therapies. This review represents an update on the latest developments in the regulatory functions of innate immune pathways such as apoptosis, toll-like receptors (TLRs), and inflammasomes against CE and AE. We suggest that apoptosis can reciprocally play a bi-functional role among the host-Echinococcus metabolite relationships in suppressive and survival mechanisms of CE. Based on the available information, further studies are needed to determine whether the orchestrated in silico strategy for designing inhibitors and interfering RNA against anti-apoptotic proteins and TLRs would be effective to improve new treatments as well as therapeutic vaccines against the E. granulosus and E. multilocularis.

Antigen-Conjugated Silica Solid Sphere as Nanovaccine for Cancer Immunotherapy

Background

Nanocarriers could deliver significantly higher amounts of antigen to antigen-presenting cells (APCs), which have great potential to stimulate humoral and cellular response in cancer immunotherapy. Thereafter, silica solid nanosphere (SiO₂) was prepared, and a model antigen (ovalbumin, OVA) was covalently conjugated on the surface of SiO₂ to form nanovaccine (OVA@SiO₂). And the application of OVA@SiO₂ for cancer immunotherapy was evaluated.

Materials and Methods

SiO₂ solid nanosphere was prepared by the Stöber method, then successively aminated by aminopropyltriethoxysilane and activated with glutaraldehyde. OVA was covalently conjugated on the surface of activated SiO₂ to obtain nanovaccine (OVA@SiO₂). Dynamic light scattering, scanning electron microscope, and transmission electron microscope were conducted to identify the size distribution, zeta potential and morphology of OVA@SiO₂. The OVA loading capacity was investigated by varying glutaraldehyde concentration. The biocompatibility of OVA@SiO₂ to DC2.4 and RAW246.7 cells was evaluated by a Cell Counting Kit-8 assay. The uptake of OVA@SiO₂ by DC2.4 and its internalization pathway were evaluated in the absence or presence of different inhibitors. The activation and maturation of bone marrow-derived DC cells by OVA@SiO₂ were also investigated. Finally, the in vivo transport of OVA@SiO₂ and its toxicity to organs were appraised.

Results

All results indicated the successful covalent conjugation of OVA on the surface of SiO₂. The as-prepared OVA@SiO₂ possessed high antigen loading capacity, which had good biocompatibility to APCs and major organs. Besides, OVA@SiO₂ facilitated antigen uptake by DC2.4 cells and its cytosolic release. Noteworthily, OVA@SiO₂ significantly promoted the maturation of dendritic cells and up-regulation of cytokine secretion by co-administration of adjuvant CpG-ODN.

Conclusion

The as-prepared SiO₂ shows promising potential for use as an antigen delivery carrier.

Particles from the Echinococcus granulosus Laminated Layer Inhibit CD40 Upregulation in Dendritic Cells by Interfering with Akt Activation

The larval stage of the cestode Echinococcus granulosus causes cystic echinococcosis in humans and livestock. This larva is protected by the millimeter-thick, mucin-based laminated layer (LL), from which materials have to be shed to allow parasite growth. We previously reported that dendritic cells (DCs) respond to microscopic pieces of the mucin gel of the LL (pLL) with unconventional maturation phenotypes, in the absence or presence of Toll-like receptor (TLR) agonists, including lipopolysaccharide (LPS).

The larval stage of the cestode Echinococcus granulosus causes cystic echinococcosis in humans and livestock. This larva is protected by the millimeter-thick, mucin-based laminated layer (LL), from which materials have to be shed to allow parasite growth. We previously reported that dendritic cells (DCs) respond to microscopic pieces of the mucin gel of the LL (pLL) with unconventional maturation phenotypes, in the absence or presence of Toll-like receptor (TLR) agonists, including lipopolysaccharide (LPS). We also reported that the presence of pLL inhibited the activating phosphorylation of the phosphatidylinositol 3-kinase (PI3K) effector Akt induced by granulocyte-macrophage colony-stimulating factor or interleukin-4. We now show that the inhibitory effect of pLL extends to LPS as a PI3K activator, and results in diminished phosphorylation of GSK3 downstream from Akt. Functionally, the inhibition of Akt and GSK3 phosphorylation are linked to the blunted upregulation of CD40, a major feature of the unconventional maturation phenotype. Paradoxically, all aspects of unconventional maturation induced by pLL depend on PI3K class I. Additional components of the phagocytic machinery are needed, but phagocytosis of pLL particles is not required. These observations hint at a DC response mechanism related to receptor-independent mechanisms proposed for certain crystalline and synthetic polymer-based particles; this would fit the previously reported lack of detection of molecular-level motifs necessary of the effects of pLL on DCs. Finally, we report that DCs exposed to pLL are able to condition DCs not exposed to the material so that these cannot upregulate CD40 in full in response to LPS.

Inefficient and abortive classical complement pathway activation by the calcium inositol hexakisphosphate component of the Echinococcus granulosus laminated layer

Persistent extracellular tissue-dwelling pathogens face the challenge of antibody-dependent activation of the classical complement pathway (CCP). A prime example of this situation is the larva of the cestode Echinococcus granulosus sensu lato, causing cystic echinococcosis. This tissue-dwelling, bladder-like larva is bounded by a cellular layer protected by the outermost acellular "laminated layer" (LL), to which host antibodies bind. The LL is made up of a mucin meshwork and interspersed nano-deposits of calcium inositol hexakisphosphate (calcium InsP₆). We previously reported that calcium InsP₆ bound C1q, apparently initiating CCP activation. The present work dissects CCP activation on the LL. Most of the C1 binding activity in the LL corresponded to calcium InsP₆, and this binding was enhanced by partial proteolysis of the mucin meshwork. The remaining C1 binding activity was attributable to host antibodies, which included CCP-activating IgG isotypes. Calcium InsP₆ made only a weak contribution to early CCP activation on the LL, suggesting inefficient C1 complex activation as reported for other polyanions. CCP activation on calcium InsP₆ gave rise to a dominant population of C3b deposited onto calcium InsP₆ itself that appeared to be quickly inactivated. Apparently as a result of inefficient initiation plus C3b inactivation, calcium InsP₆ made no net contribution to C5 activation. We propose that the LL protects the underlying parasite cells from CCP activation through the combined effects of inefficient permeation of C1 through the mucins and C1 retention on calcium InsP₆. This mechanism does not result in C5 activation, which is known to drive parasite-damaging inflammation.

New insights of the local immune response against both fertile and infertile hydatid cysts

BACKGROUND

Cystic echinococcosis is caused by the metacestode of the zoonotic flatworm Echinococcus granulosus. Within the viscera of the intermediate host, the metacestode grows as a unilocular cyst known as hydatid cyst. This cyst is comprised of two layers of parasite origin: germinal and laminated layers, and one of host origin: the adventitial layer, that encapsulates the parasite. This adventitial layer is composed of collagen fibers, epithelioid cells, eosinophils and lymphocytes. To establish itself inside the host, the germinal layer produces the laminated layer, and to continue its life cycle, generates protoscoleces. Some cysts are unable to produce protoscoleces, and are defined as infertile cysts. The molecular mechanisms involved in cyst fertility are not clear, however, the host immune response could play a crucial role.

METHODOLOGY/PRINCIPAL FINDINGS

We collected hydatid cysts from both liver and lungs of slaughtered cattle, and histological sections of fertile, infertile and small hydatid cysts were stained with haematoxylin-eosin. A common feature observed in infertile cysts was the disorganization of the laminated layer by the infiltration of host immune cells. These infiltrating cells eventually destroy parts of laminated layer. Immunohistochemical analysis of both parasite and host antigens, identify these cells as cattle macrophages and are present inside the cysts associated to germinal layer.

CONCLUSIONS/SIGNIFICANCE

This is the first report that indicates to cell from immune system present in adventitial layer of infertile bovine hydatid cysts could disrupt the laminated layer, infiltrating and probably causing the infertility of cyst.

Echinococcus granulosus Infection Results in an Increase in Eisenbergiella and Parabacteroides Genera in the Gut of Mice

Cystic echinococcosis (CE) is a chronic infectious disease caused by Echinococcus granulosus. To confirm whether the infection impacts on the gut microbiota, we established a mouse model of E. granulosus infection in this study whereby BALB/c mice were infected with micro-cysts of E. granulosus. After 4 months of infection, fecal samples were collected for high-throughput sequencing of the hypervariable regions of the 16S rRNA gene. Sequence analysis revealed a total of 13,353 operational taxonomic units (OTUs) with only 40.6% of the OTUs having genera reference information and 101 of the OTUs were significantly increased in infected mice. Bioinformatics analysis showed that the common core microbiota were not significantly changed at family level. However, two genera (Eisenbergiella and Parabacteroides) were enriched in the infected mice (P _{AMOV A} < 0.05) at genus level. Functional analysis indicated that seven pathways were altered in the E. granulosus Infection Group compared with the Uninfected Group. Spearman correlation analysis showed strong correlations of IgG, IgG1 and IgG2a with nine major genera. E. granulosus cyst infection may change the gut microbiota which may be associated with metabolic pathways.

Mechanisms underlying immune tolerance caused by recombinant Echinococcus granulosus antigens Eg mMDH and Eg10 in dendritic cells

Mice immunized with recombinant Echinococcus granulosus antigens Eg10 and Eg mMDH do not show elevated resistance to E. granulosus infection but show aggravated infection instead. To gain a deeper insight in the immune tolerance mechanisms in mice immunized with Eg10 and Eg mMDH, this study simulated the immune tolerance process in vitro by culturing bone marrow-derived dendritic cells (BMDCs) in the presence of Eg10 or Eg mMDH. Scanning electron microscopy revealed that Eg10- and Eg mMDH-treated DCs exhibited immature cell morphology, while addition of LPS to the cells induced changes in cell morphology and an increase in the number of cell-surface protrusions. This observation was consistent with the increased expression of the cell-surface molecules MHCII and CD80 in Eg10- and Eg mMDH-treated DCs pretreated with LPS. DCs exposed to the two antigens had a very weak ability to induce T-cell proliferation, but could promote the formation of Treg cells. Introduction of the indoleamine 2,3-dioxygenase (IDO) inhibitor, 1-methyl tryptopha (1-MT) enhanced the ability of the antigens to induce T cells and inhibited the induction of Treg cells. Eg mMDH-treated DCs showed a strong response to 1-MT: the DCs had high mRNA levels of IDO, IL-6, and IL-10, while 1-MT decreased the expression. In contrast, DCs treated with Eg10 did not show significant changes after 1-MT treatment. Eg mMDH inhibited DC maturation and promoted IDO expression, which, on the one hand, decreased the ability of DCs to induce T-cell proliferation, resulting in T-cell anergy, and on the other hand, induced the formation of Tregs, resulting in an immunosuppressive effect. In contrast, the escape mechanisms induced by Eg10 did not primarily depend on the IDO pathway and might involve other mechanisms that need to be further explored.

Helminth Antigen-Conditioned Dendritic Cells Generate Anti-Inflammatory Cd4 T Cells Independent of Antigen Presentation via Major Histocompatibility Complex Class II

A recently identified feature of the host response to infection with helminth parasites is suppression of concomitant disease. Dendritic cells (DCs) exposed to antigens from the tapeworm Hymenolepis diminuta significantly reduce the severity of dinitrobenzene sulfonic acid-induced colitis in mice. Here we elucidate mechanisms underlying this cellular immunotherapy. We show a requirement for Ccr7 expression on transferred H. diminuta antigen-treated (HD)-DCs, suggesting that homing to secondary lymphoid tissues is important for suppression of colitis. Furthermore, sodium metaperiodate-sensitive helminth-derived glycans are required to drive the anti-colitic response in recipient mice. Induction of Th2-type cytokines and Gata-3⁺Cd4⁺ cells in secondary lymphoid tissues is dependent on major histocompatibility complex class II (MHC II) protein expression on transferred DCs, although remarkably, transfer of MHC II^-/- HD-DCs still attenuated dinitrobenzene sulfonic acid-induced colitis in recipient mice. Moreover, transfer of Cd4⁺ splenic T cells retrieved from mice administered MHC II^-/- HD-DCs suppressed dinitrobenzene sulfonic acid-induced colitis in recipient mice. Our studies reveal that HD-DCs can suppress colitis via an alternative MHC II-independent pathway that involves, in part, mobilization of T-cell responses. These data support the utility of HD-DCs in blocking colitis, revealing a requirement for Ccr7 and providing for HD-DC autologous immunotherapy for disease in which MHC II expression and/or function is compromised.

Particles from the Echinococcus granulosus laminated layer inhibit IL-4 and growth factor-driven Akt phosphorylation and proliferative responses in macrophages

Proliferation of macrophages is a hallmark of inflammation in many type 2 settings including helminth infections. The cellular expansion is driven by the type 2 cytokine interleukin-4 (IL-4), as well as by M-CSF, which also controls homeostatic levels of tissue resident macrophages. Cystic echinococcosis, caused by the tissue-dwelling larval stage of the cestode Echinococcus granulosus, is characterised by normally subdued local inflammation. Infiltrating host cells make contact only with the acellular protective coat of the parasite, called laminated layer, particles of which can be ingested by phagocytic cells. Here we report that a particulate preparation from this layer (pLL) strongly inhibits the proliferation of macrophages in response to IL-4 or M-CSF. In addition, pLL also inhibits IL-4-driven up-regulation of Relm-α, without similarly affecting Chitinase-like 3 (Chil3/Ym1). IL-4-driven cell proliferation and up-regulation of Relm-α are both known to depend on the phosphatidylinositol (PI3K)/Akt pathway, which is dispensable for induction of Chil3/Ym1. Exposure to pLL in vitro inhibited Akt activation in response to proliferative stimuli, providing a potential mechanism for its activities. Our results suggest that the E. granulosus laminated layer exerts some of its anti-inflammatory properties through inhibition of PI3K/Akt activation and consequent limitation of macrophage proliferation.

Parasite molecules and host responses in cystic echinococcosis

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

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.

Proteomic Analysis of Excretory-Secretory Products of Mesocestoides corti Metacestodes Reveals Potential Suppressors of Dendritic Cell Functions

Accumulating evidences have assigned a central role to parasite-derived proteins in immunomodulation. Here, we report on the proteomic identification and characterization of immunomodulatory excretory-secretory (ES) products from the metacestode larva (tetrathyridium) of the tapeworm Mesocestoides corti (syn. M. vogae). We demonstrate that ES products but not larval homogenates inhibit the stimuli-driven release of the pro-inflammatory, Th1-inducing cytokine IL-12p70 by murine bone marrow-derived dendritic cells (BMDCs). Within the ES fraction, we biochemically narrowed down the immunosuppressive activity to glycoproteins since active components were lipid-free, but sensitive to heat- and carbohydrate-treatment. Finally, using bioassay-guided chromatographic analyses assisted by comparative proteomics of active and inactive fractions of the ES products, we defined a comprehensive list of candidate proteins released by M. corti tetrathyridia as potential suppressors of DC functions. Our study provides a comprehensive library of somatic and ES products and highlight some candidate parasite factors that might drive the subversion of DC functions to facilitate the persistence of M. corti tetrathyridia in their hosts.

The metacestode larval stages of life-threatening tapeworms grow within the organs of its mammalian hosts, thus causing severe and long-lasting morbidity. Immunosuppression, which mainly depends on factors that are released or leaking from the parasite, plays an important role in both survival and proliferation of the larvae. These parasite-derived molecules are potential targets for developing new anti-parasitic drugs and/or improving the effectiveness of current therapies. Moreover, an optimized use of such factors could help to minimize pathologies resulting from uncontrolled immune responses, like allergies and autoimmune diseases. The authors herein demonstrate that larvae from a parasitic cestode release factors that sufficiently support the suppression of dendritic cells, a set of innate immune cells that recognizes and initiates host immune responses against invading pathogens. Employing modern analytic proteomic tools combined with immunological bioassays, several cestode-derived candidate immunomodulators were identified. This is the first bioassay-guided comprehensive library of candidate immunomodulators from a tissue-dwelling cestode larva. This work validates the unmet value of the Mesocestoides corti system in characterizing the mechanisms of host immunomodulation by metacestodes and reveals the largest database of candidate metacestode-derived immunomodulators until date.

Immunomodulatory effects of adult Haemonchus contortus excretory/secretory products on human monocyte-derived dendritic cells

The levels of expression of surface molecules and release of cytokines and chemokines of human monocyte-derived dendritic cells were determined after their exposure to adult H. contortus excretory/secretory (ES) products or a combination of ES products and bacterial lipopolysaccharide (LPS). Worm products provoked a weak response and only partial maturation of the dendritic cells, consistent with the hyporesponsiveness and more tolerogenic immune environment present in parasitized animals and humans. Co-stimulation with LPS demonstrated that H. contortus secretions, like those of other helminths, contain immunomodulators capable of reducing some aspects of the strong T(H)1/T(H)2 response evoked by bacterial LPS. There were significant reductions in the release of some cytokine/chemokines by LPS-stimulated mdDCs and a trend (although not significant at P < 0.05) for reduced expression levels of CD40, CD80 and HLA-DR. A prominent feature was the variability in responses of dendritic cells from the four donors, even on different days in repeat experiments, suggesting that generalized conclusions may be difficult to make, except in genetically related animals. Such observations may therefore be applicable only to restricted populations. In addition, previous exposure to parasites in a target population for immunomodulatory therapy may be an important factor in assessing the likelihood of adverse reactions or failures in the treatment to worm therapy.

Induction of CD4(+) Regulatory and Polarized Effector/helper T Cells by Dendritic Cells

Dendritic cells (DCs) are considered to play major roles during the induction of T cell immune responses as well as the maintenance of T cell tolerance. Naive CD4(+) T cells have been shown to respond with high plasticity to signals inducing their polarization into effector/helper or regulatory T cells. Data obtained from in vitro generated bone-marrow (BM)-derived DCs as well as genetic mouse models revealed an important but not exclusive role of DCs in shaping CD4(+) T cell responses. Besides the specialization of some conventional DC subsets for the induction of polarized immunity, also the maturation stage, activation of specialized transcription factors and the cytokine production of DCs have major impact on CD4(+) T cells. Since in vitro generated BM-DCs show a high diversity to shape CD4(+) T cells and their high similarity to monocyte-derived DCs in vivo, this review reports data mainly on BM-DCs in this process and only touches the roles of transcription factors or of DC subsets, which have been discussed elsewhere. Here, recent findings on 1) the conversion of naive into anergic and further into Foxp3(-) regulatory T cells (Treg) by immature DCs, 2) the role of RelB in steady state migratory DCs (ssmDCs) for conversion of naive T cells into Foxp3(+) Treg, 3) the DC maturation signature for polarized Th2 cell induction and 4) the DC source of IL-12 for Th1 induction are discussed.

The laminated layer: Recent advances and insights into Echinococcus biology and evolution

The laminated layer is the unique mucin-based extracellular matrix that protects Echinococcus larvae, and thus to an important extent, shapes host-parasite relationships in the larval echinococcoses. In 2011, we published twin reviews summarizing what was known about this structure. Since then, important advances have been made. Complete genomes and some RNAseq data are now available for E. multilocularis and E. granulosus, leading to the inference that the E. multilocularis LL is probably formed by a single type of mucin backbone, while a second apomucin subfamily additionally contributes to the E. granulosus LL. Previously suspected differences between E. granulosus and E. multilocularis in mucin glycan size have been confirmed and pinned down to the virtual absence of Galβ1-3 chains in E. multilocularis. The LL carbohydrates from both species have been found to interact selectively with the Kupffer cell receptor expressed in rodent liver macrophages, highlighting the ancestral adaptations to rodents as intermediate hosts and to the liver as infection site. Finally, LL particles have been shown to possess carbohydrate-independent mechanisms profoundly conditioning non-liver-specific dendritic cells and macrophages. These advances are discussed in an integrated way, and in the context of the newly determined phylogeny of Echinococcus and its taenid relatives.

Fasciola hepatica mucin-encoding gene: expression, variability and its potential relevance in host-parasite relationship

Fasciola hepatica is the causative agent of fasciolosis, a zoonosis with significant impact both in human and animal health. Understanding the basic processes of parasite biology, especially those related to interactions with its host, will contribute to control F. hepatica infections and hence liver pathology. Mucins have been described as important mediators for parasite establishment within its host, due to their key roles in immune evasion. In F. hepatica, mucin expression is upregulated in the mammalian invasive newly excysted juvenile (NEJ) stage in comparison with the adult stage. Here, we performed sequencing of mucin cDNAs prepared from NEJ RNA, resulting in six different cDNAs clusters. The differences are due to the presence of a tandem repeated sequence of 66 bp encoded by different exons. Two groups of apomucins one with three and the other with four repeats, with 459 and 393 bp respectively, were identified. These cDNAs have open reading frames encoding Ser-Thr enriched proteins with an N-terminal signal peptide, characteristic of apomucin backbone. We cloned a 4470 bp gene comprising eight exons and seven introns that encodes all the cDNA variants identified in NEJs. By real time polymerase chain reaction and high-resolution melting approaches of individual flukes we infer that fhemuc-1 is a single-copy gene, with at least two different alleles. Our data suggest that both gene polymorphism and alternative splicing might account for apomucin variability in the fhemuc-1 gene that is upregulated in NEJ invasive stage. The relevance of this variation in host-parasite interplay is discussed.

Adoptive transfer of helminth antigen-pulsed dendritic cells protects against the development of experimental colitis in mice

Infection with helminth parasites and treatment with worm extracts can suppress inflammatory disease, including colitis. Postulating that dendritic cells (DCs) participated in the suppression of inflammation and seeking to move beyond the use of helminths per se, we tested the ability of Hymenolepis diminuta antigen-pulsed DCs to suppress colitis as a novel cell-based immunotherapy. Bone marrow derived DCs pulsed with H. diminuta antigen (HD-DCs), or PBS-, BSA-, or LPS-DCs as controls, were transferred into wild-type (WT), interleukin-10 (IL-10) knock-out (KO), and RAG-1 KO mice, and the impact on dinitrobenzene sulphonic acid (DNBS)-induced colitis and splenic cytokine production assessed 72 h later. Mice receiving HD-DCs were significantly protected from DNBS-induced colitis and of the experimental groups only these mice displayed increased Th2 cytokines and IL-10 production. Adoptive transfer of HD-DCs protected neither RAG-1 nor IL-10 KO mice from DNBS-colitis. Furthermore, the transfer of CD4(+) splenocytes from recipients of HD-DCs protected naïve mice against DNBS-colitis, in an IL-10 dependent manner. Thus, HD-DCs are a novel anti-colitic immunotherapy that can educate anti-colitic CD4(+) T cells: mechanistically, the anti-colitic effect of HD-DCs requires that the host has an adaptive immune response and the ability to mobilize IL-10.

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.

Impairment of dendritic cell function and induction of CD4(+)CD25(+)Foxp3(+) T cells by excretory-secretory products: a potential mechanism of immune evasion adopted by Echinococcus granulosus

Background

Cystic echinococcosis, caused by infection with Echinococcus granulosus, is one of the most widespread zoonotic helminth diseases. Modulation of host responses is an important strategy used by helminth parasites to promote infection. To better understand the mechanisms adopted by E. granulosus to escape host immune responses, we investigated the effects of excretory–secretory products (ES) and adult worm antigen (AWA) derived from adult E. granulosus on murine bone marrow-derived dendritic cells (BMDC).

Results

Compared with lipopolysaccharide (LPS), AWA, but not ES, induced BMDC maturation or stimulated BMDC cytokine production and co-stimulatory molecule expression (CD40, CD80 and MHC class II). Furthermore, ES-treated BMDCs pulsed with ovalbumin exhibited reduced co-stimulatory molecule expression in comparison with untreated BMDC, even in the presence of the strong Th1 inducer, CpG. Moreover, we detected the effects of ES-treated DC on T cell activation by an in vitro T cell priming assay. We observed that ES-treated BMDC co-cultured with DO11.10 transgenic CD4⁺ T cells induced the generation of CD4⁺CD25⁺Foxp3⁺ T cells. In addition, in contrast to AWA-treated BMDCs, which had markedly induced IFN-γ secretion and reduced of IL-4 levels in co-cultured T cells, ES-treated BMDCs did not modify their capacity to stimulate IFN-γ or IL-4 production by T cells.

Conclusions

We conclude that ES of adult E. granulosus inhibited DC function, impaired the development of Th1 cells induced by CpG, and induced CD4⁺CD25⁺Foxp3⁺ regulatory T cells in an IL-10-independent manner.

Macrophage proliferation, provenance, and plasticity in macroparasite infection

Macrophages have long been center stage in the host response to microbial infection, but only in the past 10–15 years has there been a growing appreciation for their role in helminth infection and the associated type 2 response. Through the actions of the IL-4 receptor α (IL-4Rα), type 2 cytokines result in the accumulation of macrophages with a distinctive activation phenotype. Although our knowledge of IL-4Rα-induced genes is growing rapidly, the specific functions of these macrophages have yet to be established in most disease settings. Understanding the interplay between IL-4Rα-activated macrophages and the other cellular players is confounded by the enormous transcriptional heterogeneity within the macrophage population and by their highly plastic nature. Another level of complexity is added by the new knowledge that tissue macrophages can be derived either from a resident prenatal population or from blood monocyte recruitment and that IL-4 can increase macrophage numbers through proliferative expansion. Here, we review current knowledge on the contribution of macrophages to helminth killing and wound repair, with specific attention paid to distinct cellular origins and plasticity potential.

Proteomic analysis of the excretory/secretory products and antigenic proteins of Echinococcus granulosus adult worms from infected dogs

Background

Cystic echinococcosis, which is caused by Echinococcus granulosus, is one of the most widespread zoonotic helminth diseases that affects humans and livestock. Dogs, which harbor adult worms in their small intestines, are a pivotal source of E. granulosus infection in humans and domestic animals. Therefore, novel molecular approaches for the prevention and diagnosis of this parasite infection in dogs need to be developed.

Results

In this study, we performed proteomic analysis to identify excretory/secretory products (ES) and antigenic proteins of E. granulosus adult worms using two-dimensional electrophoresis, tandem matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF/TOF), and Western blotting of sera from infected dogs. This study identified 33 ES product spots corresponding to 9 different proteins and 21 antigenic protein spots corresponding to 13 different proteins. Six antigenic proteins were identified for the first time.

Conclusions

The present study extended the existing proteomic data of E. granulosus and provides further information regarding host-parasite interactions and survival mechanisms. The results of this study contribute to vaccination and immunodiagnoses for E. granulosus infections.