Immunoregulation in larval Echinococcus multilocularis infection

Immunological landscape of hepatic alveolar echinococcosis: A bibliometric analysis

BACKGROUND

Hepatic alveolar echinococcosis (HAE) is a chronic parasitic disease caused by the larval stage of Echinococcus multilocularis. Although significant research has been conducted on the pathogenesis and immunological aspects of HAE, comprehensive bibliometric analyses in this area are still lacking. This study sought to fill this gap by systematically analyzing the immunological literature on HAE using bibliometric methods.

AIM

To identify research trends, key contributors, and emerging developments and offer insights to guide future research in this field.

METHODS

Research articles on HAE published between 1983 and 2023 were retrieved from the Web of Science Core Collection database. A total of 319 articles were selected for bibliometric analysis, which was conducted using the CiteSpace and VOSviewer software. The analysis focused on key variables such as publication volume, authors, journals, countries, references, and keywords.

RESULTS

The analysis revealed a significant increase in research on HAE over the past four decades, particularly after 1995. China and Switzerland emerged as the leading countries in terms of publication volume, with Bruno Gottstein and Vuitton DA identified as the most influential authors in this field. Key research areas include the interaction between the pathogen and the host immune system, as well as advances in disease diagnosis and treatment strategies. The keyword co-occurrence analysis highlighted the primary themes and identified emerging trends within the research landscape.

CONCLUSION

This study provides a comprehensive framework for understanding HAE immunology and highlights research hotspots, future directions, key contributors, and the importance of international cooperation.

FGL2: A new target molecule for coagulation and immune regulation in infectious disease

Infectious diseases are complex inflammatory-immunologic host responses caused by various pathogens, such as viruses, bacteria, parasites, and fungi. In the process of infectious disease development, immune cells are activated, and a substantial number of inflammatory factors are released within the endothelium, which results in coagulation activation and the formation of intravascular thrombi. Furthermore, infection-induced hypercoagulability amplifies the inflammatory response and immune dysregulation. Emerging evidence suggests that fibrinogen-like protein 2 (FGL2) has a crucial role in facilitating procoagulant, pro-inflammatory, and immune-regulatory responses in various infectious diseases. This review illustrates the complex procoagulation and immunoregulatory roles of FGL2, suggesting it could be a target for novel immune interventions in intractable infectious diseases.

Current status of drug therapy for alveolar echinococcosis

Alveolar echinococcosis (AE) is a chronic zoonotic parasitic disease caused by infection with Echinococcus multilocularis. AE is associated with a high mortality rate and poses a significant threat to human health. The primary treatment for AE is surgical resection of the lesions; however, owing to its long incubation period and insidious disease progression, many patients are diagnosed only after the onset of complications such as liver cirrhosis, jaundice, and portal hypertension, which preclude curative surgical intervention. For patients who are unwilling or unable to undergo surgery, lifelong administration of anti-AE medications is necessary. Benzimidazole compounds, such as albendazole and mebendazole, are the current mainstays of treatment, offering good efficacy. Nevertheless, these medications primarily inhibit parasite proliferation rather than eradicate the infection, and their long-term use can lead to significant drug-related toxic effects. Consequently, there is an urgent need to develop new therapeutic strategies that convey better efficacy and reduce the adverse effects associated with current treatments. Recent advancements in AE therapy include novel synthetic compounds such as antiviral agents, antibiotics, antineoplastic agents, immunosuppressants, and antiangiogenic agents, as well as natural compounds derived from traditional Chinese and Tibetan medicine. These new drugs show promising clinical potential because they interfere with parasitic metabolic pathways and cellular structures. This review aims to discuss recent research on AE drug therapy, including mechanisms of action, dosing regimens, signalling pathways, and therapeutic outcomes, with a goal of providing new insights and directions for the development of anti-AE drugs and summarizing current advancements in AE pharmacotherapy.

Design of a novel EmTSP-3 and EmTIP based multi-epitope vaccine against Echinococcus multilocularis infection

Background

Current treatments and prevention strategies for echinococcosis are inadequate. Recent advancements in molecular vaccine development show promise against Echinococcus granulosus; however, Echinococcus multilocularis remains a challenge. A Multi-epitope Vaccine could potentially induce specific B and T lymphocyte responses, thereby offering protection against Echinococcus multilocularis infection.

Methods

This study aimed to develop a MEV against alveolar echinococcosis. Key epitopes from the Echinococcus multilocularis proteins EmTSP3 and EmTIP were identified using immunoinformatics analyses. These analyses were conducted to assess the MEV feasibility, structural characteristics, molecular docking, molecular dynamics simulations, and immune simulations. The immunogenicity and antigenicity of the vaccine were evaluated through in vitro and in vivo experiments, employing ELISA, Western blotting, FCM, challenge infection experiments, and ELISPOT.

Results

The effective antigenicity and immunogenicity of MEV were demonstrated through immunoinformatics, as well as in vitro and in vivo experiments. In vitro experiments revealed that MEV increased the secretion of IFN-γ and IL-4 in PBMC and successfully bound to specific antibodies in patient serum. Furthermore, mice immunized with MEV developed a robust immune response, characterized by elevated levels of CD4+ and CD8+ T-cells, increased secretion of IFN-γ and IL-4 by specific Th1 and Th2 cells, and heightened serum antibody levels. Importantly, MEV reduced the weight of cysts by conferring resistance against echinococcosis. These findings suggest that MEV is a promising candidate for the prevention of Echinococcus multilocularis infection.

Conclusion

A total of 7 CTL, 7 HTL, 5 linear B-cell, and 2 conformational B-cell epitopes were identified. The vaccine has demonstrated effective antigenicity and immunogenicity against AE through molecular docking, immune simulation, molecular dynamics studies, and both in vitro and in vivo experiments. It provides effective protection against Echinococcus multilocularis infection, thereby laying a foundation for further development.

The expression of CTLA-4 in hepatic alveolar echinococcosis patients and blocking CTLA-4 to reverse T cell exhaustion in Echinococcus multilocularis-infected mice

Alveolar echinococcosis (AE) is a zoonotic parasitic disease caused by the infection of Echinococcus multilocularis (E. multilocularis) larvae. Cytotoxic T-lymphocyte antigen 4 (CTLA-4) produces inhibitory signals and induces T cell exhaustion, thereby inhibiting the parasiticidal efficacy of the liver immune system. Therefore, the purpose of this study is to explore how T-cell exhaustion contributes to AE and whether blocking CTLA-4 could reverse T cell exhaustion. Here we discovered that the expression of CTLA-4 was increased in the infiltrating margin around the lesion of the liver from AE patients by using western blot and immunohistochemistry assay. Multiple fluorescence immunohistochemistry identified that CTLA-4 and CD4/CD8 molecules were co-localized. For in vitro experiments, it was found that the sustained stimulation of E. multilocularis antigen could induce T cell exhaustion, blocking CTLA-4-reversed T cell exhaustion. For in vivo experiments, the expression of CTLA-4 was increased in the liver of E. multilocularis-infected mice, and the CTLA-4 and CD4/CD8 molecules were co-localized. Flow cytometry analysis demonstrated that the percentages of both CD4+ T cells and CD8+ T cells in the liver and peripheral blood were significantly increased and induced T exhaustion. When the mice were treated with anti-CTLA-4 antibodies, the number and weight of the lesions decreased significantly. Meanwhile, the flow cytometry results suggested that blocking CTLA-4 could effectively reverse T cell exhaustion and reactivate immune function. Our work reveals that blocking CTLA-4 could effectively reverse the T cell exhaustion caused by E. multilocularis and could be used as a novel target for the treatment of AE.

Fibrinogen-like protein 2 in inflammatory diseases: A future therapeutic target

Fibrinogen-like protein 2 (FGL2), a member of the fibrinogen family, exists as a membrane-bound protein with immune-associated coagulation activity and a soluble form possessing immunosuppressive functions. The immunomodulatory role of FGL2 is evident in fibrin deposition-associated inflammatory diseases and cancer, suggesting that FGL2 expression could be exploited as a disease biomarker and a therapeutic target. Recently, in vitro studies and knockout and transgenic animal FGL2 models have been used by us and others to reveal the involvement of FGL2 in the pathogenesis of various inflammatory diseases. This review summarizes our current knowledge of the immunomodulatory role of FGL2 in inflammatory diseases and examines the role of FGL2 as a potential therapeutic target.

Endogenous IL-33 Accelerates Metacestode Growth during Late-Stage Alveolar Echinococcosis

During the course of the infectious disease alveolar echinococcosis (AE), the larval stage of Echinococcus multilocularis develops in the liver, where an initial Th1/Th17 immune response may allow its elimination in resistant individuals. In patients susceptible to infection and disease, the Th2 response initiates later, inducing tolerance to the parasite. The role of interleukin 33 (IL-33), an alarmin released during necrosis and known to drive a Th2 immune response, has not yet been described during AE. Wild-type (WT) and IL-33-/- C57BL/6J mice were infected by peritoneal inoculation with E. multilocularis metacestodes and euthanized 4 months later, and their immune response were analyzed. Immunofluorescence staining and IL-33 enzyme-linked immunosorbent assay (ELISA) were also performed on liver samples from human patients with AE. Overall, metacestode lesions were smaller in IL-33-/- mice than in WT mice. IL-33 was detected in periparasitic tissues, but not in mouse or human serum. In infected mice, endogenous IL-33 modified peritoneal macrophage polarization and cytokine profiles. Th2 cytokine concentrations were positively correlated with parasite mass in WT mice, but not in IL-33-/- mice. In human AE patients, IL-33 concentrations were higher in parasitic tissues than in distant liver parenchyma. The main sources of IL-33 were CD31+ endothelial cells of the neovasculature, present within lymphoid periparasitic infiltrates together with FOXP3+ Tregs. In the murine model, periparasitic IL-33 correlated with accelerated parasite growth putatively through the polarization of M2-like macrophages and release of immunosuppressive cytokines IL-10 and transforming growth factor β1 (TGF-β1). We concluded that IL-33 is a key alarmin in AE that contributes to the tolerogenic effect of systemic Th2 cytokines. IMPORTANCE Infection with the metacestode stage of Echinococcus multilocularis, known as alveolar echinococcosis, is the most severe cestodosis worldwide. However, less than 1% of exposed individuals, in which the immune system is unable to control the parasite, develop the disease. The factors responsible for this interindividual variability are not fully understood. In this in vivo study comparing wild-type and IL-33-/- infected mice, together with data from human clinical samples, we determined that IL-33, an alarmin released following tissue injury and involved in the pathogenesis of cancer and asthma, accelerates the progression of the disease by modulating the periparasitic microenvironment. This suggests that targeting IL-33 could be of interest for the management of patients with AE, and that IL-33 polymorphisms could be responsible for increased susceptibility to AE.

Alveolar echinococcosis in immunocompromised hosts

BACKGROUND

Alveolar echinococcosis (AE) results of an infection with the larval stage of Echinococcus multilocularis. It has been increasingly described in individuals with impaired immune responsiveness.

OBJECTIVES

This narrative review aims at describing the presentation of AE according to the type of immune impairment, based on retrospective cohorts and case reports. Implications for patient management and future research are proposed accordingly.

SOURCES

Targeted search was conducted in PubMed using ((alveolar echinococcosis) OR (multilocularis)) AND ((immunosuppressive) OR (immunodeficiency) OR (AIDS) OR (solid organ transplant) OR (autoimmunity) OR (immune deficiency)). Only publications in English were considered.

CONTENT

Seventeen publications were found, including 13 reports of 55 AE in immunocompromised patients (AE/IS) and 4 retrospective studies of 755 AE immunocompetent patients and 115 AE/IS (13%). The cohorts included 9 (1%) solid organ transplantation (SOT) recipients, 2 (0.2%) HIV patients, 41 (4.7%) with chronic inflammatory/autoimmune diseases (I/AID) and 72 (8.3%) with malignancies. SOT, I/AID and malignancies, but not HIV infection, were significantly associated with AE (odds ratios of 10.8, 1.6, 5.9, and 1.3, respectively). Compared to AE immunocompetent patients, AE/IS was associated with earlier diagnosis (PNM stages I-II: 49/85 (58%) vs. 137/348 (39%), p < 0.001), high rate of atypical imaging (24/50 (48%) vs. 106/375 (28%), p < 0.01), and low sensitivity of serology (19/77 (25%) vs. 265/329 (81%), p < 0.001). Unusually extensive or disseminated infections were described in SOT and I/AID patients.

IMPLICATIONS

Patients who live in endemic areas should benefit from serology before onset of a long-term immunosuppressive therapy, even if the cost-benefit ratio has to be evaluated. Physicians should explain AE to immunocompromised patients and think about AE when finding a liver lesion. Further research should address gaps in knowledge of AE/IS. Especially, extensive and accurate records of AE cases have to be collected by multinational registries.

Indoleamine 2,3-dioxygenase 1 signaling orchestrates immune tolerance in Echinococcus multilocularis-infected mice

The cestode Echinococcus multilocularis larva infection causes lethal zoonotic alveolar echinococcosis (AE), a disease posing a great threat to the public health worldwide. This persistent hepatic tumor-like disease in AE patients has been largely attributed to aberrant T cell responses, of which Th1 responses are impeded, whilst Th2 and regulatory T cell responses are elevated, creating an immune tolerogenic microenvironment in the liver. However, the immune tolerance mechanisms are not fully understood. Dendritic cells (DCs) are key cellular components in facilitating immune tolerance in chronic diseases, including AE. Here, we demonstrate that indoleamine 2,3-dioxygenase 1-deficient (IDO1-/-) mice display less severe AE as compared to wild-type (WT) mice during the infection. Mechanistically, IDO1 prevents optimal T cells responses by programming DCs into a tolerogenic state. Specifically, IDO1 prevents the maturation and migration potential of DCs, as shown by the significantly enhanced expression of the antigen-presenting molecule (MHC II), costimulatory molecules (CD80 and CD86), and chemokine receptors (CXCR4 and CCR7) in infected IDO1-/- mice as compared to infected wild-type mice. More importantly, the tolerogenic phenotype of DCs is partly reverted in IDO1-/- mice, as indicated by enhanced activation, proliferation, and differentiation of both CD4+ and CD8+ - T cells upon infection with Echinococcus multilocularis, in comparison with WT mice. Interestingly, in absence of IDO1, CD4+ T cells are prone to differentiate to effector memory cells (CD44+CD62L-); in contrast, CD8+ T cells are highly biased to the central memory phenotype (CD44+CD62L+). Overall, these data are the first to demonstrate the essential role of IDO1 signaling in inducing immunosuppression in mice infected with Echinococcus multilocularis.

Primary Infection by E. multilocularis Induces Distinct Patterns of Cross Talk between Hepatic Natural Killer T Cells and Regulatory T Cells in Mice

The larval stage of the helminthic cestode Echinococcus multilocularis can inflict tumor-like hepatic lesions that cause the parasitic disease alveolar echinococcosis in humans, with high mortality in untreated patients. Opportunistic properties of the disease have been established based on the increased incidence in immunocompromised patients and mouse models, indicating that an appropriate adaptive immune response is required for the control of the disease. However, cellular interactions and the kinetics of the local hepatic immune responses during the different stages of infection with E. multilocularis remain unknown. In a mouse model of oral infection that mimics the normal infection route in human patients, the networks of the hepatic immune response were assessed using single-cell RNA sequencing (scRNA-seq) of isolated hepatic CD3⁺ T cells at different infection stages. We observed an early and sustained significant increase in natural killer T (NKT) cells and regulatory T cells (Tregs). Early tumor necrosis factor (TNF)- and integrin-dependent interactions between these two cell types promote the formation of hepatic lesions. At late time points, downregulation of programmed cell death protein 1 (PD-1) and ectonucleoside triphosphate diphosphohydrolase 1 (ENTPD1)-dependent signaling suppress the resolution of parasite-induced pathology. The obtained data provide fresh insight into the adaptive immune responses and local regulatory pathways at different infection stages of E. multilocularis in mice.

Echinococcosis Is Associated with the Increased Prevalence of Intestinal Blastocystis Infection in Tibetans and Host Susceptibility to the Blastocystis in Mice

Blastocystis is a common human intestinal protozoan parasite. Little is known about its prevalence in echinococcosis. This study tested whether Echinococcus multilocularis infection would increase host susceptibility to Blastocystis. A total of 114 fecal samples (68 hydatid disease patients and 46 healthy people) were collected from Tibetans in the Qinghai province in China. The presence of Blastocystis was identified by sequencing of the small subunit (SSU) rRNA gene. Balb/c mice were co-infected with Blastocystis and E. multilocularis and tested for host susceptibility to Blastocystis. The overall Blastocystis prevalence was 12.3%; 16.2% in the patients and 4.4% in healthy people (p < 0.05). Sequence analysis identified three known Blastocystis genotypes, including ST1, ST2, and ST3, and one unknown genotype. Experimental dual infection significantly reduced mouse survival rate (20%), induced more severe signs, and increased intestinal damages with a higher intestinal colonization level of Blastocystis. The mouse model showed that E. multilocularis infection increases host susceptibility to Blastocystis. Our study shows a significantly higher prevalence of Blastocystis in patients with liver echinococcosis and reveals that non-intestinal E. multilocularis infection increases host susceptibility to the Blastocystis. Our results highlight that E. multilocularis infection is associated with Blastocystis. These findings remind us that more attention should be paid to the gut health of the patients with a helminth infection during clinical patient care.

Echinococcus multilocularis specific antibody, systemic cytokine, and chemokine levels, as well as antigen-specific cellular responses in patients with progressive, stable, and cured alveolar echinococcosis: A 10-year follow-up

Background

The infestation with Echinococcus multilocularis larvae may persist in humans for up to decades without evident clinical symptoms. Longitudinal investigations are needed to understand the dynamic immunological processes in alveolar echinococcosis (AE) patients associated with an active and progressive, a stable or a regressive course of disease.

Methodology/Principal findings

This study evaluated the E. multilocularis specific antibody responses, systemic cytokine, and chemokine serum levels over a 10-year follow-up period, as well as cellular responsiveness in AE patients. Our results demonstrate a rapid decrease in antibodies against E. multilocularis specific antigen Em2+. Especially in cured patients, these antibodies remained negative, making them a significant predictor for cured AE. E. multilocularis specific IgG4, and indirect hemagglutination IHA decreased later in time, after around 5 years. While total IgE did not show significant dynamics over the course of disease, E. multilocularis specific IgE decreased after one to two years, and increasing levels were a significant predictor of progressive disease. There was no significant change in systemic IL-8, IL-9, CCL18 or CCL20 serum levels over time. Univariate analysis across groups indicated lower IL-8 levels in cured patients; however, this result could not be confirmed by multivariate analysis. Levels of CCL17 decreased during treatment, especially in cured patients, and thus might serve as a predictive or risk factor for progressive disease. Levels of IL-10 and CCL13 decreased during disease, especially after five and ten years of intervention. The E. multilocularis antigen (EmAg) inducible cellular productions of MCP1(CCL13), TARC(CCL17) and PARC(CCL18) were lowest in patients with cured AE and infection-free controls, while the EmAg inducible cellular production of IFN-γ increased after cure. Significant positive cytokine and chemokine correlations were observed in AE patients for IL-9, IL-10, CCL13(MCP-4), CCL17(TARC) and CCL20(LARC)(for all p<0.001). E. multilocularis specific IgG4 response correlated positively with TARC (p<0.001). Both markers enhanced over time in progressive disease and decreased after cure. The levels of IL-8, IL-10, MCP4 and LARC enhanced with AE regression.

Conclusions/Significance

Repeated biomarker surveys are advisable to evaluate progression or regression of disease during longitudinal follow-up and such analyses can support imaging techniques and improve staging of AE patients.

Alveolar echinococcosis (AE) is a severe disease caused by Echinococcus multilocularis, the fox tapeworm. Humans exposed to E. multilocularis may develop severe AE with progressive tissue and organ infiltrating growth of the larval stage. The E. multilocularis larvae appear to have developed effective immune evasion mechanisms which facilitate an asymptomatic incubation and an extended host and parasite coexistence for decades. Over a 10-year follow-up, this investigation aimed to gain a better understanding of the immunological process associated with an active and progressive, a stable or a regressive course of AE. In summary, the rapid decrease of antibodies against the E. multilocularis specific antigen Em2+, especially in cured patients, makes them a significant predictor for cured AE. The positive relation of E. multilocularis specific IgG4 responses and chemokine levels of TARC can indicate AE progression when both enhance over time. Enhanced levels of cytokines IL-8, IL-10, and chemokines MCP4 and LARC may predict AE regression. Repeated biomarker surveys are advisable to evaluate progression or regression of AE during longitudinal follow up, and such analyses can support imaging techniques and improve staging of AE patients.

An Excretory Protein of Echinococcus multilocularis Inhibits Complement Classical Pathway Activation

Introduction

Alveolar echinococcosis is a lethal zoonosis caused by Echinococcus multilocularis (E.m) larvae. The mechanism by which E.m evades host immune attacks and ensures long-term survival remains unexplained. The complement system is a cascade of sequentially activated complement proteins that results in opsonization-related phagocytosis or membrane lysis of invading organisms. Excretory/secretory proteins (ESPs) of parasites are the main antigens that induce the immune response and play important roles in the long-term survival.

Methods

We investigated the possibility that E.m inhibits complement activation through ESPs and examined the potential related mechanism. A haemolysis assay was used to determine if and how in vitro culture medium of E.m containing ESPs can inhibit complement activation. Potential ESPs were annotated using bioinformatics methods, and one ESP was subsequently expressed as a recombinant protein with a eukaryotic expression system. The ability of this protein to inhibit complement activation was also tested by haemolysis assay.

Results

These assays showed that in vitro culture medium of E.m inhibited activation of the complement classical pathway. EmuJ_000439500 encodes a protein containing seven Sushi domains, which was the only potential E.m-derived complement inhibitor (Em-CI, UniProt: A0A068Y4F2) annotated among the 653 ESPs. Recombinant Em-CI also displayed the ability to inhibit activation of the complement classical pathway.

Discussion

The discovery of Em-CI sheds light on the mechanism by which E.m escapes killing by the complement system and provides potential targets for immunotherapy for parasitic diseases.

Evaluation of inflammatory parameters in patients with hepatic hydatid disease

BACKGROUND

To the best of our knowledge, the association of inflammatory parameters with hepatic hydatid disease (HD) has not been investigated in a single study. We aimed to evaluate the potential value of inflammatory indices in this disorder.

METHODS

The retrospective study including 114 patients was performed from January 2016 to November 2019. Clinical characteristics and laboratory data for all participants were collected and analysed. The levels of inflammatory parameters were compared in the patient and control group, the predictive value of these inflammatory parameters was assessed by the logistic regression analysis and receiver operating characteristic curve, and differences between pre- and post-surgical operations were compared by pair tests.

RESULTS

Significantly higher levels of platelet distribution width (PDW), eosinophil percentage (EOS %), neutrophil to lymphocyte ratio (NLR), gamma-glutamyl transpeptidase to platelet ratio (GPR) and alkaline phosphatase to platelet ratio (APPR) and lower levels of platelet (PLT) and prognostic nutritional index (PNI) were observed in patients than in controls. Multivariate analyses showed that hydatid could induce the abnormal levels of these parameters, of which APPR and PNI had more obvious changes as compared to other parameters. The levels of PDW and APPR significantly decreased after surgical treatment.

CONCLUSIONS

Inflammatory parameters closely associated with the hepatic HD could be used in the evaluation of treatment as assistant indexes.KEY MESSAGEHydatid disease (HD) seriously endangers public health and economic development.Inflammatory parameters that are readily available and acceptable in routine clinical practice could be closely associated with HD.Inflammatory parameters could be used in the evaluation of disease development by combing with histological and radiological results in future studies.

Microcyst fluid promotes the migration and invasion of fibroblasts in the adventitial layer of alveolar echinococcosis

Alveolar echinococcosis (AE) caused by Echinococcus multilocularis (E. multilocularis), characterized by lesions composed of an aggregate of microcysts embedded in a granulomatous host's reaction. The periphery of parasite granulomas often additionally displays fibrotic reactions of varying intensity, in which E. multilocularis microenvironment fibroblasts (EMFs) laid down collagen. However, the regulation of EMFs by the infiltration of E. multilocularis microcyst fluid (MF) into granulomas remains poorly defined. This study aimed to investigate the effect of MF on migration and invasion of primary isolated EMFs cells. A mouse model of secondary infection with AE was established, and the model construction was evaluated by HE staining. EMFs were cultured in primary by tissue block adherency method. The isolated cells were identified by qPCR, immunofluorescence and Western blot. Then CCK-8 assay, cell migration/invasion assay and flow cytometry were performed to detect the effects of MF on the proliferation, migration, invasion and cell cycle of EMFs, respectively. The expressions of MMP2 and MMP9 at mRNA and protein levels in EMFs were detected by RT-qPCR and Western blot. The effect of PI3K-Akt signal transduction pathway on regulating the expression of MMPs expression was assessed by Western blot. As indicated from the results, EMFs were successfully isolated from the E. multilocularis microenvironment and identified as myofibroblasts. MF significantly facilitated the proliferation and cell cycle progression of EMFs. In addition, MF significantly improved the migration and invasion of EMFs. MF was further confirmed to up-regulate mRNA and protein expressions of MMP2 and MMP9 in EMFs, which was related to the activation of the PI3K-Akt signaling pathway. The present study demonstrates that MF can promote the migration and invasion of EMFs cells significantly, which might be via activating PI3K-Akt signaling pathway.

Alveolar echinococcosis: what triggers emergence in North America, Central Europe and Asia?

PURPOSE OF REVIEW

Infection with the larval (metacestode) stage of Echinococcus multilocularis causes alveolar echinococcosis (AE), a serious hepatic disorder. The parasite has increased its infection extensity in wildlife and domestic dogs, mainly due to urbanization and spatial extension of wildlife hosts in Europe, Asia as well as North America, resulting in emerging infection risk for humans.

RECENT FINDINGS

In hyperendemic areas such as Kyrgyzstan and China, ecological and socioeconomic changes have been associated with the unpredictable increase of AE cases. In North America, the appearance of the European-like genotype is of concern. In Europe, the annual increase of human case numbers reached a plateau even in hyperendemic situations. Therefore, we conclude that most of the exposed individuals are resistant to parasite invasion and/or to disease development. Thus, AE develops in a few healthy individuals, but preferentially in immunosuppressed patients.

SUMMARY

In the future, improved diagnostic strategies will allow more precise estimations of transmission routes including the role of food, water and direct dog contact, which should yield improved public health recommendations. Finally, understanding protective innate and acquired immune mechanisms as well as parasite-driven immune-evasion processes will be essential to develop curative therapies in nonoperable patients and, futuristically, appropriate vaccines.

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.

Hepatic Alveolar Echinococcosis

Hepatic alveolar echinococcosis (HAE) is a rare but severe zoonosis caused by the pseudotumoral intrahepatic development of the larval stage of the tapeworm Echinococcus multilocularis. HAE is present only in the Northern Hemisphere, predominantly in China. Currently, there is a significant resurgence of cases in historically endemic areas associated with emergence of HAE in countries not previously concerned. Today, in European countries, HAE is often discovered by chance; however, clinicians should be made aware of opportunistic infections that progressively emerged recently as a result of therapeutic or pathological immunosuppression. Ultrasonography is the key first-line diagnostic procedure, with specific serology providing confirmation in 95% of the cases. Albendazole, only parasitostatic, is the mainstay for treatment. Surgical resection, if feasible, is the gold standard for treatment, and more patients are currently eligible for this option because of an earlier diagnosis. The prognosis has considerably improved but remains poor in countries where access to care is less favorable.

Revisiting the Mechanisms of Immune Evasion Employed by Human Parasites

For the establishment of a successful infection, i.e., long-term parasitism and a complete life cycle, parasites use various diverse mechanisms and factors, which they may be inherently bestowed with, or may acquire from the natural vector biting the host at the infection prelude, or may take over from the infecting host, to outmaneuver, evade, overcome, and/or suppress the host immunity, both innately and adaptively. This narrative review summarizes the up-to-date strategies exploited by a number of representative human parasites (protozoa and helminths) to counteract the target host immune defense. The revisited information should be useful for designing diagnostics and therapeutics as well as vaccines against the respective parasitic infections.

Exosomal microRNA let-7-5p from Taenia pisiformis Cysticercus Prompted Macrophage to M2 Polarization through Inhibiting the Expression of C/EBP δ

Cysticercus pisiformis, the larval stage of Taenia pisiformis, causes serious illness in rabbits that severely impacts the rabbit breeding industry. An inhibitive Th2 immune response can be induced by let-7-enriched exosomes derived from T. pisiformis cysticercus. However, the underlying molecular mechanisms are not completely understood. Here, we report that exosomal miR-let-7-5p released by T. pisiformis cysticercus played a critical role in the activation of M2 macrophages. We found that overexpression of let-7-5p in M1 macrophages decreased M1 phenotype expression while promoting polarization to the M2 phenotype, which is consistent with experimental data in exosome-treated macrophages alone. In contrast, knockdown of let-7-5p in exosome-like vesicles promoted M1 polarization and decreased M2 phenotype expression. Furthermore, down-regulation of transcription factor CCAAT/enhancer-binding protein (C/EBP)-δ resulted in the decrease of M1 phenotype markers and increase of M2 phenotype markers. These results suggested that let-7 enriched in exosome-like vesicles from T. pisiformis metacestodes can induce M2 macrophage polarization via targeting C/EBP δ, which may be involved in macrophage polarization induced by T. pisiformis metacestodes. The finding helps to expand our knowledge of the molecular mechanism of immunosuppression and Th2 immune response induced by metacestodes.

Innate and adaptive immune responses following PD-L1 blockade in treating chronic murine alveolar echinococcosis

BACKGROUND

Programmed death-1 (PD-1) and programmed death ligand-1 (PD-L1) immune checkpoint blockade are efficacious in certain cancer therapies.

OBJECTIVES

The present study aimed to provide a picture about the development of innate and adaptive immune responses upon PD-L1 blockade in treating chronic murine AE.

METHODS

Immune treatment started at 6 weeks post-E. multilocularis infection, and was maintained for 8 weeks with twice per week anti-PD-L1 administration (intraperitoneal). The study included an outgroup-control with mice perorally medicated with albendazole 5 d/wk, and another one with both treatments combined. Assessment of treatment efficacy was based on determining parasite weight, innate and adaptive immune cell profiles, histopathology and liver tissue cytokine levels.

RESULTS/CONCLUSIONS

Findings showed that the parasite load was significantly reduced in response to PD-L1 blockade, and this blockade (a) contributed to T-cell activity by increasing CD4⁺ /CD8⁺ effector T cells, and decreasing Tregs; (b) had the capacity to restore DCs and Kupffer cells/Macrophages; (c) suppressed NKT and NK cells; and thus (d) lead to an improved control of E. multilocularis infection in mice. This study suggests that the PD-L1 pathway plays an important role by regulating adaptive and innate immune cells against E. multilocularis infection, with significant modulation of tissue inflammation.

Echinococcus multilocularis vesicular fluid induces the expression of immune checkpoint proteins in vitro

AIMS

Alveolar echinococcosis is a severe chronic helminthic infection that mimics a tumour-like disease. This study aimed at investigating in vitro interactions between Echinococcus multilocularis vesicular fluid (VF) and different immune checkpoints (PD-1/PD-L1, CTLA-4, LAG-3 and TIM-3).

METHODS AND RESULTS

Peripheral blood mononuclear cells (PBMC) from healthy blood donors were isolated by Ficoll. Natural killer (NK) cells were selected. Each type of cell was stimulated individually with E. multilocularis-VF. Expression of the different immune checkpoints was measured by flow cytometry on day 3 and day 6; all supernatants were used for immunoassays. Cells and supernatants from 22 healthy donors were analysed. A significant increase of PD-1, PD-L1, LAG-3 and TIM-3 was observed upon E. multilocularis-VF exposure for NK cells on day 3 (P < .05, Wilcoxon signed-rank test). A significant increase of PD-L1 and CTLA-4 was observed upon E. multilocularis-VF exposure for T cells on day 6 (P < .05, Wilcoxon signed-rank test), which was associated with increased levels of Th1 and Th2 cytokines P < .05, Wilcoxon signed-rank test).

CONCLUSION

These preliminary data suggest that immune checkpoints could be a way for E. multilocularis to modulate the host immune response during alveolar echinococcosis.

The correlations between Th1 and Th2 cytokines in human alveolar echinococcosis

Background

Alveolar echinococcosis (AE) is a zoonotic parasitic disease caused by Echinococcus multilocularis larval tapeworm infections in humans that severely impairs the health of affected patients in the northern hemisphere.

Methods

The expression levels of 20 cytokines associated with AE infection were measured by enzyme-linked immunosorbent assay, and the correlations between these cytokines were analysed in the R programming language.

Results

Serum cytokine levels differed among individuals in both the AE patient and healthy control groups. The results of the correlations among the cytokines showed obvious differences between the two groups. In the AE patients group, Th1 and Th2 cytokines formed a more complicated network than that in the healthy control group.

Conclusions

The altered correlations between Th1 and Th2 cytokines may be closely associated with AE infection, which may provide a new explanation for the essential differences between AE patients and healthy individuals.

A new dawn in the late stage of alveolar echinococcosis "parasite cancer"

Recently, it is found that there is high concentration of potassium in tumor interstitial fluid, which causes "T cell exhaustion" and even autophagy of lymphocytes in tumors. The immune mechanism of the late stage of alveolar echinococcosis (AE) is similar to that of tumor immunity. We speculate that the growth and development of the worm body, the necrosis of the worm body and the release of high concentrations of potassium after hepatocyte necrosis in the pathological process of AE may cause "T cell exhaustion" in AE patients. If this assumption can be confirmed experimentally, T cell adoptive transfer around the AE infiltration zone will be utilized to assist the treatment of AE patients with complex conditions.

Kupffer Cells: Important Participant of Hepatic Alveolar Echinococcosis

Aims: Kupffer cells (KCs) are the liver-resident macrophages and play a leading role in the regulation of liver homeostasis in physiological conditions and in pathology. The study aims to investigate the anti-echinococcosis effect of KCs and the effects of hepatic stellate cells (HSCs) activation in the progression of liver fibrosis in hepatic alveolar echinococcosis (hepatic AE).

Methods: Hematoxylin—eosin (H&E) and Masson staining were used to assess the pathological inflammatory changes and collagen deposition, respectively. Immunohistochemistry and qRT-PCR were used to detect the number of aggregates of KCs, the expression of cytokines and activation of HSCs.

Results: In the close group, H&E staining showed that the normal lobular structure was destroyed and inflammatory infiltration around the lesion could be observed, and Masson staining showed that blue collagen fibers were clearly deposited near the portal area. IHC showed that KCs surface markers CD68 and CD163, cytokine iNOS and Arg-1 were positively expressed in the vicinity of inflammatory lesions. qRT-PCR indicated that TNF-α, IL-10, and TGF-β1 secreted by KCs were significantly higher than those in the distance group (P < 0.01). It is worth noticing that the expression levels of anti-inflammatory cytokines were slightly higher than that of pro-inflammatory cytokines. Both IHC and qRT-PCR results showed that HSCs activation markers, the expression of α-SMA and Desmin significantly increased.

Conclusions: Our research indicates that KCs have immune-protective effect of anti-echinococcosis and promote liver fiber repair, and it also suggests that they have potential therapeutic value for patients with hepatic AE.

Echinococcus multilocularis inoculation induces NK cell functional decrease through high expression of NKG2A in C57BL/6 mice

BACKGROUND

Alveolar echinococcosis (AE) is caused by the larval stage of Echinococcus multilocularis (E. multilocularis), and considered as public health issue. Parasite-host immune interaction is pivotal during infection. As a subset of innate lymphoid cells, NK cells are known to play an important role during virus, bacteria, intra/extracellular parasitic infections and tumor progression. However, the possible role of NK cells in E. multilocularis infection in both human and murine is little known. Herein, the functional alteration of hepatic NK cells and their related molecules in E. multilocularis infected mice were studied.

METHODS

2000 protoscoleces (PSCs) were injected to C57BL/6 mice via the portal vein to establish secondary E. multilocularis infection. NK cells population and their related molecules (CD69, Ly49D, Ly49G2, Ly49H, Ly49I, NKG2A, NKG2D, granzyme B, IFN-γ, TNF-α) were assessed by using fluorescence-activated cell sorter (FACS) techniques and qRT-PCR. NK cell depletion was performed for further understanding the possible function of NK cells during infection.

RESULTS

The total frequencies of NK cells and NK-derived IFN-γ production were significantly reduced at designated time points (2, 4, 12 weeks). The liver resident (CD49a+DX5-) NK cells are decreased at 4 weeks after inoculation and which is significantly lower than in control mice. Moreover, in vivo antibody-mediated NK cell depletion increased parasitic load and decreased peri-parasitic fibrosis. Expression of the inhibitory receptor NKG2A was negatively related to NK- derived IFN-γ secretion.

CONCLUSIONS

Our study showed down regulates of NK cells and upper regulates of NKG2A expression on NK cells during E. multilocularis infection. Reduction of NK cell frequencies and increased NKG2A might result in low cytotoxic activity through decreased IFN-γ secretion in E. multilocularis infection. This result might be helpful to restore NK cell related immunity against E. multilocularis infection to treat alveolar echinococcosis.

Elevated incidence of alveolar echinococcosis in immunocompromised patients

Introduction

Recent experimental data has revealed that the course of alveolar echinococcosis (AE) depends on adaptive immunity. For this study, we aimed to analyze the incidence and outcome of AE in immunocompromised humans.

Material and methods

Retrospective analysis of 131 patients with a median age of 54 years treated for AE between 1971 and 2017 at a Swiss tertiary referral Centre. Fifty-two percent were females and 65 patients (50%) were diagnosed incidentally. Fourteen patients (16%) were operated on laparoscopically. Overall, median follow-up was 48 months.

Results

New diagnoses have increased fourfold in immunocompetent and tenfold in immunocompromised patients in the past decade (p ≤ 0.005). Forty-one patients (31.3%) had co-existing or previous immunosuppressive conditions including 16 malignancies (36%), 11 auto-immune diseases or immunosuppressive therapies (31%), 5 infectious diseases (11%), 4 chronic asthma conditions (9%), 2 previous transplantations (4%) and 4 other immunocompromising conditions (9%). Serum levels of anti-Em18, −Em2 and -EgHF antibodies were neither associated with immunocompetence at diagnosis nor during follow-up, but significantly decreased after treatment with benzimidazole (n = 43) or surgery (n = 88) in all patients. Adjuvant therapy for ≥1 year (p = 0.007) with benzimidazole and resection status (R0) (p = 0.002) were both correlated with recurrence-free survival. Survival at 5 and 10 years after surgery was 97% and 94%, respectively, and after conservative treatment 91% and 73%, respectively. Curative surgery (p = 0.014) and immunocompetence (p = 0.048) correlated significantly with overall survival.

Conclusion

The incidence of human AE has increased over the last 2 decades with surgical interventions resulting in excellent outcomes. We have observed an association of immunosuppressive conditions with both incidence and survival of AE eventually justifying the implementation of a screening program for patients at risk in endemic regions.

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Alveolar echinococcosis incidence increased significantly in Switzerland.

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Immunosuppression may lead to an increased susceptibility for the disease.

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Coexisting immunosuppressive conditions lead to worse survival of AE.

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Adjuvant treatment with benzimidazole increases recurrence-free survival.

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Resections with sufficient safety margin improve recurrence-free survival.

Echinococcus granulosus cyst fluid enhances epithelial-mesenchymal transition

Cystic echinococcosis is characterized by fluid-filled hydatid cysts in the liver and lungs. The cysts are surrounded by a host fibrous layer (the pericyst) which acts to isolate the parasite from surrounding tissues. Previous studies in liver cysts have indicated that the parasite may be a stimulating fibrosis. The aim of this study was to investigate whether hydatid cyst fluid (HCF) could influence the potential for fibrosis to occur in lung tissue by stimulating epithelial to mesenchymal transition (EMT) in a human lung epithelial cell line. An adenocarcinoma-derived alveolar basal epithelial cell line (A549) was used as a model for human alveolar epithelial cells (AEC II). These were cultured in vitro with HCF (UK sheep origin). Assays to investigate cell proliferation, cell migration and expression of cytoskeletal markers showed that HCF could stimulate changes indicative of EMT, including enhanced cell proliferation and migration; increased expression of mesenchymal cytoskeletal markers (fibronectin and vimentin) accompanied by a down-regulation of an epithelial marker (E-cadherin). Molecules within hydatid cyst fluid are capable of inducing phenotypic changes in A549 cells indicating that the parasite has the potential to modify lung epithelial cells which could contribute to fibrotic reactions.

Echinococcosis: Advances in the 21st Century

Echinococcosis is a zoonosis caused by cestodes of the genus Echinococcus (family Taeniidae). This serious and near-cosmopolitan disease continues to be a significant public health issue, with western China being the area of highest endemicity for both the cystic (CE) and alveolar (AE) forms of echinococcosis. Considerable advances have been made in the 21st century on the genetics, genomics, and molecular epidemiology of the causative parasites, on diagnostic tools, and on treatment techniques and control strategies, including the development and deployment of vaccines. In terms of surgery, new procedures have superseded traditional techniques, and total cystectomy in CE, ex vivo resection with autotransplantation in AE, and percutaneous and perendoscopic procedures in both diseases have improved treatment efficacy and the quality of life of patients. In this review, we summarize recent progress on the biology, epidemiology, diagnosis, management, control, and prevention of CE and AE. Currently there is no alternative drug to albendazole to treat echinococcosis, and new compounds are required urgently. Recently acquired genomic and proteomic information can provide a platform for improving diagnosis and for finding new drug and vaccine targets, with direct impact in the future on the control of echinococcosis, which continues to be a global challenge.

Subcutaneous Inoculation of Echinococcus multilocularis Induces Delayed Regeneration after Partial Hepatectomy

Alveolar echinococcosis (AE) is caused by the larval stage of echinococcus multilocularis (E. multilocularis), and hepatectomy is the main modality in hepatic AE patients. Liver regeneration after partial hepatectomy (PHx) in such patients is challenging, and further investigation is needed. Thus far, knowledge regarding the possible impact of E. multilocularis on liver regeneration after PHx is limited. Herein, a subcutaneous infection model of E. multilocularis was developed in C57 BL/6 mice, and after 3 months, PHx was performed. Plasma and liver samples were harvested under inhalational isofluorane (2%) anaesthesia at designated post-PHx time points (0, 24, 48, 96 and 168 h). The parameters included the future remnant liver/body weight ratio (FLR/BW), liver function tests (AST and ALT) and related cytokines (TNF-α, IL-6, Factor V, HMGB1, TGF-β, TSP-1, and TLR4) and proteins (MyD88 and STAT3). To assess the proliferation intensity of hepatocytes, BrdU, Ki67 and PAS staining were carried out in regenerated liver tissue. The FLR/BW in the infected group from 48 h after surgery was lower than that in the control group. The BrdU positive hepatocyte proportions reached their peak at 48 h in the control group and 96 h in the infected group and then gradually decreased. During the first 48 h after surgery, both the AST and ALT levels in the infected group were lower; however, these levels were altered from 96 h after surgery. In the infected group, the concentrations and mRNA expression levels of the pre-inflammatory cytokines TNF-α and IL-6 demonstrated a delayed peak. Moreover, post-operatively, the TGF-β and TSP-1 levels showed high levels in the infected group at each different time-point compared to those in the control group; however, high levels of TGF-β were observed at 96 h in the control group. The MyD88 and STAT3 protein expression levels in the infected group were markedly higher than those in the control group 96 h after surgery. Delayed liver regeneration after PHx was observed in the C57 BL/6 mice with the subcutaneous infection of E. multilocularis in the current study. This phenomenon could be partially explained by the alteration in the pro-inflammatory cytokines in the immunotolerant milieu induced by chronic E. multilocularis infection.

A Rare Case of Pancreatic Tail Hydatid Cyst with Incidental Adenocarcinoma of the Pancreatic Body

Pancreatic hydatid cyst is a rare disease found mostly in endemic regions. Having no specific clinical signs, it may present with tension related abdominal pain, dyspepsia, a palpable mass, and signs of external pressure on the surrounding organs in accordance with localization of the lesion. Pancreatic carcinoma as a neoplastic pathology with poor prognosis can have various clinical presentations changing with localization of the tumor which sometimes has cystic components. Due to the distinct nature of these pathologies, surgical approach can be fairly different. In this report, we present a case of a 70-year-old patient who had an isolated hydatid cyst in the tail of the pancreas with an incidental pancreatic carcinoma in the corpus of the pancreas. The patient was treated with a subtotal pancreatectomy, having no problems in the postoperative period leading to uncomplicated discharge.

Immunotherapy of alveolar echinococcosis via PD-1/PD-L1 immune checkpoint blockade in mice

The growth potential of the tumour‐like Echinococcus multilocularis metacestode (causing alveolar echinococcosis, AE) is directly dependent upon the nature/function of the periparasitic adaptive host immune‐mediated processes. PD‐1/PD‐L1 pathway (programmed cell death 1), which inhibits lymphocytic proliferation in tumour development, is over‐expressed at the chronic stage of AE. We tested the impact of a PD‐1/PD‐L1 pathway blockade on the outcome of both chronic AE (intraperitoneal metacestode inoculation, secondary AE and SAE) and acute AE (peroral egg infection, primary AE and PAE). To assess the parasite proliferation potential, we measured parasite mass weight for SAE and liver lesion number for PAE. In both models, the parasite load was significantly decreased in response to anti‐PD‐L1 antibody treatment. In SAE, anti‐PDL1 administration was associated with increased Th1 response parameters and decreased Treg responses, while in PAE anti‐PDL1 administration was associated with fewer lesions in the liver and decreased Treg/Th2 responses. Our findings highly suggested that a PD‐1/PD‐L1 pathway blockade triggered the host immune responses in favour of an immune‐mediated control of E. multilocularis proliferation. Based on this, future studies that combine PD‐1/PD‐L1 blockade with a parasitostatic albendazole medication may yield in a putatively curative therapeutic approach to control alveolar echinococcosis.

Plasma IL-23 and IL-5 as surrogate markers of lesion metabolic activity in patients with hepatic alveolar echinococcosis

Fluorodeoxyglucose (FDG) uptake by alveolar echinococcosis (AE) liver lesions is a signal of their metabolic activity and of disease progression. In order to find a surrogate marker for this status, we investigated whether parameters of the peripheral and/or periparasitic immune responses were associated with metabolic activity in a prospective case-control study of 30 AE patients and 22 healthy controls. Levels of 18 cytokines and chemokines, representative of innate and adaptive immune responses, were assessed in plasma and peripheral cells of two groups of patients with (MAAE) and without (MIAE) metabolically active lesions, and in the liver of MAAE patients. Mixed cytokine profile was observed in the peripheral blood of AE patients, with a predominance of Th2, Th17 and Treg responses. Among the detected markers only plasma IL-5 and IL-23, more elevated in MAAE patients, were found discriminant. Discrimination between MAAE and MIAE patients obtained by using IL-23 was improved when IL-5 was used in combination. The combination of elevated levels of IL-5 and IL-23 is significantly associated with FDG uptake at PET scan. It offers a new tool for the follow-up of AE patients which could substitute to FDG-PET whenever non-available to assess disease progression.

Soluble fibrinogen like protein 2 (sFGL2), the novel effector molecule for immunoregulation

Soluble fibrinogen-like protein 2 (sFGL2) is the soluble form of fibrinogen-like protein 2 belonging to the fibrinogen-related protein superfamily. It is now well characterized that sFGL2 is mainly secreted by regulatory T cell (Treg) populations, and exerts potently immunosuppressive activities. By repressing not only the differentiation and proliferation of T cells but also the maturation of dendritic cells (DCs), sFGL2 acts largely as an immunosuppressant. Moreover, sFGL2 also induces apoptosis of B cells, tubular epithelial cells (TECs), sinusoidal endothelial cells (SECs), and hepatocytes. This mini-review focuses primarily on the recent literature with respect to the signaling mechanism of sFGL2 in immunomodulation, and discusses the clinical implications of sFGL2 in transplantation, hepatitis, autoimmunity, and tumors.

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.

T-cell tolerance and exhaustion in the clearance of Echinococcus multilocularis: role of inoculum size in a quantitative hepatic experimental model

The local immune mechanisms responsible for either self-healing or sustained chronic infection are not clear, in the development of E. multilocularis larvae. Here, we developed a suitable experimental model that mimics naturally infected livers, according to the parasite load. We demonstrated that local cellular immunity and fibrogenesis are actually protective and fully able to limit metacestode growth in the liver of low or medium dose-infected mice (LDG or MDG), or even to clear it, while impairment of cellular immunity is followed by a more rapid and severe course of the disease in high dose-infected mice (HDG). And recruitment and/ or proliferation of memory T cells (including CD4 Tem, CD8 Tcm and CD8 Tem) and imbalance of T1/T2/T17/Treg-type T cells in liver were not only associated with clearance of the parasite infection in LDG, but also with increased hepatic injury in HDG; in particular the dual role of CD8 T cells depending on the parasite load and the various stages of metacestode growth. Besides, we first demonstrate the association between LAG3- or 2B4-expressing T cells exhaustion and HD inocula in late stages. Our quantitative experimental model appears fully appropriate to study immunomodulation as a therapeutic strategy for patients with Alveolar Echinococcosis.

Echinococcus multilocularis vesicular fluid inhibits activation and proliferation of natural killer cells

Alveolar echinococcosis is a severe chronic helminthic disease that mimics slow-growing liver cancer. The immune evasion strategy of Echinococcus multilocularis Leuckart, 1863 remains poorly understood. The aim of this study was to investigate in vitro the impact of E. multilocularis vesicular fluid (Em-VF) on peripheral blood mononuclear cells (PBMC) and on natural killer (NK) cells. PBMC and NK cells were exposed to Em-VF (1 µg/ml) during six days. The effect of Em-VF was assessed on CD69, viability and proliferation, and on and transforming growth factor β (TGF-β), interferon γ (IFN-γ), interleukin 17 (IL-17) and interleukin 10, using flow cytometry and ELISA, respectively. Exposure to Em-VF had no bearing on PBMC's viability, proliferation and expression of CD69. In contrast, higher levels of IL-17 at day three and of TGF-β at day six were observed in PBMC supernatant after exposure to Em-VF (p < 0.05, Wilcoxon signed-rank test). Exposure to Em-VF induced a significant decrease of CD69 expression of NK cells at day three and a significant decrease of proliferation of NK cells at day six (p < 0.05, Wilcoxon signed-rank test). In contrast, NK cells viability and levels of cytokines did not vary significantly over Em-VF stimulation. Exposure to Em-VF had a significant bearing on activation and proliferation of NK cells. NK cells may play an important role in the immune response of the host against E. multilocularis.

Depletion of FoxP3+ Tregs improves control of larval Echinococcus multilocularis infection by promoting co-stimulation and Th1/17 immunity

Introduction

The growth potential of the tumor‐like Echinococcus multilocularis metacestode (causing alveolar echinococcosis, AE) is directly linked to the nature/function of the periparasitic host immune‐mediated processes. Previous studies had shown that regulatory T cells (Tregs) become gradually up‐regulated in the course of both chronic human and murine AE. Thus we now tackled the role of FoxP3⁺ Tregs and FoxP3⁺‐Treg‐regulated immune response in contributing to the control of this helminthic infection.

Methods

The infection outcome in E. multilocularis‐infected DEREG mice was measured upon determining parasite load (wet weight of parasitic metacestode tissue). Flow cytometry and qRT‐PCR were used to assess Treg, Th17‐, Th1‐, Th2‐type immune responses and antigen presenting cell activation.

Results

We showed that E. multilocularis‐infected DEREG‐mice treated with DT (as compared to infected control DEREG‐mice without DT application) exhibited a significantly lower parasite load, associated with a persisting capacity of co‐stimulation, and an increased Th1/Th17‐polarization.

Conclusions

FoxP3⁺ Tregs appear as one of the key players in immune regulatory processes favoring (i) metacestode survival by inhibiting the maturation potential of co‐stimulatory activity and (ii) T cell exhaustion (suppressing Th1/Th17‐type immune responses). We showed as well that prospectively, targeting FoxP3⁺ Tregs could be an option to develop an immunotherapy against AE.

Albendazole increases the inflammatory response and the amount of Em2-positive small particles of Echinococcus multilocularis (spems) in human hepatic alveolar echinococcosis lesions

Background

Alveolar echinococcosis (AE) is caused by the metacestode stage of Echinococcus multilocularis. The inflammatory response to this infection is influenced by the interaction of the parasite with the host. We aimed to analyze human liver lesions infected with Echinococcus multilocularis and the changes of the cellular infiltrates during albendazole (ABZ) treatment.

Methodology/Principal findings

We analyzed liver tissue samples from 8 untreated patients, 5 patients treated with two daily doses of 400 mg ABZ for up to two months and 7 patients treated for more than two months with the same ABZ therapy. A broad panel of monoclonal antibodies was used to characterize the lesion by immunohistochemistry. A change in the cellular infiltrate was observed between the different chemotherapy times. During the initial phases of treatment an increase in CD15⁺ granulocytes and CD68⁺ histocytes as well as in small particles of Echinococcus multilocularis (spems) was observed in the tissue surrounding the metacestode. Furthermore, we observed an increase in CD4⁺ T cells, CD20⁺ B cells and CD38⁺ plasma cells during a longer duration of treatment.

Conclusions/Significance

ABZ treatment of AE leads to morphological changes characterized by an initial, predominantly acute, inflammatory response which is gradually replaced by a response of the adaptive immune system.

Alveolar echinococcosis (AE) is a life-threatening disease in humans caused by the larval stages of E. multilocularis. It has been shown that the infection in humans is associated with a modulated immune response. Depending on multiple factors, such as the stage of disease, total or partial surgical resection and albendazole (ABZ) therapy are treatments of choice. ABZ is known as a parasitostatic drug that has to be administered for years to suppress metacestode development. Here we compared human liver lesions before and after short and long term treatment with ABZ by immunohistochemistry using a broad panel of antibodies. We found a change in the cellular infiltrate, characterized by a shift to an infiltrate rich in T cells, B cells and plasma cells during long-term treatment with ABZ, including a pronounced detection of small particles of E. multilocularis (spems). We argue that ABZ treatment is likely to change the cellular infiltrate, leading to an enhancement of the host immune response during treatment.

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.